Calcium dependence of polycystin-2 channel activity is modulated by phosphorylation at Ser812.
Polycystin-2 (PC-2) is a non-selective cation channel that, when mutated, results in autosomal dominant polycystic kidney disease. In an effort to understand the regulation of this channel, we investigated the role of protein phosphorylation in PC-2 function. We demonstrated the direct incorporation of phosphate into PC-2 in cells and tissues and found that this constitutive phosphorylation occurs at Ser(812), a putative casein kinase II (CK2) substrate domain. Ser(812) can be phosphorylated by CK2 in vitro and substitution S812A results in failure to incorporate phosphate in cultured epithelial cells. Non-phosphorylated forms of PC-2 traffic normally in the endoplasmic reticulum and cilial compartments and retain homo- and hetero-multimerization interactions with PC-2 and polycystin-1, respectively. Single-channel studies of PC-2, S812A, and a substitution mutant, T721A, not related to phosphorylation show that PC-2 and S812A function as divalent cation channels with similar current amplitudes across a range of holding potentials; the T721A channel is not functional. Channel open probabilities for PC-2 and S812A show a bell-shaped dependence on cytoplasmic Ca(2+) but there is a shift in this Ca(2+) dependence such that S812A is 10-fold less sensitive to Ca(2+) activation/inactivation than the wild type PC-2 channel. In vivo analysis of PC-2-dependent enhanced intracellular Ca(2+) transients found that S812A resulted in enhanced transient duration and relative amplitude intermediate between control cells and those overexpressing wild type PC-2. Phosphorylation at Ser(812) modulates PC-2 channel activity and factors regulating this phosphorylation are likely to play a role in the pathogenesis of polycystic kidney disease.
Cai
Yiqiang
Y
Department of Internal Medicine, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA.
Anyatonwu
Georgia
G
Okuhara
Dayne
D
Lee
Kyu-Beck
KB
Yu
Zhiheng
Z
Onoe
Tamehito
T
Mei
Chang-Lin
CL
Qian
Qi
Q
Geng
Lin
L
Wiztgall
Ralph
R
Ehrlich
Barbara E
BE
Somlo
Stefan
S
D000818:Animals; D001665:Binding Sites; D019921:Biotinylation; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D047390:Casein Kinase II; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005799:Genes, Dominant; D005982:Glutathione Transferase / Q000378:metabolism; D006031:Glycosylation; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D009154:Mutation; D010710:Phosphates / Q000737:chemistry; D010766:Phosphorylation; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000737:chemistry* / Q000378:metabolism; D050396:TRPP Cation Channels; D013997:Time Factors
D002118:Calcium; D047390:Casein Kinase II; D018076:DNA, Complementary; D005982:Glutathione Transferase; D008565:Membrane Proteins; D010710:Phosphates; D017346:Protein Serine-Threonine Kinases; D012694:Serine; D050396:TRPP Cation Channels