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The behavior of stem cells is regulated by mechanical cues in their niche that continuously vary due to extracellular matrix (ECM) remodeling, pulsated mechanical stress exerted by blood flow, and/or cell migration. However, it is still unclear how dynamics of mechanical cues influence stem cell lineage commitment, especially in a 3D microenvironment where mechanosensing differs from that in a 2D microenvironment. In the present study, we investigated how temporally varying mechanical signaling regulates expression of the early growth response 1 gene (Egr1), which we recently discovered to be a 3D matrix-specific mediator of mechanosensitive neural stem cell (NSC) lineage commitment. Specifically, we temporally controlled the activity of Ras homolog family member A (RhoA), which is known to have a central role in mechanotransduction, using our previously developed Arabidopsis thaliana cryptochrome-2-based optoactivation system. Interestingly, pulsed RhoA activation induced Egr1 upregulation in stiff 3D gels only, whereas static light stimulation induced an increase in Egr1 expression across a wide range of 3D gel stiffnesses. Actin assembly inhibition limited Egr1 upregulation upon RhoA activation, implying that RhoA signaling requires an actin-involved process to upregulate Egr1. Consistently, static-light RhoA activation rather than pulsed-light activation restricted neurogenesis in soft gels. Our findings indicate that the dynamics of RhoA activation influence Egr1-mediated stem cell fate within 3D matrices in a matrix stiffness-dependent manner.

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S-palmitoylation is a reversible lipid modification catalyzed by 23 S-acyltransferases with a conserved zinc finger aspartate-histidine-histidine-cysteine (zDHHC) domain that facilitates targeting of proteins to specific intracellular membranes. Here we performed a gain-of-function screen in the mouse and identified the Golgi-localized enzymes zDHHC3 and zDHHC7 as regulators of cardiac hypertrophy. Cardiomyocyte-specific transgenic mice overexpressing zDHHC3 show cardiac disease, and S-acyl proteomics identified the small GTPase Rac1 as a novel substrate of zDHHC3. Notably, cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice is preceded by enhanced Rac1 S-palmitoylation, membrane localization, activity, downstream hypertrophic signaling, and concomitant induction of all Rho family small GTPases whereas mice overexpressing an enzymatically dead zDHHC3 mutant show no discernible effect. However, loss of Rac1 or other identified zDHHC3 targets Gαq/11 or galectin-1 does not diminish zDHHC3-induced cardiomyopathy, suggesting multiple effectors and pathways promoting decompensation with sustained zDHHC3 activity. Genetic deletion of Zdhhc3 in combination with Zdhhc7 reduces cardiac hypertrophy during the early response to pressure overload stimulation but not over longer time periods. Indeed, cardiac hypertrophy in response to 2 weeks of angiotensin-II infusion is not diminished by Zdhhc3/7 deletion, again suggesting other S-acyltransferases or signaling mechanisms compensate to promote hypertrophic signaling. Taken together, these data indicate that the activity of zDHHC3 and zDHHC7 at the cardiomyocyte Golgi promote Rac1 signaling and maladaptive cardiac remodeling, but redundant signaling effectors compensate to maintain cardiac hypertrophy with sustained pathological stimulation in the absence of zDHHC3/7.

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Heart failure is one of the leading causes of death worldwide. RhoA, a small GTPase, governs actin dynamics in various tissue and cell types, including cardiomyocytes; however, its involvement in cardiac function has not been fully elucidated. Here, we generated cardiomyocyte-specific RhoA conditional knockout (cKO) mice, which demonstrated a significantly shorter lifespan with left ventricular dilation and severely impaired ejection fraction. We found that the cardiac tissues of the cKO mice exhibited structural disorganization with fibrosis and also exhibited enhanced senescence compared with control mice. In addition, we show that cardiomyocyte mitochondria were structurally abnormal in the aged cKO hearts. Clearance of damaged mitochondria by mitophagy was remarkably inhibited in both cKO cardiomyocytes and RhoA-knockdown HL-1 cultured cardiomyocytes. In RhoA-depleted cardiomyocytes, we reveal that the expression of Parkin, an E3 ubiquitin ligase that plays a crucial role in mitophagy, was reduced, and expression of N-Myc, a negative regulator of Parkin, was increased. We further reveal that the RhoA-Rho kinase axis induced N-Myc phosphorylation, which led to N-Myc degradation and Parkin upregulation. Re-expression of Parkin in RhoA-depleted cardiomyocytes restored mitophagy, reduced mitochondrial damage, attenuated cardiomyocyte senescence, and rescued cardiac function both in vitro and in vivo. Finally, we found that patients with idiopathic dilated cardiomyopathy without causal mutations for dilated cardiomyopathy showed reduced cardiac expression of RhoA and Parkin. These results suggest that RhoA promotes Parkin-mediated mitophagy as an indispensable mechanism contributing to cardioprotection in the aging heart.

