Prolyl Isomerase Research Articles

Role of dehydrin-FK506-binding protein complex in enhancing drought tolerance through the ABA-mediated signaling pathway

Dehydrins (DHNs) have been reported to act as chaperones to combat drought stress. While in this study, we explored a novel nuclear complex of Oryza sativa FKBP and YSK2-type dehydrin (OsDhn-Rab16D), associated with ABA signaling to impart drought stress tolerance. The transcript levels of OsDhn-Rab16D in rice seedlings were induced in response to drought, abscisic acid (ABA) and H2O2 exposure. Ectopic expression of OsDhn-Rab16D transgenic lines showed enhanced tolerance to both osmotic stresses caused by PEG and drought. Using the yeast two-hybrid (Y2H) assay, O. sativa FKBP (a prolyl cis-trans isomerase) was identified as an interacting partner of OsDhn-Rab16D. Fluorescence signals between OsDhn-Rab16D and OsFKBP were observed in the nucleus. The pull-down assay confirmed the physical interaction between OsDhn-Rab16D and OsFKBP. qRT-PCR of drought and ABA-responsive gene reveals the higher transcript abundance in PEG-treated transgenic lines. Moreover, under drought conditions, transgenic lines maintain membrane integrity and increase the lignification in adventitious rice roots due to the higher expression level of catalase and lignin biosynthesis enzyme, respectively, as compared with wild-type. Overall, our findings suggest that OsDhn-Rab16D and OsFKBP complex involved in ABA-responsive drought stress signaling in rice and probably act as a positive transcriptional co-regulator, in addition, to act as chaperones.

The Multiple Roles of Peptidyl Prolyl Isomerases in Brain Cancer.

Peptidyl prolyl isomerases (PPIases) are broadly expressed enzymes that accelerate the cis-trans isomerization of proline peptide bonds. The most extensively studied PPIase family member is protein interacting with never in mitosis A1 (PIN1), which isomerizes phosphorylated serine/threonine–proline bonds. By catalyzing this specific cis-trans isomerization, PIN1 can alter the structure of its target proteins and modulate their activities in a number of different ways. Many proteins are targets of proline-directed phosphorylation and thus PIN1-mediated isomerization of proline bonds represents an important step in the regulation of a variety of cellular mechanisms. Numerous other proteins in addition to PIN1 are endowed with PPIase activity. These include other members of the parvulin family to which PIN1 belongs, such as PIN4, as well as several cyclophilins and FK506-binding proteins. Unlike PIN1, however, these other PPIases do not isomerize phosphorylated serine/threonine–proline bonds and have different substrate specificities. PIN1 and other PPIases are overexpressed in many types of cancer and have been implicated in various oncogenic processes. This review will discuss studies providing evidence for multiple roles of PIN1 and other PPIases in glioblastoma and medulloblastoma, the most frequent adult and pediatric primary brain tumors.

Regulation of the Minichromosome Maintenance Protein 3 (MCM3) Chromatin Binding by the Prolyl Isomerase Pin1

Human Pin1 is a peptidyl prolyl cis/trans isomerase with a unique preference for phosphorylated Ser/Thr-Pro substrate motifs.Here we report that MCM3 (minichromosome maintenance complex component 3) is a novel target of Pin1. MCM3 interacts directly with the WW domain of Pin1. Proline-directed phosphorylation of MCM3 at S112 and T722 are crucial for the interaction with Pin1. MCM3 as a subunit of the minichromosome maintenance heterocomplex MCM2–7 is part of the pre-replication complex responsible for replication licensing and is implicated in the formation of the replicative helicase during progression of replication. Our data suggest that Pin1 coordinates phosphorylation-dependently MCM3 loading onto chromatin and its unloading from chromatin, thereby mediating S phase control.

Adaptor Protein p66Shc: A Link Between Cytosolic and Mitochondrial Dysfunction in the Development of Diabetic Retinopathy.

