Molecular Mechanism of Rap1A‐Dependent Activation of PLCɛ

Abstract

Phospholipase C (PLC) enzymes hydrolyze phosphatidylinositol lipids to produce diacylglycerol (DAG) and inositol phosphates, leading to the activation of protein kinase C (PKC) and downstream signaling pathways, including cell growth and survival. The PLCɛ subfamily is a key player in cardiovascular function, where it contributes to maximum contractility. However, prolonged activation of PLCɛ results in cardiac hypertrophy and heart failure through its ability to regulate the expression of hypertrophic genes. This process is regulated by the small GTPase Rap1A, which is activated downstream of β‐adrenergic receptors. Rap1A binds to the C‐terminal Ras association (RA) domain of PLCɛ, simultaneously translocating the complex to the perinuclear region and activating PLCɛ. PLCɛ also contains an N‐terminal CDC25 domain, which has guanine nucleotide exchange factor (GEF) activity for Rap1A resulting in a feed forward activation loop and sustained lipid hydrolysis. However, the molecular mechanism of this process is not known. In this work, we seek to characterize the interactions between Rap1A and PLCɛ using structural and functional studies to map the Rap1A binding site on PLCɛ and determine whether activation results in conformational changes that release autoinhibition and/or increase membrane association. These studies provide the first molecular details of the Rap1A‐dependent activation of PLCɛ and open the door to the development of new therapeutic strategies for treating cardiac hypertrophy.Support or Funding InformationThis research is supported by the American Heart Association Predoctoral Fellowship 18PRE33990057 to M.S., American Heart Association Grant Scientist Development Grant 16SDG29920017 to A.M.L. and the NIH NLHBI 1R01HL 141076‐01 to A.M.L. SAXS data was collected and analyzed with the assistance of S. Chakravarthy at Argonne National Laboratory.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.