Role Of Protein Phosphatases Research Articles

Role of Protein Phosphatases in Tumor Angiogenesis: Assessing PP1, PP2A, PP2B and PTPs Activity.

Tumor angiogenesis, the formation of new blood vessels to support tumor growth and metastasis, is a complex process regulated by a multitude of signaling pathways. Dysregulation of signaling pathways involving protein kinases has been extensively studied, but the role of protein phosphatases in angiogenesis within the tumor microenvironment remains less explored. However, among angiogenic pathways, protein phosphatases play critical roles in modulating signaling cascades. This review provides a comprehensive overview of the involvement of protein phosphatases in tumor angiogenesis, highlighting their diverse functions and mechanisms of action. Protein phosphatases are key regulators of cellular signaling pathways by catalyzing the dephosphorylation of proteins, thereby modulating their activity and function. This review aims to assess the activity of the protein tyrosine phosphatases and serine/threonine phosphatases. These phosphatases exert their effects on angiogenic signaling pathways through various mechanisms, including direct dephosphorylation of angiogenic receptors and downstream signaling molecules. Moreover, protein phosphatases also crosstalk with other signaling pathways involved in angiogenesis, further emphasizing their significance in regulating tumor vascularization, including endothelial cell survival, sprouting, and vessel maturation. In conclusion, this review underscores the pivotal role of protein phosphatases in tumor angiogenesis and accentuate their potential as therapeutic targets for anti-angiogenic therapy in cancer.

Molecular Role of Protein Phosphatases in Alzheimer’s and Other Neurodegenerative Diseases

Alzheimer’s disease (AD) is distinguished by the gradual loss of cognitive function, which is associated with neuronal loss and death. Accumulating evidence supports that protein phosphatases (PPs; PP1, PP2A, PP2B, PP4, PP5, PP6, and PP7) are directly linked with amyloid beta (Aβ) as well as the formation of the neurofibrillary tangles (NFTs) causing AD. Published data reported lower PP1 and PP2A activity in both gray and white matters in AD brains than in the controls, which clearly shows that dysfunctional phosphatases play a significant role in AD. Moreover, PP2A is also a major causing factor of AD through the deregulation of the tau protein. Here, we review recent advances on the role of protein phosphatases in the pathology of AD and other neurodegenerative diseases. A better understanding of this problem may lead to the development of phosphatase-targeted therapies for neurodegenerative disorders in the near future.

Serine/Threonine Protein Phosphatases 1 and 2A in Lung Endothelial Barrier Regulation.

Vascular barrier dysfunction is characterized by increased permeability and inflammation of endothelial cells (ECs), which are prominent features of acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and sepsis, and a major complication of the SARS-CoV-2 infection and COVID-19. Functional impairment of the EC barrier and accompanying inflammation arises due to microbial toxins and from white blood cells of the lung as part of a defensive action against pathogens, ischemia-reperfusion or blood product transfusions, and aspiration syndromes-based injury. A loss of barrier function results in the excessive movement of fluid and macromolecules from the vasculature into the interstitium and alveolae resulting in pulmonary edema and collapse of the architecture and function of the lungs, and eventually culminates in respiratory failure. Therefore, EC barrier integrity, which is heavily dependent on cytoskeletal elements (mainly actin filaments, microtubules (MTs), cell-matrix focal adhesions, and intercellular junctions) to maintain cellular contacts, is a critical requirement for the preservation of lung function. EC cytoskeletal remodeling is regulated, at least in part, by Ser/Thr phosphorylation/dephosphorylation of key cytoskeletal proteins. While a large body of literature describes the role of phosphorylation of cytoskeletal proteins on Ser/Thr residues in the context of EC barrier regulation, the role of Ser/Thr dephosphorylation catalyzed by Ser/Thr protein phosphatases (PPases) in EC barrier regulation is less documented. Ser/Thr PPases have been proposed to act as a counter-regulatory mechanism that preserves the EC barrier and opposes EC contraction. Despite the importance of PPases, our knowledge of the catalytic and regulatory subunits involved, as well as their cellular targets, is limited and under-appreciated. Therefore, the goal of this review is to discuss the role of Ser/Thr PPases in the regulation of lung EC cytoskeleton and permeability with special emphasis on the role of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) as major mammalian Ser/Thr PPases. Importantly, we integrate the role of PPases with the structural dynamics of the cytoskeleton and signaling cascades that regulate endothelial cell permeability and inflammation.

