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Long Term Memory and Prions

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

updated 12/12/2015

 

Possible biochemical mechanism underlying long-term memories identified

Why is a prion-like molecular state necessary for persistence of memory? Could a transient memory be made permanent with a “Limitless” NZT-type neurotropic drug — or permanently forgotten?

It’s a nagging question: why do some of our memories fade away, while others last forever? Now scientists at the Stowers Institute for Medical Research have identified a possible biochemical mechanism: a specific synaptic protein called Orb2 can either block or maintain neural synapses (connections between neurons), which create and maintain long-term memories.

So for a memory to persist, the synaptic connections must be kept strong. But how? The researchers previously identified a synaptic protein called CPEB that is responsible for maintaining the strength of such connections in the sea slug (a model organism used in memory research). Recently, they identified a similar protein, called Orb2, in the fruit fly.

Now, using a fruit fly model system, they found that the synaptic connections are kept strong by the transformation of Orb2 from one molecular state to another. And that transformation causes Orb2 molecules to solidify and strengthen the memory connections in the brain.

The authors conclude their paper, published in the current issue of the journal Cell, with several questions. How and what triggers this transformation, how long does it persist? Is the continued presence of a prion-like state necessary for the persistence of memory, and is it correlated with or predictive of long-lasting memory? And most interestingly: can a transient memory about to be forgotten be stabilized by artificial recruitment of the prion-like state (perhaps by a neurotropic compound)?

And what about that ironic link with prions, associated with neurodegenerative disorders? Are prions some twisted form of memory that could one day even have value? We’ll be keeping an eye on where this fascinating research leads.

Technical details: the memory switch

In their latest study, the researchers determined that Orb2 exists in two distinct physical states: monomeric (a single molecule that can bind to other molecules) and oligomeric (a molecular complex).

Like CPEB, oligomeric Orb2 is prion-like — that is, it’s a self-copying cluster. (But unlike prions, oligomeric Orb2 and CPEB are not toxic.) Monomeric Orb2 represses, and oligomeric Orb2 activates a crucial step in the complex cellular process that leads to protein synthesis.

During this crucial step, messenger RNA (mRNA), which is an RNA copy of a gene’s recipe for a protein, is translated by the cell’s ribosome into the sequence of amino acids that will make up a newly synthesized protein. The monomeric form of Orb2 binds to the target mRNA, keeping it in a repressed state.

The Stowers scientists also determined that prion-like Orb2 not only activates translation into amino acids but imparts its translational state to nearby monomer forms of Orb2. As a result, monomeric Orb2 is transformed into prion-like Orb2, so its role in translation switches from repression to activation.

Self-sustaining activation maintains synaptic activity

Stowers Associate Investigator Kausik Si, Ph.D. thinks this switch is the possible mechanism by which fleeting experiences create an enduring memory. “Because of the self-sustaining nature of the prion-like state, this creates a local and self-sustaining translation activation of Orb2-target mRNA, which maintains the changed state of synaptic activity over time,” says Si.

The discovery that the two distinct states of Orb2 have opposing roles in the translation process provides “for the first time a biochemical mechanism of synapse-specific persistent translation and long-lasting memory,” he states.

“To our knowledge, this is the first example of a prion-based protein switch that turns a repressor into an activator,” Si adds. “The recruitment of distinct protein complexes at the non-prion and prion-like forms to create altered activity states indicates the prion-like behavior is in essence a protein conformation-based switch.

“Through this switch, a protein can lose or gain a function that can be maintained over time in the absence of the original stimuli. Although such a possibility has been anticipated prior to this study, there was no direct evidence.”

The research builds upon previous studies by Si and Eric Kandel, M.D., of Columbia University and other scientists. These studies revealed that both short-term and long-term memories are created in synapses.

 

Abstract of Amyloidogenic Oligomerization Transforms Drosophila Orb2 from a Translation Repressor to an Activator

Memories are thought to be formed in response to transient experiences, in part through changes in local protein synthesis at synapses. In Drosophila, the amyloidogenic (prion-like) state of the RNA binding protein Orb2 has been implicated in long-term memory, but how conformational conversion of Orb2 promotes memory formation is unclear. Combining in vitro and in vivo studies, we find that the monomeric form of Orb2 represses translation and removes mRNA poly(A) tails, while the oligomeric form enhances translation and elongates the poly(A) tails and imparts its translational state to the monomer. The CG13928 protein, which binds only to monomeric Orb2, promotes deadenylation, whereas the putative poly(A) binding protein CG4612 promotes oligomeric Orb2-dependent translation. Our data support a model in which monomeric Orb2 keeps target mRNA in a translationally dormant state and experience-dependent conversion to the amyloidogenic state activates translation, resulting in persistent alteration of synaptic activity and stabilization of memory.

 

New Finding on Synapse Destruction May Open Path to Alzheimer’s Therapy

http://www.genengnews.com/gen-news-highlights/new-finding-on-synapse-destruction-may-open-path-to-alzheimer-s-therapy/81252029/

A team led by scientists at the University of New South Wales in Australia say they have discovered how connections between brain cells are destroyed in the early stages of Alzheimer’s disease. They believe their work opens up a new avenue for research on possible treatments for the degenerative brain condition.

“One of the first signs of Alzheimer’s disease is the loss of synapses—the structures that connect neurons in the brain,” noted study leader, Vladimir Sytnyk, Ph.D., of the UNSW School of Biotechnology and Biomolecular Sciences. “Synapses are required for all brain functions, and particularly for learning and forming memories. In Alzheimer’s disease, this loss of synapses occurs very early on, when people still only have mild cognitive impairment, and long before the nerve cells themselves die. We have identified a new molecular mechanism which directly contributes to this synapse loss, a discovery we hope could eventually lead to earlier diagnosis of the disease and new treatments.”

