Molecular Mechanism of Rap1A‐Dependent Activation of PLCɛ

Abstract

Phospholipase C (PLC) enzymes hydrolyze phosphatidylinositol lipids to produce diacylglycerol (DAG) and inositol phosphates, to activate protein kinase C (PKC) and downstream signaling pathways, including cell growth and survival. The PLCɛ subfamily has emerged as a key player in cardiovascular health, where it is required for maximum contractility. However, prolonged activation of PLCɛ results in cardiac hypertrophy and heart failure through its ability to regulate hypertrophic gene expression. 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. However, the molecular mechanism of this process is not known. 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 opens the door to the development of new therapeutic strategies for treating cardiac hypertrophy.Support or Funding InformationAmerican Heart Association Scientist Development Grant (16SDG29920017) to A.M.L.; Purdue Center for Cancer ResearchThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Structural Insights into Phospholipase Cɛ Function

“…Stereochemical correctness of the structure was analyzed using Molprobity 89 . 79,80 . This data suggests the EF1/2 hands are not required for thermostability and may not stably associate with the core of the enzyme.…”

“…Chem.) 80 . We are currently validating the interfaces using site-directed mutagenesis to determine if some or all of the residues are important for the interactions between the RA1 domain and the EF3/4 hands and the C2 domain.…”