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Sci. Signal., 17 December 2013
Vol. 6, Issue 306, p. ra108
[DOI: 10.1126/scisignal.2004405]

RESEARCH ARTICLES

PLC{varepsilon}, PKD1, and SSH1L Transduce RhoA Signaling to Protect Mitochondria from Oxidative Stress in the Heart

Sunny Y. Xiang1, Kunfu Ouyang2, Bryan S. Yung1, Shigeki Miyamoto1, Alan V. Smrcka3, Ju Chen2, and Joan Heller Brown1*

1 Department of Pharmacology, University of California, San Diego, San Diego, CA 92093, USA.
2 Department of Medicine, University of California, San Diego, San Diego, CA 92093, USA.
3 School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA.

Abstract: 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 C{varepsilon} (PLC{varepsilon}) to increase the phosphorylation and activation of protein kinase D1 (PKD1). Genetic deletion of either PKD1 or its upstream regulator PLC{varepsilon} 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 PLC{varepsilon} 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.

* Corresponding author. E-mail: jhbrown{at}ucsd.edu

Citation: S. Y. Xiang, K. Ouyang, B. S. Yung, S. Miyamoto, A. V. Smrcka, J. Chen, J. H. Brown, PLC{varepsilon}, PKD1, and SSH1L Transduce RhoA Signaling to Protect Mitochondria from Oxidative Stress in the Heart. Sci. Signal. 6, ra108 (2013).

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