Submitted on December 20, 2007
Accepted on January 31, 2008
Mediation of Angiotensin II-induced Ca2+ signaling by polycystin 2
in glomerular mesangial cells
Juan Du1, Min Ding2, Sherry Sours-Brothers3, Sarabeth Graham2, and Rong Ma2*
1 Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas, United States; Physiology, Anhui Medical University, Hefei, Anhui, China
2 Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas, United States
3 Fort Worth, Texas, United States; Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas, United States
* To whom correspondence should be addressed. E-mail: rma{at}hsc.unt.edu.
Ca2+ influx across the plasma membrane is a major component of mesangial cell (MC) response to vasoconstrictors. Polycystin 2 (PC2), the protein product of the gene mutated in type 2 autosomal dominant polycystic kidney disease, has been shown to function as a non-selective cation channel in a variety of cell types. The present study was performed to test the hypothesis that PC2 and its binding partners constitute a Ca2+-permeable channel and contribute to angiotensin II (Ang II)-induced Ca2+ signaling in MCs. Western blot and immunocytochemistry showed PC2 expression in cultured human MCs. The existence of PC2 in MCs was further confirmed by immunohistochemsitry in rat kidney sections. Co-immunoprecipitation displayed a selective interaction of PC2 with TRPC1 and TRPC4. Cell-attached patch clamp experiments revealed that Ang II-induced membrane currents were enhanced by over-expression of pkd2, but significantly inhibited by knockdown of pkd2, 30 µM Gd3+ (a PC2 channel blocker), and dominant negative pkd2 mutant (pkd2-D511V). Corresponding to the increase in channel currents, Ang II stimulation increased expression of PC2 on the cell surface of MCs as well as interaction with TRPC1 and TRPC4. Furthermore, Ang II-induced MC contraction was significantly reduced in pkd2-knocked down MCs. These data suggest that PC2 selectively assembles with TRPC1 and TRPC4 to form channel complexes mediating Ang II-induced Ca2+ responses in MCs.