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ObjectiveTo explore the intervention mechanism of Xiangsha Liujunzi Tang in rats with functional dyspepsia （FD） based on the Ras homolog gene family member A （RhoA）/Rho-associated coiled-coil containing protein kinase 2 （ROCK2）/Myosin phosphatase target Subunit 1 （MYPT1） pathway. MethodSixty male SD suckling rats in SPF grades were randomly divided into blank group （n=10） and model group （n=50）. The comprehensive modeling method （gavage administration of iodoacetamide+exhaustion of swimming+disturbance of hunger and satiety） was used to replicate the rat model of FD. After successful replication of the model， the rats in the model group were randomly divided into model group， mosapride group， and high， middle， and low-dose Xiangsha Liujunzi Tang groups， with 10 rats in each group. Rats in the blank group and model group were given 10 mL kg-1·d-1 normal saline， those in the mosapride group were given 1.35 mg·kg-1·d-1 mosapride， and those in the high， middle， and low-dose Xiangsha Liujunzi Tang groups were given 12， 6， and 3 g·kg-1·d-1 Xiangsha Liujunzi Tang， respectively. The intervention lasted 14 days. The general living conditions of rats were observed before and after modeling and administration， and the 3-hour food intake and body mass of rats were measured. After intervention， the intestinal propulsion rate of rats was measured， and the pathological changes in the gastric tissue were observed by hematoxylin-eosin （HE） staining. The content of choline acetyl transferase （ChAT） and vasoactive intestinal peptide （VIP） in the medulla oblongata and gastric tissue homogenate was determined by enzyme-linked immunosorbent assay （ELISA）， the distribution of adenosine triphosphate （ATP） enzyme in gastric antrum smooth muscle was observed by frozen section staining， and the protein expression levels of RhoA， ROCK2， and phosphorylated-myosin phosphatase target subunit 1 （p-MYPT1） in the gastric tissue were detected by Western blot. ResultCompared with the blank group， the model group had withered hair， lazy movement， slow action， poor general living condition， lower 3-hour food intake， body mass， and lower intestinal propulsion rate （P<0.05）， whereas no obvious abnormality in gastric histopathology. In the model group， the content of ChAT in the medulla oblongata and gastric tissue decreased， the content of VIP in gastric tissue increased， the distribution of ATP enzyme in gastric antrum smooth muscle decreased significantly， and the protein expression levels of RhoA， ROCK2， and p-MYPT1 in the gastric tissue decreased significantly （P<0.05）. As compared with the model group， the general living condition of rats in each intervention group was significantly improved， and the 3-hour food intake， body mass， and intestinal propulsion rate were significantly increased （P<0.05）. There was no significant difference in gastric pathology in the intervention groups. The content of ChAT in the medulla oblongata and gastric tissue increased significantly， the content of VIP in the gastric tissue decreased， the distribution of ATP enzyme in gastric antrum smooth muscle increased significantly， and the protein expression levels of RhoA， ROCK2， and p-MYPT1 in the gastric tissue increased significantly （P<0.05）. The intervention effect of Xiangsha Liujunzi Tang group on the above indexes was dose-dependent. ConclusionXiangsha Liujunzi Tang can effectively improve the general living condition and gastric motility of rats with FD， and its specific mechanism may be related to the activation of the RhoA/ROCK2/MYPT1 pathway in the gastric tissue to regulate smooth muscle relaxation and contraction and promote gastric motility.

