Pin1 Expression Research Articles

Auxin and cytokinin control formation of the quiescent centre in the adventitious root apex of arabidopsis

Background and AimsAdventitious roots (ARs) are part of the root system in numerous plants, and are required for successful micropropagation. In the Arabidopsis thaliana primary root (PR) and lateral roots (LRs), the quiescent centre (QC) in the stem cell niche of the meristem controls apical growth with the involvement of auxin and cytokinin. In arabidopsis, ARs emerge in planta from the hypocotyl pericycle, and from different tissues in in vitro cultured explants, e.g. from the stem endodermis in thin cell layer (TCL) explants. The aim of this study was to investigate the establishment and maintenance of the QC in arabidopsis ARs, in planta and in TCL explants, because information about this process is still lacking, and it has potential use for biotechnological applications.MethodsExpression of PR/LR QC markers and auxin influx (LAX3)/efflux (PIN1) genes was investigated in the presence/absence of exogenous auxin and cytokinin. Auxin was monitored by the DR5::GUS system and cytokinin by immunolocalization. The expression of the auxin-biosynthetic YUCCA6 gene was also investigated by in situ hybridization in planta and in AR-forming TCLs from the indole acetic acid (IAA)-overproducing superroot2-1 mutant and its wild type.Key ResultsThe accumulation of auxin and the expression of the QC marker WOX5 characterized the early derivatives of the AR founder cells, in planta and in in vitro cultured TCLs. By determination of PIN1 auxin efflux carrier and LAX3 auxin influx carrier activities, an auxin maximum was determined to occur at the AR tip, to which WOX5 expression was restricted, establishing the positioning of the QC. Cytokinin caused a restriction of LAX3 and PIN1 expression domains, and concomitantly the auxin biosynthesis YUCCA6 gene was expressed in the apex.ConclusionsIn ARs formed in planta and TCLs, the QC is established in a similar way, and auxin transport and biosynthesis are involved through cytokinin tuning.

Interaction between Meristem Tissue Layers Controls Phyllotaxis

Phyllotaxis and vein formation are among the most conspicuous patterning processes in plants. The expression and polarization of the auxin efflux carrier PIN1 is the earliest marker for both processes, with mathematical models indicating that PIN1 can respond to auxin gradients and/or auxin flux. Here, we use cell-layer-specific PIN1 knockouts and partial complementation of auxin transport mutants to examine the interaction between phyllotactic patterning, which occurs primarily in the L1 surface layer of the meristem, and midvein specification in the inner tissues. We show that PIN1 expression in the L1 is sufficient for correct organ positioning, as long as the L1-specific influx carriers are present. Thus, differentiation of inner tissues can proceed without PIN1 or any of the known polar transporters. On theoretical grounds, we suggest that canalization of auxin flux between an auxin source and an auxin sink may involve facilitated diffusion rather than polar transport.

Expression of peptidyl-prolyl isomerase PIN1 and its role in the pathogenesis of extrahepatic cholangiocarcinoma

The phosphorylation of proteins on serine/threonine residues that immediately precede proline (pSer/Thr-Pro) is a key signaling mechanism by which cell cycle regulation and cell differentiation and proliferation occur. The peptidyl-prolyl isomerase PIN1-catalyzed conformational changes of the pSer/Thr-Pro motifs may have profound effects on the function of numerous oncogenic and cell signaling pathways. To date, no studies have examined the expression of PIN1 and its potential role in the pathogenesis of extrahepatic cholangiocarcinoma (ECC). Therefore, the present study performed an immunohistochemistry analysis of the expression of PIN1 in 67 cases of ECC and evaluated its association with clinicopathological factors. In addition, the role of PIN1 was examined using synthetic small interfering RNA (siRNA) to silence PIN1 gene expression in human CC RBE cells. Positive PIN1 expression was observed in 35 of the 67 (52.2%) ECC cases and was predominantly localized to the nucleus of the tumor cells. The immunoreactive score for PIN1 was significantly higher in the tumor cells (4.07±0.4) compared with the adjacent benign bile duct cells (1.19±0.4) (P<0.001). PIN1 expression was significantly correlated with tumor cell proliferation (Ki-67 labeling index; P=0.024). Silencing PIN1 expression using siRNA significantly decreased the proliferation, migration and invasion of the tumor cells. In conclusion, the results indicated that the expression of PIN1 may play a key role in the development and progression of ECC.

