RhoA Allosterically Activates Phospholipase Cε via its EF Hands

Abstract

Phospholipase C{varepsilon} (PLC{varepsilon}) cleaves phosphatidylinositol lipids to increase intracellular Ca2+ and activate protein kinase C (PKC) in response to stimulation of cell surface receptors. PLC{varepsilon} is activated via direct binding of small GTPases at the cytoplasmic leaflets of cellular membranes. In the cardiovascular system, the RhoA GTPase regulates PLC{varepsilon} to initiate a pathway that protects against ischemia/reperfusion injuries, but the underlying molecular mechanism is not known. We present here the cryo-electron microscopy (cryo-EM) reconstruction of RhoA bound to PLC{varepsilon}, showing that the G protein binds a unique insertion within the PLC{varepsilon} EF hands. Deletion of or mutations to this PLC{varepsilon} insertion decrease RhoA-dependent activation without impacting regulation by other G proteins. Together, our data support a model wherein RhoA binding to PLC{varepsilon} allosterically activates the lipase and increases its interactions with the membrane, resulting in maximum activity and cardiomyocyte survival.