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Abstract: TH-PO177

Klotho Protects Diabetic Nephropathy via Inhibiting Orai1 and TRPC5/6 Channels in Podocytes

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Kim, Ji-Hee, Department of Physiology, Yonsei University Wonju College of Medicine, Wonjusi, Korea (the Republic of)
  • Dang, Bao Thi Ngoc, Department of Physiology, Yonsei University Wonju College of Medicine, Wonjusi, Korea (the Republic of)
  • Hwang, Kyu-Hee, Department of Physiology, Yonsei University Wonju College of Medicine, Wonjusi, Korea (the Republic of)
  • Pham, Nghia Thi, Department of Physiology, Yonsei University Wonju College of Medicine, Wonjusi, Korea (the Republic of)
  • Eom, Minseob, Department of Pathology, Yonsei University Wonju College of Medicine, Wonjusi, Korea (the Republic of)
  • Cha, Seung-Kuy, Department of Physiology, Yonsei University Wonju College of Medicine, Wonjusi, Korea (the Republic of)
Background

Klotho protein is predominantly produced in the kidney, where it regulates multiple renal ion channels to protect the kidney filter and renal diseases. Podocytes play a vital role in kidney filter function and are primary pathologic target for diabetic nephropathy (DN). Perturbation of Ca2+ signaling has been implicated in podocyte dysfunction leading to DN. Here we demonstrated that Klotho ameliorates podocyte injury by stabilizing Orai1 and TRPC5/6 channel-mediated Ca2+ signaling to prevent DN.

Methods

Type 2 diabetic db/db mice received i.p. injections of Klotho protein three times a week. The albumin/creatinine ratio, proteins & mRNA levels were analyzed at 11, 15 and 19-week-old db/db mice and db/m was used as a control group. Live-cell imaging and immunocytochemistry were performed in immortalized mouse podocytes.

Results

In a type 2 diabetic db/db mouse model, Klotho and synaptopodin were downregulated, while Orai1, TRPC5, and TRPC6 were overexpressed in early and late periods, respectively. Soluble Klotho suppressed Orai1- and TRPC5/6-mediated Ca2+ entry in mouse cultured podocytes via inhibiting growth factors and/or insulin signaling. Mechanistically, soluble Klotho reduced cell surface abundance of Orai1 and TRPC5/6, but not TRPC3 by suppressing phosphoinositide-3-kinase-dependent trafficking of these channels. In addition, soluble Klotho downregulated protein expression of Orai1 and TRPC6 by inhibiting growth factor-driven SGK1 activation. Functionally exaggerated actin remodeling by Orai1 and TRPC6 activation was ameliorated by soluble Klotho. Notably, administration of Klotho protein in db/db mice suppressed phosphorylation of SGK1 and rescued dissolution of synaptopodin and WT-1. Finally, Klotho ameliorated podocyte foot process disruption and proteinuria in db/db mice.

Conclusion

Taken together, our results suggest that Klotho protects proteinuria and podocyte actin cytoskeletal remodeling through stabilizing Ca2+ signaling mediated by Orai1 and TRPC5/6, which provides a new potential therapeutic strategy for the treatment of DN.

Funding

  • Government Support – Non-U.S.