Diabetes increases oxidative stress in the retina and dysfunctions their mitochondria, accelerating capillary cell apoptosis. A 66 kDa adaptor protein, p66Shc, is considered as a sensor of oxidative stress-induced apoptosis. In the pathogenesis of diabetic retinopathy, a progressive disease, reactive oxygen species (ROS) production by activation of a small molecular weight G-protein (Ras-related C3 botulinum toxin substrate 1 [Rac1])-Nox2 signaling precedes mitochondrial damage. Rac1 activation is facilitated by guanine exchange factors (GEFs), and p66Shc increases Rac1-specific GEF activity of Son of Sevenless 1 (Sos1). p66Shc also possesses oxidoreductase activity and can directly stimulate mitochondrial ROS generation. Our aim was to investigate the role of p66Shc in the development of diabetic retinopathy and mechanism of its transcription. High glucose increased p66Shc expression in human retinal endothelial cells, and elevated acetylated histone 3 lysine 9 (H3K9) levels and transcriptional factor p53 binding at its promoter. Glucose also augmented interactions between Rac1 and Sos1 and activated Rac1-Nox2. Phosphorylation of p66Shc was increased, allowing it to interact with peptidyl prolyl isomerase to facilitate its localization inside the mitochondria, culminating in mitochondrial damage. P66shc-small interfering RNA (siRNA) inhibited glucose-induced Rac1 activation and mitochondrial damage. Similar results are observed in retinal microvessels from diabetic rats. This is the first report identifying the role of p66Shc in the development of diabetic retinopathy and implicating increased histone acetylation in its transcriptional regulation. Thus, p66Shc has dual role in the development of diabetic retinopathy; its regulation in the early stages of the disease should impede Rac1-ROS production and, in the later stages, prevent mitochondrial damage and initiation of a futile cycle of free radicals.

The transcription-independent mitochondrial cell death pathway is defective in non-transformed cells containing the Pro47Ser variant of p53

ABSTRACTApproximately half of all human cancers contain mutations in the TP53 tumor suppressor. In addition to mutations, there are single nucleotide polymorphisms (SNPs) in TP53 that can dampen p53 function, and can increase cancer risk and decrease the efficacy of cancer therapy. Approximately 6% of Africans and 1% of African-Americans express a p53 allele with a serine instead of proline at position 47 (Pro47Ser, or S47). The S47 variant is associated with increased breast cancer risk in pre-menopausal African Americans, and in a mouse model for the S47 variant, mice are predisposed to spontaneous cancers. We recently showed that the S47 variant is impaired for p53-mediated apoptosis in response to radiation and some genotoxic agents, particularly cisplatin. Here we identify the mechanism for impaired apoptosis of S47 in response to cisplatin. We show that following cisplatin treatment, the S47 variant shows normal stabilization and serine 15 phosphorylation, but reduced ability to bind to the peptidyl prolyl isomerase PIN1, which controls the mitochondrial localization of p53. This is accompanied by impaired mitochondrial localization of S47, along with decreased induction of cleaved caspase-3. Interestingly, we show that this defect occurs only for cisplatin and not for camptothecin. These findings show that normal tissues may respond differently to genotoxic stress depending upon this TP53 genotype. These data suggest that toxicity to cisplatin may be decreased in S47 individuals, and that this compound may be a superior treatment option for these individuals.

Sporadic Alzheimer Disease and That Developing in Down’s Syndrome: The Immune System Attacking Self Rather Than Suppressing Infectious Disease Invaders, Toll Like Receptors Triggering Excessive Cytosolic Calcium, Excess Calcineurin Activation, Overexpress

Alzheimer Disease may result from excessive stimulation of the innate immune system from development of underlying opportunistic infections and impaired age related self recognition as non-self, due to immunodeficiency and immunosenescence, resulting in excessive inflammation and runaway Beta-amyloid production (a component of the innate immune system) causing cytosolic calcium overload. Excessive cytosolic calcium may cause over activation of calcineurin and inactivation of cis-trans prolyl isomerase (Pin1), with subsequent loss of dendritic spine maintenance, and synaptic destruction. Improving immune function, identifying and treating infections, avoiding runaway Beta-amyloid production and inhibiting calcineurin in a manner similar to that utilized in preventing tissue transplant rejection, may lead to improved prevention and treatment of Alzheimer Disease.

Prolyl isomerase Pin1: a promoter of cancer and a target for therapy

Pin1 is the only known peptidyl-prolyl cis–trans isomerase (PPIase) that specifically recognizes and isomerizes the phosphorylated Serine/Threonine-Proline (pSer/Thr-Pro) motif. The Pin1-mediated structural transformation posttranslationally regulates the biofunctions of multiple proteins. Pin1 is involved in many cellular processes, the aberrance of which lead to both degenerative and neoplastic diseases. Pin1 is highly expressed in the majority of cancers and its deficiency significantly suppresses cancer progression. According to the ground-breaking summaries by Hanahan D and Weinberg RA, the hallmarks of cancer comprise ten biological capabilities. Multiple researches illuminated that Pin1 contributes to these aberrant behaviors of cancer via promoting various cancer-driving pathways. This review summarized the detailed mechanisms of Pin1 in different cancer capabilities and certain Pin1-targeted small-molecule compounds that exhibit anticancer activities, expecting to facilitate anticancer therapies by targeting Pin1.

Pin1 Modulation in Physiological Status and Neurodegeneration. Any Contribution to the Pathogenesis of Type 3 Diabetes?

Prolyl isomerases (Peptidylprolyl isomerase, PPIases) are enzymes that catalyze the isomerization between the cis/trans Pro conformations. Three subclasses belong to the class: FKBP (FK506 binding protein family), Cyclophilin and Parvulin family (Pin1 and Par14). Among Prolyl isomerases, Pin1 presents as distinctive feature, the ability of binding to the motif pSer/pThr-Pro that is phosphorylated by kinases. Modulation of Pin1 is implicated in cellular processes such as mitosis, differentiation and metabolism: The enzyme is dysregulated in many diverse pathological conditions, i.e., cancer progression, neurodegenerative (i.e., Alzheimer’s diseases, AD) and metabolic disorders (i.e., type 2 diabetes, T2D). Indeed, Pin1 KO mice develop a complex phenotype of premature aging, cognitive impairment in elderly mice and neuronal degeneration resembling that of the AD in humans. In addition, since the molecule modulates glucose homeostasis in the brain and peripherally, Pin1 KO mice are resistant to diet-induced obesity, insulin resistance, peripheral glucose intolerance and diabetic vascular dysfunction. In this review, we revise first critically the role of Pin1 in neuronal development and differentiation and then focus on the in vivo studies that demonstrate its pivotal role in neurodegenerative processes and glucose homeostasis. We discuss evidence that enables us to speculate about the role of Pin1 as molecular link in the pathogenesis of type 3 diabetes i.e., the clinical association of dementia/AD and T2D.

Cyclophilin A Function in Mammary Epithelium Impacts Jak2/Stat5 Signaling, Morphogenesis, Differentiation, and Tumorigenesis in the Mammary Gland.

The prolyl isomerase cyclophilin A (CypA) regulates the Jak2/Stat5 pathway, which is necessary for mammary differentiation and the pathogenesis of breast cancer. In this study, we assessed the role of this isomerase during mammary gland development and erbB2-driven tumorigenesis. Genetic deletion of CypA resulted in delayed mammary gland morphogenesis and differentiation with corresponding decrease in Jak2/Stat5 activation; mammary gland cross-transplantation confirmed this defect was epithelial in nature. Analysis of mammary stem and progenitor populations revealed significant disruption of epithelial maturation. Loss of CypA in the erbB2 transgenic mouse model revealed a marked increase in mammary tumor latency that correlated with decreased Stat5 activation, associated gene expression, and reduced epithelial cell proliferation. These results demonstrate an important role for CypA in the regulation of Jak2/Stat5-mediated biology in mammary epithelium, identifying this isomerase as a novel target for therapeutic intervention.Significance: These findings reveal cyclophilin A functions in normal mammary epithelial development and ErbB2-driven mammary tumorigenesis and suggest therapies targeting cyclophilin A may be efficacious for breast cancer treatment.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/14/3877/F1.large.jpg Cancer Res; 78(14); 3877-87. ©2018 AACR.

PIN1 is a new therapeutic target of craniosynostosis.

