A regulatory role of polycystin-1 on cystic fibrosis transmembrane conductance regulator plasma membrane expression.
Autosomal dominant polycystic kidney disease (ADPKD) is caused by genetic mutations in either PKD1 or PKD2, the genes that encode polycystin-1 (PC-1) and polycystin-2 (PC-2), respectively. ADPKD is characterized by the formation of multiple, progressive, fluid-filled renal cysts. To elucidate the mechanism of fluid secretion by ADPKD cysts, we examined the effect of PC-1 on the plasma membrane expression of cystic fibrosis transmembrane conductance regulator (CFTR), a key Cl(-) secretory protein. Five stably transfected MDCK lines were used in this study: two transfected with empty vector (control cells) and three expressing human PC-1 (PC-1 cells). The cAMP-induced endogenous short circuit currents (I(sc)) were smaller in PC-1 cells than in control cells. Compared to control cells, PC-1 cells transiently expressing pEGFP-CFTR showed significant reduction of whole cell cAMP-activated Cl(-) currents. Cell surface biotinylation experiments also indicated a reduction in surface expression of CFTR in PC-1 cells compared to control. Furthermore, studies using CHO cells transiently expressing PC-1 and CFTR suggest the importance of the PC-1 COOH-terminus in the observed reduction of CFTR plasma membrane expression. No differences in either endogeneous K(+) currents or P2Y receptor responses were observed between PC-1 and control cells, indicating the specificity of PC-1's action. These results indicate that PC-1 selectively maintains low cell surface expression of CFTR. Moreover, these findings suggest that the malfunction of PC-1 enhances plasma membrane expression of CFTR, thus causing abnormal Cl(-)secretion into the cyst lumen.
Ikeda
Masahiro
M
Department of Physiology, Johns Hopkins University School of Medicine 725 N. olfe St., Baltimore, MD 21205, USA. wguggino@jhmi.edu
Fong
Peying
P
Cheng
Jie
J
Boletta
Alessandra
A
Qian
Feng
F
Zhang
Xue-Mei
XM
Cai
Hui
H
Germino
Gregory G
GG
Guggino
William B
WB
D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology*; D018118:Chloride Channels / Q000235:genetics / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000235:genetics; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000235:genetics; D050396:TRPP Cation Channels / Q000378:metabolism*; D014162:Transfection
D018118:Chloride Channels; D000242:Cyclic AMP; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D049452:Green Fluorescent Proteins; D017228:Hepatocyte Growth Factor; D011993:Recombinant Fusion Proteins; D050396:TRPP Cation Channels