Roles of phosphatases in eukaryotic DNA replication initiation control

In eukaryotes, the phosphorylation of replication initiation factors by protein kinases is crucial to DNA replication control. This control ensures that the genome is only copied once per cell cycle and that replication occurs in a timely manner, minimising stress. Indeed, uncontrolled DNA replication initiation causes genome instability and occurs early on in cancer development. Here we discuss the known roles of protein phosphatases in replication initiation as part of cell cycle control and the DNA damage response. We highlight how dephosphorylation ensures that DNA replication initiation events are robust, dynamic, and spatially regulated. As many kinases involved in replication control are targets for new chemotherapies, an understanding of the role of phosphatases may give critical insights into cancer treatment.

Prognostic and Immunological Role of PPP1R14A as a Pan-Cancer Analysis Candidate.

Despite emerging evidence revealing the remarkable roles of protein phosphatase 1 regulatory inhibitor subunit 14A (PPP1R14A) in cancer tumorigenesis and progression, no pan-cancer analysis is available. A comprehensive investigation of the potential carcinogenic mechanism of PPP1R14A across 33 tumors using bioinformatic techniques is reported for the first time. PPP1R14A is downregulated in major malignancies, and there is a significant correlation between the PPP1R14A expression and the prognosis of patients. The high expression of PPP1R14A in most cases was associated with poor overall survival (OS), disease-specific survival (DSS), and progress-free interval (PFI) across patients with various malignant tumors, including adrenocortical carcinoma (ACC) and bladder urothelial carcinoma (BLCA), indicated through pan-cancer survival analysis. Receiver operating characteristic (ROC) analysis subsequently exhibited that the molecule has high reference significance in diagnosing a variety of cancers. The frequency of PPP1R14A genetic changes including genetic mutations and copy number alterations (CNAs) in uterine carcinosarcoma reached 16.07%, and these alterations brought misfortune to the survival and prognosis of cancer patients. In addition, methylation within the promoter region of PPP1R14A DNA was enhanced in a majority of cancers. Downregulated phosphorylation levels of phosphorylation sites including S26, T38, and others in most cases took place in several tumors, such as breast cancer and colon cancer. PPP1R14A remarkably correlated with the levels of infiltrating cells and immune checkpoint genes. Our research on the carcinogenic effect of PPP1R14A in different tumors is comprehensively summarized and analyzed and provides a theoretical basis for future therapeutic and immunotherapy strategies.

High male specific contribution of the X-chromosome to individual global recombination rate in dairy cattle

BackgroundMeiotic recombination plays an important role in reproduction and evolution. The individual global recombination rate (GRR), measured as the number of crossovers (CO) per gametes, is a complex trait that has been shown to be heritable. The sex chromosomes play an important role in reproduction and fertility related traits. Therefore, variants present on the X-chromosome might have a high contribution to the genetic variation of GRR that is related to meiosis and to reproduction.ResultsWe herein used genotyping data from 58,474 New Zealand dairy cattle to estimate the contribution of the X-chromosome to male and female GRR levels. Based on the pedigree-based relationships, we first estimated that the X-chromosome accounted for 30% of the total additive genetic variance for male GRR. This percentage was equal to 19.9% when the estimation relied on a SNP-BLUP approach assuming each SNP has a small contribution. We then carried out a haplotype-based association study to map X-linked QTL, and subsequently fine-mapped the identified QTL with imputed sequence variants. With this approach we identified three QTL with large effect accounting for 7.7% of the additive genetic variance of male GRR. The associated effects were equal to + 0.79, − 1.16 and + 1.18 CO for the alternate alleles. In females, the estimated contribution of the X-chromosome to GRR was null and no significant association with X-linked loci was found. Interestingly, two of the male GRR QTL were associated with candidate genes preferentially expressed in testis, in agreement with a male-specific effect. Finally, the most significant QTL was associated with PPP4R3C, further supporting the important role of protein phosphatase in double-strand break repair by homologous recombination.ConclusionsOur study illustrates the important role the X-chromosome can have on traits such as individual recombination rate, associated with testis in males. We also show that contribution of the X-chromosome to such a trait might be sex dependent.

