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Posts Tagged ‘Prolyl isomerase’


Phosphatidyl-5-Inositol Signaling by Pin1

 

Reporter: Larry H Bernstein, MD, FCAP

 

Regulation of Phosphatidylinositol-5-Phosphate Signaling by Pin1 Determines Sensitivity to Oxidative Stress

Willem-Jan Keune et al.
Increasing the abundance of the phospholipid PtdIns5P protects cells from oxidative stress.
Science Signaling   27 nov 2012; 5:252.
  1. T cell receptor (TCR) and costimulatory molecule mediated signaling
  2. culminate in maximal cytokine mRNA production and stability.
The transcriptional responses to co-stimulatory T cell signaling involve calcineurin and NF-AT, which
    • can be antagonized by interference with the cis-trans peptidyl-prolyl isomerases (PPIase), cyclophilin A and FKBP.
Signaling molecules downstream of CD28
    • which are essential for the stabilization of cytokine mRNAs are largely unknown.

Pin1, a third member of the PPIase family

    • mediates the post-transcriptional regulation of Th1 cytokines by activated T cells.

Blockade of Pin1 by pharmacologic or genetic means

  • greatly attenuated IFN-γ, IL-2 and CXCL-10 mRNA
    • stability,
    • accumulation and
    • protein expression after cell activation.

In vivo, Pin1 blockade prevented

  • both the acute and chronic rejection of MHC mismatched, orthotopic rat lung transplants by
  • reducing the expression of IFN-γ and CXCL-10.

Combined transcriptional and post-transcriptional blockade with

    • cyclosporine A and the Pin1 inhibitor, juglone, was synergistic.

These data suggest Pin1 inhibitors should be explored for use as immunosuppressants and employed with available calcineurin inhibitors to reduce toxicity and enhance effectiveness.
Esnault S, Braun RK, Shen Z-J, Xiang Z, Heninger E, et al. (2007)
Pin1 Modulates the Type 1 Immune Response. PLoS ONE 2(2): e226.  http://dx. doi.org/10.1371/journal.pone.0000226

Mixed-lineage kinase 3 phosphorylates prolyl-isomerase Pin1 to regulate its nuclear translocation and cellular function
Velusamy Rangasamya,1, Rajakishore Mishraa,1, Gautam Sondarvaa, Subhasis Dasa, et al.
Loyola University Chicago, Maywood, IL 60153;  Beth Israel Deaconess Medical Center, Boston, MA 02115; University of Mississippi Medical Center, Jackson, MS 39216;
University of Wisconsin, Madison, WI 53705; Hines Veterans Affairs Medical Center, Hines, IL 60141; and College of Veterinary Medicine, Iowa State University, Ames, IA 50011
Edited* by Michael Karin, University of California, San Diego School of Medicine, La Jolla, CA, and approved April 11, 2012
Nuclear protein peptidyl-prolyl isomerase Pin1-mediated prolyl isomerization is

  • an essential and novel regulatory mechanism for protein phosphorylation.

Therefore, tight regulation of Pin1 localization and catalytic activity is

  • crucial for its normal nuclear functions.

Pin1 is commonly dysregulated during oncogenesis and likely contributes to these pathologies; The mechanism by which Pin1 catalytic activity and nuclear localization are increased is unknown.
Here we demonstrate that

  1. mixed-lineage kinase 3 (MLK3), a MAP3K family member,
  2. phosphorylates Pin1 on a Ser138 site
  3. to increase its catalytic activity and nuclear translocation.
This phosphorylation event

  1. drives the cell cycle and
  2. promotes cyclin D1 stability and centrosome amplification.

Pin1 pSer138 is significantly

  • up-regulated in breast tumors and
  • is localized in the nucleus.

These findings collectively suggest that the MLK3-Pin1 signaling cascade plays a critical role

  1. in regulating the cell cycle,
  2. centrosome numbers, and
  3. oncogenesis. breast cancer

JNK Peptidyl-prolyl isomerase Pin1 plays a critical role in

  • regulating cellular homeostasis by
  • isomerizing the prolyl bond preceded by
  • a phosphorylated Ser or Thr residue (pSer/Thr-Pro) (1).

