Phosphatidylinositol (4,5) ‐bisphosphate targets DOC2B to the plasma membrane

DOC2B is a high‐affinity Ca2+ sensor that translocates from the cytosol to the plasma membrane (PM) and promotes vesicle priming and fusion. However, the molecular mechanism underlying its translocation and targeting to the PM in living cells is not completely understood. DOC2B interacts in vitro with the PM components phosphatidylserine, phosphatidylinositol (4,5)‐bisphosphate [PI(4,5)P2] and target SNAREs (t‐SNAREs). Here we show that PI(4,5)P2 hydrolysis at the PM of living cells abolishes DOC2B translocation, whereas manipulations of t‐SNAREs and other phosphoinositides have no effect. Moreover, we were able to redirect DOC2B to intracellular membranes by synthesizing PI(4,5)P2 in those membranes. Molecular dynamics simulations and mutagenesis in the calcium and PI(4,5)P2‐binding sites strengthened our findings, demonstrating that both calcium and PI(4,5)P2 are required for the DOC2B–PM association and revealing multiple PI(4,5)P2–C2B interactions. In addition, we show that DOC2B translocation to the PM is ATP‐independent, and occurs in a diffusion‐like manner. Our data suggest that the Ca2+‐triggered translocation of DOC2B is diffusion‐driven and aimed at PI(4,5)P2‐containing membranes. Synopsis DOC2B, a Ca2+ sensor, translocates from the cytosol to the plasma membrane (PM) upon calcium elevation and affects vesicle fusion. We show that DOC2B translocation is diffusion‐driven and targeted to the PM by specific interactions with PI(4,5)P2, which...
Source: Traffic - Category: Research Authors: Tags: ORIGINAL ARTICLE Source Type: research