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ObjectiveTo investigate the effects of Yishen Daluo prescription （YSDL） on Ras homolog（Rho）/Rho-associated coiled-coil containing protein kinase（ROCK）signaling pathway in mice with experimental autoimmune encephalomyelitis （EAE） based on the silencing of β-arrestin1 gene. MethodSixty C57BL/6 female mice were randomly divided into a blank group， a model group， a virus group， a YSDL group， a virus + YSDL group， and a prednisone acetate group （hormone group）. The EAE model was induced in mice except for those in the normal group. Adeno-associated virus（AAV）solution （150 μL， 1×1011 vg·mL-1） was injected into the tail vein of each mouse in the virus group and the virus + YSDL group on the 4th day of immunization. Drugs were administered on the 8th day of modeling. Specifically， normal saline was given to the mice in the normal group，the model group，and the virus group at 10 mL∙kg-1， prednisone acetate suspension to those in the hormone group at 3.9 g∙kg-1，and YSDL to those in other groups at 20 g∙kg-1 for 14 consecutive days. The mice were weighed and scored every day. The neurological function scores of mice in each group were recorded every day after immunization. Hematoxylin-eosin （HE） staining was used to determine the inflammatory response and lesion location in the brain tissues and spinal cord tissues of mice. The protein expression of β-arrestin1，Ras homolog gene family member A（RhoA）， and Rho-associated coiled-coil forming protein kinase Ⅰ（ROCK Ⅰ） in spinal cord and brain tissues of EAE mice was determined by Western blot. ResultCompared with the model group， the virus group and the virus + YSDL group showed decreased neurological function scores （P<0.01），and the YSDL group also showed decreased neurological function scores（P<0.05）. HE results showed that there was obvious inflammatory reaction in the central nervous system （CNS） of the model group， which was alleviated to varying degrees in other groups compared with the model group. Western blot results showed that compared with the blank group， the model group showed increased protein expression levels of β-arrestin1， RhoA， and ROCK Ⅰ in the spinal cord tissues （P<0.01）. Compared with the model group， the virus group， the YSDL group， the virus + YSDL group， and the hormone group showed decreased protein expression levels of β-arrestin1， RhoA， and ROCKⅠ in the spinal cord tissues （P<0.01）. Compared with the blank group， the model group showed increased protein expression levels of β-arrestin1， RhoA， and ROCK Ⅰ in the brain tissues （P<0.01）. Compared with the model group， the virus group， the YSDL group， the virus + YSDL group， and the hormone group showed decreased protein expression level of β-arrestin1 in the brain tissues （P<0.01）， and the virus group and the YSDL group showed decreased protein expression levels of RhoA， and ROCKⅠ in the brain tissues （P<0.05）. Additionally， the virus + YSDL group and the hormone group showed decreased protein expression levels of RhoA and ROCKⅠ in the brain tissues （P<0.01）. ConclusionYSDL can improve the clinical symptoms of EAE mice and improve the inflammatory response of CNS. The mechanism is presumably attributed to the fact that YSDL inhibits the expression of β-arrestin1 in CNS，thereby reducing the expression of Rho/ROCK signaling pathway. Furthermore， YSDL may have a synergistic effect with the inhibition of β-arrestin1 gene expression.

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AIMS: Liver cirrhosis defines by regenerative nodules and fibrotic septa, causing a complication called cirrhotic cardiomyopathy (CCM) with chronotropic hypo-responsiveness. In addition to lowering cholesterol levels, statins yield antioxidant and anti-inflammatory effects. In liver diseases animal models, statins have been shown to decrease hepatic inflammation, fibrogenesis, and portal pressure (PP). Therefore, we evaluated the atorvastatin effect on the heart in cirrhotic rats. MATERIALS AND METHODS: Bile duct ligation (BDL) or sham operation performed on male Wistar rats and grouped as cirrhotic; BDL/Saline, BDL/Ator-7d(days) (Atorvastatin 15 mg/kg/day), and BDL/Ator-14d groups, or control; Sham/Saline, Sham/Ator-7d, and Sham/Ator-14d groups. Corrected QT interval (QTc interval), chronotropic responses, serum brain natriuretic peptides (BNP), heart tumor necrosis factor-α (TNF-α), nuclear factor erythroid 2-related factor 2 (Nrf2), and malondialdehyde (MDA) levels were studied along with atrial Ras homolog family member A (RhoA) and endothelial nitric oxide synthase (eNOS) gene expression. KEY FINDINGS: The chronotropic responses decreased in BDL/Saline and increased in BDL/Ator-7d group. The QTc interval, BNP, TNF-α, and MDA levels increased in BDL/Saline and decreased in BDL/Ator-14d group. The Nrf2 level did not change in BDL/Saline and increased in BDL/Ator-14d group. The liver inflammation and fibrosis increased in BDL/Saline and did not affect BDL/Ator-7d and BDL/Ator-14d groups. The RhoA expression was down-regulated in BDL/Saline, BDL/Ator-7d, and BDL/Ator-14d groups. The eNOS expression did not change in BDL/Saline and down-regulated in BDL/Ator-14d group. SIGNIFICANCE: Atorvastatin alleviates the chronotropic hypo-responsiveness and down-regulates the atrial RhoA and eNOS gene expression along with anti-inflammatory, antioxidant, and anti-stress effects in CCM.

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Ras homolog gene family member A (RhoA) is a small GTPase of the Rho family involved in regulating multiple signal transduction pathways that influence a diverse range of cellular functions. RhoA and many of its downstream effector proteins are highly expressed in the nervous system, implying an important role for RhoA signaling in neurons and glial cells. Indeed, emerging evidence points toward a role of aberrant RhoA signaling in neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis. In this review, we summarize the current knowledge of RhoA regulation and downstream cellular functions with an emphasis on the role of RhoA signaling in neurodegenerative diseases and the therapeutic potential of RhoA inhibition in neurodegeneration.

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ObjectiveTo investigate the protective effect and mechanism of Achyranthis Bidentatae Radix-Paeoniae Radix Alba on dopaminergic neurons in Parkinson's disease mouse model with the syndrome of ascendant hyperactivity of liver Yang. MethodThe C57BL/6 mice were randomly assigned into normal group， a model group， low-， medium， and high-dose （3.25， 6.5， 13 g·kg-1） Achyranthis Bidentatae Radix-Paeoniae Radix Alba groups， and a selegiline group （0.01 g·kg-1）. The mouse model of Parkinson's disease with the syndrome of ascendant hyperactivity of liver yang was established by intragastric administration of Fuzitang combined with intraperitoneal injection of 1-methyl-4-phenyl-1，2，3，6-tetrahydropyridine （MPTP）. The behavioral changes were evaluated by rotarod test and pole test. The protein levels of Ras homolog gene family member A （RhoA）， Rho-associated coiled-coil containing protein kinase 2 （ROCK2）， myosin light chain 1 （MLC1）， and α-synuclein in the substantia nigra were determined by Western blot. Real-time fluorescence quantitative PCR （Real-time PCR） was employed to determine the mRNA levels of RhoA， ROCK2， and MLC1 in the substantia nigra. Enzyme-linked immunosorbent assay （ELISA） was used to measure the levels of tumor necrosis factor-α （TNF-α） and interleukin-1β （IL-1β）. The ultrastructural changes of mouse neurons were observed under a transmission electron microscope. ResultCompared with the normal group， the modeling shortened the latency to fall， increased the average total time in the pole test （P<0.01）， and up-regulated the levels of RhoA， ROCK2， MLC1， TNF-α， α-synuclein， and IL-1β in the substantia nigra （P<0.05）. Compared with the model group， different doses of Achyranthis Bidentatae Radix-Paeoniae Radix Alba and selegiline prolonged the latency to fall， shortened the average total time in the pole test （P<0.05， P<0.01）， and down-regulated the levels of ROCK2， MLC1， α-synuclein， TNF-α， and IL-1β in a dose-dependent manner （P<0.05）. Further， the modeling decreased the number of cytoplasmic organelles and caused mitochondrial swelling and abnormal shape of endoplasmic reticulum compared with the normal group. The neurons in high-dose Achyranthis Bidentatae Radix-Paeoniae Radix Alba and selegiline groups showed intact nuclei， clear cell boundary， and normal endoplasmic reticulum shape. ConclusionThe combination of Achyranthis Bidentatae Radix and Paeoniae Radix Alba may improve the motor coordination ability of Parkinson's disease mouse model with the syndrome of ascendant hyperactivity of liver yang by inhibiting the neuroinflammation mediated by the RhoA/ROCK2 signaling pathway in the brain.

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ObjectiveTo observe the effect of icariin on the recombinant Ras homolog family member A （RhoA）/Rho-associated coiled-coil forming protein kinase （ROCK） signaling pathway in rats with Alzheimer's disease （AD）， and to explore the mechanism of icariin in ameliorating the neuronal and dendritic damage. MethodThe β-amyloid 1-42 （Aβ1-42， 2.5 g·L-1） was used to induce AD in rats via lateral ventricle injection， and the rats were divided into a model group， a low-dose icariin group （0.03 g·kg-1）， a middle-dose icariin group （0.06 g·kg-1）， a high-dose icariin group （0.09 g·kg-1）， and a control group. The control group and the model group were given an equal volume of normal saline at a dose of 10 mL·kg-1. The cognitive function of rats was assessed by the Morris water maze. The pathological morphology of the rat hippocampal CA1 area was observed by Nissl staining. Dendritic spine density and dendritic length in the CA1 region of the hippocampus were observed by Golgi-Cox staining. Real-time quantitative polymerase chain reaction （Real-time PCR） was used to detect the mRNA expression levels of tumor necrosis factor-α （TNF-α）， interleukin （IL）-1β， IL-6， RhoA， ROCK1， and ROCK2 in the hippocampus. Western blot assay was used to detect the protein expression levels of TNF-α， IL-1β， IL-6， RhoA， ROCK1， and ROCK2 in the hippocampus. ResultAs compared with the control group， the escape latency of the rats in the model group was increased （P<0.01）， while the number of crossing the platform and the dwelling time in the target quadrant were decreased （P<0.01）. As compared with the model group， the escape latency of the rats in the middle and high-dose icariin groups was decreased （P<0.05， P<0.01）， while the number of crossing the platform and the dwelling time in the target quadrant were increased （P<0.05， P<0.01）. As compared with the control group， the number of neurons， dendritic spine density， and dendritic length in the hippocampal CA1 area of the rats in the model group were decreased （P<0.01）. As compared with the model group， the number of neurons， dendritic spine density， and dendritic length in the hippocampus of the rats in the middle and high-dose icariin groups were increased （P<0.05， P<0.01）. As compared with the control group， the mRNA and protein expression levels of TNF-α， IL-1β， IL-6， RhoA， ROCK1， and ROCK2 in the hippocampus of the rats in the model group were increased （P<0.01）. As compared with the model group， the mRNA and protein expression levels of TNF-α， IL-1β， IL-6， RhoA， ROCK1， and ROCK2 in the hippocampus of the rats in the middle and high-dose icariin groups were decreased （P<0.05， P<0.01）. ConclusionIcariin improves cognitive function and neuronal and dendritic damage in AD by inhibiting the RhoA/ROCK signaling pathway.

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Cells can switch between Rac1 (lamellipodia-based) and RhoA (blebbing-based) migration modes, but the molecular mechanisms regulating this shift are not fully understood. Diacylglycerol kinase ζ (DGKζ), which phosphorylates diacylglycerol to yield phosphatidic acid, forms independent complexes with Rac1 and RhoA, selectively dissociating each from their common inhibitor RhoGDI. DGKζ catalytic activity is required for Rac1 dissociation but is dispensable for RhoA dissociation; instead, DGKζ stimulates RhoA release via a kinase-independent scaffolding mechanism. The molecular determinants that mediate the selective targeting of DGKζ to Rac1 or RhoA signaling complexes are unknown. Here, we show that protein kinase Cα (PKCα)-mediated phosphorylation of the DGKζ MARCKS domain increased DGKζ association with RhoA and decreased its interaction with Rac1. The same modification also enhanced DGKζ interaction with the scaffold protein syntrophin. Expression of a phosphomimetic DGKζ mutant stimulated membrane blebbing in mouse embryonic fibroblasts and C2C12 myoblasts, which was augmented by inhibition of endogenous Rac1. DGKζ expression in differentiated C2 myotubes, which have low endogenous Rac1 levels, also induced substantial membrane blebbing via the RhoA-ROCK pathway. These events were independent of DGKζ catalytic activity, but dependent upon a functional C-terminal PDZ-binding motif. Rescue of RhoA activity in DGKζ-null cells also required the PDZ-binding motif, suggesting that syntrophin interaction is necessary for optimal RhoA activation. Collectively, our results define a switch-like mechanism whereby DGKζ phosphorylation by PKCα plays a role in the interconversion between Rac1 and RhoA signaling pathways that underlie different cellular migration modes.

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Deleted-in-liver cancer 1 (DLC1) exerts its tumor suppressive function mainly through the Rho-GTPase-activating protein (RhoGAP) domain. When activated, the domain promotes the hydrolysis of RhoA-GTP, leading to reduced cell migration. DLC1 is kept in an inactive state by an intramolecular interaction between its RhoGAP domain and the DLC1 sterile α motif (SAM) domain. We have shown previously that this autoinhibited state of DLC1 may be alleviated by tensin-3 (TNS3) or PTEN. We show here that the TNS3/PTEN-DLC1 interactions are mediated by the C2 domains of the former and the SAM domain of the latter. Intriguingly, the DLC1 SAM domain was capable of binding to specific peptide motifs within the C2 domains. Indeed, peptides containing the binding motifs were highly effective in blocking the C2-SAM domain-domain interaction. Importantly, when fused to the tat protein-transduction sequence and subsequently introduced into cells, the C2 peptides potently promoted the RhoGAP function in DLC1, leading to decreased RhoA activation and reduced tumor cell growth in soft agar and migration in response to growth factor stimulation. To facilitate the development of the C2 peptides as potential therapeutic agents, we created a cyclic version of the TNS3 C2 domain-derived peptide and showed that this peptide readily entered the MDA-MB-231 breast cancer cells and effectively inhibited their migration. Our work shows, for the first time, that the SAM domain is a peptide-binding module and establishes the framework on which to explore DLC1 SAM domain-binding peptides as potential therapeutic agents for cancer treatment.