Phosphatase inhibition by sodium orthovanadate displays anti-inflammatory action by suppressing AKT-IKKβ signaling in RAW264.7 cells

Sodium orthovanadate (Na3VO4) is an inhibitor of phosphatases that acts as a phosphate analog and is being developed as an anti-diabetes drug. Phosphatases play important roles in inflammatory signal pathways by modulating the removal of phosphate moieties of key signaling proteins. However, the role of protein phosphatases on the inflammatory response has not been fully established. In this study, we investigated how phosphatases can control the inflammatory response using Na3VO4 in LPS-stimulated RAW264.7 cells and explored the molecular mechanisms by NO assay, mRNA analysis, immunoblotting analysis, kinase assay, luciferase reporter gene assay, and mutation strategy. Na3VO4 decreased the release of nitric oxide (NO) and suppressed the expression of pro-inflammatory genes at the transcriptional level, without cytotoxicity. The translocation of nuclear factor (NF)-κB subunits into the nucleus and the level of p-IκBα were reduced by Na3VO4, as was IKKβ activity. Na3VO4 inhibited NF-κB-Luc activity under AKT1/2 and IKKβ overexpression. However, the inhibitory effect of Na3VO4 against NF-κB-Luc was not observed in the group overexpressing both AKT2 and IKKβ-M10, a mutant in which the 10 serine residues in the autophosphorylated region of the C-terminal were replaced with alanine. Na3VO4 directly decreased the activity of protein phosphatase 1α (PP1α) and protein phosphatase 2 A (PP2A) by 95%. Phosphatase inhibition by Na3VO4 also selectively suppressed AKT-IKKβ signaling by directly blocking the phosphatase activity of PP1 and PP2A, consequently down-regulating NF-κB and inflammatory gene expression. Therefore, these results suggest that vanadium compounds including Na3VO4 can be developed as anti-inflammatory drugs.

Adopting a Phosphoproteomics Approach to Investigate a Role for Protein Phosphatase 2A (PP2A) Regulatory Subunit B55α in Cardiac β-Adrenergic Receptor Signalling

Protein kinases are recognised as integral regulators of phosphorylation within beta-adrenergic receptor (β-AR) signalling pathways in the heart. In contrast, the role of protein phosphatases and dephosphorylation in β-AR pathways is less well defined. In vitro evidence suggests that protein phosphatase 2A (PP2A) regulatory subunit B55α may modulate gene transcription as a key downstream effector of β-AR signalling in cardiomyocytes. The goal of this study was to determine how loss of PP2A-B55α impacts β-AR signalling in cardiomyocytes.

Partial purification and characterization of protein phosphatases from bovine adrenal medulla

Control of neurosecretion and synthesis of neurotransmitters appears to be regulated through second messengers that change the phosphorylation state of critical enzymes and proteins. Relatively little is known about the role of protein kinases in these processes in neuronal cells and even less is known about the role of protein phosphatases. We have examined the phosphatase activities of the bovine adrenal medulla using chromatographic separation, substrate specificity and inhibitor sensitivity. When fractionated, using an HPLC ion exchange DEAE column, four distinct peaks (peaks I,II,III and IV) of phosphatase activity were observed in the supernatant of homogenized bovine adrenal medulla. These phosphatases have distinctly different specific activities toward different substrates. Peak IV which contains most of the activity toward phosphocasein, showed preferential dephosphorylation of the α subunit of phosphorylase kinase relative to the β subunit and was strongly inhibited by okadaic acid, attributes of the type 2A phosphatase. The apparent molecular weight of phosphatase peak IV is also comparable to the heterotrimeric form of the known protein phosphatase type 2A of mammalian cells.