Prolyl-isomerase-1 (pin1) mediates hyperglycemia-induced oxidative stress, endothelial function and vascular inflammation: insights in patients with type 2 diabetes

Purpose: Prolyl-isomerase-1 (Pin1) regulates function of protein substrates through isomerization of peptide bonds that link phosphoserine or phosphothreonine to proline. Pin1 triggers reactive oxygen species (ROS) production and inflammation in human cancer. Whether Pin1 is involved in cardiovascular disease remains largely unknown. This study investigates the role of Pin1 in diabetes-related vascular dysfunction. Methods: Human aortic endothelial cells (HAECs) were exposed to normal (NG, 5mmol/L) or high glucose concentrations (HG, 25 mmol/L) in the presence or in the absence of Pin1 pharmacological inhibitor Juglone or siRNA-mediated knockdown. Diabetes was induced in C57/B6 male mice (aged 4-6 months) by streptozocin and animals were treated i.v. with Pin1 siRNA or Juglone i.p for 30 days. Endothelial function was assessed by dose-response curve with acetylcoline. Protein expression was assessed by immunoblotting. Mitochondrial ROS were measured by ESR spectroscopy. Immunoprecipitation was performed to show the interaction of Pin1 with phosphorylated p66Shc and NFkB subunit p65. In parallel, Pin1 gene expression was assessed in peripheral blood monocytes (PBM) of 30 patients with type 2 diabetes (T2DM) and 18 healthy age-matched controls and correlated with flow-mediated vasodilation (FMD) of the brachial artery, urinary 8-isoprostaglandinF2α (8-isoPGF2α) as a marker of oxidative stress, and plasma adhesion molecules VCAM-1, ICAM-1 and MCP-1. Results: Pin1 expression markedly increased in HAECs exposed to HG (289±22% vs NG, p<0.01) and aortas of diabetic mice (216±32% vs controls, p<0.05). Immunoprecipitation showed that Pin1 recognizes phosphoserine motifs of the pro-oxidant mitochondrial adaptor p66Shc as well as NFkB subunit p65. Interestingly, Juglone or Pin1siRNA prevented p66Shc-induced ROS production and suppressed upregulation of adhesion molecules VCAM-1, ICAM-1 and MCP-1 via inhibition of p65 nuclear translocation. In vivo knockdown of Pin1 or Juglone in diabetic mice protected against hyperglycemia-induced endothelial dysfunction, ROS production and vascular inflammation. Of note, Pin1 mRNA was significantly upregulated in PBM of T2DM patients as compared with healthy controls (370±97 vs. 25±28, p<0.01) and correlated with glycated haemoglobin (r=0.44, p<0.05), FMD (r=-0.36,p<0.01), urinary 8-isoPGF2α (r=0.39, p<0.05), as well as VCAM-1 (r=0.56, p<0.05) and ICAM-1 (r=0.53, p<0.05). Conclusions: This study shows for the first time that Pin1 may critically contribute to oxidative stress, endothelial dysfunction and vascular inflammation in patients with type 2 diabetes.

The effect of okadaic acid–induced tau hyperphosphorylation on Pin1 expression in primary cortical neurons

The effect of okadaic acid–induced tau hyperphosphorylation on Pin1 expression in primary cortical neurons

The Peptidyl-prolyl Isomerase Pin1 Up-regulation and Proapoptotic Function in Dopaminergic Neurons: RELEVANCE TO THE PATHOGENESIS OF PARKINSON DISEASE

