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Rho Proteins (rho + protein)
Selected AbstractsStatin-induced apoptosis linked with membrane farnesylated Ras small G protein depletion, rather than geranylated Rho proteinJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2005Sumio Matzno Rhabdomyolysis is a severe adverse effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins). This myopathy is strongly enhanced by the combination with statins and fibrates, another hypolipidaemic agent. We have evaluated the initial step of statin-induced apoptosis by the detection of membrane flip-flop using flow cytometric analysis. L6 rat myoblasts were treated with various statins (atorvastatin (3 ,m), cerivastatin (3 ,m), fluvastatin (3 ,m), pravastatin (3 mm), or simvastatin (3 ,m)) for 2, 4 or 6 h followed by reacting with FITC-conjugated annexin V for the detection of initial apoptosis signal (flip-flop). Various statin-treated myoblasts were significantly stained with FITC-annexin V at 6 h, whereas they were not detected at 2 h. Moreover, immunoblot analysis indicated that when the cells were treated with cerivastatin (3 ,m), membrane-associated Ras protein was activated and detached until 6 h, resulting in cell death through the consequent activation of caspase-8. On the other hand, since cytosolic Ras activation did not activate, there is still an unknown mechanism in statin-related Ras depletion. In conclusion, statin-induced apoptosis in muscular tissue was directly initiated by the farnesyl-anchored Ras protein depletion from cell membrane with subsequent apoptosis. [source] Sphingosine 1-phosphate induces cell contraction via calcium-independent/Rho-dependent pathways in undifferentiated skeletal muscle cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2004L. Formigli We have previously shown that sphingosine 1-phosphate (S1P) can induce intracellular Ca2+ mobilization and cell contraction in C2C12 myoblasts and that the two phenomena are temporally unrelated. Although Ca2+ -independent mechanisms of cell contraction have been the focus of numerous studies on Ca2+ sensitization of smooth muscle, comparatively less studies have focused on the role that these mechanisms play in the regulation of skeletal muscle contractility. Phosphorylation and activation of myosin by Rho-dependent kinase mediate most of Ca2+ -independent contractile responses. In the present study, we examined the potential role of Rho/Rho-kinase cascade activation in S1P-induced C2C12 cell contraction. First, we showed that depletion of Ca2+, by pre-treatment with BAPTA, did not affect S1P-induced myoblastic contractility, whereas it abolished S1P-induced Ca2+ transients. These results correlated with the absence of troponin C and with the immature cytoskeletal organization of these cells. Experimental evidence demonstrating the involvement of Rho pathway in S1P-stimulated myoblast contraction included: the activation/translocation of RhoA to the membrane in response to agonist-stimulation in cells depleted of Ca2+ and the inhibition of dynamic changes of the actin cytoskeleton in cells where Rho functions had been inhibited either by overexpression of RhoGDI, a physiological inhibitor of GDP dissociation from Rho proteins, or by pretreatment with Y-27632, a specific Rho kinase inhibitor. Contribution of protein kinase C in this cytoskeletal rearrangement was also evaluated. However, the pretreatment with Gö6976 or rottlerin, specific inhibitors of PKC, and PKC,, respectively, failed to inhibit the agonist-induced myoblastic contraction. Single particle tracking of G-actin fluorescent probe was performed to statistically evaluate actin cytoskeletal dynamics in response to S1P. Stimulation with S1P was also able to increase the phosphorylation level of myosin light chain II. In conclusion, our results strongly suggest that Ca2+ -independent/Rho-Rho kinase-dependent pathways may exert an important role in S1P-induced myoblastic cell contraction. J. Cell. Physiol. 198: 1,11, 2004© 2003 Wiley-Liss, Inc. [source] Statins enhance toll-like receptor 4-mediated cytokine gene expression in astrocytes: Implication of Rho proteins in negative feedback regulationJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2008Gregory W. Konat Abstract Toll-like receptors (TLRs) are sentinels of innate immunity that recognize pathogenic molecules and trigger inflammatory response. Because inflammatory mediators are detrimental to the host, the TLR response is regulated by feedback inhibition. Statins, the inhibitors of isoprenoid biosynthesis, have been shown to be potent modulators of TLR activity, and this modulation may provide insight regarding mechanisms of the feedback inhibition. In the present study, we examined feedback mechanisms that regulate TLR4 activity in astrocytes using statins to perturb postligational signaling. Astrocytic cultures established from newborn rat brains were exposed to lipopolysaccharide (LPS), the ligand for TLR4. The up-regulation of expression of genes encoding interleukin (IL)-1,, IL-6, and tumor necrosis factor-, (TNF,) was determined by real-time RT-PCR. Pretreatment of the cells with either atorvastatin or simvastatin enhanced the LPS-induced up-regulation of cytokine gene expression. The most profound enhancement of approximately 17-fold was observed for the Il-6 gene. The enhancements for the Tnfa and Il-1b genes were approximately 5- and 3.5-fold, respectively. Mevalonate fully reversed the effects of statins, indicating that these drugs act through the inhibition of isoprenoid synthesis. The inhibition of protein geranylgeranylation, but not protein farnesylation, mimicked the effects of statins, strongly indicating that the enhancement is mediated by the Rho proteins. In support of this notion, pretreatment of cells with toxin B, a specific inhibitor of the Rho proteins, also enhanced LPS-triggered up-regulation of the cytokine genes. These results indicate that the Rho proteins are involved in the activation of negative feedback inhibition of TLR4 signaling in astrocytes. © 2007 Wiley-Liss, Inc. [source] | ||||||||||