Okadaic Acid Time-Resolved Absorption and Resonance FT-IR and Raman Biospectroscopy and Density Functional Theory (DFT) Investigation of Vibronic-Mode Coupling Structure in Vibrational Spectra Analysis

Okadaic acid, C₄₄H₆₈O₁₃, is a toxin produced by several species of dinoflagellates, and is known to accumulate in both marine sponges and shellfish. One of the primary causes of diarrhetic shellfish poisoning, Okadaic acid is a potent inhibitor of specific protein phosphatases and is known to have a variety of negative effects on cells. A polyketide, polyether derivative of a C38 fatty acid, Okadaic acid and other members of its family have shined light upon many biological processes both with respect to dinoflagellate polyketide synthesis as well as the role of protein phosphatases in cell growth. Parameters such as FT-IR and Raman vibrational wavelengths and intensities for single crystal Okadaic Acid are calculated using density functional theory and were compared with empirical results. The investigation about vibrational spectrum of cycle dimers in crystal with carboxyl groups from each molecule of acid was shown that it leads to create Hydrogen bonds for adjacent molecules. The current study aimed to investigate the possibility of simulating the empirical values. Analysis of vibrational spectrum of Okadaic Acid is performed based on theoretical simulation and FT-IR empirical spectrum and Raman empirical spectrum using density functional theory in levels of HF/6-31G^*, HF/6-31++G^*^*, MP2/6-31G, MP2/6-31++G^*^*, BLYP/6-31G, BLYP/6-31++G^*^*, B3LYP/6-31G and B3LYP6-31-HEG^*^*. Vibration modes of methylene, carboxyl acid and phenyl cycle are separately investigated. The obtained values confirm high accuracy and validity of results obtained from calculations.

Effects of PP2A/Nrf2 on experimental diabetes mellitus-related cardiomyopathy by regulation of autophagy and apoptosis through ROS dependent pathway

Diabetes mellitus-related cardiomyopathy (DMCMP) has been defined as ventricular dysfunction that occurs in diabetic patients independent of a recognized cause such as coronary artery disease or hypertension. Mechanisms underlying DMCMP have not been fully elucidated. In this study, the roles of protein phosphatase 2A/nuclear factor NF-E2-related factor 2 (PP2A/Nrf2) in experimental DMCMP induced by high glucose were studied in vitro and in vivo. The results showed that high glucose could induce experimental DMCMP and increase ROS generation, increase the expression and nuclear translocation of Nrf2, down-regulate the expression of PI3K/Akt/mTOR and up-regulate the expression of ERK, and activate the autophagy of cardiomyocytes. The activity or expression of PP2A in DMCMP increased. PP2A could up-regulate the expression of Nrf2 and promote cardiomyocytes autophagy and apoptosis. Inhibition of PP2A could reduce the expression of Nrf2 and inhibit the autophagy and apoptosis of cardiomyocytes. The results suggested that hyperglycemic-induced experimental DMCMP may be related to up-regulating the expression of Nrf2 through PP2A/Nrf2 pathway. These results will be helpful to elucidate the pathogenesis and mechanism of DMCMP and find targets for the development of new drugs to prevent or treat DMCMP.

Serine/threonine protein phosphatase 1 (PP1) controls growth and reproduction in Schistosoma japonicum.

Schistosomiasis is a human parasitic disease caused by flatworms of the genus Schistosoma. Adult female schistosomes produce numerous eggs that are responsible for the pathogenesis and transmission of the disease, and the maturation of female gonads depends on the permanent pairing of females and males. Signaling protein kinases have been proven to control female gonad differentiation after pairing; however, little is known about the roles of protein phosphatases in the developmental and reproductive biology of schistosomes. Here we explored 3 genes encoding catalytic subunits of serine/threonine protein phosphatase 1 (PP1c) that were structurally and evolutionarily conserved in Schistosoma japonicum. In situ hybridization showed transcripts of 3 Sj-pp1c genes mainly localized in the reproductive organs and tissues. Triple knockdown of Sj-pp1c genes by RNA interference caused stunted growth and decreased pairing stability of worm pairs, as well as a remarkable reduction in cell proliferation activity and defects in reproductive maturation and fecundity. Transcriptomic analysis post-RNA interference suggested that Sj-pp1c genes are involved in controlling worm development and maturation mainly by regulating cell proliferation, eggshell synthesis, nutritional metabolism, cytoskeleton organization, and neural process. Our study provides the first insight into the fundamental contribution of Sj-PP1c to molecular mechanisms underlying the reproductive biology of schistosomes.-Zhao, L., Lu, Z., He, X., Mughal, M. N., Fang, R., Zhou, Y., Zhao, J., Gasser, R. B., Grevelding, C. G., Ye, Q., Hu, M. Serine/threonine protein phosphatase 1 (PP1) controls growth and reproduction in Schistosoma japonicum.

Role of Protein Phosphatase 1 and Inhibitor of Protein Phosphatase 1 in Nitric Oxide-Dependent Inhibition of the DNA Damage Response in Pancreatic β-Cells.

Nitric oxide is produced at micromolar levels by pancreatic β-cells during exposure to proinflammatory cytokines. While classically viewed as damaging, nitric oxide also activates pathways that promote β-cell survival. We have shown that nitric oxide, in a cell type-selective manner, inhibits the DNA damage response (DDR) and, in doing so, protects β-cells from DNA damage-induced apoptosis. This study explores potential mechanisms by which nitric oxide inhibits DDR signaling. We show that inhibition of DDR signaling (measured by γH2AX formation and the phosphorylation of KAP1) is selective for nitric oxide, as other forms of reactive oxygen/nitrogen species do not impair DDR signaling. The kinetics and broad range of DDR substrates that are inhibited suggest that protein phosphatase activation may be one mechanism by which nitric oxide attenuates DDR signaling in β-cells. While protein phosphatase 1 (PP1) is a primary regulator of DDR signaling and an inhibitor of PP1 (IPP1) is selectively expressed only in β-cells, disruption of either IPP1 or PP1 does not modify the inhibitory actions of nitric oxide on DDR signaling in β-cells. These findings support a PP1-independent mechanism by which nitric oxide selectively impairs DDR signaling and protects β-cells from DNA damage-induced apoptosis.

Protein phosphatases at the nuclear envelope.

The nuclear envelope (NE) is a unique topological structure formed by lipid membranes (Inner and Outer Membrane: IM and OM) interrupted by open channels (Nuclear Pore complexes). Besides its well-established structural role in providing a physical separation between the genome and the cytoplasm and regulating the exchanges between the two cellular compartments, it has become quite evident in recent years that the NE also represents a hub for localized signal transduction. Mechanical, stress, or mitogen signals reach the nucleus and trigger the activation of several pathways, many effectors of which are processed at the NE. Therefore, the concept of the NE acting just as a barrier needs to be expanded to embrace all the dynamic processes that are indeed associated with it. In this context, dynamic protein association and turnover coupled to reversible post-translational modifications of NE components can provide important clues on how this integrated cellular machinery functions as a whole. Reversible protein phosphorylation is the most used mechanism to control protein dynamics and association in cells. Keys to the reversibility of the system are protein phosphatases and the regulation of their activity in space and time. As the NE is clearly becoming an interesting compartment for the control and transduction of several signalling pathways, in this review we will focus on the role of Protein Phosphatases at the NE since the significance of this class of proteins in this context has been little explored.