Parkinson disease (PD) is a chronic neurodegenerative disease characterized by a slow and progressive degeneration of dopaminergic neurons in substantia nigra. The pathophysiological mechanisms underlying PD remain unclear. Pin1, a major peptidyl-prolyl isomerase, has recently been associated with certain diseases. Notably, Ryo et al. (Ryo, A., Togo, T., Nakai, T., Hirai, A., Nishi, M., Yamaguchi, A., Suzuki, K., Hirayasu, Y., Kobayashi, H., Perrem, K., Liou, Y. C., and Aoki, I. (2006) J. Biol. Chem. 281, 4117-4125) implicated Pin1 in PD pathology. Therefore, we sought to systematically characterize the role of Pin1 in PD using cell culture and animal models. To our surprise we observed a dramatic up-regulation of Pin1 mRNA and protein levels in dopaminergic MN9D neuronal cells treated with the parkinsonian toxicant 1-methyl-4-phenylpyridinium (MPP(+)) as well as in the substantia nigra of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. Notably, a marked expression of Pin1 was also observed in the substantia nigra of human PD brains along with a high co-localization of Pin1 within dopaminergic neurons. In functional studies, siRNA-mediated knockdown of Pin1 almost completely prevented MPP(+)-induced caspase-3 activation and DNA fragmentation, indicating that Pin1 plays a proapoptotic role. Interestingly, multiple pharmacological Pin1 inhibitors, including juglone, attenuated MPP(+)-induced Pin1 up-regulation, α-synuclein aggregation, caspase-3 activation, and cell death. Furthermore, juglone treatment in the MPTP mouse model of PD suppressed Pin1 levels and improved locomotor deficits, dopamine depletion, and nigral dopaminergic neuronal loss. Collectively, our findings demonstrate for the first time that Pin1 is up-regulated in PD and has a pathophysiological role in the nigrostriatal dopaminergic system and suggest that modulation of Pin1 levels may be a useful translational therapeutic strategy in PD.

Maternal control of PIN1 is required for female gametophyte development in Arabidopsis.

Land plants are characterised by haplo-diploid life cycles, and developing ovules are the organs in which the haploid and diploid generations coexist. Recently it has been shown that hormones such as auxin and cytokinins play important roles in ovule development and patterning. The establishment and regulation of auxin levels in cells is predominantly determined by the activity of the auxin efflux carrier proteins PIN-FORMED (PIN). To study the roles of PIN1 and PIN3 during ovule development we have used mutant alleles of both genes and also perturbed PIN1 and PIN3 expression using micro-RNAs controlled by the ovule specific DEFH9 (DEFIFICENS Homologue 9) promoter. PIN1 down-regulation and pin1-5 mutation severely affect female gametophyte development since embryo sacs arrest at the mono- and/or bi-nuclear stages (FG1 and FG3 stage). PIN3 function is not required for ovule development in wild-type or PIN1-silenced plants. We show that sporophytically expressed PIN1 is required for megagametogenesis, suggesting that sporophytic auxin flux might control the early stages of female gametophyte development, although auxin response is not visible in developing embryo sacs.

Essential role of Pin1 via STAT3 signalling and mitochondria‐dependent pathways in restenosis in type 2 diabetes

Type 2 diabetes (T2D) is associated with accelerated restenosis rates after angioplasty. We have previously proved that Pin1 played an important role in vascular smooth muscle cell (VSMC) cycle and apoptosis. But neither the role of Pin1 in restenosis by T2D, nor the molecular mechanism of Pin1 in these processes has been elucidated. A mouse model of T2D was generated by the combination of high-fat diet (HFD) and streptozotocin (STZ) injections. Both Immunohistochemistry and Western blot revealed that Pin1 expression was up-regulated in the arterial wall in T2D mice and in VSMCs in culture conditions mimicking T2D. Next, increased activity of Pin1 was observed in neointimal hyperplasia after arterial injury in T2D mice. Further analysis confirmed that 10% serum of T2D mice and Pin1-forced expression stimulated proliferation, inhibited apoptosis, enhanced cell cycle progression and migration of VSMCs, whereas Pin1 knockdown resulted in the converse effects. We demonstrated that STAT3 signalling and mitochondria-dependent pathways played critical roles in the involvement of Pin1 in cell cycle regulation and apoptosis of VSMCs in T2D. In addition, VEGF expression was stimulated by Pin1, which unveiled part of the mechanism of Pin1 in regulating VSMC migration in T2D. Finally, the administration of juglone via pluronic gel onto injured common femoral artery resulted in a significant inhibition of the neointima/media ratio. Our findings demonstrated the vital effect of Pin1 on the VSMC proliferation, cell cycle progression, apoptosis and migration that underlie neointima formation in T2D and implicated Pin1 as a potential therapeutic target to prevent restenosis in T2D.

