RhoGEF Trio Regulates Radial Migration of Projection Neurons via Its Distinct Domains / 神经科学通报·英文版

The radial migration of cortical pyramidal neurons (PNs) during corticogenesis is necessary for establishing a multilayered cerebral cortex. Neuronal migration defects are considered a critical etiology of neurodevelopmental disorders, including autism spectrum disorders (ASDs), schizophrenia, epilepsy, and intellectual disability (ID). TRIO is a high-risk candidate gene for ASDs and ID. However, its role in embryonic radial migration and the etiology of ASDs and ID are not fully understood. In this study, we found that the in vivo conditional knockout or in utero knockout of Trio in excitatory precursors in the neocortex caused aberrant polarity and halted the migration of late-born PNs. Further investigation of the underlying mechanism revealed that the interaction of the Trio N-terminal SH3 domain with Myosin X mediated the adherence of migrating neurons to radial glial fibers through regulating the membrane location of neuronal cadherin (N-cadherin). Also, independent or synergistic overexpression of RAC1 and RHOA showed different phenotypic recoveries of the abnormal neuronal migration by affecting the morphological transition and/or the glial fiber-dependent locomotion. Taken together, our findings clarify a novel mechanism of Trio in regulating N-cadherin cell surface expression via the interaction of Myosin X with its N-terminal SH3 domain. These results suggest the vital roles of the guanine nucleotide exchange factor 1 (GEF1) and GEF2 domains in regulating radial migration by activating their Rho GTPase effectors in both distinct and cooperative manners, which might be associated with the abnormal phenotypes in neurodevelopmental disorders.

Study on mechanism of IL-1β mediating vascular calcium desensitization in septic rats through down-regulating Rho kinase activity / 重庆医学

Objective To investigate the mechanism of interleukin-1β(IL-1β) mediating the vascular calcium desensitization of septic rats by down-regulating Rho kinase activity.Methods Thirty-two SD rats were randomly divided into the sham operation group,cecal ligation and puncture (CLP) 3 h group,CLP 6 h group and CLP 12 h group,8 cases in each group.The septic rat was duplicated by CLP.Then the plasma IL-1β level and calcium sensitivity of superior mesenteric arteries (SMAs) were detected at different time points.Their correlation was analyzed.VSMCc derived from SMAs were cultured and incubated with different concentrations of human recombinant IL-1β for 24 h.Then the influences of IL-1β on the MLC20 phosphorylation level,Rho kinase activity,G protein expression level and RhoGEF activity were observed.Results The calcium sensitivity of SMAs after CLP 3 h began to decrease(P＜0.05),while plasma IL-1β level began to increase after CLP 6 h (P＜0.05),the change trend of SMAs calcium sensitivity was negatively correlated with plasma IL-1β level change(P＜0.05).IL-1β could decrease the phosphorylation level of VSMCs myosin light chain(MLC20) and Rho kinase activity(P＜0.05),up-regulate Gα11 expression and down-regulate Gα12 expression,but had no obvious effect on Gαq and Gα13 expression(P＞0.05).IL-1β could significantly reduce RhoGEF and PDZ-RhoGEF activity(P＜0.05) but significantly increase p63 Rho GEF activity(P＜0.05).Conclusion IL-1β induces the decrease of PDZ-RhoGEF and Rho kinase activity by down-regulating Gα12 expression,causes the decrease of MLC20 phosphorylation level,thus mediates the occurrence of calcium desensitization in septic rat;in addition,IL-1β may cause the increase of p63 RhoGEF activity by upregulating Gα11 expression,thus mediates the increase of vascular calcium sensitivity in septic rats,but the total effect is the decrease of calcium sensitivity.

Study on mechanism of IL-1β mediating vascular calcium desensitization in septic rats through down-regulating Rho kinase activity / 重庆医学

Objective To investigate the mechanism of interleukin-1β(IL-1β) mediating the vascular calcium desensitization of septic rats by down-regulating Rho kinase activity.Methods Thirty-two SD rats were randomly divided into the sham operation group,cecal ligation and puncture (CLP) 3 h group,CLP 6 h group and CLP 12 h group,8 cases in each group.The septic rat was duplicated by CLP.Then the plasma IL-1β level and calcium sensitivity of superior mesenteric arteries (SMAs) were detected at different time points.Their correlation was analyzed.VSMCc derived from SMAs were cultured and incubated with different concentrations of human recombinant IL-1β for 24 h.Then the influences of IL-1β on the MLC20 phosphorylation level,Rho kinase activity,G protein expression level and RhoGEF activity were observed.Results The calcium sensitivity of SMAs after CLP 3 h began to decrease(P＜0.05),while plasma IL-1β level began to increase after CLP 6 h (P＜0.05),the change trend of SMAs calcium sensitivity was negatively correlated with plasma IL-1β level change(P＜0.05).IL-1β could decrease the phosphorylation level of VSMCs myosin light chain(MLC20) and Rho kinase activity(P＜0.05),up-regulate Gα11 expression and down-regulate Gα12 expression,but had no obvious effect on Gαq and Gα13 expression(P＞0.05).IL-1β could significantly reduce RhoGEF and PDZ-RhoGEF activity(P＜0.05) but significantly increase p63 Rho GEF activity(P＜0.05).Conclusion IL-1β induces the decrease of PDZ-RhoGEF and Rho kinase activity by down-regulating Gα12 expression,causes the decrease of MLC20 phosphorylation level,thus mediates the occurrence of calcium desensitization in septic rat;in addition,IL-1β may cause the increase of p63 RhoGEF activity by upregulating Gα11 expression,thus mediates the increase of vascular calcium sensitivity in septic rats,but the total effect is the decrease of calcium sensitivity.

Increased p190RhoGEF expression in activated B cells correlates with the induction of the plasma cell differentiation

Previously, we demonstrated that the p190 Rho guanine nucleotide exchange factor (p190RhoGEF) was induced following CD40 stimulation of B cells. In this study, we examined whether p190RhoGEF and a downstream effector molecule RhoA are required for B cell differentiation. Expression of p190RhoGEF positively correlated with the expression of surface markers and transcriptional regulators that are characteristic of mature B cells with plasma cell (PC) phenotypes. Moreover, either the overexpression of p190RhoGEF or the expression of a constitutively active RhoA drove cellular differentiation toward PC phenotypes. B cell maturation was abrogated in cells that overexpressed p190RhoGEF and a dominant-negative form of RhoA simultaneously. CD40-mediated maturation events were also abrogated in cells that overexpressed either dominant-negative p190RhoGEF or RhoA. Together, these data provide evidence that p190RhoGEF signaling through RhoA in CD40-activated B cells drives the induction of the PC differentiation.