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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 ? subunit (Gq(Q209L), 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.

SUBMITTER: Wang L

PROVIDER: S-EPMC4463190 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Gq signaling causes glomerular injury by activating TRPC6.

Wang Liming L Jirka Grant G Rosenberg Paul B PB Buckley Anne F AF Gomez Jose A JA Fields Timothy A TA Winn Michelle P MP Spurney Robert F RF

The Journal of clinical investigation 20150406 5

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 (Gq(Q209L), referred to herein as GqQ>L) is specifically expressed in podocytes and examined the effects of this mut ...[more]

PMID: 25844902

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Project description:BackgroundRenal ischemic reperfusion injury (RIRI) is the most hackneyed cause of acute renal injury with high incidence. As a slit diaphragm (SD), TRPC6 (transient receptor potential channel 6) can maintain the structure and function of glomerular podocytes, and its activation has been reported to prominently alleviate ischemia reperfusion (I/R). However, the specific mechanism of TRPC6 in RIRI is uncertain.MethodsThe TRPC6 specific shRNA or overexpressing plasmid was used to decrease or increase TRPC6 level in HK-2 cells, respectively. Subsequently, the OGD/R (oxygen-glucose deprivation and re-oxygenation) HK-2 cells and RIRI model rats was established to examine the effect of TRPC6 in RIRI in vitro. After processing, viability was confirmed with MTT; cell necrosis was analyzed with flow cytometry; necrosis and autophagy-related proteins were verified with Western blot; free Zn2+ was tested with an Zn2+ fluorescent probe; and cell autophagy was monitored with MDC (monodansylcadaverine) method. Furthermore, TRPC6 agonist (OGA) or TRPC6 inhibitor (SKF96365) were introduced to increase or inhibit the activity of TRPC6 in RIRI model rats, and the kidney injury was assessed with H&E staining and RIP1 and PARP-1 expressions were examined with IHC (immunohistochemistry) staining.ResultsOur results verified TRPC6 could markedly enhance viability, Zn2+ influx, and autophagy, and suppressed necrosis in OGD/R HK-2 cells. In addition, increase of Zn2+ or autophagy activation produced similar results to TRPC6 overexpression in viability, autophagy, and necrosis of OGD/R HK-2 cells. Rescue experiment results also showed TRPC6 could prevent necrosis and facilitate Zn2+ influx and autophagy of OGD/R HK-2 cells by inducing Zn2+ influx and autophagy. Moreover, TRPC6 could ameliorate kidney injury, block necrosis, and enhance autophagy in RIRI model rats by promoting Zn2+ influx and autophagy.ConclusionsTRPC6 could prevent necrosis and induce autophagy to alleviate RIRI by accelerating Zn2+ influx and autophagy. This shows TRPC6/Zn2+ influx/autophagy might be a novel therapeutic strategy for RIRI.

Project description:Necroptosis, oxidative stress, and inflammation are major contributors to the pathogenesis of ischemic acute kidney injury. Necrostatin-1 (Nec-1), an inhibitor of the kinase domain of receptor-interacting protein kinase-1 (RIP1), has been reported to regulate renal ischemia and reperfusion (I/R) injury; however, its underlying mechanism of action remains unclear. HK-2 cells were used to create an in vitro I/R model, in which the cells were subjected to hypoxia, followed by 2, 6, and 12 h of reoxygenation. For the in vivo study, a rat model of renal I/R was established in which samples of rat blood serum and kidney tissue were harvested after reperfusion to assess renal function and detect histological changes. Cell viability and necroptosis were analyzed using the Cell Counting Kit (CCK)-8 assay and flow cytometry, respectively. The expression levels of molecules associated with necroptosis, oxidative stress, and inflammation were determined by real-time PCR, western blotting, immunofluorescence staining, and ELISA. Luciferase and chromatin immunoprecipitation (ChIP) assays were performed to confirm the relevant downstream signaling pathway. We found that pretreatment with Nec-1 significantly decreased hypoxia-inducible factor-1? (HIF-1?) and miR-26a expression, as well as the levels of factors associated with necroptosis (RIP1, RIP3, and Sirtuin-2), oxidative stress (malondialdehyde [MDA], NADP+/NADPH ratio), and inflammation (interleukin [IL]-1?, IL-10, and tumor necrosis factor alpha [TNF-?]) in I/R injury cells and the rat model. However, these effects could be reversed by miR-26a overexpression or TRPC6 knockdown. Mechanistic studies demonstrated that HIF-1? directly binds to the promoter region of miR-26a, and that TRPC6 is a potential target gene for miR-26a. Our findings indicate that Nec-1 can effectively protect against renal I/R injury by inhibiting necroptosis, oxidative stress, and inflammation, and may exert its effects through mediation of the HIF-1?/miR-26a/TRPC6/PARP1 signaling pathway.

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Gq signaling causes glomerular injury by activating TRPC6.

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Gq signaling causes glomerular injury by activating TRPC6.

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