Pin1-Nanog expression in human glioma is correlated with advanced tumor progression

The stemness gene Nanog has been shown to play an important role in tumor development, including glioma. Nanog is phosphorylated at multiple Ser/Thr-Pro motifs, which promotes the interaction between Nanog and the prolyl isomerase Pin1, leading to Nanog stabilization by suppressing its ubiquitination. The present study investigated the expression and relationship of Pin1 and Nanog in human gliomas. Significantly higher mRNA and protein expression levels of Pin1 and Nanog were demonstrated in 120 glioma specimens of different pathological grades by RT-PCR, immunohistochemistry staining and western blot analysis. The relative levels of Pin1 expression, as well as Nanog expression, were significantly positively correlated with pathological grade. Moreover, a positive correlation of Pin1 and Nanog expression in human gliomas was noted. Co-localization of Pin1 and Nanog was observed in the perinuclear space in the cytoplasm of glioma cells detected by immunofluorescence staining. Significantly positive correlation between Pin1 and Nanog in gliomas indicated that Pin1 and Nanog may be related to tumorigenesis and development of glioma cells.

In This Issue

HomeCirculation ResearchVol. 112, No. 9In This Issue Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBIn This Issue Originally published26 Apr 2013https://doi.org/10.1161/RES.0b013e318295dbe3Circulation Research. 2013;112:1201Role of Pin1 in Cardiac Hypertrophy (p 1244)Ramping up, or reducing, Pin1 activity attenuates cardiac hypertrophy, report Toko et al.The Ser-Pro and Thr-Pro motifs in proteins are recognized and phosphorylated by proline-directed kinases such as Akt and MEK. These phosphorylation events are like light switches that can turn the target proteins on or off. But, the lights can also be dimmed or brightened by Pin1, a small protein that binds to phosphorylated Ser-Pro and Thr-Pro and adjusts the intensity of activation or repression. Pin-1 thus fine tunes a variety of cellular signaling pathways. However, little is known of the protein's activity in cardiomyocytes. Toko and colleagues discovered that Pin1 is highly expressed in the newborn mouse heart, but that its expression decreases by almost half as mice age. An exception to this phenomenon was pressure overload, when the expression of Pin1 was increased dramatically. Investigating, how different levels of Pin1 affected pressure-induced hypertrophy, the team found that mice lacking Pin1 maintained better cardiac function, exhibited fewer signs of hypertrophy and were more likely to survive following pressure overload than their wild type counterparts. Surprisingly over-expression of Pin1 also attenuated hypertrophy. The team deciphered that both under and over-expression of Pin1, via different pathways, reduced the activity of MEK—a known instigator of hypertrophy. Tweaking Pin1 balance in either direction might be beneficial in treating hypertrophy, say the authors.Download figureDownload PowerPointRelationship Among Cardiogenic Progenitor Cells (p 1253)Dey et al identify differences between cardiogenic progenitor cells.Accumulating evidence suggests that the heart does not solely consist of terminally differentiated cells, but that it could also undergo regeneration. Indeed, a number of cardiogenic cell types have been discovered in the heart and in the bone marrow. The existence of these cells has sparked excitement regarding their potential use in reparative therapies. But whether these cardiogenic cells are in anyway related to one another has not been established. Dey et al isolated three populations of mouse progenitor cells from the heart—ckit+, Sca1+ and SP—and two from the bone marrow—ckit+ and MSCs. They extracted RNA from each and compared their transcriptional profiles. They found that cardiac-derived progenitors and bone marrow-derived progenitors were very different from each other, with the cardiac-derived cells tending to express higher levels of matrix and cell-to-cell attachment factors, and the bone marrow cells expressing higher levels of cell cycle factors. Even the two ckit+ populations differed substantially. Of the three cardiac populations, the team determined that Sca1+ cells were the most closely related to differentiated cardiomyocytes, while the ckit+ cells were the most primitive, suggesting the three progenitor types might represent distinct differentiation stages. The improved understanding progenitor population relatedness should help in designing future cardiac repair strategies, say the authors.Download figureDownload PowerPointAdiponectin and Muscle Insulin Delivery/Action (p 1263)Zhao et al figure out how adiponectin improves the action of insulin in muscle.The hormone adiponectin circulates in the blood and is known to enhance insulin action. Indeed, low plasma levels of adiponection are associated with insulin resistance and diabetes in humans and mice, while replenishing adiponectin levels in mice improves insulin sensitivity. Adiponectin also promotes nitric oxide production in endothelial cells, and thus induces vasodilation. Now Zhao and colleagues show that it is this vasodilatory activity that enables adiponectin to improve insulin sensitivity. They found that injecting rats with adiponectin increases plasma nitric oxide levels, consequently increasing blood volume in the hindlimb skeletal muscle. Insulin uptake into the muscle also increased as did the rate of whole-body glucose disposal in response to insulin administration. These effects of adiponectin were blocked by inhibiting nitric oxide synthase—the enzyme responsible for producing nitric oxide—confirming that vasodilation was required for the increased insulin sensitivity. The authors explained that vasodilation expands the endothelial exchange surface for uptake of insulin, and suggest that targeting the muscle vasculature and hypoadiponectinemia could be important for the prevention and treatment of insulin-resistance and type 2 diabetes.Download figureDownload PowerPoint Previous Back to top Next FiguresReferencesRelatedDetails April 26, 2013Vol 112, Issue 9 Advertisement Article InformationMetrics © 2013 American Heart Association, Inc.https://doi.org/10.1161/RES.0b013e318295dbe3 Originally publishedApril 26, 2013 PDF download Advertisement

