Polycystin-1 interacts with inositol 1,4,5-trisphosphate receptor to modulate intracellular Ca2+ signaling with implications for polycystic kidney disease.
The PKD1 or PKD2 genes encode polycystins (PC) 1 and 2, which are associated with polycystic kidney disease. Previously we demonstrated that PC2 interacts with the inositol 1,4,5-trisphosphate receptor (IP(3)R) to modulate Ca(2+) signaling. Here, we investigate whether PC1 also regulates IP(3)R. We generated a fragment encoding the last six transmembrane (TM) domains of PC1 and the C-terminal tail (QIF38), a section with the highest homology to PC2. Using a Xenopus oocyte Ca(2+) imaging system, we observed that expression of QIF38 significantly reduced the initial amplitude of IP(3)-induced Ca(2+) transients, whereas a mutation lacking the C-terminal tail did not. Thus, the C terminus is essential to QIF38 function. Co-immunoprecipitation assays demonstrated that through its C terminus, QIF38 associates with the IP(3)-binding domain of IP(3)R. A shorter PC1 fragment spanning only the last TM and the C-terminal tail also reduced IP(3)-induced Ca(2+) release, whereas another C-terminal fragment lacking any TM domain did not. Thus, only endoplasmic reticulum-localized PC1 can modulate IP(3)R. Finally, we show that in the polarized Madin-Darby canine kidney cells, heterologous expression of full-length PC1 resulted in a smaller IP(3)-induced Ca(2+) response. Overexpression of the IP(3)-binding domain of IP(3)R reversed the inhibitory effect of PC1, suggesting interaction of full-length PC1 (or its cleavage forms) with endogenous IP(3)R in Madin-Darby canine kidney cells. These results indicate that the behavior of full-length PC1 in mammalian cells is congruent with that of PC1 C-terminal fragments in the oocyte system. These data demonstrate that PC1 inhibits Ca(2+) release, perhaps opposing the effect of PC2, which facilitates Ca(2+) release through the IP(3)R.
Li
Yun
Y
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Santoso
Netty G
NG
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Yu
Shengqiang
S
Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Woodward
Owen M
OM
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Qian
Feng
F
Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Guggino
William B
WB
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205. Electronic address: wguggino@jhmi.edu.
D000818:Animals; D020013:Calcium Signaling; D002460:Cell Line; D016764:Cell Polarity / Q000235:genetics; D004285:Dogs; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D007690:Polycystic Kidney Diseases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D050396:TRPP Cation Channels / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
D053496:Inositol 1,4,5-Trisphosphate Receptors; D050396:TRPP Cation Channels