Kidney Week

Abstract: TH-PO567

Diminished TRPV4 Activity and Glycosylation Contributes to Compromised [Ca2+]i Homeostasis in Human ADPKD Cells

Session Information

• Cystic Kidney Diseases - I
  November 02, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Genetic Diseases of the Kidney

• 801 Cystic Kidney Diseases

Authors

• Tomilin, Viktor N, University of Texas Health Science Center-Houston, Houston, Texas, United States

Viktor N Tomilin,

• Zaika, Oleg L., University of Texas Health Science Center-Houston, Houston, Texas, United States

Oleg L. Zaika,

• Reif, Gail, University of Kansas Medical Center, Kansas City, Kansas, United States

Gail Reif,

• Wallace, Darren P., University of Kansas Medical Center, Kansas City, Kansas, United States

Darren P. Wallace,

• Pochynyuk, Oleh, University of Texas Health Science Center-Houston, Houston, Texas, United States

Oleh Pochynyuk,

Background

PKD is a devastating clinical pathology leading to a decline in kidney function due to development of fluid-filled cysts. No effective pharmacological treatments exist for PKD patients. Defective flow-mediated [Ca²⁺]_i responses and disrupted [Ca²⁺]_i homeostasis have been repeatedly associated with the development of PKD. Our previous work in rodents demonstrated that the activity of the Ca2+-permeable TRPV4 channel is imperative for flow-mediated [Ca2+]i responses in the distal renal tubule. TRPV4 function is dramatically decreased in isolated cystic cell monolayers and systemic stimulation of TRPV4 interferes with PKD progression in PCK 453 rats, an ARPKD model.

Results

Here, we determined the role of TRPV4 in Ca2+ signaling in human ADPKD and normal human kidney (NHK) cells. ADPKD cells failed to respond to flow and had significantly lower basal [Ca2+]i levels compared to NHK cells, consistent with our previous work (Yamaguchi et al. J. Am. Soc. Nephrol. 17, 2006). Application of TRPV4 antagonist, HC-067047 significantly reduced basal [Ca2+]i levels in NHK cells but had no measurable effect in ADPKD cells. TRPV4 activator, GSK1016790A elicited more than two times higher [Ca2+]i response in NHK than in ADPKD cells. GSK1016790A-mediated responses were precluded by HC-067047 or a Ca2+-free media. Patch clamp analysis revealed significantly lower basal TRPV4 single channel activity and diminished responses to GSK101670A in ADPKD cells. Consistent with our previous results in an ARPKD rat model, we detected a marked decrease in TRPV4 glycosylation in human ADPKD cells pointing to the common mechanism of compromised mechanosensitive [Ca2+]i responses for both PKD forms. TRPV4 glycosylation and activity were dramatically reduced in cultured distal tubule cells upon silencing of polycystin 1 expression. Moreover, blockade of glycosylation with tunicamycin significantly inhibited TRPV4 activity pointing to a mechanism of reduced TRPV4 function in ADPKD cells.

Conclusion

Taken together, TRPV4 glycosylation and function are greatly diminished in human ADPKD cells, contributing importantly to aberrant [Ca2+]i signaling and deficient responses to flow. We speculate that TRPV4 stimulation might be beneficial in restoring [Ca2+]i homeostasis in cyst cells thereby counteracting ADPKD progression in humans.

Funding

• Private Foundation Support