ERK1/2-dependent bestrophin-3 expression prevents ER-stress-induced cell death in renal epithelial cells by reducing CHOP.
Upon endoplasmic reticulum (ER) stress induction, cells endeavor to survive by engaging the adaptive stress response known as the unfolded protein response or by removing aggregated proteins via autophagy. Chronic ER stress culminates in apoptotic cell death, which involves induction of pro-apoptotic CHOP. Here, we show that bestrophin-3 (Best-3), a protein previously associated with Ca(2+)-activated Cl(-) channel activity, is upregulated by the ER stressors, thapsigargin (TG), tunicamycin (TUN) and the toxic metal Cd(2+). In cultured rat kidney proximal tubule cells, ER stress, CHOP and cell death were induced after 6h by Cd(2+) (25μM), TG (3μM) and TUN (6μM), were associated with increased cytosolic Ca(2+) and downstream formation of reactive oxygen species and attenuated by the Ca(2+) chelator BAPTA-AM (10μM), the antioxidant α-tocopherol (100μM), or overexpression of catalase (CAT). Immunofluorescence staining showed Best-3 expression in the plasma membrane, nuclei and intracellular compartments, though not in the ER, in cultured cells and rat kidney cortex sections. Best-3 mRNA was augmented by ER stress and signaled through increased Ca(2+), oxidative stress and ERK1/2 phosphorylation, because it was attenuated by α-tocopherol, CAT expression, BAPTA-AM, calmodulin kinase inhibitor calmidazolium (40μM), ERK1/2 inhibitor U0126 (10μM), and ERK1/2 RNAi. Knockdown of Best-3 resulted in decreased cell number consequentially of cell death, as determined by nuclear staining and PARP-1 cleavage. Furthermore, reduced ER stress-cell death by Best-3 overexpression is attributed to diminished CHOP. Since Best-3 overexpression did not affect upstream signaling pathways, we hypothesize that Best-3 possibly interferes with CHOP transcription. From our novel observations, we conclude that ERK1/2-dependent Best-3 activation regulates cell fate decisions during ER stress by suppressing CHOP induction and death.
Institute of Physiology & Pathophysiology, ZBAF, University of Witten/Herdecke, Witten, Germany. wing-kee.lee@uni-wh.de
Wing-Kee
WK
Lee
Prabir K
PK
Chakraborty
Eleni
E
Roussa
Natascha A
NA
Wolff
Frank
F
Thévenod
D000818:Animals; D000075002:Bestrophins; D002104:Cadmium / Q000633:toxicity; D002118:Calcium / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D019070:Cell Lineage / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D019610:Cytoprotection / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology*; D007668:Kidney; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D051742:Transcription Factor CHOP / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
C568920:Best3 protein, rat; D000075002:Bestrophins; D018118:Chloride Channels; D017382:Reactive Oxygen Species; D002104:Cadmium; D014415:Tunicamycin; D051742:Transcription Factor CHOP; D019284:Thapsigargin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium