Gq signaling causes glomerular injury by activating TRPC6
Liming Wang, … , Michelle P. Winn, Robert F. Spurney
Liming Wang, … , Michelle P. Winn, Robert F. Spurney
Published April 6, 2015
Citation Information: J Clin Invest. 2015;125(5):1913-1926. https://doi.org/10.1172/JCI76767.
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Research Article Nephrology

Gq signaling causes glomerular injury by activating TRPC6

Abstract

Familial forms of focal segmental glomerulosclerosis (FSGS) have been linked to gain-of-function mutations in the gene encoding the transient receptor potential channel C6 (TRPC6). GPCRs coupled to Gq signaling activate TRPC6, suggesting that Gq-dependent TRPC6 activation underlies glomerular diseases. Here, we developed a murine model in which a constitutively active Gq α subunit (GqQ209L, referred to herein as GqQ>L) is specifically expressed in podocytes and examined the effects of this mutation in response to puromycin aminonucleoside (PAN) nephrosis. We found that compared with control animals, animals expressing GqQ>L exhibited robust albuminuria, structural features of FSGS, and reduced numbers of glomerular podocytes. Gq activation stimulated calcineurin (CN) activity, resulting in CN-dependent upregulation of TRPC6 in murine kidneys. Deletion of TRPC6 in GqQ>L-expressing mice prevented FSGS development and inhibited both tubular damage and podocyte loss induced by PAN nephrosis. Similarly, administration of the CN inhibitor FK506 reduced proteinuria and tubular injury but had more modest effects on glomerular pathology and podocyte numbers in animals with constitutive Gq activation. Moreover, these Gq-dependent effects on podocyte injury were generalizable to diabetic kidney disease, as expression of GqQ>L promoted albuminuria, mesangial expansion, and increased glomerular basement membrane width in diabetic mice. Together, these results suggest that targeting Gq/TRPC6 signaling may have therapeutic benefits for the treatment of glomerular diseases.

Authors

Liming Wang, Grant Jirka, Paul B. Rosenberg, Anne F. Buckley, Jose A. Gomez, Timothy A. Fields, Michelle P. Winn, Robert F. Spurney

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Figure 1

Effect of GqQ>L induction on PAN nephrosis.

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Effect of GqQ>L induction on PAN nephrosis. (A) PAN caused a signific...
(A) PAN caused a significant increase in albuminuria in mice expressing GqQ>L. There was significantly less albuminuria induced by PAN in control mice (CTRL) than in GqQ>L mice. (B and C) Treatment with PAN caused a significant increase in the percentage of mice that developed FSGS. Cystic structures were seen in a few glomeruli in GqQ>L mice (B, lower left panel), which likely indicates the accumulation of lipids or proteins in the cytoplasm of epithelial cells. Scale bars: 10 μm. (D) Treatment with PAN induced tubule dilation and casts in GqQ>L mice. Scale bars: 40 μm. (E) Podocyte numbers were significantly reduced by treatment with PAN in GqQ>L mice compared with numbers in both control mice treated with PAN and untreated control mice. (F and G) Treatment with PAN caused a significant decrease in both SYN and WT1 expression in GqQ>L mice. For albuminuria and the histologic studies, 17 control and 14 GqQ>L mice were used. Four controls and 5 GqQ>L mice were used for the immunoblotting experiments. To assess podocyte numbers, samples from 11 untreated controls, 9 controls treated with PAN, and 13 GqQ>L mice treated with PAN were used. *P < 0.05, †P < 0.01, and ‡P < 0.005 versus the indicated groups by Fisher’s exact test for histologic data and by ANOVA, followed by Bonferroni’s post-hoc analysis, for the other studies.