Apical membrane segregation of phosphatidylinositol-4,5-bisphosphate influences parathyroid hormone 1 receptor compartmental signaling and localization via direct regulation of ezrin in LLC-PK1 cells

摘要: The parathyroid hormone 1 receptor (PTH1R), a primary regulator of mineral ion homeostasis, is expressed on both the apical and basolateral membranes kidney proximal tubules in LLC-PK1 cell line. In cells, PTH1R subpopulations are far more effective at signaling via phospholipase (PLC) than counterparts, revealing presence compartmental signaling. Apical localization dependent upon direct interactions with ezrin, an actin-membrane cross-linking scaffold protein. Ezrin undergoes activation process that phosphorylation binding to phosphatidylinositol-4,5-bisphosphate (PIP2), lipid selectively concentrated surfaces polarized epithelia. Consistently, intracellular probe for PIP2, GFP-PLCδ1-PH, localizes directly overlapping ezrin expression. Activation shifts GFP-PLCδ1-PH from membrane cytosol membranes, reflecting domain-specific PLC hydrolysis PIP2. This likely due substrate PLC. PIP2 degradation using membrane-directed phosphatase induces de-phosphorylation, processes consistent inactivation. also expression brush border microvilli markedly blunts PTH-elicited MAPK pathway. Transient HEK293 cells plasma microvilli-like surface projections contain As result, enhances PTH mediated pathway this model increasing total Collectively, these findings demonstrate segregation domains not only promotes subsequent formation containing scaffold, but ensures ample propagating