The team studied a specific protein in the brain, neural cell adhesion molecule 2 (NCAM2), one of a family of molecules that physically connects the membranes of synapses and help stabilize these long lasting synaptic contacts between neurons. The researchers paper (“Aβ-dependent reduction of NCAM2-mediated synaptic adhesion contributes to synapse loss in Alzheimer’s disease”) is published in Nature Communications.

Using post-mortem brain tissue from people with and without the condition, they discovered that synaptic NCAM2 levels in the part of the brain known as the hippocampus were low in those with Alzheimer’s disease. They also showed in mice studies and in the laboratory that NCAM2 was broken down by beta-amyloid, which is the main component of the plaques that build up in the brains of people with the disease.

“Our research shows the loss of synapses is linked to the loss of NCAM2 as a result of the toxic effects of beta-amyloid,” pointed out Dr. Sytnyk. “It opens up a new avenue for research on possible treatments that can prevent the destruction of NCAM2 in the brain.”

 

Aβ-dependent reduction of NCAM2-mediated synaptic adhesion contributes to synapse loss in Alzheimer’s disease

Iryna Leshchyns’kaHeng Tai LiewClaire ShepherdGlenda M. HallidayClaire H. StevensYazi D. KeLars M. Ittner & Vladimir Sytnyk
Nature Communications Nov 2015; 6(8836)        doi:10.1038/ncomms9836

Alzheimer’s disease (AD) is characterized by synapse loss due to mechanisms that remain poorly understood. We show that the neural cell adhesion molecule 2 (NCAM2) is enriched in synapses in the human hippocampus. This enrichment is abolished in the hippocampus of AD patients and in brains of mice overexpressing the human amyloid-β (Aβ) precursor protein carrying the pathogenic Swedish mutation. Aβ binds to NCAM2 at the cell surface of cultured hippocampal neurons and induces removal of NCAM2 from synapses. In AD hippocampus, cleavage of the membrane proximal external region of NCAM2 is increased and soluble extracellular fragments of NCAM2 (NCAM2-ED) accumulate. Knockdown of NCAM2 expression or incubation with NCAM2-ED induces disassembly of GluR1-containing glutamatergic synapses in cultured hippocampal neurons. Aβ-dependent disassembly of GluR1-containing synapses is inhibited in neurons overexpressing a cleavage-resistant mutant of NCAM2. Our data indicate that Aβ-dependent disruption of NCAM2 functions in AD hippocampus contributes to synapse loss.

 

Learning and memory processes depend on the number and correct functioning of synapses in the brain. Cell adhesion molecules are enriched in the pre- and postsynaptic membranes. These molecules physically connect synaptic membranes, providing mechanical stabilization of synaptic contacts1, 2, 3, are necessary for the formation of new synapses during neuronal development4, 5, and maintain and regulate synaptic plasticity in adults6, 7, 8, 9, 10.

Alzheimer’s disease (AD) is a neurodegenerative brain condition predominantly of the aging population. One of the earliest signs of AD is the loss of synapses11, which can at least partially be linked to the toxicity mediated by Aβ12, 13, 14, a peptide that accumulates in the brains of AD patients. The impact of AD on synaptic adhesion and the role of synaptic cell adhesion molecules in the progression of the disease remains poorly understood.

The neural cell adhesion molecule 2 (NCAM2), sometimes designated OCAM, belongs to the immunoglobulin superfamily of cell adhesion molecules. NCAM2 participates in homophilic trans-interactions15, 16. During human embryonic development, NCAM2 is expressed in several tissues, including lung, liver, and kidney with the highest expression in the brain17. The expression level of NCAM2 peaks around postnatal day 21 and remains high during adulthood15, suggesting that the protein is necessary both during development and in adult brains. Accordingly, studies with cultured neurons and in NCAM2 deficient mice show that NCAM2 is important for the development of the brain, and the olfactory system in particular18, 19.

The NCAM2 gene is located on chromosome 21 in humans and NCAM2 overexpression has been suggested to be one of the factors contributing to the symptoms of Down syndrome17, which presents with early-onset AD pathology. Single-nucleotide polymorphisms in the NCAM2 gene have been reported as a risk factor related to the progression of AD in the Japanese population20. A recent genome-wide association study has found an association between single-nucleotide polymorphisms in the NCAM2 gene and levels of Aβ in the cerebrospinal fluid in humans, suggesting that NCAM2 is involved in the pathogenic pathway to the senile plaques that concentrate in AD brains21. Since genetic association studies indicate a link between NCAM2 and AD, we have analysed whether AD pathology influences levels of NCAM2 in synapses. Our results indicate that the synaptic adhesion mediated by NCAM2 is highly susceptible to Aβ toxicity and that proteolytic fragments of NCAM2 generated in an Aβ-dependent manner can directly contribute to the induction of synapse disassembly.

 

Synaptic NCAM2 is reduced in the hippocampus in AD

To analyse whether functions of NCAM2 are affected in AD, frozen post-mortem brain tissue of AD patients and non-affected controls (n=10 each) was analysed by western blot with antibodies against NCAM2. The detailed demographic data for the subjects analysed are presented inSupplementary Table 1. Total levels of NCAM2 were slightly increased in the hippocampus, but not significantly affected in the cerebellum or superior temporal cortex in AD (Supplementary Fig. 1). In contrast, levels of VGLUT1, a presynaptic marker-protein of excitatory synapses, were reduced in AD hippocampus (Supplementary Fig. 1), indicating a loss of excitatory synapses. Levels of VGAT, a presynaptic marker-protein of inhibitory synapses, were not significantly affected in any brain region analysed (Supplementary Fig. 1).

Changes in the protein levels in brain homogenates do not necessarily reflect changes in the protein levels in synapses. To analyse whether the synaptic function of NCAM2 is affected in AD, we compared the enrichment of NCAM2 in synaptosomes isolated from the brain tissue of individuals with AD and non-affected controls by western blot analysis of synaptosomes and total homogenates of the brains used for synaptosome preparations. Equal total protein amounts from each probe were applied to the gels to compensate for any possible differences in the yield of synaptosomes because of the synapse loss observed in AD. Western blot analysis with antibodies against actin, VGLUT1, VGAT, synaptophysin (a general presynaptic marker-protein), and PSD95 (a postsynaptic marker-protein), showed that these proteins were enriched to similar levels in synaptosomes from AD and control brains, indicating similar purities of intact synaptosome isolations (Fig. 1a). Western blot analysis showed that in control individuals NCAM2 was highly enriched in synaptosomes from the hippocampus and to a lower degree in synaptosomes from the temporal cortex and cerebellum (Fig. 1a,b). This synaptic enrichment of NCAM2 was significantly reduced in synaptosomes from AD hippocampi (Fig. 1a,b). The synaptic enrichment of NCAM2 was slightly lower in the AD versus control cerebellum, however the difference was not statistically significant (Fig. 1a,b).

 

Figure 1: Synaptic accumulation of NCAM2 is reduced in the hippocampus of AD-affected individuals.

Figure 2: Cleavage of the membrane-adjacent extracellular fragment of NCAM2 is increased in AD brains.

Figure 3: The extracellular domain of NCAM2 binds to Aβ.

Cleavage of NCAM2aa682-701 is increased in AD brains

NCAM2 binds to Aβ in vitro

Figure 4: NCAM2 accumulates in excitatory synapses of cultured hippocampal neurons.

NCAM2 accumulates in excitatory synapses of cultured hippocampal neurons.

http://www.nature.com/ncomms/2015/151127/ncomms9836/images_article/ncomms9836-f4.jpg

(a) Low-magnification image of a cultured hippocampal neuron labelled by indirect immunofluorescence with antibodies against NCAM2, synaptophysin and MAP2. Note expression of NCAM2 along MAP2 positive dendrites. NCAM2 is also expressed in astrocytes (marked a) which are present in these cultures. Scale bar, 20μm. (b) High-magnification image of dendrites of neurons co-labelled with antibodies against NCAM2, synaptophysin and MAP2. Arrows show clusters of NCAM2 partially overlapping with synaptophysin accumulations. NCAM2-negative synapses are also observed (arrowheads). Scale bar, 10μm. (c) High-magnification image of a dendrite of a cultured hippocampal neuron labelled with antibodies against NCAM2, synaptophysin and PSD95. NCAM2 clusters partially overlap with accumulations of PSD95 and synaptophysin (arrows). Scale bar, 10μm. Three-dimensional analysis of the co-localization within the outlined area is on the right. Z-stack has been acquired with 0.15μm steps. The xz and yz sections along the dashed lines on the xy image are shown. Note co-localization of the NCAM2 cluster with synaptic markers. (d) Negative control, that is, labelling performed without primary antibodies, is shown. Scale bar, 10μm.

 

Figure 5: Aβ1–42 oligomers bind to NCAM2 at the cell surface of neurons.

Figure 6: Levels of NCAM2 are reduced in synaptosomes of cultured hippocampal neurons treated with Aβ1-42 oligomers.

Figure 7: NCAM2 co-localizes with Aβ1-42 in brains of APP23 transgenic mice.

Figure 8: NCAM2 binds to Aβ and its synaptic accumulation is reduced in the hippocampus of APP23 transgenic mice.

Aβ removes NCAM2 from synapses of hippocampal neurons

Western blot analysis showed that levels of soluble NCAM2 with the molecular weight of ~100kDa were significantly increased in culture medium from Aβ1-42-treated hippocampal neurons (Fig. 6b), further indicating that Aβ1-42 induces removal of NCAM2 off the neuronal cell surface. In contrast, levels of the soluble proteolytic products of CHL1, another synaptic cell adhesion molecule of the immunoglobulin superfamily26, 27, were not changed in the culture medium from Aβ1-42-treated hippocampal neurons (Fig. 6b). Incubation with Aβ1-42 did not increase levels of soluble NCAM2 in the culture medium from cortical neurons (Fig. 6b), suggesting that cortical neurons are more resistant to Aβ1-42-dependent NCAM2 proteolysis.

Aβ binds to and removes NCAM2 from synapses in APP23 mice

Disruption of NCAM2 adhesion promotes synapse disassembly

Figure 9: Disruption of NCAM2 functions at the neuronal cell surface promotes glutamatergic synapse disassembly.

Disruption of NCAM2 functions at the neuronal cell surface promotes glutamatergic synapse disassembly.

http://www.nature.com/ncomms/2015/151127/ncomms9836/images_article/ncomms9836-f9.jpg

(ae) Cultured hippocampal neurons were either mock-treated or incubated with the recombinant soluble extracellular domains of NCAM2 (NCAM2-ED), antibodies against the extracellular domain of NCAM2 (NCAM2mAb), or Aβ1-42 oligomers. In a,b, neurons were labelled with antibodies against the extracellular domain of GluR1 before permeabilization of membranes with detergent, and co-labelled with antibodies against synaptophysin after permeabilization of membranes with detergent. Representative images of dendrites are shown (a). Note co-localization of cell surface GluR1 accumulations with synaptophysin clusters in mock-treated neurons, and increased levels of non-synaptic cell surface GluR1 accumulations in neurons treated with NCAM2-ED, NCAM2mAb or Aβ1-42. Graphs (b) show the percentage of synaptic and non-synaptic GluR1 clusters relative to total number of GluR1 clusters along dendrites and numbers of synaptophysin accumulations per dendrite length (mean+s.e.m.). *P<0.0001 (analysis of variance with Dunnett’s multiple comparison test, n>80 dendrites from 20 neurons were analysed in each group). In c, neurons were labelled with antibodies against the extracellular domain of NR1 before permeabilization of membranes with detergent, and co-labelled with antibodies against synaptophysin after permeabilization of membranes with detergent. Graphs show the percentage of synaptic and non-synaptic NR1 clusters relative to total number of NR1 clusters along dendrites (mean+s.e.m.). *P<0.0001 (analysis of variance with Dunnett’s multiple comparison test, n>85 dendrites from 20 neurons were analysed). In d,e, neurons were co-labelled with fluorescent phalloidin and synaptophysin antibodies. Representative images of dendrites are shown in d. Note higher labelling intensity and co-localization with synaptophysin of the phalloidin-labelled polymerized actin accumulations in control neurons versus neurons treated with Aβ1-42, NCAM2-ED or NCAM2mAb. Note increased numbers of filopodia and lamellipodia in neurons treated with Aβ1-42, NCAM2-ED or NCAM2 mAb. Graphs (e) show ratio of the dendrite area-to-length and phalloidin labelling intensity of dendrites of neurons. Mean values+s.e.m. are shown. *P<0.0001 (analysis of variance with Dunnett’s multiple comparison test, n=50 dendrites from 20 neurons were analysed in each group). Scale bar, 10μm (in a,d).

Cleavage-resistant NCAM2 reduces Aβ-dependent synapse loss

Figure 10: Aβ1-42 reduces the number of GluR1-containing synapses in the NCAM2-dependent manner.

http://www.nature.com/ncomms/2015/151127/ncomms9836/images_article/ncomms9836-f10.jpg

(a) Representative images of dendrites of cultured hippocampal neurons transfected either with control negative miRNA (negative miR) or NCAM2miR and either mock-treated or incubated with Aβ1-42. Transfected neurons were identified by fluorescence of GFP, which is co-expressed together with miRNA. Neurons were co-labelled with antibodies against cell surface GluR1 and synaptophysin. Note that the number of synaptic GluR1 clusters is reduced and the number of non-synaptic GluR1 clusters is increased in neurons transfected with NCAM2miR. Scale bar, 10μm. (b,c) Graphs show mean+s.e.m. percentage of synaptic and non-synaptic GluR1 clusters relative to the total number of GluR1 clusters along dendrites (b) and numbers of synaptophysin accumulations per dendrite length normalized to the mean number in mock-treated neurons (c) for neurons described in (a). (df) Graphs show mean+s.e.m. percentage of synaptic and non-synaptic GluR1 clusters relative to the total number of GluR1 clusters along dendrites (d), number of synaptophysin accumulations per dendrite length normalized to the mean number in mock-treated neurons (e), and area/length ratio (f) in cultured hippocampal neurons transfected either with GFP alone or co-transfected with GFP and non-mutated NCAM2 (NCAM2WT) or NCAM2D693A mutant and either mock-treated or incubated with Aβ1-42. (g,h) Graphs show mean+s.e.m. percentage of non-synaptic GluR1 clusters relative to the total number of GluR1 clusters along dendrites (g) and area/length ratio (h) in cultured hippocampal neurons co-transfected with NCAM2 miR and either GFP, non-mutated NCAM2 (WT) or NCAM2D693A mutant (D693A) and either mock-treated or incubated with Aβ1-42. In bh, *P<0.01 (compared as indicated), ˆP<0.01 (compared with mock-treated neurons transfected with negative miR (b), GFP (df) or co-transfected with NCAM2miR and GFP (gh)), analysis of variance with Tukey’s multiple comparison test, n>50 dendrites from 20 neurons were analysed in each group.

 

Taken together, our results indicate that Aβ affects the numbers of GluR1-containing glutamatergic synapses in a NCAM2-dependent manner.

Alzheimer’s disease is characterized by loss of synapses, which is the strongest correlate of cognitive decline11, 29, 30, 31, 32 and possibly one of the earliest events in AD pathogenesis30, 33. Synapses are long lasting contacts between neurons, which are stabilized by a number of cell adhesion molecules that concentrate in pre- and postsynaptic membranes2, 5. Cell adhesion molecules play an essential role in maintaining synapse functionality and stability. Although cell adhesion molecules of many families are required for the synapse integrity8, 10, elimination of even one type of synaptic cell adhesion molecule is often sufficient to induce abnormalities in synapse ultrastructure and protein composition6, 7. In the present study, we show that levels of the synaptic cell adhesion molecule NCAM2 are markedly reduced in hippocampal synapses in AD brains and Aβ-forming APP23 mice. Our observations that disruption of NCAM2 interactions at the cell surface, knockdown of NCAM2 expression and Aβ exposure result in reduced numbers of glutamatergic synapses in hippocampal neurons suggest that abnormalities in NCAM2-mediated synaptic adhesion contribute to synapse loss in AD.

Although the mechanisms of synapse disassembly in AD remain poorly understood, previous studies indicated that synapse loss can be linked to Aβ-induced toxicity12, 34, 35. Our observations showing that synaptic levels of NCAM2 are similarly reduced in APP23 mice and in cultured hippocampal neurons from wild-type mice exposed to Aβ argue in favour of Aβ-dependent mechanisms in the disruption of NCAM2-mediated synaptic adhesion. We however do not exclude that other factors, such as disrupted trafficking of NCAM2 to synapses, may also contribute to the reduction of NCAM2 levels at synapses. Strikingly, the effects of Aβ on synaptic targeting of NCAM2 were particularly strong in hippocampal but not cortical or cerebellar neurons. The enhanced susceptibility of synaptic NCAM2 to Aβ-dependent proteolysis may therefore contribute to selective vulnerability of the hippocampus to AD.

Our observations that NCAM2 directly interacts with synthetic Aβ1-42, that Aβ1-42 forms a molecular complex with NCAM2 at the neuronal cell surface and that complexes of NCAM2 and oligomers of Aβ can be isolated from APP23 mouse brains, indicate that NCAM2 may function as a previously unrecognized receptor for Aβ at the neuronal cell surface. Previous studies have shown that Aβ can also bind to other cell adhesion molecules at the neuronal cell surface, among which are the prion protein36 and L137. In addition, a number of cell adhesion molecules have been shown to interact with APP, including the neural cell adhesion molecule 1 (NCAM1)38 and TAG1 (ref. 39). It remains to be investigated whether the NCAM2/Aβ complex comprises other adhesion molecules and cell surface proteins. Interestingly, NCAM1, a homologue of NCAM2, binds to prion protein40 and L1 (ref. 41). However, in spite of homology to NCAM2, NCAM1 binds to a region of APP which is different to the Aβ-containing region38.

…..

Taken together, we show that Aβ induces synaptic loss and proteolysis of NCAM2 in cell culture and APP transgenic mouse models, providing a mechanistic explanation for synaptic NCAM2 changes in AD brains. The detrimental effects of proteolyically cleaved extracellular NCAM2 on synapses may augment the Aβ toxicity in the pathogenesis of AD. The exact molecular mechanisms underlying Aβ-induced NCAM2 changes, and to which degree it contributes to onset and progression of disease remains to be established. Nevertheless, our data reveal a new role of NCAM2 in AD that warrants further investigation.

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Notable Awards – 2015

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Breakthrough Prizes Give Top Scientists the Rock Star Treatment

“By challenging conventional thinking and expanding knowledge over the long term, scientists can solve the biggest problems of our time,” Mr. Zuckerberg said in a statement. “The Breakthrough Prize honors achievements in science and math so we can encourage more pioneering research and celebrate scientists as the heroes they truly are.”

Left, Karl Deisseroth, Stanford School of Medicine; Edward S. Boyden of the McGovern Institute for Brain Research at M.I.T.CreditLeft, Winni Wintermeyer for The New York Times; Dominick Reuter/M.I.T. News

http://i1.nyt.com/images/2015/11/08/science/08breakthrough_comp_1/08breakthrough_comp_1-tmagArticle.jpg

Karl Deisseroth and Edward S. Boyden
Optogenetics

Karl Deisseroth, a professor at Stanford University and a Howard Hughes Medical Institute investigator, and Edward S. Boyden, a professor at the Massachusetts Institute of Technology, each received $3 million for their roles in the development of optogenetics, a technique that allows scientists to use light to turn neurons and groups of neurons on and off.

The technique is transforming the study of the brain because it allows scientists to test ideas about how the brain works. It has already been used to turn a kind of aggression on and off in flies, and thirst on and off in mice, pinpointing the brain cells involved.

The technique is universally praised, but the question of who will be recognized for its development is an issue for any prize committee. Dr. Boyden, Dr. Deisseroth and three other scientists published a paper in 2005that is recognized as a breakthrough. They demonstrated how to reliably control mammalian neurons with light, making widespread use of the technique inevitable.

Their paper built on earlier work, as much of science does. Opsins, light-sensitive chemicals that are crucial to optogenetics, have been studied since the 1970s. And the fact that optogenetics could be done was demonstrated in 2002.

In 2013, the European Brain Prize recognized six scientists for work on optogenetics, including Dr. Boyden and Dr. Deisseroth.

JAMES GORMAN

 

http://i1.nyt.com/images/2015/11/08/science/08Breakthrough4/08Breakthrough4-tmagArticle.jpg

John Hardy
Alzheimer’s research

Alzheimer’s disease was a complete mystery in the late 1980s. In autopsies, pathologists could see the ravages left in patients’ brains, but how and why did the process start? There were rare families in which the disease seemed to be inherited, though, and perhaps there was a gene mutation that might provide a clue to what goes awry. The problem was finding those families.

In the late 1980s, a woman who lived in Nottingham, England, contacted John Hardy at University College London and asked if he and his team wanted to study her family. Her father was one of 10 siblings, five of whom had developed Alzheimer’s disease, and she could trace the disease back for three generations. Their investigation led to the discovery of a gene mutation that, if inherited, always caused the disease. The gene was presenilin, and its protein was the amyloid precursor protein, or APP. Every person in that family who inherited the gene overproduced amyloid and got the disease. For the first time, scientists had a clue to what starts the horrendous destruction of brain cells in Alzheimer’s disease. And for the first time, by putting that gene mutation in mice, they could study Alzheimer’s in a lab animal, look for drugs to block the gene’s effects and finally use the tools of science to look for a cure.

GINA KOLATA

http://i1.nyt.com/images/2015/11/08/science/08Breakthrough-Hobbs/08Breakthrough-Hobbs-tmagArticle.jpg

Helen Hobbs
Cholesterol research

Helen Hobbs, a professor at the University of Texas Southwestern Medical Center and a Howard Hughes Medical Institute investigator, and her colleague Jonathan Cohen were intrigued when they read a short paper describing a French family with stunningly high levels of LDL cholesterol, the dangerous kind, and early deaths from heart attacks and strokes. The family members turned out to have a mutation in a gene, PCSK9, whose function was unknown. Dr. Hobbs and Dr. Cohen began to wonder: If too much PCSK9 caused heart disease, would people who made too little be protected? They scrutinized genetic data from a federal study and found that about 2.5 percent of blacks had a mutation that destroyed one copy of the gene; 3.2 percent of whites had a mutation that hobbled a copy of the gene but did not destroy it. In both cases, less PCSK9 was made and LDL levels were low. The people with the mutations seemed almost immune to heart disease, even if they had other risk factors like high blood pressure, smoking or diabetes.

What would happen if someone had both copies of PCSK9 destroyed? Dr. Hobbs found one young woman, an aerobics instructor, without PCSK9. She was healthy and fertile even though her LDL level was 14, lower than seemed possible (the average is 100). That discovery led to a race among drug companies to make cholesterol-lowering drugs that mimicked the effects of the PCSK9 mutations. The result is drugs that can make LDL levels plunge to the 30s, the 20s, even the teens. The first two such PCSK9 inhibitors were approved this year for people with high cholesterol levels who cannot get them down with statins and are at high risk of heart disease.

GINA KOLATA

 

TED Prize Goes to Archaeologist Who Combats Looting With Satellite Technology
http://static01.nyt.com/images/2015/11/09/arts/09SPACE/09SPACE-master675.jpg
http://www.nytimes.com/2015/11/09/arts/international/ted-grant-goes-to-archaeologist-who-combats-looting-with-satellite-technology.html

 

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Author: Tilda Barliya PhD

Alzheimer disease (AD) is among the most common brain disorders affecting the elderly population the world over, and is projected to become a major health problem with grave socio-economic implications in the coming decade (1a, 1b). Alzheimer’s disease arises in large part from the body’s inability to clear these naturally occurring proteins. As amyloid beta levels increase, they tend to aggregate and contribute to the brain “plaques” found in Alzheimer’s disease. There are still no effective treatments to prevent, halt, or reverse Alzheimer’s disease, but research advances over the past three decades could change this gloomy picture. Genetic studies demonstrate that the disease has multiple causes (2). Interdisciplinary approaches have been used to reveal the molecular mechanism of the disease including; biochemistry,  molecular and cell biology and transgenic mice models.  Progress in chemistry, radiology, and systems biology is beginning to provide useful biomarkers, and the emergence of personalized medicine is poised to transform pharmaceutical development and clinical trials. However, investigative and drug development efforts should be diversified to fully address the multifactoriality of the disease (2). A nice research review shows  for example, the effects of cancer drugs on AD treatment (3).

Nanotechnology Solutions for Alzheimer

Dr. Amir Nazem and Dr. G. Ali Mansoori described in their paper “Nanotechnology Solutions for Alzheimer’s Disease: Advances in Research Tools, Diagnostic Methods and Therapeutic Agents”
that he development of nanotechnology approaches for early-stage diagnosis of AD is quite promising but acknowledge that scientists are still at the very beginning of the ambitious project of designing effective drugs and methods for the regeneration of the central nervous system (4). Figure 1- Nanotechnology solutions of AD.

Applications of nanotechnology in AD therapy including:

  • Nanodiagnostics including imaging
  • Targeted drug delivery and controlled release
  • Regenerative medicine

These inclued: neuroprotections against oxidative stress anti-amyloid therapeutics, neuroregeneration and drug delivery beyond the blood brain barrier (BBB) are discussed and analyzed.

All of these applications could improve the treatment approach of AD and other neurodegenerative diseases.

Nanotechnology and Diagnostics:

The diagnosis of AD during life remains difficult and a definite diagnosis of AD relies on histopathological confirmation at post-mortem or by cerebral biopsy.  An early clinical diagnosis can be made if patients  are tested by trained neuropsychologists. The great problem is not that mild cognitive impairment  (MCI) cannot be diagnosed, but that the patients do not see doctor until severely affected (5).

During the last decade, research efforts have focused on developing  cerebrospinal fluid (CSF) biomarkers for AD. The diagnostic performance of the CSF  biomarkers: Tau protein, the 42-amino acid form of beta amyloid (Aβ42) and Amyloid  Precursor Protein are of great importance. One possible biomarker for Alzheimer’s is  amyloid beta-derived diffusible ligands (ADDL). The correlation of CSF ADDL levels  with disease state offers promise for improved AD diagnosis and early treatment. Singh et al have developed ADDL-specific monoclonal antibodies with an ultrasensitive,  nanoparticle-based protein detection strategy termed biobarcode amplification (BCA) (5).

The BCA strategy used by Klein, Mirkin and coworkers makes clever use of nanoparticles as DNA carriers to enable millionfold improvements over ELISA sensitivity. CSF is first exposed to monoclonal anti-ADDL antibodies bound to magnetic microparticles. After ADDL binding, the microparticles are separated with a magnetic field and washed before addition of secondary antibodies bound to DNA:Au nanoparticle conjugates. These conjugates conatin covalently bound DNA as well as complementary “barcode” DNA that is attached via hybridization. Unreacted antibody:DNA:Au nanoparticle conjugates are removed during second magnetic separation, after which elevated temperature and low-salt conditions release the barcode DNA for analysis.

“Such a sensor must be able to transmit any biomarker detection event to an external device that records the transmitted signals and reports an estimated amount for the concentration of AD biomarkers in the CSF. Of course, in order to send such biosensor to a place exposing with CSF, it is necessary to design noninvasive approaches.” (4)

Nanotechnology and treatment:

Presently there exist no therapeutic methods available for curing AD [84]. The cure for AD would require therapeutics that will cease the disease progress and will reverse its resultant damages. Today, common medications for AD are symptomatic and aim at the disrupted neurotransmission between the degenerated neurons. Examples of such medications are acetylcholine esterase inhibitors, including tacrine, donepezil, rivastigmine and galantamine (4).

Design of each mechanistic therapeutic is for targeting a different stage of the AD pathogenetic process and therefore help to cease the progress of the disease. Currently there are 5 mechanistic therapeutic molecular approaches:

  • Inhibition of Aβ production;
  • Inhibition of Aβ oligomerization,
  • Anti-inflammation,
  • Cholesterol homeostasis modulating;
  • Metal chelation

The nanotechnology approaches are:

  • Drug discovery and monitoring
  • Controlled release
  • Targeted drug delivery

For example: Neuroprotection

Oxidative stress and amyloid induced toxicity are two basic toxicity processes in AD pathogenesis.

Oxidative stress protection:

Fullerene is a nanotechnology building block and can be used to design neuroprotective compounds. It’s chemical structure is known for it’s anti-oxidative and free-scavenger potentials. Applications of functionalized fullerene derivatives including carboxyfullerene and hydroxyfullerene (fullerenols), are promising in discovery of new drugs for AD; however further research on their pharmacodynamic and pharmacokinetic properties is necessary.

Anti-amyloid protections:

Nanotechnology has recently offered some antiamyloid neuroprotective approaches against the cellular and synaptic toxicity of oligomeric and fibrillar (polymeric) Aβ species. The current ongoing nanotechnology research categories on anti-amyloid neuroprotective approaches are the following three:

  1. Prevention from assembly of Aβ monomers
  2. Breaking and resolubilization of the oligomeric or fibrillar (polymeric) Aβ species
  3. Prevention from toxic effects of Aβ

Summary:

AD is a very common disease worldwide,  Solving the major problems of early diagnosis and effective cure for AD requires interdisciplinary research efforts. Research on the basic pathogenetic mechanisms of the disease has provided new insight for designing diagnostic and therapeutic methods. Nanotechnology has great potential in aiding and providing tools for diagnosing and treating AD. However, these research combining nanotechnology is still at very early stages and continuous understanding of the disease, neuronal protection and regeneration are needed in order to alleviate the symptoms of the disease.

Ref.
1a. D. G. Georganopoulou et al., “Nanoparticle-based Detection in Cerebral Spinal Fluid of a Soluble Pathogenic Biomarker for Alzheimer’s Disease”, Proc. Natl Acad Sci., 102 (2005) 2273-2276

1b D.A. Davis, W. Klein and L. Chang, “Nanotechnology-based Approaches to Alzheimer’s Clinical Diagnostics”, Nanoscape, 3 (2006) 13-17.
Read more: http://www.nanowerk.com/spotlight/spotid=23726.php#ixzz2NWlx6jYa

2. Huang Y and Mucke L. Alzheimer mechanisms and therapeutic strategies. Cell. 2012 Mar 16;148(6):1204-22.

http://www.cell.com/abstract/S0092-8674(12)00278-4

http://www.ncbi.nlm.nih.gov/pubmed/22424230

3. Cancer Drug Shows Promise in Alzheimer’s Treatment: Helps clear plaque and improve brain function in mice. Alzheimer’s Disease Research is a program of the American Health Assistance Foundation. http://www.nanowerk.com/spotlight/spotid=5262.php

4. Amir Nazem1, G. Ali Mansoori. Nanotechnology solutions for Alzheimer’s disease: advances in research tools, diagnostic methods and therapeutic agents. J Alzheimers Dis. 2008 Mar;13(2):199-223.  http://www.ncbi.nlm.nih.gov/pubmed/18376062?dopt=Abstract.

Full text: http://www.uic.edu/labs/trl/1.OnlineMaterials/08-Nanotechnology_Solutions_for_Alzheimer’s_Disease.pdf

5. Shinjini Singh, Mritunjai Singh, I. S. Gambhir*. Nanotechnology for Alzheimer’s Disease Detection. Digest Journal of Nanomaterials and Biostructures Vol. 3, No.2, June 2008, p. 75 – 79 .

http://www.chalcogen.infim.ro/Singh-Gambhir.pdf

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Curated by: Dr. Venkat S. Karra, Ph.D.

A human brain showing frontotemporal lobar deg...

The number of patients with dementia have been increasing exponentially with the aging of society.  The development of AD research has clarified that the pathogenesis of AD is initiated by amyloidosis with secondary tauopathy and provided a strategy for investigating drugs that may improve or cure AD.

Mild cognitive impairment (MCI) as a prodromal stage of AD and the pathogenesis of Dementia with Lewy bodies (DLB) and Frontotemporal lobar degeneration (FTLD) as a non-AD type dementia have also been elucidated. Currently, a consortium study by the Alzheimer Disease Neuroimaging initiative (ADNI) is being performed to establish global clinical evidence regarding a neuropsychiatric test battery, CSF biomarkers, neuroimaging including MRI, FDG-PET, and amyloid PET to predict progression from MCI to AD and to promote studies of basic therapy for AD [1].

Several new biomarkers such as Aβ oligomer, α-synuclein, and TDP-43 are now under investigation for further determination of their usefulness to detect AD and other non-AD type dementia.

Cerebrospinal Fluid Aβ40, Aβ42, Tau, and Phosphorylated Tau biomarkers have been used for a clinical diagnosis of AD, discrimination from the Vascular dementia (VaD) and non-AD type dementia, exclusion of treatable dementia and MCI, prediction of AD onset and evaluation of the clinical trials of an anti-Aβ antibody, Aβ vaccine therapy, and secretase inhibitors [2–4].

In the current study Schoonenboom et al., [10] conducted a large cohort of patients with different types of dementia to determine how amyloid β 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) levels behave in CSF.

Aβ is produced mainly in the nerve cells of the brain, and it is secreted about 12 hours later into the CSF, then excreted through the blood-brain barrier 24 hours later into blood (Aβ clearance), and finally degraded in the reticuloendothelial system. Aβ levels are regulated in strict equilibrium among the brain, CSF, and blood [6, 7]. Aβ levels are high while awake and low while a sleep suggesting the presence of a daily change in the CSF Aβ amounts and it is because Aβ amounts in CSF are controlled by orexin and thus collection of CSF by lumbar puncture early in morning in a fasting state is recommended [5].

In AD brains, Aβ42 forms insoluble amyloids and accumulates as insoluble amyloid fibrils in the brain. The reason Aβ42 levels are decreased in the CSF of AD patients is considered to be caused by deterioration of physiologic Aβ clearance into the CSF in AD brains [2, 3]. CSF total tau levels increase slightly with aging. However, CSF tau levels show a 3-fold greater increase in AD patients than in normal controls [8].