Abstract 771: Pin1 regulates the dynamics of c-Myc DNA binding to facilitate target gene regulation and oncogenesis.

Abstract The c-Myc oncoprotein is generally considered to be a master regulator of gene transcription by virtue of its ability to activate or repress the expression of a large percentage of all genes. However, mechanisms that direct c-Myc's recruitment to DNA and target gene selection to elicit specific cellular functions have not been well elucidated. Here, we report that the Pin1 prolyl-isomerase regulates c-Myc transcriptional activity by altering c-Myc's association with target gene promoters. Specifically, we show that Pin1 enhances the recruitment of Serine62-phosphorylated c-Myc along with its co-activators to selected target gene promoters during gene activation, followed by promoting c-Myc's release associated with its degradation, resulting in cyclic c-Myc DNA binding. This facilitates c-Myc's activation of target genes associated with an increase in elongating RNA Polymerase II in the gene body. Genes impacted by this mechanism are involved in cell growth and metabolism, resulting in enhanced pro-proliferative activity, even while controlling c-Myc expression. In cancer cells with impaired c-Myc degradation, Pin1 still regulates cyclic c-Myc DNA binding, even though it no longer enhances c-Myc degradation. This allows for simultaneous high expression of Pin1 and c-Myc in cancer, which can drive a gene expression pattern that we show is enriched in poor outcome subtypes of breast cancer. This study provides new insight into mechanisms regulating c-Myc DNA binding and oncogenic activity, it reveals a novel role for Pin1 in transcription factor regulation, and it elucidates a mechanism that can contribute to oncogenic cooperation between Pin1 and c-Myc. Citation Format: Amy Farrell, Carl Pelz, Xiaoyan Wang, Colin Daniel, Yulong Su, Mahnaz Janghorban, Soren Impey, Rosalie C. Sears. Pin1 regulates the dynamics of c-Myc DNA binding to facilitate target gene regulation and oncogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 771. doi:10.1158/1538-7445.AM2013-771

Decursin Exerts Anti‐cancer Activity in MDA‐MB‐231 Breast Cancer Cells Via Inhibition of the Pin1 Activity and Enhancement of the Pin1/p53 Association

