Novel crystal structure of calcium independent phospholipase iPLA2β: mechanism of activity regulation and membrane localization

Abstract

Calcium-independent phospholipase iPLA2β (also known as PLA2G6 or PNPLA9) is a signaling enzyme which hydrolyzes phospholipids to generate potent lipid second messengers in response to stress or injury. The enzyme is a product of the PARK14 gene with strong genetic link to a spectrum of neurodegenerative disorders including Parkinson's disease (PD). Alterations in iPLA2β function have demonstrated its role in other human pathologies including cardiovascular disease, cancer and diabetes. Mechanisms of its activation and tissue-specific functions remain poorly understood. This contrasts with known enzymatic activity and several well-characterized signaling cascades implicated in agonist-induced arachidonic acid release, insulin secretion, vascular constriction/relaxation, store-operated calcium-entry, cellular proliferation, migration and autophagy. We have solved a crystal structure of the full-length mammalian iPLA2β (short variant). The crystal structure significantly revises existing mechanistic models. It demonstrated unexpected oligomeric structure and the conformation of catalytic and auxiliary protein-interaction domains. The structure suggests the mechanisms of inhibition by calmodulin, activation through the autoacylation reaction and the potential role of ATP in stabilizing ankyrin repeats. The novel crystal structure together with biochemical studies has immediate implications for the mechanisms of the phospholipase activity, of the inhibition and activation as well as of the potential mechanism of tissue specific cellular localization. It provides a well-defined framework to investigate the role of neurodegenerative mutations and the function of iPLA2β in the brain as well as its role in other diseases. Support or Funding Information American Heart Association Grant-in-Aid #0665513Z, Center for Advancement of Science in Space (CASIS) grant CASIS-2012-1, NIH/NINDS grant R21NS094854, to S.K. The mechanism of iPLA2b inhibition by calmodulin (a) and activation and interaction with membrane and membrane proteins (b). This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.