RhoA induces mitophagy through PINK1 stabilization to confer cardioprotection

Abstract

An established feature of cardiac disease involves an increasing presence of dysfunctional mitochondria in the heart. Mitophagy is a key player in maintaining mitochondrial quality and thereby regulates cellular homeostasis. For instance, inhibition of mitophagy has been shown to exacerbate cardiac injury induced by oxidative stress. RhoA is a small G‐protein that serves as a proximal downstream effector of numerous GPCRs and is also responsive to oxidative stress. Activation of RhoA has been previously shown to protect the heart against stress; however, its specific role in mitophagy has not been determined. Here, we explored the possibility that RhoA signaling regulates mitophagy and in turn, provides cardioprotection. Adenoviral overexpression of RhoA in neonatal rat ventricular myocytes increased both endogenous and exogenous PINK1 levels as well as mitochondrial Parkin levels, leading to mitophagy assessed by EM analysis. Although RhoA expression did not affect PINK1 mRNA levels, it did inhibit PINK1 protein degradation, thus stabilizing PINK1 protein. Depolarization of the mitochondrial membrane potential is well established to stabilize PINK1 at the mitochondria. Interestingly, however, RhoA expression did not change the mitochondrial membrane potential. Thus the basis for PINK1 accumulation at mitochondria in response to RhoA appears to be unique. siRNA‐mediated knockdown and pharmacological inhibition of PKD, an established downstream effector of RhoA, reversed RhoA‐induced stabilization of PINK1. However, overexpression of PKD alone was not sufficient to stabilize PINK1. Active RhoA accumulates at mitochondria and this response is completely inhibited by PKD inhibition, suggesting a potential role of PKD dependent mitochondrial RhoA distribution in regulating PINK1 stability. While extrapolating the role of RhoA signaling in cardiac disease, myocardial infarction induced by ligation of the left anterior descending artery was reduced in adult mice expressing constitutively active RhoA through cardiac‐specific MLC2v promoter driven adeno‐associated virus serotype 9 when compared to that of wild‐type (WT) mice. Furthermore, although both WT and cardiac specific RhoA knockout (KO) mice around 18 weeks old revealed no overt signs of cardiac dysfunction, at around 45 weeks old, KO mice not only showed hypertrophy and fibrosis, but also revealed contractile dysfunction. Currently, we are investigating the specific contribution of RhoA‐induced mitophagy in these cardiac disease models. Taken together, our results suggest that RhoA stabilizes PINK1 through its PKD‐mediated translocation to the mitochondria, subsequently inducing mitophagy in a manner uniquely independent of the conventional pathway and thus, could confer cardioprotection against stresses. Support or Funding Information This work was supported by American Heart Association grant 19TPA34910011 to S. Miyamoto.

Prompt Graft Cooling Enhances Cardioprotection during Heart Transplantation Procedures through the Regulation of Mitophagy

“…Our data represent the first time that appropriate mitophagy has been linked with a beneficial adaptive response to protect against I/R injury during heart transplantation. Our data further demonstrate that heart grafts tolerated ischemic injury by using a mitophagy stimulator (rapamycin), which is consistent with other reports indicating that mitophagy is a key player in maintaining mitochondrial quality and, thus, conferring cardioprotection against stress [ 27 ]. Mitophagy has, therefore, emerged as a promising therapeutic target that may be essential in determining when and how heart transplantation patients are protected from I/R injury.…”