The peptidyl-prolyl cis/trans isomerase Pin1 is overexpressed in a wide variety of cancer cells and thus considered as an important target molecule for cancer therapy. This study demonstrates that decursin, a bioactive compound from Angelica gigas, exert the anti-cancer effect against breast cancer cells via regulation of Pin1 and its related signaling molecules. We observed that decursin induced G1 arrest with decrease in cyclin D1 level in Pin1-expressing breast cancer cells MDA-MB-231, but not Pin1-non-expressing breast cancer cells MDA-MB-157. In addition, decursin significantly reduced protein expression and enzymatic activity of Pin1 in MDA-MB-231 cells. Further, we found that decursin treatment enhanced the p53 expression level and failed to down-regulate Pin1 in the cells transfected with p53 siRNA, indicating the importance of p53 in the decursin-mediated Pin1 inhibition in MDA-MB-231 cells. Decursin stimulated association between Pin1 to p53. Moreover, decursin facilitated p53 transcription in MDA-MB-231 cells. Overall, our current study suggests the potential of decursin as an attractive cancer therapeutic agent for breast cancer by targeting Pin1 protein.

Prolyl Isomerase Pin1 Regulated Signaling Pathway Revealed by Pin1 +/+ and Pin1 −/− Mouse Embryonic Fibroblast Cells

Pin1 (peptidylprolyl cis/trans isomerase, NIMA-interacting 1) plays a key role in a number of diseases including cancer and Alzheimer disease. Previous studies have identified a wide range of phosphoproteins as Pin1 substrates. Related pathways were analyzed separately. The aim of this study was to provide a comprehensive picture involving Pin1 regulation. A genome-wide mRNA expression microarray was carried out using the RNA isolation from Pin1 (+/+) and Pin1 (-/-) mouse embryonic fibroblast (MEF) cells. Signaling pathways regulated by Pin1 were analyzed with the utility of KEGG pathway and GO annotation. An expression pattern regulated by Pin1 was revealed. A total of 606 genes, 375 being up-regulated and 231 down-regulated, were differentially expressed when comparing Pin1 +/+ to Pin1 -/- MEF cells. Totally 48 pathways were shown to be regulated by Pin1 expression in KEGG pathway analysis. In the GO annotation system, 19 processes on biological processes, 15 processes on cellular components, and 18 processes on molecular functions were found to be in the regulation of Pin1 expression. Pathways related to immune system and cancer showed most significant association with Pin1 regulation. Pin1 is an important regulator in a wide range of signaling pathways that were related to immune system and cancer.

CGMP modulates Arabidopsis lateral root formation through regulation of polar auxin transport

The phytohormone auxin participates in lateral root formation and primary root growth in plants. The auxin gradient formation is mainly regulated by the direction of polar auxin transport (PAT). PAT requires PIN family proteins, which are auxin transport facilitators and contribute to the establishment and maintenance of auxin gradients and mediate multiple developmental processes. Here, we report the effect of the 3', 5'-cyclic guanosine monophosphate (cGMP), an important second messenger, on postembryonic developmental of Arabidopsis lateral root. We find that enhanced cGMP level through the application of the membrane permeable cGMP analog 8-Br-cGMP, promotes the initiation of lateral root primordia and formation of lateral root. 6-Anilino-5,8-quinolinedione (Ly83583, the guanylate cyclase inhibitor) negatively regulates the process. cGMP also mediates acropetal auxin transport and basipetal auxin transport in the root. We further find that 8-Br-cGMP and Ly83583 change the expression of auxin transport genes and alter the polar localization and expression of PIN1 and PIN2 proteins. Moreover, Ly83583 affects actin organization and localization. Taken together, we propose that cGMP affects auxin transport and auxin gradient through modulation PINs proteins localization and expression. cGMP regulates postembryonic formation of Arabidopsis lateral root through the crosstalk with PAT.

