Polycystin-2 associates with the polycystin-1 homolog, suREJ3, and localizes to the acrosomal region of sea urchin spermatozoa.
Polycystin-2, the protein mutated in type 2 autosomal dominant polycystic kidney disease, is an integral transmembrane protein with nonselective cation channel activity. Here we report on the sea urchin sperm homolog of polycystin-2 (suPC2). Like other polycystin-2 family members, suPC2 is a six-pass transmembrane protein containing C-terminal cytoplasmic EF hand and coiled-coil domains. The protein localizes exclusively to the plasma membrane over the sperm acrosomal vesicle. This localization coincides with the previously reported localization of the sea urchin PC1 homolog, suREJ3. Co-immunoprecipitation shows that suPC2 and suREJ3 are associated in the membrane. The location of suPC2 suggests that it may function as a cation channel mediating the sperm acrosome reaction. The low cation selectivity of PC2 channels would explain data indicating that Na(+) and Ca(2+) may enter sea urchin sperm through the same channel during the acrosome reaction.
Neill
Anna T
AT
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA. aneill@ucsd.edu
Moy
Gary W
GW
Vacquier
Victor D
VD
D000177:Acrosome / Q000378:metabolism / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D012617:Sea Urchins / Q000378:metabolism*; D016415:Sequence Alignment; D017385:Sequence Homology; D050396:TRPP Cation Channels
D008565:Membrane Proteins; D011506:Proteins; D011956:Receptors, Cell Surface; D050396:TRPP Cation Channels; C099881:egg jelly ligand receptors, Strongylocentrotus purpuratus