A sea urchin egg jelly peptide induces a cGMP-mediated decrease in sperm intracellular Ca(2+) before its increase.
Speract, a sperm-activating peptide (SAP) from sea urchin eggs, increases the intracellular concentration of Ca(2+) ([Ca(2+)]i) and modulates sperm motility. We measured the initial sperm response to speract using its caged analog and observed, for the first time, a small but significant decrease in sperm [Ca(2+)]i before the increase. Both directions of the [Ca(2+)]i change were completely blocked in high K(+) seawater. Using membrane-permeant caged cyclic nucleotides (cNMP), only cGMP induced the decrease in [Ca(2+)]i although both cGMP and cAMP increased the [Ca(2+)]i. The decrease in the [Ca(2+)]i induced by cGMP was more notable following a second photolytic event, once [Ca(2+)]i had been elevated by an initial flash. This pattern of [Ca(2+)]i change was confirmed in individual sperm. These results together with pharmacological evidence suggest that the initial [Ca(2+)]i decrease is due to a Na(+)/Ca(2+) exchanger activity, stimulated by hyperpolarization mediated by K(+) efflux through cGMP-regulated K(+) channels.
Nishigaki
Takuya
T
Department of Developmental Genetics and Molecular Physiology, Institute of Biotechnology, UNAM, Cuernavaca, Morelos 62210, Mexico. takuya@ibt.unam.mx
Wood
Christopher D
CD
Tatsu
Yoshiro
Y
Yumoto
Noboru
N
Furuta
Toshiaki
T
Elias
David
D
Shiba
Kogiku
K
Baba
Shoji A
SA
Darszon
Alberto
A
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D020013:Calcium Signaling; D016764:Cell Polarity; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D009712:Nucleotides, Cyclic / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D010782:Photolysis; D012617:Sea Urchins; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D014466:Ultraviolet Rays
C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D009712:Nucleotides, Cyclic; D009842:Oligopeptides; D019831:Sodium-Calcium Exchanger; C028364:speract; D000242:Cyclic AMP; D013890:Thiourea; D006152:Cyclic GMP; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine