Posts Tagged ‘Central Nervous System’

Reporter: Adina Hazan, PhD

Elizabeth Unger from the Tian group at UC Davis, Jacob Keller from the Looger lab from HHMI, Michael Altermatt from the Gradinaru group at California Institute of Technology, and colleagues did just this, by redesigned the binding pocket of periplasmic binding proteins (PBPs) using artificial intelligence, such that it became a fluorescent sensor specific for serotonin. Not only this, the group showed that it could express and use this molecule to detect serotonin on the cell, tissue, and whole animal level.

By starting with a microbial PBP and early version of an acetyl choline sensor (iAChSnFR), the scientists used machine learning and modeling to redesign the binding site to exhibit a higher affinity and specificity to serotonin. After three repeats of mutagenesis, modeling, and library readouts, they produced iSeroSnFR. This version harbors 19 mutations compared to iAChSnFR0.6 and a Kd of 310 µM. This results in an increase in fluorescence in HEK293T cells expressing the serotonin receptor of 800%. Of over 40 neurotransmitters, amino acids, and small molecules screened, only two endogenous molecules evoked some fluorescence, but at significantly higher concentrations.

To acutely test the ability of the sensor to detect rapid changes of serotonin in the environment, the researchers used caged serotonin, a technique in which the serotonin is rapidly released into the environment with light pulses, and showed that iSeroSnFR accurately and robustly produced a signal with each flash of light. With this tool, it was then possible to move to ex-vivo mouse brain slices and detect endogenous serotonin release patterns across the brain. Three weeks after targeted injection of iSeroSnFR to specifically deliver the receptor into the prefrontal cortex and dorsal striatum, strong fluorescent signal could be detected during perfusion of serotonin or electrical stimulation.

Most significantly, this molecule was also shown to be detected in freely moving mice, a tool which could offer critical insight into the acute role of serotonin regulation during important functions such as mood and alertness. Through optical fiber placements in the basolateral amygdala and prefrontal cortex, the team measured dynamic and real-time changes in serotonin release in fear-trained mice, social interactions, and sleep wake cycles. For example, while both areas of the brain have been established as relevant to the fear response, they reliably tracked that the PFC response was immediate, while the BSA displayed a delayed response. This additional temporal resolution of neuromodulation may have important implications in neurotransmitter pharmacology of the central nervous system.

This study provided the scientific community with several insights and tools. The serotonin sensor itself will be a critical tool in the study of the central nervous system and possibly beyond. Additionally, an AI approach to mutagenesis in order to redesign a binding pocket of a receptor opens new avenues to the development of pharmacological tools and may lead to many new designs in therapeutics and research.


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English: Schematic sketch showing the transpor...

English: Schematic sketch showing the transport types at the blood-brain barrier. Deutsch: Schematische Darstellung der Transportmechanismen an der Blut-Hirn-Schranke. Français : Schéma des types de transport à travers la barrière hémato-encéphalique (Photo credit: Wikipedia)

Larry H Bernstein, MD

Provided without comment.  Quite interesting.

novel protease resistant peptide shuttles able to cross the blood-brain barrier (BBB) by binding to a specific brain receptor


A Catalan Research Institute based in Barcelona (Spain) has identified novel protease resistant peptide shuttles able to cross the blood-brain barrier (BBB) by binding to a specific brain receptor. These shuttles are a powerful alternative to carry a wide variety of small and large molecules as cargos. This represents a novel opportunity to develop new delivery carriers able to cross actively a range of biological barriers.

New and innovative aspects

These compounds are novel drug delivery carriers that provide a non-invasive, non-antigenic, stable and receptor-specific way to transport drugs across the Blood-Brain Barrier and into the Central Nervous System.

These compounds show high permeability, biocompatibility, good solubility in water and resistance to proteases.


The treatment of most neurological disorders has not been fully addressed mainly because of the neuroprotective role of the blood-brain barrier (BBB) that hinders the delivery of many diagnostic and therapeutic agents into the brain. Consequently, therapeutic molecules and genes that might otherwise be effective in diagnosis and therapy do not cross the BBB in adequate amounts: 98% of compounds smaller than 400Da and 100% of larger ones do not reach further drug development stages.

Most central nervous system (CNS) diseases, however, are complex disorders with difficult molecular targets that require larger, safer and more selective drugs. As a result, brain tumors, neurodegenerative diseases such as Parkinson’s and Alzheimer’s, and central nervous system (CNS) diseases such as schizophrenia are not successfully treated. Therefore, finding an efficient CNS delivery system is one of the major challenges in neurological treatment and one our technology can potentially overcome.

One of the best approaches for drug delivery to the brain is the use of endogenous transport mechanisms, such as receptor-mediated transcystosis. Peptides are biocompatible molecules able to transport cargos (i.e. therapeutic compounds) to specific tissues such as the brain. However, one of the main limitations of peptides as therapeutic agents is their low stability in plasma.

The use of non-natural amino acids in peptidic sequences can circumvent this problem because they are resistant to human serum proteases. Using this approach, we obtained several modified peptides. Two of them were selected based on their protease resistance and transport capacity across the blood-brain barrier, using a specific endogenous receptor. Both peptides showed enhanced membrane permeability in vitro in comparison to standard peptides and even greater stability in plasma (over 24h).

Main advantages of its use

Novel delivery technology that provides a non-invasive, non-antigenic, permeable, stable, soluble and receptor-specific way to transport drugs across the BBB and into the CNS.

This technology may ultimately allow the delivery of therapeutic agents, even large ones, across the BBB and other biological barriers, thus increasing the effectiveness of existing or new drugs.

Potential of application in a wide number of fields and in transport through various biological barriers.


Biotechnological and Pharmaceutical companies specialized in drug discovery, drug delivery, neurological disorders, tools to cross the Blood-brain barrier. The final aim is to increase the efficiency of existing molecules for the treatment of neurological disorders.

Molecule and treatment design, drug manufacture, treatment of neurological disorders, drug delivery across the blood-brain barrier (BBB).

Intellectual property status

This invention is protected by a priority application in Spain and we plan to apply for a PCT in due time.


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