RRC ID 67486
Author MacVicar TD, Mannack LV, Lees RM, Lane JD.
Title Targeted siRNA Screens Identify ER-to-Mitochondrial Calcium Exchange in Autophagy and Mitophagy Responses in RPE1 Cells.
Journal Int J Mol Sci
Abstract Autophagy is an important stress response pathway responsible for the removal and recycling of damaged or redundant cytosolic constituents. Mitochondrial damage triggers selective mitochondrial autophagy (mitophagy), mediated by a variety of response factors including the Pink1/Parkin system. Using human retinal pigment epithelial cells stably expressing autophagy and mitophagy reporters, we have conducted parallel screens of regulators of endoplasmic reticulum (ER) and mitochondrial morphology and function contributing to starvation-induced autophagy and damage-induced mitophagy. These screens identified the ER chaperone and Ca2+ flux modulator, sigma non-opioid intracellular receptor 1 (SIGMAR1), as a regulator of autophagosome expansion during starvation. Screens also identified phosphatidyl ethanolamine methyl transferase (PEMT) and the IP3-receptors (IP3Rs) as mediators of Parkin-induced mitophagy. Further experiments suggested that IP3R-mediated transfer of Ca2+ from the ER lumen to the mitochondrial matrix via the mitochondrial Ca2+ uniporter (MCU) primes mitochondria for mitophagy. Importantly, recruitment of Parkin to damaged mitochondria did not require IP3R-mediated ER-to-mitochondrial Ca2+ transfer, but mitochondrial clustering downstream of Parkin recruitment was impaired, suggesting involvement of regulators of mitochondrial dynamics and/or transport. Our data suggest that Ca2+ flux between ER and mitochondria at presumed ER/mitochondrial contact sites is needed both for starvation-induced autophagy and for Parkin-mediated mitophagy, further highlighting the importance of inter-organellar communication for effective cellular homeostasis.
Volume 16(6)
Pages 13356-80
Published 2015-6-11
DOI 10.3390/ijms160613356
PII ijms160613356
PMID 26110381
PMC PMC4490499
MeSH Autophagy* Calcium / metabolism* Cells, Cultured Endoplasmic Reticulum / metabolism* Humans Inositol 1,4,5-Trisphosphate Receptors / genetics Inositol 1,4,5-Trisphosphate Receptors / metabolism Mitochondria / metabolism Mitochondria / pathology* Phosphatidylethanolamine N-Methyltransferase / genetics Phosphatidylethanolamine N-Methyltransferase / metabolism RNA, Small Interfering / genetics* Receptors, sigma / antagonists & inhibitors* Receptors, sigma / genetics Retinal Pigment Epithelium / cytology Retinal Pigment Epithelium / metabolism* Ubiquitin-Protein Ligases / genetics Ubiquitin-Protein Ligases / metabolism
IF 4.556
Human and Animal Cells DT40(RCB1464)