Regulation of ryanodine receptor-dependent calcium signaling by polycystin-2

Departments of *Pharmacology,
^†Medicine,
^‡Genetics, and
^§Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8066

Edited by Andrew R. Marks, Columbia University College of Physicians and Surgeons, New York, NY, and approved February 22, 2007 (received for review November 21, 2006)

Abstract

Mutations in polycystin-2 (PC2) cause autosomal dominant polycystic kidney disease. A function for PC2 in the heart has not been described. Here, we show that PC2 coimmunoprecipitates with the cardiac ryanodine receptor (RyR2) from mouse heart. Biochemical assays showed that the N terminus of PC2 binds the RyR2, whereas the C terminus only binds to RyR2 in its open state. Lipid bilayer electrophysiological experiments indicated that the C terminus of PC2 functionally inhibited RyR2 channel activity in the presence of calcium (Ca²⁺). Pkd2 ^−/− cardiomyocytes had a higher frequency of spontaneous Ca²⁺ oscillations, reduced Ca²⁺ release from the sarcoplasmic reticulum stores, and reduced Ca²⁺ content compared with Pkd2 ^+/+ cardiomyocytes. In the presence of caffeine, Pkd2 ^−/− cardiomyocytes exhibited decreased peak fluorescence, a slower rate of rise, and a longer duration of Ca²⁺ transients compared with Pkd2 ^+/+. These data suggest that PC2 is important for regulation of RyR2 function and that loss of this regulation of RyR2, as occurs when PC2 is mutated, results in altered Ca²⁺ signaling in the heart.

Footnotes

^¶To whom correspondence should be addressed. E-mail: barbara.ehrlich{at}yale.edu
Author contributions: G.I.A., S.S., and B.E.E. designed research; G.I.A. and M.E. performed research; M.E. and X.T. contributed new reagents/analytic tools; G.I.A. and B.E.E. analyzed data; and G.I.A., S.S., and B.E.E. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Abbreviations:

PC,

polycystin;

ADPKD,

autosomal dominant polycystic kidney disease;

TRP,

transient receptor potential;

SR,

sarcoplasmic reticulum;

InsP3,

inositol 1,4,5-trisphosphate;

InsP3R,

InsP3 receptor;

CPC2,

C terminus of PC2;

RyR,

ryanodine receptor;

RyR2,

cardiac ryanodine receptor;

NPC2,

N terminus of PC2;

SERCA-2a,

sarco/endoplasmic reticulum Ca2+-ATPase 2a.