Protective effect of nectandrin B, a potent AMPK activator on neointima formation: inhibition of Pin1 expression through AMPK activation

Neointima is considered a critical event in the development of vascular occlusive disease. Nectandrin B from nutmeg functions as a potent AMP-activated protein kinase (AMPK) activators. The present study addressed whether nectandrin B inhibits intimal hyperplasia in guide wire-injured arteries and examined its molecular mechanism. Neointima was induced by guide wire injury in mouse femoral arteries. Cell proliferation and mechanism studies were performed in rat vascular smooth muscle cells (VSMC) culture model. Nectandrin B increased AMPK activity in VSMC. Nectandrin B inhibited the cell proliferation induced by PDGF and DNA synthesis. Moreover, treatment of nectandrin B suppressed neointima formation in femoral artery after guide wire injury. We have recently shown that Pin1 plays a critical role in VSMC proliferation and neointima formation. Nectandrin B potently blocked PDGF-induced Pin1 and cyclin D1 expression and nectandrin B's anti-proliferation effect was diminished in Pin1 overexpressed VSMC. PDGF-induced phosphorylation of ERK and Akt was marginally affected by nectandrin B. However, nectandrin B increased the levels of p53 and its downstream target p21 and, also reversibly decreased the expression of E2F1 and phosphorylated Rb in PDGF-treated VSMC. AMPK inhibition by dominant mutant form of adenovirus rescued nectandrin B-mediated down-regulation of Pin1 and E2F1. Nectandrin B inhibited VSMC proliferation and neointima formation via inhibition of E2F1-dependent Pin1 gene transcription, which is mediated through the activation of an AMPK/p53-triggered pathway.

Interaction of PLS and PIN and hormonal crosstalk in Arabidopsis root development

Understanding how hormones and genes interact to coordinate plant growth is a major challenge in developmental biology. The activities of auxin, ethylene, and cytokinin depend on cellular context and exhibit either synergistic or antagonistic interactions. Here we use experimentation and network construction to elucidate the role of the interaction of the POLARIS peptide (PLS) and the auxin efflux carrier PIN proteins in the crosstalk of three hormones (auxin, ethylene, and cytokinin) in Arabidopsis root development. In ethylene hypersignaling mutants such as polaris (pls), we show experimentally that expression of both PIN1 and PIN2 significantly increases. This relationship is analyzed in the context of the crosstalk between auxin, ethylene, and cytokinin: in pls, endogenous auxin, ethylene and cytokinin concentration decreases, approximately remains unchanged and increases, respectively. Experimental data are integrated into a hormonal crosstalk network through combination with information in literature. Network construction reveals that the regulation of both PIN1 and PIN2 is predominantly via ethylene signaling. In addition, it is deduced that the relationship between cytokinin and PIN1 and PIN2 levels implies a regulatory role of cytokinin in addition to its regulation to auxin, ethylene, and PLS levels. We discuss how the network of hormones and genes coordinates plant growth by simultaneously regulating the activities of auxin, ethylene, and cytokinin signaling pathways.

Role of Pin1 Protein in the Pathogenesis of Nonalcoholic Steatohepatitis in a Rodent Model

Nonalcoholic steatohepatitis (NASH) is a disorder characterized by simultaneous fat accumulation and chronic inflammation in the liver. In this study, Pin1 expression was revealed to be markedly increased in the livers of mice with methionine choline-deficient (MCD) diet-induced NASH, a rodent model of NASH. In addition, Pin1 KO mice were highly resistant to MCD-induced NASH, based on a series of data showing simultaneous fat accumulation, chronic inflammation, and fibrosis in the liver. In terms of Pin1-induced fat accumulation, it was revealed that the expression levels of peroxisome proliferator-activated receptor α and its target genes were higher in the livers of Pin1 KO mice than in controls. Thus, resistance of Pin1 KO mice to hepatic steatosis is partially attributable to the lack of Pin1-induced down-regulation of peroxisome proliferator-activated receptor α, although multiple other mechanisms are apparently involved. Another mechanism involves the enhancing effect of hematopoietic Pin1 on the expressions of inflammatory cytokines such as tumor necrosis factor and monocyte chemoattractant protein 1 through NF-κB activation, eventually leading to hepatic fibrosis. Finally, to distinguish the roles of hematopoietic or nonhematopoietic Pin1 in NASH development, mice lacking Pin1 in either nonhematopoietic or hematopoietic cells were produced by bone marrow transplantation between wild-type and Pin1 KO mice. The mice having nonhematopoietic Pin1 exhibited fat accumulation without liver fibrosis on the MCD diet. Thus, hepatic Pin1 appears to be directly involved in the fat accumulation in hepatocytes, whereas Pin1 in hematopoietic cells contributes to inflammation and fibrosis. In summary, this is the first study to demonstrate that Pin1 plays critical roles in NASH development. This report also raises the possibility that hepatic Pin1 inhibition to the appropriate level might provide a novel therapeutic strategy for NASH.