E2/ER β Enhances Calcineurin Protein Degradation and PI3K/Akt/MDM2 Signal Transduction to Inhibit ISO-Induced Myocardial Cell Apoptosis.

Secretion of multifunctional estrogen and its receptor has been widely considered as the reason for markedly higher frequency of heart disease in men than in women. 17β-Estradiol (E2), for instance, has been reported to prevent development of cardiac apoptosis via activation of estrogen receptors (ERs). In addition, protein phosphatase such as protein phosphatase 1 (PP1) and calcineurin (PP2B) are also involved in cardiac hypertrophy and cell apoptosis signaling. However, the mechanism by which E2/ERβ suppresses apoptosis is not fully understood, and the role of protein phosphatase in E2/ERβ action also needs further investigation. In this study, we observed that E2/ERβ inhibited isoproterenol (ISO)-induced myocardial cell apoptosis, cytochrome c release and downstream apoptotic markers. Moreover, we found that E2/ERβ blocks ISO-induced apoptosis in H9c2 cells through the enhancement of calcineurin protein degradation through PI3K/Akt/MDM2 signaling pathway. Our results suggest that supplementation with estrogen and/or overexpression of estrogen receptor β gene may prove to be effective means to treat stress-induced myocardial damage.

Role of Protein Phosphatase 1 in Angiogenesis and Odontoblastic Differentiation of Human Dental Pulp Cells

IntroductionThe aims of this study were to examine the immunolocalization of protein phosphatase 1 (PP1) in developing mouse pulp tissue and to explore the role of PP1 in odontoblastic differentiation and in vitro angiogenesis in human dental pulp cells (HDPCs). MethodsImmunolocalization of PP1 was assessed in developing mouse pulp tissue. Odontogenic differentiation was examined by alkaline phosphatase activity, alizarin red staining, and reverse transcriptase polymerase chain reaction. Angiogenesis was evaluated by endothelial cell migration and capillary tube formation. Signaling pathways were analyzed by Western blotting and confocal immunofluorescence. ResultsPP1 expression was detected in preodontoblasts, odontoblasts, dental pulp cells, and endothelial cells within pulp tissue during the crown formed, root formation, and root completion stages. PP1 messenger RNA (mRNA) and protein levels were up-regulated at the late mineralization stage during odontogenic differentiation of HDPCs. The PP1 activator C2 ceramide increased alkaline phosphatase activity, mineralized nodule formation, and mRNA expression of dentin matrix protein 1 and dentin sialophosphoprotein. In contrast, knockdown by PP1 small interfering RNA inhibited odontoblastic differentiation. Moreover, PP1 activator up-regulated mRNA expression of angiogenic genes in HDPCs and increased the migration and capillary tube formation of endothelial cells, whereas PP1 small interfering RNA showed opposite effects. C2 ceramide increased levels of bone morphogenetic protein 2, phosphorylation of Smad 1/5/8, and mRNA expression of runt-related transcription factor 2 and osterix. ConclusionsThis study provides the first evidence that PP1 might be a potent regulator of developing pulp tissue in vivo and odontoblastic differentiation and angiogenesis in HDPCs in vitro and may have clinical implications for pulp/dentin regeneration or reparative dentinogenesis.

The neglected messengers: Control of cardiac myofilaments by protein phosphatases

Cardiac myofilaments act as the central contractile apparatus of heart muscle cells. Covalent modification of constituent proteins through phosphorylation is a rapid and powerful mechanism to control myofilament function, and is increasingly seen as a mechanism of disease. While the relationship between protein kinases and cardiac myofilaments has been widely examined, the impact of protein dephosphorylation by protein phosphatases is poorly understood. This review outlines the mechanisms by which the mostly widely expressed protein phosphatases in cardiac myocytes regulate myofilament function, and the emerging role of myofilament-associated protein phosphatases in heart failure. The importance of regulatory subunits and subcellular compartmentalization in determining the functional impact of protein phosphatases on myofilament and myocardial function is also discussed, as are discrepancies about the roles of protein phosphatases in regulating myofilament function. The potential for targeting these molecular messengers in the treatment of heart failure is discussed as a key future direction.

