title: Plasma membrane calcium ATPase is concentrated in the head of sea urchin spermatozoa.
abstract: Plasma membrane Ca2+ATPases (PMCAs) export Ca2+ from cells in a highly regulated manner, providing fine-tuning to the maintenance of intracellular Ca2+ concentrations. There are few studies of PMCAs in spermatozoa, which is surprising considering the importance of this enzyme in all cell types. Here we describe the primary structure and localization of the PMCA of sea urchin spermatozoa (suPMCA). The suPMCA is 1,154 amino acids and has 56% identity and 76% similarity to all 4 human PMCA isoforms. The suPMCA shares the features of a typical PMCA, including domains for calmodulin binding, ATP binding, ATPase phosphorylation, and 10 putative transmembrane segments with two large cytoplasmic loops. Southern blots show that suPMCA is a single copy gene. Treatment of live sea urchin sperm with the PMCA inhibitor, 5-(-6)-carboxyeosin, results in elevations of intracellular Ca2+ and loss of flagellar motility. Immunoblotting and immunoflorescence show that suPMCA is concentrated in the sperm head plasma membrane. In previous work, we showed that a plasma membrane K+ dependent Na+/Ca2+ exchanger (suNCKX), which also keeps Ca2+ low in these cells, is concentrated in the sperm flagellum. Thus, the sperm head and flagellum localize different gene products, both functioning to keep intracellular Ca2+ low, while the sperm swims in seawater containing 10 mM Ca2+.
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0202, USA. hgunarat@ucsd.edu
authors.forename: Herath Jayantha
authors.initials: HJ
authors.lastname: Gunaratne
authors.forename: Anna T
authors.initials: AT
authors.lastname: Neill
authors.forename: Victor D
authors.initials: VD
authors.lastname: Vacquier
mesh_terms: D020101:Acrosome Reaction / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004801:Eosine Yellowish-(YS) / Q000031:analogs & derivatives / Q000494:pharmacology; D018628:Gene Dosage; D007150:Immunohistochemistry; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D053499:Plasma Membrane Calcium-Transporting ATPases; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013077:Sperm Head / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D013081:Sperm Motility / Q000187:drug effects; D013094:Spermatozoa / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D047270:Strongylocentrotus purpuratus / Q000201:enzymology* / Q000235:genetics
chemical_list: D002147:Calmodulin; D027682:Cation Transport Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium; D004801:Eosine Yellowish-(YS)