title: Plasma membrane calcium ATPase 4 (PMCA4) co-ordinates calcium and nitric oxide signaling in regulating murine sperm functional activity.
abstract: Reduced sperm motility (asthenospermia) and resulting infertility arise from deletion of the Plasma Membrane Ca2+-ATPase 4 (Pmca4) gene which encodes the highly conserved Ca2+efflux pump, PMCA4. This is the major Ca2+clearance protein in murine sperm. Since the mechanism underlying asthenospermia in PMCA4's absence or reduced activity is unknown, we investigated if sperm PMCA4 negatively regulates nitric oxide synthases (NOSs) and when absent NO, peroxynitrite, and oxidative stress levels are increased. Using co-immunoprecipitation (Co-IP) and Fluorescence Resonance Energy Transfer (FRET), we show an association of PMCA4 with the NOSs in elevated cytosolic [Ca2+] in capacitated and Ca2+ionophore-treated sperm and with neuronal (nNOS) at basal [Ca2+] (ucapacitated sperm). FRET efficiencies for PMCA4-eNOS were 35% and 23% in capacitated and uncapacitated sperm, significantly (p < 0.01) different, with the molecules being <10 nm apart. For PMCA4-nNOS, this interaction was seen only for capacitated sperm where FRET efficiency was 24%, significantly (p < 0.05) higher than in uncapacitated sperm (6%). PMCA4 and the NOSs were identified as interacting partners in a quaternary complex that includes Caveolin1, which co-immunoprecipitated with eNOS in a Ca2+-dependent manner. In Pmca4-/-sperm NOS activity was elevated twofold in capacitated/uncapacitated sperm (vs. wild-type), accompanied by a twofold increase in peroxynitrite levels and significantly (p < 0.001) increased numbers of apoptotic germ cells. The data support a quaternary complex model in which PMCA4 co-ordinates Ca2+and NO signaling to maintain motility, with increased NO levels resulting in asthenospermia in Pmca4-/-males. They suggest the involvement of PMCA4 mutations in human asthenospermia, with diagnostic relevance.
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware.
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Olli
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware.
authors.forename: Kun
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware.
authors.forename: Deni S
authors.initials: DS
authors.lastname: Galileo
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware.
authors.forename: Patricia A
authors.identifier: http://orcid.org/0000-0002-6903-3703
authors.initials: PA
authors.lastname: Martin-DeLeon
mesh_terms: D000818:Animals; D017209:Apoptosis; D053627:Asthenozoospermia / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051242:Caveolin 1 / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D005298:Fertility; D031541:Fluorescence Resonance Energy Transfer; D020022:Genetic Predisposition to Disease; D008297:Male; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D009097:Multienzyme Complexes; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D018384:Oxidative Stress; D030421:Peroxynitrous Acid / Q000378:metabolism; D010641:Phenotype; D013081:Sperm Motility; D013094:Spermatozoa / Q000201:enzymology* / Q000473:pathology
chemical_list: D000252:Calcium-Transporting ATPases; D051242:Caveolin 1; D009097:Multienzyme Complexes; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D030421:Peroxynitrous Acid; C495541:Cav1 protein, mouse; C000589038:ATP2B4 protein, mouse; C496321:Nos1 protein, mouse; C496315:Nos3 protein, mouse
keywords: asthenospermia; calcium efflux pump; infertility; oxidative stress; sperm damage