G?_q and the Phospholipase C?3 X-Y Linker Regulate Adsorption and Activity on Compressed Lipid Monolayers.

ABSTRACT: Phospholipase C? (PLC?) enzymes are peripheral membrane proteins required for normal cardiovascular function. PLC? hydrolyzes phosphatidylinositol 4,5-bisphosphate, producing second messengers that increase intracellular Ca²⁺ level and activate protein kinase C. Under basal conditions, PLC? is autoinhibited by its C-terminal domains and by the X-Y linker, which contains a stretch of conserved acidic residues required for interfacial activation. Following stimulation of G protein-coupled receptors, the heterotrimeric G protein subunit G?_q allosterically activates PLC? and helps orient the activated complex at the membrane for efficient lipid hydrolysis. However, the molecular basis for how the PLC? X-Y linker, its C-terminal domains, G?_q, and the membrane coordinately regulate activity is not well understood. Using compressed lipid monolayers and atomic force microscopy, we found that a highly conserved acidic region of the X-Y linker is sufficient to regulate adsorption. Regulation of adsorption and activity by the X-Y linker also occurs independently of the C-terminal domains. We next investigated whether G?_q-dependent activation of PLC? altered interactions with the model membrane. G?_q increased PLC? adsorption in a manner that was independent of the PLC? regulatory elements and targeted adsorption to specific regions of the monolayer in the absence of the C-terminal domains. Thus, the mechanism of G?_q-dependent activation likely includes a spatial component.

SUBMITTER: Hudson BN 

PROVIDER: S-EPMC7885793 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature