Referenced in: none

Automatically associated channels: TRP , TRPM , TRPML , TRPML1

Title: A TRP channel in the lysosome regulates large particle phagocytosis via focal exocytosis.

Authors: Mohammad Samie, Xiang Wang, Xiaoli Zhang, Andrew Goschka, Xinran Li, Xiping Cheng, Evan Gregg, Marlene Azar, Yue Zhuo, Abigail G Garrity, Qiong Gao, Susan Slaugenhaupt, Jim Pickel, Sergey N Zolov, Lois S Weisman, Guy M Lenk, Steve Titus, Marthe Bryant-Genevier, Noel Southall, Marugan Juan, Marc Ferrer, Haoxing Xu

Journal, date & volume: Dev. Cell, 2013 Sep 16 , 26, 511-24

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/23993788

Abstract
Phagocytosis of large extracellular particles such as apoptotic bodies requires delivery of the intracellular endosomal and lysosomal membranes to form plasmalemmal pseudopods. Here, we identified mucolipin TRP channel 1 (TRPML1) as the key lysosomal Ca2+ channel regulating focal exocytosis and phagosome biogenesis. Both particle ingestion and lysosomal exocytosis are inhibited by synthetic TRPML1 blockers and are defective in macrophages isolated from TRPML1 knockout mice. Furthermore, TRPML1 overexpression and TRPML1 agonists facilitate both lysosomal exocytosis and particle uptake. Using time-lapse confocal imaging and direct patch clamping of phagosomal membranes, we found that particle binding induces lysosomal PI(3,5)P2 elevation to trigger TRPML1-mediated lysosomal Ca2+ release specifically at the site of uptake, rapidly delivering TRPML1-resident lysosomal membranes to nascent phagosomes via lysosomal exocytosis. Thus phagocytic ingestion of large particles activates a phosphoinositide- and Ca2+-dependent exocytosis pathway to provide membranes necessary for pseudopod extension, leading to clearance of senescent and apoptotic cells in vivo.