It is thought that the rise in CSF total tau is related to degeneration of axons and neurons and to severe destructive disease of the nervous system. Several diseases show slightly increased tau levels such as VaD, multiple sclerosis, AIDS dementia, head injury, and tauopathy. However, CSF tau levels show significant increases in Creutzfeldt-Jakob disease (CJD) and meningoencephalitis [8].

These biomarkers can be measured with an Amyloid ELISA Kit (Wako), which is commercially available and used worldwide. The ELISA kit was developed in Japan by Suzuki et al. and shows extremely high sensitivity and reproducibility [9]. INNOTEST β-AMYLOID1-42 (Innogenetics), for Aβ42 is used widely in Europe and America.

Several assay kits for total tau and phosphorylated tau are also used for the measurement of CSF tau. Currently, total tau is measured using INNOTEST hTau Ag (Innogenetics). There are 3 ELISA systems for measurement of phosphorylated tau that recognize the special phosphorylation sites at Ser199 (Mitsubishi Chemical Corp.), Thr181 (Innogenetics) and Thr231 (Applied NeuroSolutions Inc.), and phosphorylated tau levels are increased in CSF of AD on assays using these kits. Of these 3 kits, INNOTEST PHOSPHO-TAU (181) (Innogenetics) is commercially available and used widely. Recently, INNO-BIA AlzBio3 by Innogenetics has been able to measure Aβ1-42, total tau, and P-tau181P simultaneously in 75 μL of CSF, which is a very small amount of CSF.

In the current study researchers used the following strategy to collect Baseline CSF and Aβ42, t-tau, and p-tau (at amino acid 181) were measured in CSF by ELISA:

Types of patients with Alzheimer disease (AD) = 512 patients
Types of patients with other types of dementia (OD) = 272 patients
Types of patients with a psychiatric disorder (PSY) = 135 patients
Types of patients with subjective memory complaints (SMC) = 275 patients
Autopsy was obtained in a subgroup of about 17 patients.

The study suggested that CSF Aβ42, t-tau, and p-tau are useful in differential dementia diagnosis, whereas in DLB, FTLD, VaD, and CBD, a substantial group exhibited a CSF AD biomarker profile, which requires more autopsy confirmation in the future.

The study found a correct classification of patients with AD (92%) and patients with OD (66%)  when CSF Aβ42 and p-tau were combined.
Patients with progressive supranuclear palsy had normal CSF biomarker values in 90%.

Patients with Creutzfeldt-Jakob disease demonstrated an extremely high CSF t-tau at a relatively normal CSF p-tau.

CSF AD biomarker profile was seen in

47% of patients with dementia with Lewy bodies (DLB),

38% in corticobasal degeneration (CBD), and

30% in frontotemporal lobar degeneration (FTLD) and vascular dementia (VaD).

PSY and SMC patients had normal CSF biomarkers in 91% and 88%.

Older patients are more likely to have a CSF AD profile.

Concordance between clinical and neuropathologic diagnosis was 85%.

CSF markers reflected neuropathology in 94%.

The study concluded that CSF Aβ42, t-tau, and p-tau are useful in differential dementia diagnosis. However, in DLB, FTLD, VaD, and CBD, a substantial group exhibit a CSF AD biomarker profile, which requires more autopsy confirmation in the future.

References:

1. R. C. Petersen, P. S. Aisen, L. A. Beckett et al., “Alzheimer’s Disease Neuroimaging Initiative (ADNI): clinical characterization,” Neurology, vol. 74, no. 3, pp. 201–209, 2010.

2. M. Shoji and M. Kanai, “Cerebrospinal fluid Aβ40 and Aβ42: natural course and clinical usefulness,” Journal of Alzheimer’s Disease, vol. 3, no. 3, pp. 313–321, 2001.

3. M. Shoji, M. Kanai, E. Matsubara et al., “The levels of cerebrospinal fluid Aβ40 and Aβ42(43) are regulated age-dependently,” Neurobiology of Aging, vol. 22, no. 2, pp. 209–215, 2001.

4. M. Kanai, E. Matsubara, K. Isoe et al., “Longitudinal study of cerebrospinal fluid levels of tau, Aβ1-40, and Aβ1-42(43) in Alzheimer’s disease: a study in Japan,” Annals of Neurology, vol. 44, no. 1, pp. 17–26, 1998.

5. J. E. Kang, M. M. Lim, R. J. Bateman et al., “Amyloid-β dynamics are regulated by orexin and the sleep-wake cycle,” Science, vol. 326, no. 5955, pp. 1005–1007, 2009.

6. M. Shoji, T. E. Golde, J. Ghiso et al., “Production of the Alzheimer amyloid β protein by normal proteolytic processing,” Science, vol. 258, no. 5079, pp. 126–129, 1992.

7. R. J. Bateman, E. R. Siemers, K. G. Mawuenyega et al., “A γ-secretase inhibitor decreases amyloid-β production in the central nervous system,” Annals of Neurology, vol. 66, no. 1, pp. 48–54, 2009.

8. M. Shoji, E. Matsubara, T. Murakami et al., “Cerebrospinal fluid tau in dementia disorders: a large scale multicenter study by a Japanese study group,” Neurobiology of Aging, vol. 23, no. 3, pp. 363–370, 2002.

9. N. Suzuki, T. T. Cheung, X. D. Cai et al., “An increased percentage of long amyloid β protein secreted by familial amyloid β protein precursor (βAPP) mutants,” Science, vol. 264, no. 5163, pp. 1336–1340, 1994.

Source:

10. N.S.M. Schoonenboom et al., Cerebrospinal fluid markers for differential dementia diagnosis in a large memory clinic cohort

For further insight read the following excellent review article by M. Shoji

Biomarkers of Dementia

Special thanks to Wikipedia for excellent relevant pictures and keyword links.

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