Overexpression of the prolyl isomerase PIN1 promotes cell growth in osteosarcoma cells

PIN1 was recently identified as a peptidyl-prolyl cis-trans isomerase (PPIase). It binds to and isomerizes specific pSer/Thr-Pro motifs and catalytically induces conformational changes after phosphorylation. PIN1 plays an important role in several cellular events, such as cell cycle progression, transcriptional regulation, RNA processing, cell proliferation and differentiation. The relationship between PIN1 and osteosarcoma has not been previously studied. In the present study, we investigated the expression pattern of PIN1 in human osteosarcoma tissues and the role of PIN1 in osteosarcoma generation and development. The expression levels of PIN1 were detected by immunohistochemistry and western blotting. Results demonstrated that the expression of PIN1, cyclinD1 and β-catenin were significantly higher in human osteosarcoma tissues compared to normal tissues. The invitro effects of PIN1 overexpression were studied in human osteosarcoma cell lines. Adenovirus-mediated PIN1 overexpression significantly stimulated the proliferation of MG-63 and U2-OS osteosarcoma cells by 148±10.5and187±21.5%, respectively. In FACS analysis, U2-OS cells displayed significant levels of arrest in cell cycle progression at the G0/G1 phase. Consistent with increased cell growth, levels of cyclinD1 and cyclinE and their associated cyclin-dependent kinases, CDK4 and CDK6, were enhanced in PIN1-overexpressed cells compared with the control virus-transfected cells. When the PIN1 inhibitor juglone was added to the cells, the proliferative effects of PIN1 were abolished. These results suggest that PIN1 may play an important role in tumorigenesis and tumor progression of osteosarcoma and therefore, provide a new target for gene therapy.

Tau pathology modulates Pin1 post-translational modifications and may be relevant as biomarker

A prerequisite to dephosphorylation at Ser–Pro or Thr–Pro motifs is the isomerization of the imidic peptide bond preceding the proline. The peptidyl-prolyl cis/trans isomerase named Pin1 catalyzes this mechanism. Through isomerization, Pin1 regulates the function of a growing number of targets including the microtubule-associated tau protein and is supposed to be deregulated Alzheimer's disease (AD). Using proteomics, we showed that Pin1 is posttranslationally modified on more than 5 residues, comprising phosphorylation, N-acetylation, and oxidation. Although Pin1 expression remained constant, Pin1 posttranslational two-dimensional pattern was modified by tau overexpression in a tau-inducible neuroblastoma cell line, in our THY-Tau22 mouse model of tauopathy as well as in AD. Interestingly, in all of these systems, Pin1 modifications were very similar. In AD brain tissue when compared with control, Pin1 is hyperphosphorylated at serine 16 and found in the most insoluble hyperphosphorylated tau fraction of AD brain tissue. Furthermore, in all tau pathology conditions, acetylation of Pin1 may also contribute to the differences observed. In conclusion, Pin1 displays several posttranslational modifications, which are specific in tauopathies and may be useful as biomarker.

Androgen receptor serine 81 mediates Pin1 interaction and activity

Hormone-dependent tumors are characterized by deregulated activity of specific steroid receptors, allowing aberrant expression of many genes involved in cancer initiation, progression and metastasis. In prostate cancer, the androgen receptor (AR) protein has pivotal functions, and over the years it has been the target of different drugs. AR is a nuclear receptor whose activity is regulated by a phosphorylation mechanism controlled by hormone and growth factors. Following phosphorylation, AR interacts with many cofactors that closely control its function. Among such cofactors, Pin1 is a peptidyl-prolyl isomerase that is involved in the control of protein phosphorylation and has a prognostic value in prostate cancer. In the present study, we demonstrate that ARSer81 is involved in the interaction with Pin1, and that this interaction is important for the transcriptional activity of AR. Since Pin1 expression positively correlates with tumor grade, our results suggest that Pin1 can participate in this process by modulating AR function.