Store–Operated Ca2+ Channels in Mesangial Cells Inhibit Matrix Protein Expression

Abstract

Accumulation of extracellular matrix derived from glomerular mesangial cells is an early feature of diabetic nephropathy. Ca 2+ signals mediated by store-operated Ca 2+ channels regulate protein production in a variety of cell types. The aim of this study was to determine the effect of store-operated Ca 2+ channels in mesangial cells on extracellular matrix protein expression. In cultured human mesangial cells, activation of store-operated Ca 2+ channels by thapsigargin significantly decreased fibronectin protein expression and collagen IV mRNA expression in a dose-dependent manner. Conversely, inhibition of the channels by 2-aminoethyl diphenylborinate significantly increased the expression of fibronectin and collagen IV. Similarly, overexpression of stromal interacting molecule 1 reduced, but knockdown of calcium releaseactivated calcium channel protein 1 (Orai1) increased fibronectin protein expression. Furthermore, 2-aminoethyl diphenylborinate significantly augmented angiotensin II-induced fibronectin protein expression, whereas thapsigargin abrogated high glucose-and TGF-b1-stimulated matrix protein expression. In vivo knockdown of Orai1 in mesangial cells of mice using a targeted nanoparticle siRNA delivery system resulted in increased expression of glomerular fibronectin and collagen IV, and mice showed significant mesangial expansion compared with controls. Similarly, in vivo knockdown of stromal interacting molecule 1 in mesangial cells by recombinant adeno-associated virus-encoded shRNA markedly increased collagen IV protein expression in renal cortex and caused mesangial expansion in rats. These results suggest that store-operated Ca 2+ channels in mesangial cells negatively regulate extracellular matrix protein expression in the kidney, which may serve as an endogenous renoprotective mechanism in diabetes.

Impairment of hepatic nuclear factor-4α binding to theStim1promoter contributes to high glucose-induced upregulation of STIM1 expression in glomerular mesangial cells

“…Like in platelets and vascular endothelial cells (4,58), prolonged HG treatment in MCs increased STIM1/Orai1 protein expression levels and augmented SOCE. In a recent study (53), we further showed that activation of STIM1/Orai1-mediated SOCs reduced fibronectin and collagen type IV expression, suggesting a renoprotective effect of SOCE. Thus, the increase in STIM1/Orai1-mediated SOCE in response to diabetes/HG might be a compensatory mechanism in the kidney to counteract kidney damages induced by diabetes/HG.…”

“…Knockdown of HNF4␣ reduced fibronectin and collagen type IV protein expression in human MCs. Our previous in vitro and in vivo study (53) demonstrated that activation of SOCs suppressed extracellular matrix protein expression. Since HNF4␣ repressed STIM1 expression and reduced SOCE, we speculated that knockdown of HNF4␣ should decrease extracellular matrix protein expression by enhancing SOCE.…”

siRNA Delivery to the Glomerular Mesangium Using Polycationic Cyclodextrin Nanoparticles Containing siRNA

“…Another limitation of the current study is that we only reported mesangial knockdown of a reporter protein (EGFP) in a transgenic mouse model rather than an endogenous, biologically relevant, mesangial protein. We have performed follow-up experiments that demonstrate knockdown of the endogenous mesangial protein Orai1in mice [36]. Therefore, we believe the knockdown of EGFP reported in this study will be generalizable to other mesangial protein targets.…”

Store-operated calcium entry and diabetic complications

“…92 Consistently, downregulation of SOC function in mesangial cells significantly increased extracellular matrix protein expression in cultured mesangial cells or in glomeruli/renal cortices in animals. 92 Thus, SOC in mesangial cells is an anti-fibrotic mechanism in kidney. It is possible that the early attenuation of SOCE in mesangial cells caused by high glucose described above 62 contributes to the early pathological changes in diabetic glomerulus (deposition of extracellular matrix proteins and mesangial expansion), but the later enhancement of SOCE is a compensatory response to counteract detrimental pathways in diabetic kidneys.…”