title: Transglutaminase-dependent RhoA activation and depletion by serotonin in vascular smooth muscle cells.
abstract: The small G protein RhoA plays a major role in several vascular processes and cardiovascular disorders. Here we analyze the mechanisms of RhoA regulation by serotonin (5-HT) in arterial smooth muscle. 5-HT (0.1-10 microM) induced activation of RhoA followed by RhoA depletion at 24-72 h. Inhibition of 5-HT1 receptors reduced the early phase of RhoA activation but had no effect on 5-HT-induced delayed RhoA activation and depletion, which were suppressed by the 5-HT transporter inhibitor fluoxetine and the transglutaminase inhibitor monodansylcadaverin and in type 2 transglutaminase-deficient smooth muscle cells. Coimmunoprecipitations demonstrated that 5-HT associated with RhoA both in vitro and in vivo. This association was calcium-dependent and inhibited by fluoxetine and monodansylcadaverin. 5-HT promotes the association of RhoA with the E3 ubiquitin ligase Smurf1, and 5-HT-induced RhoA depletion was inhibited by the proteasome inhibitor MG132 and the RhoA inhibitor Tat-C3. Simvastatin, the Rho kinase inhibitor Y-27632, small interfering RNA-mediated RhoA gene silencing, and long-term 5-HT stimulation induced Akt activation. In contrast, inhibition of 5-HT-mediated RhoA degradation by MG132 prevented 5-HT-induced Akt activation. Long-term 5-HT stimulation also led to the inhibition of the RhoA/Rho kinase component of arterial contraction. Our data provide evidence that 5-HT, internalized through the 5-HT transporter, is transamidated to RhoA by transglutaminase. Transamidation of RhoA leads to RhoA activation and enhanced proteasomal degradation, which in turn is responsible for Akt activation and contraction inhibition. The observation of transamidation of 5-HT to RhoA in pulmonary artery of hypoxic rats suggests that this process could participate in pulmonary artery remodeling and hypertension.
authors.affiliation: INSERM U533 Institut du Thorax, Université de Nantes, 44322 Nantes cedex 3, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Guilluy
authors.forename: Malvyne
authors.initials: M
authors.lastname: Rolli-Derkinderen
authors.forename: Pierre-Louis
authors.initials: PL
authors.lastname: Tharaux
authors.forename: Gerry
authors.initials: G
authors.lastname: Melino
authors.forename: Pierre
authors.initials: P
authors.lastname: Pacaud
authors.forename: Gervaise
authors.initials: G
authors.lastname: Loirand
mesh_terms: D000818:Animals; D001011:Aorta; D015687:Cell Hypoxia; D017931:DNA Primers; D004789:Enzyme Activation; D006973:Hypertension / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D011651:Pulmonary Artery / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D011503:Transglutaminases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D034741:RNA, Small Interfering; D012701:Serotonin; D011503:Transglutaminases; D020742:rhoA GTP-Binding Protein