Store-operated calcium entry suppressed the TGF-{beta}1/Smad3 signaling pathway in glomerular mesangial cells

Our previous study demonstrated that the abundance of extracellular matrix proteins was suppressed by store-operated Ca2+ entry (SOCE) in mesangial cells (MCs). The present study was conducted to investigate the underlying mechanism focused on the transforming growth factor-β1 (TGF-β1)/Smad3 pathway, a critical pathway for ECM expansion in diabetic kidneys. We hypothesized that SOCE suppressed ECM protein expression by inhibiting this pathway in MCs. In cultured human MCs, we observed that TGF-β1 (5 ng/ml for 15 h) significantly increased Smad3 phosphorylation, as evaluated by immunoblot. However, this response was markedly inhibited by thapsigargin (1 µM), a classical activator of store-operated Ca2+ channels. Consistently, both immunocytochemistry and immunoblot showed that TGF-β1 significantly increased nuclear translocation of Smad3, which was prevented by pretreatment with thapsigargin. Importantly, the thapsigargin effect was reversed by lanthanum (La3+; 5 µM) and GSK-7975A (10 µM), both of which are selective blockers of store-operated Ca2+ channels. Furthermore, knockdown of Orai1, the pore-forming subunit of the store-operated Ca2+ channels, significantly augmented TGF-β1-induced Smad3 phosphorylation. Overexpression of Orai1 augmented the inhibitory effect of thapsigargin on TGF-β1-induced phosphorylation of Smad3. In agreement with the data from cultured MCs, in vivo knockdown of Orai1 specific to MCs using a targeted...

Source: AJP: Renal Physiology - September 11, 2017 Category: Urology & Nephrology Authors: Chaudhari, S., Li, W., Wang, Y., Jiang, H., Ma, Y., Davis, M. E., Zuckerman, J. E., Ma, R. Tags: RESEARCH ARTICLE Source Type: research