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Transforming growth factor-ß (TGF-ß)-induced differentiation of orbital fibroblasts into myofibroblasts is an important pathogenesis of Graves' ophthalmopathy (GO) and leads to orbital tissue fibrosis. In the present study, we explored the antifibrotic effects of simvastatin and ROCK inhibitor Y-27632 in primary cultured GO orbital fibroblasts and tried to explain the molecular mechanisms behind these effects. Both simvastatin and Y-27632 inhibited TGF-ß-induced α-smooth muscle actin (α-SMA) expression, which serves as a marker of fibrosis. The inhibitory effect of simvastatin on TGF-ß-induced RhoA, ROCK1, and α-SMA expression could be reversed by geranylgeranyl pyrophosphate, an intermediate in the biosynthesis of cholesterol. This suggested that the mechanism of simvastatin-mediated antifibrotic effects may involve RhoA/ROCK signaling. Furthermore, simvastatin and Y-27632 suppressed TGF-ß-induced phosphorylation of ERK and p38. The TGF-ß-mediated α-SMA expression was suppressed by pharmacological inhibitors of p38 and ERK. These results suggested that simvastatin inhibits TGF-ß-induced myofibroblast differentiation via suppression of the RhoA/ROCK/ERK and p38 MAPK signaling pathways. Thus, our study provides evidence that simvastatin and ROCK inhibitors may be potential therapeutic drugs for the prevention and treatment of orbital fibrosis in GO.

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GNA13, the α subunit of a heterotrimeric G protein, mediates signaling through G-protein-coupled receptors (GPCRs). GNA13 is up-regulated in many solid tumors, including prostate cancer, where it contributes to tumor initiation, drug resistance, and metastasis. To better understand how GNA13 contributes to tumorigenesis and tumor progression, we compared the entire transcriptome of PC3 prostate cancer cells with those cells in which GNA13 expression had been silenced. This analysis revealed that GNA13 levels affected multiple CXC-family chemokines. Further investigation in three different prostate cancer cell lines singled out pro-tumorigenic CXC motif chemokine ligand 5 (CXCL5) as a target of GNA13 signaling. Elevation of GNA13 levels consistently induced CXCL5 RNA and protein expression in all three cell lines. Analysis of the CXCL5 promoter revealed that the -505/+62 region was both highly active and influenced by GNA13, and a single NF-κB site within this region of the promoter was critical for GNA13-dependent promoter activity. ChIP experiments revealed that, upon induction of GNA13 expression, occupancy at the CXCL5 promoter was significantly enriched for the p65 component of NF-κB. GNA13 knockdown suppressed both p65 phosphorylation and the activity of a specific NF-κB reporter, and p65 silencing impaired the GNA13-enhanced expression of CXCL5. Finally, blockade of Rho GTPase activity eliminated the impact of GNA13 on NF-κB transcriptional activity and CXCL5 expression. Together, these findings suggest that GNA13 drives CXCL5 expression by transactivating NF-κB in a Rho-dependent manner in prostate cancer cells.

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The tight junctional pore-forming protein claudin-2 (CLDN-2) mediates paracellular Na+ and water transport in leaky epithelia and alters cancer cell proliferation. Previously, we reported that tumor necrosis factor-α time-dependently alters CLDN-2 expression in tubular epithelial cells. Here, we found a similar expression pattern in a mouse kidney injury model (unilateral ureteral obstruction), consisting of an initial increase followed by a drop in CLDN-2 protein expression. CLDN-2 silencing in LLC-PK1 tubular cells induced activation and phosphorylation of guanine nucleotide exchange factor H1 (GEF-H1), leading to Ras homolog family member A (RHOA) activation. Silencing of other claudins had no such effects, and re-expression of an siRNA-resistant CLDN-2 prevented RHOA activation, indicating specific effects of CLDN-2 on RHOA. Moreover, kidneys from CLDN-2 knockout mice had elevated levels of active RHOA. Of note, CLDN-2 silencing reduced LLC-PK1 cell proliferation and elevated expression of cyclin-dependent kinase inhibitor P27 (P27KIP1) in a GEF-H1/RHOA-dependent manner. P27KIP1 silencing abrogated the effects of CLDN-2 depletion on proliferation. CLDN-2 loss also activated myocardin-related transcription factor (MRTF), a fibrogenic RHOA effector, and elevated expression of connective tissue growth factor and smooth muscle actin. Finally, CLDN-2 down-regulation contributed to RHOA activation and smooth muscle actin expression induced by prolonged tumor necrosis factor-α treatment, because they were mitigated by re-expression of CLDN-2. Our results indicate that CLDN-2 suppresses GEF-H1/RHOA. CLDN-2 down-regulation, for example, by inflammation, can reduce proliferation and promote MRTF activation through RHOA. These findings suggest that the initial CLDN-2 elevation might aid epithelial regeneration, and CLDN-2 loss could contribute to fibrotic reprogramming.