This isomerization by Pin1 regulates the biological function of several target proteins, including

  • cell-cycle regulators,
  • protooncogenes,
  • tumor suppressors, and
  • transcription factors (2).
Due to its role in controlling the cell cycle, apoptosis, growth, and stress responses, Pin1 has been linked to the pathogenesis of human diseases, including
  • cancer (3, 4),
  • asthma (5),
  • Alzheimer’s disease (AD) (6), and
  • Parkinson disease (PD) (7).

It is thus quite likely that tight regulation of Pin1 catalytic activity or expression is important for normal physiology. It is reported that Pin1 is

  • overexpressed in most types of cancer (8), whereas
  • its expression is diminished in AD brains (2).

Accumulating evidence suggests that Pin1 isomerase activity

  • and thus function are regulated by posttranslational modifications (2).

Pin1 function is also dependent on its

  • predominant nuclear localization (2),
    • consistent with its substrates being involved in transcription and cell-cycle progression.

It was recently reported that Pin1 nuclear import is regulated by a novel nuclear localization sequence in the PPIase domain, composed of basic amino acids (9). Nonetheless, the detailed mechanism that regulates Pin1 nuclear translocation is still not known. It also remains unknown whether any posttranslational modification of Pin1 can regulate its nuclear translocation or catalytic activity, and therefore directly affect its function.

Stereospecific gating of functional motions in Pin1
Andrew T. Namanjaa, Xiaodong J. Wangb, Bailing Xub, et al.
University of Notre Dame, Notre Dame, IN 46556; Virginia Tech, Blacksburg, VA 24061
Edited by Peter E. Wright, The Scripps Research Institute, La Jolla, CA, and approved June 2, 2011
Pin1 is a modular enzyme that

  • accelerates the cis-trans isomerization of phosphorylated-Ser/Thr-Pro (pS/T-P) motifs
  • found in numerous signaling proteins regulating cell growth and neuronal survival.

We have used NMR to investigate the interaction of Pin1 with three related ligands that include

  1. a pS-P substrate peptide, and
  2. two pS-P substrate analogue inhibitors
    • locked in the cis and trans conformations.

We compared the

  • ligand binding modes and
  • binding-induced changes
    • in Pin1 side-chain flexibility.

The cis and trans binding modes differ, and

  • produce different mobility in Pin1.

The cis-locked inhibitor and substrate produced a

  • loss of side-chain flexibility
    • along an internal conduit of conserved hydrophobic residues,
    • connecting the domain interface with the isomerase active site.

The trans-locked inhibitor

  • produces a weaker conduit response.

Thus, the conduit response is stereoselective. We further show

  • interactions between the peptidyl-prolyl isomerase and
  • Trp-Trp (WW) domains
    • amplify the conduit response, and
    • alter binding properties at the remote peptidyl-prolyl isomerase active site.

These results suggest that

  • specific input conformations can gate dynamic changes that support intraprotein communication.

Such gating may help control the propagation of chemical signals by Pin1, and other modular signaling proteins.

allostery ∣ protein dynamics ∣ ligand dynamics ∣ protein evolution
Phospho-serine/threonine-proline (pS/T-P) motifs are
signaling motifs within
intrinsically disordered loops of cell cycle proteins (1).
The imide bond between the pS/T and P residues can adopt

  • either the cis or trans conformation.

These conformations differ

  • in their susceptibility to kinases and phosphatases

that propagate the chemical signals governing the cell cycle.
Accordingly, the cell must regulate the cis/trans populations of these pS/T-P motifs

  • to ensure proper signal routing.

In this context, the peptidyl-prolyl isomerase Pin1 has emerged as a critical regulator (2, 3). Pin1 is a reversible enzyme that

  • catalyzes the cis-trans isomerization of the pS/T-P imide linkages (2, 3) of other signaling proteins, such as
  1. CDC25C,
  2. p53,
  3. c-Myc,
  4. NF-kB,
  5. cyclin D1, and
  6. tau (3).

Pin1 engages when external events, such as

  • S/T (de)-phosphorylation, change the cis-trans equilibrium.

Pin1 then

  1. catalyzes the cis-trans isomerization, thereby
  2. accelerating the approach to the new equilibrium (1).

Pin1 is a modular protein of 163 residues consisting of a

  • WW domain (1–39) and a larger
  • peptidyl-prolyl isomerase (PPIase) domain (50–163) (Fig. 1).

A flexible linker connects the two domains.