Gain-of-function mutations in fibroblast growth factor receptors (FGFRs) cause congenital skeletal anomalies, including craniosynostosis (CS), which is characterized by the premature closure of craniofacial sutures. Apert syndrome (AS) is one of the severest forms of CS, and the only treatment is surgical expansion of prematurely fused sutures in infants. Previously, we demonstrated that the prolyl isomerase peptidyl-prolyl cis–trans isomerase interacting 1 (PIN1) plays a critical role in mediating FGFR signaling and that Pin1+/− mice exhibit delayed closure of cranial sutures. In this study, using both genetic and pharmacological approaches, we tested whether PIN1 modulation could be used as a therapeutic regimen against AS. In the genetic approach, we crossbred Fgfr2S252W/+, a mouse model of AS, and Pin1+/− mice. Downregulation of Pin1 gene dosage attenuated premature cranial suture closure and other phenotypes of AS in Fgfr2S252W/+ mutant mice. In the pharmacological approach, we intraperitoneally administered juglone, a PIN1 enzyme inhibitor, to pregnant Fgfr2S252W/+ mutant mice and found that this treatment successfully interrupted fetal development of AS phenotypes. Primary cultured osteoblasts from Fgfr2S252W/+ mutant mice expressed high levels of FGFR2 downstream target genes, but this phenotype was attenuated by PIN1 inhibition. Post-translational stabilization and activation of Runt-related transcription factor 2 (RUNX2) in Fgfr2S252W/+ osteoblasts were also attenuated by PIN1 inhibition. Based on these observations, we conclude that PIN1 enzyme activity is important for FGFR2-induced RUNX2 activation and craniofacial suture morphogenesis. Moreover, these findings highlight that juglone or other PIN1 inhibitors represent viable alternatives to surgical intervention for treatment of CS and other hyperostotic diseases.

Abstract 2825: PIN1-SCFFBW7 proteolytic signaling regulates the Fanconi anemia pathway

Abstract Genome instability caused by defective DNA repair mechanisms is a hallmark of cancer and drives tumorigenesis. The Fanconi anemia (FA) DNA repair pathway contributes to the integrity of the genome by resolving DNA interstrand cross-links (ICLs) encountered during DNA replication. Deregulation of the FA pathway is associated with cancer predisposition and affects therapeutic outcomes against DNA-damaging cytotoxic chemotherapy. FANCD2 monoubiquitination by a multi-subunit ubiquitin E3 ligase, the FA core complex, is an essential gateway that connects the DNA damage response to enzymatic steps of DNA ICL repair. We have previously identified FAAP20 as a critical component of the FA pathway; and demonstrated that the phosphorylation of the Cdc4 phospho-degron (CPD) motif in FAAP20 by GSK3β is required for its proteasomal degradation mediated by the E3 ligase, SCFFBW7 complex. However, the upstream signaling that governs the FAAP20 phosphorylation status and its detailed mode of action for FAAP20 degradation remain elusive. Here, we show that PIN1, a phosphorylation-specific prolyl isomerase, is a key regulator of the integrity of the FA core complex and, therefore, FA pathway activity as a whole. By catalyzing a proline cis-trans isomerization of the phosphorylated backbone and thereby converting the substrate into a conformation that is favorable or refractory to downstream proteolytic signaling, PIN1 modulates the rate of protein turnover. We demonstrate that PIN1 interacts and catalyzes a phosphorylated Ser48-Pro49 motif of FAAP20 and by inducing a conformational change of FAAP20, PIN1 enhances the affinity of FAAP20 with PP2A (Protein phosphatase 2), the phosphatase of the CPD motif in FAAP20 and thereby prevents its degradation from the GSK3β-FBW7 mediated proteolytic signaling. Collectively, our studies uncover PIN1-dependent isomerization as a new regulatory mechanism for DNA ICL repair. Given that PIN1 overexpression is prevalent in diverse human cancers, identifying a way to regulate PIN1 activity in the FA pathway may help develop a PIN1 inhibitor as a chemosensitizer for cytotoxic chemotherapy to increase its therapeutic efficacy. Citation Format: Jingming Wang, Bryan Chan, Michael Tong, Markus Seeliger, Hyungjin Kim. PIN1-SCFFBW7 proteolytic signaling regulates the Fanconi anemia pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2825.

