González-Perrett S, Kim K, Ibarra C, Damiano A E, Zotta E, Batelli M, Harris P C, Reisin I L, Arnaout M A, Cantiello H F
Laboratorio de Conales Ionicos, Departamento de Fisicoquimica y Quimica Analitica, Facultad de Farmacia y Bioquimica, Buenos Aires, Argentina.
Proc Natl Acad Sci U S A. 2001 Jan 30;98(3):1182-7. doi: 10.1073/pnas.98.3.1182.
Defects in polycystin-2, a ubiquitous transmembrane glycoprotein of unknown function, is a major cause of autosomal dominant polycystic kidney disease (ADPKD), whose manifestation entails the development of fluid-filled cysts in target organs. Here, we demonstrate that polycystin-2 is present in term human syncytiotrophoblast, where it behaves as a nonselective cation channel. Lipid bilayer reconstitution of polycystin-2-positive human syncytiotrophoblast apical membranes displayed a nonselective cation channel with multiple subconductance states, and a high perm-selectivity to Ca2+. This channel was inhibited by anti-polycystin-2 antibody, Ca2+, La3+, Gd3+, and the diuretic amiloride. Channel function by polycystin-2 was confirmed by patch-clamping experiments of polycystin-2 heterologously infected Sf9 insect cells. Further, purified insect cell-derived recombinant polycystin-2 and in vitro translated human polycystin-2 had similar ion channel activity. The polycystin-2 channel may be associated with fluid accumulation and/or ion transport regulation in target epithelia, including placenta. Dysregulation of this channel provides a mechanism for the onset and progression of ADPKD.
多囊蛋白-2是一种功能未知的普遍存在的跨膜糖蛋白，其缺陷是常染色体显性多囊肾病（ADPKD）的主要病因，该病的表现为在靶器官中形成充满液体的囊肿。在此，我们证明多囊蛋白-2存在于足月人类合体滋养层细胞中，在那里它表现为一种非选择性阳离子通道。对多囊蛋白-2阳性的人类合体滋养层细胞顶端膜进行脂质双层重建，显示出一种具有多种亚电导状态的非选择性阳离子通道，并且对Ca2+具有高度的渗透选择性。该通道受到抗多囊蛋白-2抗体、Ca2+、La3+、Gd3+和利尿药阿米洛利的抑制。通过对多囊蛋白-2异源感染的Sf9昆虫细胞进行膜片钳实验，证实了多囊蛋白-2的通道功能。此外，纯化的昆虫细胞衍生的重组多囊蛋白-2和体外翻译的人类多囊蛋白-2具有相似的离子通道活性。多囊蛋白-2通道可能与包括胎盘在内的靶上皮细胞中的液体蓄积和/或离子转运调节有关。该通道的失调为ADPKD的发病和进展提供了一种机制。
