ERK1/2-dependent bestrophin-3 expression prevents ER-stress-induced cell death in renal epithelial cells by reducing CHOP

作者：Lee Wing Kee^*; Chakraborty Prabir K; Roussa Eleni; Wolff Natascha A; Thevenod Frank

来源：Biochimica et Biophysica Acta-Molecular Cell Research, 2012, 1823(10): 1864-1876.

DOI：10.1016/j.bbamcr.2012.06.003

• Reactive oxygen species
• ERK
• Calcium
• Apoptosis
• Unfolded protein response

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 Ca2+-activated Cl- channel activity, is upregulated by the ER stressors, thapsigargin (TG), tunicamycin (TUN) and the toxic metal Cd2+. In cultured rat kidney proximal tubule cells, ER stress, CHOP and cell death were induced after 6 h by Cd2+ (25 mu M), TG (3 mu M) and TUN (6 mu M), were associated with increased cytosolic Ca2+ and downstream formation of reactive oxygen species and attenuated by the Ca2+ chelator BAPTA-AM (10 mu M), the antioxidant a-tocopherol (100 mu M), 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 Ca2+, oxidative stress and ERK1/2 phosphorylation, because it was attenuated by a-tocopherol, CAT expression, BAPTA-AM, calmodulin kinase inhibitor calmidazolium (40 mu M), ERK1/2 inhibitor U0126 (10 mu M), 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.

• 出版日期2012-10