Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA.
J Cell Sci. 2020 Dec 24;133(24):jcs255562. doi: 10.1242/jcs.255562.
Approximately 15% of autosomal dominant polycystic kidney disease (ADPKD) is caused by variants in encodes polycystin-2, which forms an ion channel in primary cilia and endoplasmic reticulum (ER) membranes of renal collecting duct cells. Elevated internal Ca modulates polycystin-2 voltage-dependent gating and subsequent desensitization - two biophysical regulatory mechanisms that control its function at physiological membrane potentials. Here, we refute the hypothesis that Ca occupancy of the polycystin-2 intracellular EF hand is responsible for these forms of channel regulation, and, if disrupted, results in ADPKD. We identify and introduce mutations that attenuate Ca-EF hand affinity but find channel function is unaltered in the primary cilia and ER membranes. We generated two new mouse strains that harbor distinct mutations that abolish Ca-EF hand association but do not result in a PKD phenotype. Our findings suggest that additional Ca-binding sites within polycystin-2 or Ca-dependent modifiers are responsible for regulating channel activity.
常染色体显性遗传多囊肾病（ADPKD）约有 15%是由 编码的多囊蛋白-2 变异引起的，该蛋白在肾脏集合管细胞的初级纤毛和内质网（ER）膜中形成离子通道。升高的细胞内 Ca2+ 调节多囊蛋白-2 电压依赖性门控和随后的脱敏——这两种生物物理调节机制控制其在生理膜电位下的功能。在这里，我们驳斥了这样一种假设，即多囊蛋白-2 细胞内 EF 手的 Ca2+ 占据负责这些通道调节形式，如果被破坏，则会导致 ADPKD。我们鉴定并引入了突变，这些突变削弱了 Ca-EF 手的亲和力，但发现通道功能在初级纤毛和 ER 膜中没有改变。我们生成了两种新的小鼠品系，它们携带不同的突变，这些突变消除了 Ca-EF 手的结合，但不会导致 PKD 表型。我们的研究结果表明，多囊蛋白-2 内的其他 Ca2+ 结合位点或 Ca2+ 依赖性调节剂负责调节通道活性。