Highlights of This Issue

Aberrant glycosylation is one of the hallmarks of cancer, and cancer cell glycans serve as tumor biomarkers. Glycosylation modulates the functions of glycoproteins; however, the functional significance of protein glycosylation in cancer progression remains poorly defined. Here, β1,6GlcNAc-branched N-glycan–suppressing and N-glycan–defective β4-integrin expressing cell model systems were used to demonstrate that N-glycosylation of β4-integrin contributes to tumor progression. It was determined that β4-integrin clustering by galectin-3–mediated cross-linking of β1,6GlcNAc-branched N-glycans on β4-integrin activates PI3K/Akt signaling, thereby promoting cancer cell behavior. Thus, N-glycosylation of β4-integrin represents a potential therapeutic target for cancer.Adaptive cellular responses induced by cancer therapeutics are emerging as an important mechanism for acquired resistance to chemotherapies. In this study, Fang and colleagues identified olaparib-induced FOXM1 expression as an adaptive response that induces the expression of homologous recombination (HR) repair genes. Knockdown of olaparib-induced FOXM1 expression by RNAi or pharmacologic inhibition by thiostrepton downregulates the expression of HR repair genes, increases DNA damage and PARP1 trapping, and enhances sensitivity to olaparib. This study highlights the important role of FOXM1 in the adaptive response to olaparib, and that targeting the adaptive response mediated by FOXM1 extends the efficacy of PARP inhibitors.A major problem that limits the effectiveness of cancer chemotherapeutics is the development of drug resistance. Recently, dysregulation of the Hippo pathway core component LATS has been implicated in this process, but its underlying mechanisms remain unknown. Now, Yeung and colleagues functionally characterize a novel signaling pathway in which anti-tubulin drugs activate Cdk1 and phosphorylate LATS, which then binds prolyl isomerase Pin1 and inhibits its anti-apoptotic function. Importantly, loss of LATS phosphorylation reduces taxol-induced cell death. Together, this work provides new insight into the anti-tubulin drug response and demonstrates the Cdk1-LATS-Pin1 signaling axis as a promising target for treatment.ATP-binding cassette (ABC) transporters are a known mechanism of drug resistance, however multiple clinical trials targeting ABCB1 have failed. Thus, it is hypothesized here, that ABC transporters aggravate cancer biology by exporting endogenous lipid mediator sphingosine-1-phosphate (S1P) regardless of drugs. S1P generated by SphK1 and exported via ABCC1 aggravated cancer in a malicious feed-forward manner by amplifying the S1P axis in vitro, and worsened cancer progression in vivo. Patients with high levels of both SphK1 and ABCC1 have worse survival. While, ABCB1, which does not export S1P, did not demonstrate these findings. This suggests a critical role for the S1P axis in breast cancer progression.

Changes in Corticotrope Gene Expression Upon Increased Expression of Peptidylglycine α-Amidating Monooxygenase.

Throughout evolution, secretion has played an essential role in the ability of organisms and single cells to survive in the face of a changing environment. Peptidylglycine α-amidating monooxygenase (PAM) is an integral membrane monooxygenase, first identified for its role in the biosynthesis of neuroendocrine peptides released by the regulated secretory pathway. PAM was subsequently identified in Chlamydomonas reinhardtii, a unicellular green alga, where it plays an essential role in constitutive secretion and in ciliogenesis. Reduced expression of C. reinhardtii PAM resulted in significant changes in secretion and ciliogenesis. Hence, a screen was performed for transcripts and proteins whose expression responded to changes in PAM levels in a mammalian corticotrope tumor cell line. The goal was to identify genes not previously known to play a role in secretion. The screen identified transcription factors, peptidyl prolyl isomerases, endosomal/lysosomal proteins, and proteins involved in tissue-specific responses to glucose and amino acid availability that had not previously been recognized as relevant to the secretory pathway. Perhaps reflecting the dependence of PAM on molecular oxygen, many PAM-responsive genes are known to be hypoxia responsive. The data highlight the extent to which the performance of the secretory pathway may be integrated into a wide diversity of signaling pathways.

Knockdown of the prolyl isomerase Pin1 inhibits Hep-2 cell growth, migration, and invasion by targeting the β-catenin signaling pathway.