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Objective: To investigate the correlation between Ras homolog gene family member A (RhoA) gene in Wnt/PCP signaling pathway and acute exacerbation chronic obstructive pulmonary disease (AECOPD) traditional Chinese medicine(TCM)syndrome, attempting to provide an objective standard for the diagnosis of AECOPD TCM syndrome. Method: The 100 AECOPD patients were collected and divided into 5 groups:phlegm turbid obstructing lung syndrome,, phlegm-heat obstructing lung syndrome, syndrome of orifices confused by phlegm, deficiency of pulmonary and renal Qi, and edema due to yang deficiency, with 20 people in each group. 15 normal people were selected as a normal control group. All patients received fasting hemospasia, using a kit to extract blood total RibonucleicA(RNA) according to instructions. Real-time quantitative polymerase chain reaction (Real-time PCR) was adopted to detect the mRNA expression of RhoA gene in blood of patients with AECOPD TCM syndrome, and to explore the correlation. Result: There was no difference between phlegm-heat obstructing lung syndrome group and syndrome of orifices confused by phlegm group. The mRNA expression of RhoA gene in phlegm turbid obstructing lung syndrome group, phlegm-heat obstructing lung syndrome group, syndrome of orifices confused by phlegm group, deficiency of pulmonary and renal Qi group, and edema due to Yang deficiency group were significantly higher than that in normal group (PConclusion: The significant difference in mRNA relative expression of RhoA gene in Wnt/PCP signaling pathway among the five AECOPD TCM syndrome groups may provide some objective diagnostic criteria for AECOPD TCM syndromes and reveal their disease severity.

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The GTPase RhoA is a major player in many different regulatory pathways. RhoA catalyzes GTP hydrolysis, and its catalysis is accelerated when RhoA forms heterodimers with proteins of the guanine nucleotide exchange factor (GEF) family. Neuroepithelial cell transforming gene 1 (Net1) is a RhoA-interacting GEF implicated in cancer, but the structural features supporting the RhoA/Net1 interaction are unknown. Taking advantage of a simple production and purification process, here we solved the structure of a RhoA/Net1 heterodimer with X-ray crystallography at 2-Å resolution. Using a panel of several techniques, including molecular dynamics simulations, we characterized the RhoA/Net1 interface. Moreover, deploying an extremely simple peptide-based scanning approach, we found that short peptides (penta- to nonapeptides) derived from the protein/protein interaction region of RhoA could disrupt the RhoA/Net1 interaction and thereby diminish the rate of nucleotide exchange. The most inhibitory peptide, EVKHF, spanning residues 102-106 in the RhoA sequence, displayed an IC50 of ∼100 µm without further modifications. The peptides identified here could be useful in further investigations of the RhoA/Net1 interaction region. We propose that our structural and functional insights might inform chemical approaches for transforming the pentapeptide into an optimized pseudopeptide that antagonizes Net1-mediated RhoA activation with therapeutic anticancer potential.

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Phospholipase C (PLC) enzymes hydrolyze membrane phosphatidylinositol 4,5 bisphosphate (PIP2) and regulate Ca2+ and protein kinase signaling in virtually all mammalian cell types. Chronic activation of the PLCϵ isoform downstream of G protein-coupled receptors (GPCRs) contributes to the development of cardiac hypertrophy. We have previously shown that PLCϵ-catalyzed hydrolysis of Golgi-associated phosphatidylinositol 4-phosphate (PI4P) in cardiac myocytes depends on G protein ßγ subunits released upon stimulation with endothelin-1. PLCϵ binds and is directly activated by Ras family small GTPases, but whether they directly interact with Gßγ has not been demonstrated. To identify PLCϵ domains that interact with Gßγ, here we designed various single substitutions and truncations of WT PLCϵ and tested them for activation by Gßγ in transfected COS-7 cells. Deletion of only a single domain in PLCϵ was not sufficient to completely block its activation by Gßγ, but blocked activation by Ras. Simultaneous deletion of the C-terminal RA2 domain and the N-terminal CDC25 and cysteine-rich domains completely abrogated PLCϵ activation by Gßγ, but activation by the GTPase Rho was retained. In vitro reconstitution experiments further revealed that purified Gßγ directly interacts with a purified fragment of PLCϵ (PLCϵ-PH-RA2) and increases PIP2 hydrolysis. Deletion of the RA2 domain decreased Gßγ binding and eliminated Gßγ stimulation of PIP2 hydrolysis. These results provide first evidence that Gßγ directly interacts with PLCϵ and yield insights into the mechanism by which ßγ subunits activate PLCϵ.