  1. Both domains are specific for pS/T-P motifs (1).
  2. The WW domain serves as a docking module, whereas
  3. catalysis is the sole province of the PPIase domain.

Earlier structural studies of Pin1 revealed

  1. conformational changes upon substrate interaction, thus
  2. motivating flexibility-function studies of Pin1 (4–6).
Peptidyl-prolyl Isomerase Pin1 Controls Down-regulation of Conventional Protein Kinase C Isozymes
JBC Papers in Press, Feb 8, 2012.       http://dx.doi.org/10.1074/jbc.M112.349753

H Abrahamsen, AK O’Neill, N Kannan, N Kruse¶, et al.
From the University of California, San Diego, La Jolla, California 92093
Background: Conventional PKC isozymes have a putative Pin1

  • isomerization sequence at their turn motif phosphorylation site.
Results: Pin1 binds conventional PKCs and

    • promotes their activation-induced down-regulation.
Conclusion: Pin1 isomerizes the phosphorylated turn motif of conventional PKC isozymes,

    • priming them for subsequent down-regulation.
Significance: Pin1 provides a switch regulating the lifetime of conventional PKCs. The down-regulation or cellular depletion of protein kinase C (PKC)
  • attendant to prolonged activation by phorbol esters is a
  • widely described property of this key family of signaling enzymes.

However, neither the mechanism of down-regulation nor whether this mechanism occurs following stimulation by physiological agonists is known.
**the peptidylprolyl isomerase Pin1 provides a timer for the lifetime of conventional PKC isozymes,

  • converting the enzymes into a species that can be dephosphorylated and ubiquitinated
  • following activation induced by either phorbol esters or natural agonists.

The regulation by Pin1 requires both the catalytic activity of the isomerase and the presence of a Pro immediately following the phosphorylated Thr of
the turn motif phosphorylation site,

  • one of two C-terminal sites that is phosphorylated during the maturation of PKC isozymes.
  • the second C-terminal phosphorylation site, the hydrophobic motif, docks
    • Pin1 to PKC.

Our data are consistent with a model in which Pin1

  • binds the hydrophobic motif of conventional PKC isozymes to catalyze the isomerization of the phospho-Thr-Pro peptide bond at the turn motif, thus
  • converting these PKC  isozymes into species that can be efficiently down-regulated following activation.

The peptidyl-prolyl cis-trans isomerase Pin1 is emerging as an important regulator of signal transduction pathways (1).

Pin1-catalyzed isomerization plays a key role in the control of normal cellular functions, most notably proliferation where

    • Pin1 is essential for cell cycle progression (2).

Pin1 belongs to the Parvulin family of peptidyl-prolyl cis-trans isomerases and is the only member that

  • specifically isomerizes phospho-(Ser/Thr)-Pro ((Ser(P)/Thr(P))-Pro) motifs (3):
  1. the enzyme displays an 1000-fold selectivity for peptides phosphorylated on the
  2. Ser/Thr preceding the Pro compared with unphosphorylated peptides (3).
Pin1induced conformational changes in target proteins

  • affect a variety of protein properties from
    • folding to
    • regulation of activity and stability.

As a consequence, deregulation of phosphorylation steps and their attendant conformational changes often lead to disease (4). For example, Pin1 is
downregulated in degenerating neurons from Alzheimer disease patients, correlating with age-dependent neurodegeneration (5).
Pin1 has also been implicated in cancer progression:
levels of this protein are increased in many cancers, including those of the

    • breast,
    • prostate,
    • brain,
    • lung, and
    • colon (6–9).

Thus, Pin1 has been proposed to function as a catalyst for oncogenic pathways (10). The molecular mechanisms that lead to disease progression

  • most likely involve postphosphorylation conformational changes
    • catalyzed by Pin1
    • that are required for downstream effects.
Related articles
The human immunophilin protein FKBP12 colored ...

The human immunophilin protein FKBP12 colored by hydrophobicity (white = hydrophobic) with bound FK506, an immunosuppressant used in treating organ transplant patients to prevent rejection. FKBP also has unrelated prolyl isomerase activity. (Photo credit: Wikipedia)

The human immunophilin protein FKBP12 colored ...

The human immunophilin protein FKBP12 colored by secondary structure with bound FK506, an immunosuppressant used in treating organ transplant patients to prevent rejection. FKBP also has unrelated prolyl isomerase activity. (Photo credit: Wikipedia)

 

 

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