Soluble α-klotho anchors TRPV5 to the distal tubular cell membrane independent of FGFR1 by binding TRPV5 and galectin-1 simultaneously

2021 ◽  
Author(s):  
Jinho Lee ◽  
Kyung Don Ju ◽  
Hyo Jin Kim ◽  
Bodokhsuren Tsogbadrakh ◽  
Hyunjin Ryu ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Distal Tubule ◽  
Transient Receptor Potential Vanilloid ◽  
Calcium Excretion ◽  
Tubular Cells ◽  
Calcium Reabsorption ◽  
Transient Receptor

Hypercalciuria is one of early manifestations of diabetic nephropathy (DN). This is partially due to a decrease in the expression of renal transient receptor potential vanilloid type 5 (TRPV5), which is responsible for renal calcium reabsorption. Soluble klotho was previously determined to increase TRPV5 by cleaving sialic acid, causing TRPV5 to bind to membrane protein galectin-1. However, a recent study showed that soluble klotho binds to α2-3-sialyllactose - where sialic acid is located - on TRPV5, rather than cleave it. Here, we report that soluble klotho tethers TRPV5 on the membrane by binding both TRPV5 and galectin-1, thereby protecting membrane TRPV5 from diabetes-induced endocytosis. We injected recombinant soluble α-klotho protein (rKL) into db/db and db/m mice for 8 weeks and collected urine and the kidney. We administered rKL, AZD4547 (FGFR1 inhibitor), and OTX008 (Galectin 1 inhibitor) to cultured mouse distal tubular cells, with or without 30 mM high glucose (HG) exposure. db/db mice showed increased renal calcium excretion and decreased renal TRPV5 expression. rKL treatment reversed this change. In vitro, TRPV5 expression in distal tubular cells decreased under HG conditions, and rKL successfully upregulated TRPV5 with or without FGF23. Also, immunofluorescence showed co-localization of klotho, TRPV5, and galectin-1 in distal tubule cells, suggesting that klotho binds to both TRPV5 and galectin 1. Moreover, when both FGFR1 and galectin-1 were inhibited, rKL failed to increase TRPV5 under HG conditions. Our results indicate that soluble klotho prevents TRPV5 from degradation and subsequent diabetes-induced endocytosis by anchoring TRPV5 through binding with both TRPV5 and galectin-1.

Calcium reabsorption in the distal tubule: regulation by sodium, pH, and flow

2013 ◽  
Vol 304 (5) ◽  
pp. F585-F600 ◽  
Author(s):  
Olivier Bonny ◽  
Aurélie Edwards
Keyword(s):  
Transient Receptor Potential ◽  
Collecting Duct ◽  
Receptor Potential ◽  
Distal Tubule ◽  
Sodium Reabsorption ◽  
Transient Receptor Potential Vanilloid ◽  
Transport Pathways ◽  
Complex Interactions ◽  
Calcium Reabsorption ◽  
Transient Receptor

We developed a mathematical model of Ca2+ transport along the late distal convoluted tubule (DCT2) and the connecting tubule (CNT) to investigate the mechanisms that regulate Ca2+ reabsorption in the DCT2-CNT. The model accounts for apical Ca2+ influx across transient receptor potential vanilloid 5 (TRPV5) channels and basolateral Ca2+ efflux via plasma membrane Ca2+-ATPase pumps and type 1 Na+/Ca2+ exchangers (NCX1). Model simulations reproduce experimentally observed variations in Ca2+ uptake as a function of extracellular pH, Na+, and Mg2+ concentration. Our results indicate that amiloride enhances Ca2+ reabsorption in the DCT2-CNT predominantly by increasing the driving force across NCX1, thereby stimulating Ca2+ efflux. They also suggest that because aldosterone upregulates both apical and basolateral Na+ transport pathways, it has a lesser impact on Ca2+ reabsorption than amiloride. Conversely, the model predicts that full NCX1 inhibition and parathyroidectomy each augment the Ca2+ load delivered to the collecting duct severalfold. In addition, our results suggest that regulation of TRPV5 activity by luminal pH has a small impact, per se, on transepithelial Ca2+ fluxes; the reduction in Ca2+ reabsorption induced by metabolic acidosis likely stems from decreases in TRPV5 expression. In contrast, elevations in luminal Ca2+ are predicted to significantly decrease TRPV5 activity via the Ca2+-sensing receptor. Nevertheless, following the administration of furosemide, the calcium-sensing receptor-mediated increase in Ca2+ reabsorption in the DCT2-CNT is calculated to be insufficient to prevent hypercalciuria. Altogether, our model predicts complex interactions between calcium and sodium reabsorption in the DCT2-CNT.

scholarly journals Novel role of transient receptor potential vanilloid 2 in the regulation of cardiac performance

2014 ◽  
Vol 306 (4) ◽  
pp. H574-H584 ◽  
Author(s):  
Jack Rubinstein ◽  
Valerie M. Lasko ◽  
Sheryl E. Koch ◽  
Vivek P. Singh ◽  
Vinicius Carreira ◽  
...  
Keyword(s):  
Vascular Function ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Transient Receptor Potential Vanilloid ◽  
Wild Type ◽  
Transient Receptor ◽  
Systolic And Diastolic Function ◽  
Myocyte Contractility

Transient receptor potential cation channels have been implicated in the regulation of cardiovascular function, but only recently has our laboratory described the vanilloid-2 subtype (TRPV2) in the cardiomyocyte, though its exact mechanism of action has not yet been established. This study tests the hypothesis that TRPV2 plays an important role in regulating myocyte contractility under physiological conditions. Therefore, we measured cardiac and vascular function in wild-type and TRPV2−/− mice in vitro and in vivo and found that TRPV2 deletion resulted in a decrease in basal systolic and diastolic function without affecting loading conditions or vascular tone. TRPV2 stimulation with probenecid, a relatively selective TRPV2 agonist, caused an increase in both inotropy and lusitropy in wild-type mice that was blunted in TRPV2−/− mice. We examined the mechanism of TRPV2 inotropy/lusitropy in isolated myocytes and found that it modulates Ca2+ transients and sarcoplasmic reticulum Ca2+ loading. We show that the activity of this channel is necessary for normal cardiac function and that there is increased contractility in response to agonism of TRPV2 with probenecid.

scholarly journals Blockade of Transient Receptor Potential Vanilloid 4 Enhances Antioxidation after Myocardial Ischemia/Reperfusion

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Qiongfeng Wu ◽  
Kai Lu ◽  
Zhaoyang Zhao ◽  
Binbin Wang ◽  
Huixia Liu ◽  
...  
Keyword(s):  
Myocardial Ischemia ◽  
Transient Receptor Potential ◽  
Ischemia Reperfusion ◽  
Receptor Potential ◽  
Nuclear Accumulation ◽  
Transient Receptor Potential Vanilloid ◽  
Antioxidative Stress ◽  
Transient Receptor ◽  
Myocardial Ischemia Reperfusion

Antioxidative stress provides a cardioprotective effect during myocardial ischemia/reperfusion (I/R). Previous research has demonstrated that the blockade of transient receptor potential vanilloid 4 (TRPV4) attenuates myocardial I/R injury. However, the underlying mechanism remains unclear. The current study is aimed at investigating the antioxidative activity of TRPV4 inhibition and elucidating the underlying mechanisms in vitro and ex vivo. We found that the inhibiting TRPV4 by the selective TRPV4 blocker HC-067047 or specific TRPV4-siRNA significantly reduces reactive oxygen species (ROS) and methane dicarboxylic aldehyde (MDA) levels in H9C2 cells exposed to hypoxia/reoxygenation (H/R). Meanwhile, the activity of antioxidative enzymes, particularly superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), is enhanced. Furthermore, after H/R, HC-067047 treatment increases the expression of P-Akt and the translocation of nuclear factor E2-related factor 2 (Nrf2) and related antioxidant response element (ARE) mainly including SOD, GSH-Px, and catalase (CAT). LY294002, an Akt inhibitor, suppresses HC-067047 and specific TRPV4-siRNA-induced Nrf2 expression and its nuclear accumulation. Nrf2 siRNA attenuates HC-067047 and specific TRPV4-siRNA-induced ARE expression. In addition, treatment with LY294002 or Nrf2 siRNA significantly attenuates the antioxidant and anti-injury effects of HC-067047 in vitro. Finally, in experiments on isolated rat hearts, we confirmed the antioxidative stress roles of TRPV4 inhibition during myocardial I/R and the application of exogenous H2O2. In conclusion, the inhibition of TRPV4 exerts cardioprotective effects through enhancing antioxidative enzyme activity and expressions via the Akt/Nrf2/ARE pathway.

scholarly journals Structure-based characterization of novel TRPV5 inhibitors

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Taylor ET Hughes ◽  
John Smith Del Rosario ◽  
Abhijeet Kapoor ◽  
Aysenur Torun Yazici ◽  
Yevgen Yudin ◽  
...  
Keyword(s):  
Rational Design ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Parent Compound ◽  
Specific Inhibitor ◽  
Receptor Potential ◽  
Selective Inhibition ◽  
Transient Receptor Potential Vanilloid ◽  
Calcium Reabsorption ◽  
Transient Receptor

Transient receptor potential vanilloid 5 (TRPV5) is a highly calcium selective ion channel that acts as the rate-limiting step of calcium reabsorption in the kidney. The lack of potent, specific modulators of TRPV5 has limited the ability to probe the contribution of TRPV5 in disease phenotypes such as hypercalcemia and nephrolithiasis. Here, we performed structure-based virtual screening (SBVS) at a previously identified TRPV5 inhibitor binding site coupled with electrophysiology screening and identified three novel inhibitors of TRPV5, one of which exhibits high affinity, and specificity for TRPV5 over other TRP channels, including its close homologue TRPV6. Cryo-electron microscopy of TRPV5 in the presence of the specific inhibitor and its parent compound revealed novel binding sites for this channel. Structural and functional analysis have allowed us to suggest a mechanism of action for the selective inhibition of TRPV5 and lay the groundwork for rational design of new classes of TRPV5 modulators.

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