There is increasing evidence indicating that peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (Pin1) plays a decisive role in a variety of cancers. Nevertheless, its function in laryngeal squamous cell carcinoma (LSCC) has not been elaborated. The aim of this study is to determine the role of Pin1 in LSCC. Here, we established stably transfected Hep-2 cells with low expression of Pin1. Intriguingly, cell proliferation, migration, and invasion was significantly inhibited in Pin1-silenced Hep-2 cells. Similarly, knockdown of Pin1 induced apoptosis of Hep-2 cells, as evidenced by increased expression of cleaved-caspase-3, cleaved-PARP, and bax, and decreased expression of bcl2. We also demonstrated that silencing of Pin1 down-regulated β-catenin and cyclin D1 expression. Inversely, over-expression of β-catenin reversed the inhibiting effect of Pin1 silencing on Hep-2 cells. Moreover, we proved that knockdown of Pin1 inhibited tumorigenesis of Hep-2 cells in vivo. Taken together, we demonstrate that silencing of Pin1 effectively suppresses the growth of Hep-2 cells through β-catenin, indicating that Pin1 possess the potential to serve as a therapeutic target for the treatment of LSCC.

Inhibition and Substrate Specificity Properties of FKBP22 from a Psychrotrophic Bacterium, Shewanella sp. SIB1.

SIB1 FKBP22 is a peptidyl prolyl cis-trans isomerase (PPIase) member from a psychrotrophic bacterium, Shewanella sp. SIB1, consisting of N- and C-domains responsible for dimerization and catalytic PPIase activity, respectively. This protein was assumed to be involved in cold adaptation of SIB1 cells through its dual activity of PPIase activity and chaperone like-function. Nevertheless, the catalytic inhibition by FK506 and its substrate specificity remain unknown. Besides, ability of SIB1 FKBP22 to inhibit phosphatase activity of calcinuerin is also interesting to be studied since it may reflect wider cellular functions of SIB1 FKBP22. In this study, we found that wild type (WT) SIB1 FKBP22 bound to FK506 with IC50 of 77.55nM. This value is comparable to that of monomeric mutants (NNC-FKBP22, C-domain+ and V37R/L41R mutants), yet significantly higher than that of active site mutant (R142A). In addition, WT SIB1 FKBP22 and monomeric variants were found to prefer hydrophobic residues preceding proline. Meanwhile, R142A mutant has wider preferences on bulkier hydrophobic residues due to increasing hydrophobicity and binding pocket space. Surprisingly, in the absence of FK506, SIB1 FKBP22 and its variants inhibited, with the exception of N-domain, calcineurin phosphatase activity, albeit low. The inhibition of SIB1 FKBP22 by FK506 is dramatically increased in the presence of FK506. Altogether, we proposed that local structure at substrate binding pocket of C-domain plays crucial role for the binding of FK506 and peptide substrate preferences. In addition, C-domain is essential for inhibition, while dimerization state is important for optimum inhibition through efficient binding to calcineurin.

Alzheimer's Disease, Dendritic Spines, and Calcineurin Inhibitors: A New Approach?

Therapeutics to effectively treat Alzheimer's disease (AD) are lacking. In vitro, animal and human studies have implicated the excessive activation of the protein phosphatase calcineurin (CN) as an early step in the pathogenesis of AD. We discuss recent data showing that the prolyl isomerase Pin1 is suppressed by CN-mediated dephosphorylation induced by Aβ42 signaling. Pin1 loss directly leads to the reductions in dendritic spines and synapses characteristic of early AD pathology. Pin1 activity, and synapse and dendritic spine numbers are rescued by FK506, a highly specific and United States Food and Drug Administration approved CN inhibitor. Solid organ transplant recipients chronically treated with FK506 showed much lower AD incidence than expected. As such, we suggest prospective clinical trials to determine if systemic FK506 can normalize CN activity in the brain, preserve Pin1 function and support synaptic health in early AD.

Liposomal delivery of a Pin1 inhibitor complexed with cyclodextrins as new therapy for high-grade serous ovarian cancer

Pin1, a prolyl isomerase that sustains tumor progression, is overexpressed in different types of malignancies. Functional inactivation of Pin1 restrains tumor growth and leaves normal cells unaffected making it an ideal pharmaceutical target. Although many studies on Pin1 have focused on malignancies that are influenced by sex hormones, studies in ovarian cancer have lagged behind. Here, we show that Pin1 is an important therapeutic target in high-grade serous epithelial ovarian cancer. Knock down of Pin1 in ovarian cancer cell lines induces apoptosis and restrains tumor growth in a syngeneic mouse model. Since specific and non-covalent Pin1 inhibitors are still limited, the first liposomal formulation of a Pin1 inhibitor was designed. The drug was efficiently encapsulated in modified cyclodextrins and remotely loaded into pegylated liposomes. This liposomal formulation accumulates preferentially in the tumor and has a desirable pharmacokinetic profile. The liposomal inhibitor was able to alter Pin1 cancer driving-pathways trough the induction of proteasome-dependent degradation of Pin1 and was found to be effective in curbing ovarian tumor growth in vivo.

Listeria Membrane Protrusion Collapse: Requirement of Cyclophilin A for Listeria Cell-to-Cell Spreading.

Listeria generate actin-rich tubular protrusions at the plasma membrane that propel the bacteria into neighboring cells. The precise molecular mechanisms governing the formation of these protrusions remain poorly defined. In this study, we demonstrate that the prolyl cis-trans isomerase (PPIase) cyclophilin A (CypA) is hijacked by Listeria at membrane protrusions used for cell-to-cell spreading. Cyclophilin A localizes within the F-actin of these structures and is crucial for their proper formation, as cells depleted of CypA have extended actin-rich structures that are misshaped and are collapsed due to changes within the F-actin network. The lack of structural integrity within the Listeria membrane protrusions hampers the microbes from spreading from CypA null cells. Our results demonstrate a crucial role for CypA during Listeria infections.

P-78 - Role of thiol redox regulation in the mitochondrial signaling network

Reactive oxygen species (ROS) are not only damaging molecules but are also involved in redox signaling events. In mitochondria, thiol redox state is finely tuned mainly by the thioredoxin and the glutathione systems. Cyclophilin D (CypD), a key regulator of mitochondrial permeability transition, was recently shown to be subjected to redox regulation. In particular, CypD was recognized to directly interact with thioredoxin 2 and peroxiredoxin 3 of the thioredoxin system. In addition, the CypD prolyl cis-trans isomerase activity was shown to depend on its redox state with a higher catalytic efficiency in its reduced status. An important player in mitochondrial thiol redox regulation is glutaredoxin 2 (Grx2). This enzyme normally resides in the mitochondrial matrix as an inactive dimer coordinating a [2Fe-2S]2+ cluster. However, oxidative stress induction can trigger protein monomerization and activation. In this context, it has been observed that Grx2 is extremely active as a disulfide reductase in conditions of glutathione depletion and thioredoxin system inhibition. Thus, Grx2 seems very efficient in the recovery of a proper redox balance. In conclusion, thiol redox regulation, by tuning the activity of specific enzymes, has a key role in mitochondrial signaling pathways.

The IL-33-PIN1-IRAK-M axis is critical for type 2 immunity in IL-33-induced allergic airway inflammation

Interleukin 33 (IL-33) is among the earliest-released cytokines in response to allergens that orchestrate type 2 immunity. The prolyl cis-trans isomerase PIN1 is known to induce cytokines for eosinophil survival and activation by stabilizing cytokines mRNAs, but the function of PIN1 in upstream signaling pathways in asthma is unknown. Here we show that interleukin receptor associated kinase M (IRAK-M) is a PIN1 target critical for IL-33 signaling in allergic asthma. NMR analysis and docking simulations suggest that PIN1 might regulate IRAK-M conformation and function in IL-33 signaling. Upon IL-33-induced airway inflammation, PIN1 is activated for binding with and isomerization of IRAK-M, resulting in IRAK-M nuclear translocation and induction of selected proinflammatory genes in dendritic cells. Thus, the IL-33-PIN1-IRAK-M is an axis critical for dendritic cell activation, type 2 immunity and IL-33 induced airway inflammation.