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 7

Effect of GqQ>L on diabetic kidney disease.

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Effect of GqQ>L on diabetic kidney disease. (A) Albuminuria was enhan...
(A) Albuminuria was enhanced at 16 and 20 weeks of age in Akita mice expressing GqQ>L (Gq Akita mice). (B and C) Mesangial expansion was increased in Gq Akita mice. Scale bars: 10 μm. (D and E) Nodular, subepithelial thickening of the GBM was seen in Gq Akita mice, which was associated with an increase in average GBM width. Focal areas of FP flattening were also observed (arrows). (F) Total collagen content was increased in both groups of Akita mice. (G and H) Trpc6 and Rcan1 mRNA levels were increased in glomerular preparations from WT Akita mice. Cox2 mRNA was increased in Gq Akita mice. In contrast, mRNA levels for Trpc6 and Rcan1 were decreased in Gq Akita mice compared with levels in WT Akita mice. For the albuminuria and histologic studies, 18 WT Akita mice and 8 Gq Akita mice were used. For the collagen studies, 16 WT Akita mice, 7 Gq Akita mice, and 15 nondiabetic age- and sex-matched controls were used. Three WT Akita mice, 2 Gq Akita mice, and 3 WT controls were used for the TEM studies. For qRT-PCR, samples from 13 WT controls, 16 WT Akita mice, and 7 Gq Akita mice were used. Red blood cells are labeled in the capillary loops. *P < 0.05 or †P < 0.01 versus the indicated groups using Fisher’s exact test for mesangial expansion data and ANOVA, followed by Bonferroni’s post-hoc analysis, for the other studies.