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Aberrant activation of Rho GTPase Rac1 has been observed in various tumor types, including pancreatic cancer. Rac1 activates multiple signaling pathways that lead to uncontrolled proliferation, invasion and metastasis. Thus, inhibition of Rac1 activity is a viable therapeutic strategy for proliferative disorders such as cancer. Here we identified small molecule inhibitors that target the nucleotide-binding site of Rac1 through in silico screening. Follow up in vitro studies demonstrated that two compounds blocked active Rac1 from binding to its effector PAK1. Fluorescence polarization studies indicate that these compounds target the nucleotide-binding site of Rac1. In cells, both compounds blocked Rac1 binding to its effector PAK1 following EGF-induced Rac1 activation in a dose-dependent manner, while showing no inhibition of the closely related Cdc42 and RhoA activity. Furthermore, functional studies indicate that both compounds reduced cell proliferation and migration in a dose-dependent manner in multiple pancreatic cancer cell lines. Additionally, the two compounds suppressed the clonogenic survival of pancreatic cancer cells, while they had no effect on the survival of normal pancreatic ductal cells. These compounds do not share the core structure of the known Rac1 inhibitors and could serve as additional lead compounds to target pancreatic cancers with high Rac1 activity.

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Sphingosine-1-phosphate (S1P), a bioactive lysophospholipid, is generated and released at sites of tissue injury in the heart and can act on S1P1, S1P2, and S1P3 receptor subtypes to affect cardiovascular responses. We established that S1P causes little phosphoinositide hydrolysis and does not induce hypertrophy indicating that it does not cause receptor coupling to Gq. We previously demonstrated that S1P confers cardioprotection against ischemia/reperfusion by activating RhoA and its downstream effector PKD. The S1P receptor subtypes and G proteins that regulate RhoA activation and downstream responses in the heart have not been determined. Using siRNA or pertussis toxin to inhibit different G proteins in NRVMs we established that S1P regulates RhoA activation through Gα13 but not Gα12, Gαq, or Gαi. Knockdown of the three major S1P receptors using siRNA demonstrated a requirement for S1P3 in RhoA activation and subsequent phosphorylation of PKD, and this was confirmed in studies using isolated hearts from S1P3 knockout (KO) mice. S1P treatment reduced infarct size induced by ischemia/reperfusion in Langendorff perfused wild-type (WT) hearts and this protection was abolished in the S1P3 KO mouse heart. CYM-51736, an S1P3-specific agonist, also decreased infarct size after ischemia/reperfusion to a degree similar to that achieved by S1P. The finding that S1P3 receptor- and Gα13-mediated RhoA activation is responsible for protection against ischemia/reperfusion suggests that selective targeting of S1P3 receptors could provide therapeutic benefits in ischemic heart disease.

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Establishment of a proper balance of excitatory and inhibitory connectivity is achieved during development of cortical networks and adjusted through synaptic plasticity. The neural cell adhesion molecule (NCAM) and the receptor tyrosine kinase EphA3 regulate the perisomatic synapse density of inhibitory GABAergic interneurons in the mouse frontal cortex through ephrin-A5-induced growth cone collapse. In this study, it was demonstrated that binding of NCAM and EphA3 occurred between the NCAM Ig2 domain and EphA3 cysteine-rich domain (CRD). The binding interface was further refined through molecular modeling and mutagenesis and shown to be comprised of complementary charged residues in the NCAM Ig2 domain (Arg-156 and Lys-162) and the EphA3 CRD (Glu-248 and Glu-264). Ephrin-A5 induced co-clustering of surface-bound NCAM and EphA3 in GABAergic cortical interneurons in culture. Receptor clustering was impaired by a charge reversal mutation that disrupted NCAM/EphA3 association, emphasizing the importance of the NCAM/EphA3 binding interface for cluster formation. NCAM enhanced ephrin-A5-induced EphA3 autophosphorylation and activation of RhoA GTPase, indicating a role for NCAM in activating EphA3 signaling through clustering. NCAM-mediated clustering of EphA3 was essential for ephrin-A5-induced growth cone collapse in cortical GABAergic interneurons, and RhoA and a principal effector, Rho-associated protein kinase, mediated the collapse response. This study delineates a mechanism in which NCAM promotes ephrin-A5-dependent clustering of EphA3 through interaction of the NCAM Ig2 domain and the EphA3 CRD, stimulating EphA3 autophosphorylation and RhoA signaling necessary for growth cone repulsion in GABAergic interneurons in vitro, which may extend to remodeling of axonal terminals of interneurons in vivo.

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