Glycogen Synthase Kinase 3 Beta Controls Presenilin-1-Mediated Endoplasmic Reticulum Ca²? Leak Directed to Mitochondria in Pancreatic Islets and ?-Cells.

ABSTRACT: BACKGROUND/AIMS:In pancreatic ?-cells, the intracellular Ca²? homeostasis is an essential regulator of the cells major functions. The endoplasmic reticulum (ER) as interactive intracellular Ca²? store balances cellular Ca²?. In this study basal ER Ca²? homeostasis was evaluated in order to reveal potential ?-cell-specificity of ER Ca²? handling and its consequences for mitochondrial Ca²?, ATP and respiration. METHODS:The two pancreatic cell lines INS-1 and MIN-6, freshly isolated pancreatic islets, and the two non-pancreatic cell lines HeLA and EA.hy926 were used. Cytosolic, ER and mitochondrial Ca²? and ATP measurements were performed using single cell fluorescence microscopy and respective (genetically-encoded) sensors/dyes. Mitochondrial respiration was monitored by respirometry. GSK3? activity was measured with ELISA. RESULTS:An atypical ER Ca²? leak was observed exclusively in pancreatic islets and ?-cells. This continuous ER Ca²? efflux is directed to mitochondria and increases basal respiration and organellar ATP levels, is established by GSK3?-mediated phosphorylation of presenilin-1, and is prevented by either knockdown of presenilin-1 or an inhibition/knockdown of GSK3?. Expression of a presenlin-1 mutant that mimics GSK3?-mediated phosphorylation established a ?-cell-like ER Ca²? leak in HeLa and EA.hy926 cells. The ER Ca²? loss in ?-cells was compensated at steady state by Ca²? entry that is linked to the activity of TRPC3. CONCLUSION:Pancreatic ?-cells establish a cell-specific ER Ca²? leak that is under the control of GSK3? and directed to mitochondria, thus, reflecting a cell-specific intracellular Ca²? handling for basal mitochondrial activity.

SUBMITTER: Klec C 

PROVIDER: S-EPMC6459368 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature