1Department of Pharmacology, University of California, San Diego, San Diego, CA 92093, USA.
Sci Signal. 2013 Dec 17;6(306):ra108. doi: 10.1126/scisignal.2004405.
Activation of the small guanosine triphosphatase RhoA can promote cell survival in cultured cardiomyocytes and in the heart. We showed that the circulating lysophospholipid sphingosine 1-phosphate (S1P), a G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor (GPCR) agonist, signaled through RhoA and phospholipase Cε (PLCε) to increase the phosphorylation and activation of protein kinase D1 (PKD1). Genetic deletion of either PKD1 or its upstream regulator PLCε inhibited S1P-mediated cardioprotection against ischemia/reperfusion injury. Cardioprotection involved PKD1-mediated phosphorylation and inhibition of the cofilin phosphatase Slingshot 1L (SSH1L). Cofilin 2 translocates to mitochondria in response to oxidative stress or ischemia/reperfusion injury, and both S1P pretreatment and SSH1L knockdown attenuated translocation of cofilin 2 to mitochondria. Cofilin 2 associates with the proapoptotic protein Bax, and the mitochondrial translocation of Bax in response to oxidative stress was also attenuated by S1P treatment in isolated hearts or by knockdown of SSH1L or cofilin 2 in cardiomyocytes. Furthermore, SSH1L knockdown, like S1P treatment, increased cardiomyocyte survival and preserved mitochondrial integrity after oxidative stress. These findings reveal a pathway initiated by GPCR agonist-induced RhoA activation, in which PLCε signals to PKD1-mediated phosphorylation of cytoskeletal proteins to prevent the mitochondrial translocation and proapoptotic function of cofilin 2 and Bax and thereby promote cell survival.
小分子鸟苷三磷酸酶 RhoA 的激活可以促进培养的心肌细胞和心脏中的细胞存活。我们表明，循环溶血磷脂鞘氨醇 1-磷酸（S1P），一种 G 蛋白（异三聚体鸟苷酸结合蛋白）偶联受体（GPCR）激动剂，通过 RhoA 和磷脂酶 Cε（PLCε）信号转导，增加蛋白激酶 D1（PKD1）的磷酸化和激活。PKD1 或其上游调节因子 PLCε 的基因缺失抑制了 S1P 介导的对缺血/再灌注损伤的心脏保护作用。心脏保护作用涉及 PKD1 介导的丝氨酸苏氨酸激酶 Slingshot 1L（SSH1L）磷酸化和抑制。在氧化应激或缺血/再灌注损伤时，肌动蛋白丝切割蛋白 cofilin 2 易位到线粒体，S1P 预处理和 SSH1L 敲低均减弱了 cofilin 2 向线粒体的易位。Cofilin 2 与促凋亡蛋白 Bax 结合，氧化应激时 Bax 向线粒体的易位也被 S1P 处理、SSH1L 或 cofilin 2 的敲低在分离的心脏或心肌细胞中减弱。此外，SSH1L 敲低，如 S1P 处理，增加了氧化应激后心肌细胞的存活并维持了线粒体的完整性。这些发现揭示了一种由 GPCR 激动剂诱导的 RhoA 激活引发的途径，其中 PLCε 信号转导至 PKD1 介导的细胞骨架蛋白磷酸化，以防止肌动蛋白丝切割蛋白 cofilin 2 和 Bax 的线粒体易位和促凋亡功能，从而促进细胞存活。