Role of protein phosphatases in genitourinary cancers.

The prevalence of genitourinary cancers has been increasing rapidly worldwide over the past 10 years. Advances in diagnosis and treatment have improved the oncological outcomes of patients with genitourinary cancer. However, the precise mechanisms of cancer development are largely unknown. Among various biological mechanisms, reversible phosphorylation is crucial for regulating the activities of many proteins in cancer cells. In contrast to protein kinases, the roles of cellular protein phosphatases have not been fully elucidated. However, emerging evidence suggests that various protein phosphatases are involved in genitourinary cancer development and have potential for cancer treatment. In the present review, we focus on recent progress in protein phosphatases regarding genitourinary cancers. We also explore the development of new strategies for cancer therapy using protein phosphatase and related molecules.

Abstract 96: Simvastatin Prevents TGF-β1-induced SMAD2/3 Phosphorylation Involved in Ventricular Fibrosis: Role of Protein Phosphatases

Background: Ventricular fibrosis leads to progressive cardiac dysfunction and heart failure (HF). Statins are reported to reduce cardiac fibrosis through the cholesterol-independent pathway, but mechanisms remain elusive. We hypothesize simvastatin reduced TGF-β1-induced ventricular fibrosis through activation of SMAD protein phosphatase Mg 2+ /Mn 2+ -1A (PPM1A), -2A (PP2A). Methods: In the absence and presence of TGF-β1 (5ng) with or without simvastatin (1μM), the rate of fibroblast proliferation (doubling time), myofibroblast differentiation (ICC), α-SMA mRNA (RT-PCR) and protein expression (Western blot) and the release of collagen synthesis markers, pro-collagen type I C-terminal peptide (PICP) and pro-collagen type III N-terminal peptide (PIIINP), in the media (ELISA) were determined along with protein interaction between SMAD2/3 and PPM1A or PP2A (Co-IP) and SMAD2/3 phosphorylation (Western blot). Results: Simvastatin reduced the effect of TGF-β1 on hVF proliferation by 47% (50000 to 26500), p<0.01; myofibroblast differentiated population from 48% (avg 48/100) to 11% (avg 11/100), p<0.01; expression of α-SMA mRNA by 76%, p<0.01; and protein by 60%, p<0.05. Simvastatin also decreased release of PICP by 66%, p<0.01, and PIIINP by 83%, p<0.01, into the media. Time-dependent increases in SMAD2/3 phosphorylation were reduced by simvastatin through activation of protein phosphatases PPM1A and PP2A by interacting with SMAD2/3. Conclusion: Involvement of PPM1A and PP2A in the anti-fibrotic effect of simvastatin reveals novel signaling mediators that may be selectively targeted for prevention of myocardial injury-induced ventricular fibrosis and HF.

Burst-Dependent Bidirectional Plasticity in the Cerebellum Is Driven by Presynaptic NMDA Receptors.

Numerous studies have shown that cerebellar function is related to the plasticity at the synapses between parallel fibers and Purkinje cells. How specific input patterns determine plasticity outcomes, as well as the biophysics underlying plasticity of these synapses, remain unclear. Here, we characterize the patterns of activity that lead to postsynaptically expressed LTP using both in vivo and in vitro experiments. Similar to the requirements of LTD, we find that high-frequency bursts are necessary to trigger LTP and that this burst-dependent plasticity depends on presynaptic NMDA receptors and nitric oxide (NO) signaling. We provide direct evidence for calcium entry through presynaptic NMDA receptors in a subpopulation of parallel fiber varicosities. Finally, we develop and experimentally verify a mechanistic plasticity model based on NO and calcium signaling. The model reproduces plasticity outcomes from data and predicts the effect of arbitrary patterns of synaptic inputs on Purkinje cells, thereby providing a unified description of plasticity.