Regulation of human sperm motility and hyperactivation components by calcium, calmodulin, and protein phosphatases.
The role of Ca2+, calmodulin, and protein phosphatases on motility and hyperactivation of noncapacitated, capacitating, and detergent-permeabilized reactivated human sperm was examined. In noncapacitated sperm, W7 inhibited percent motility (%MOT), curvilinear velocity (VCL), amplitude of lateral head displacement (ALH), and percent hyperactivation (%HYP) in an extracellular Ca2+ concentration-dependent manner (p < .05). However, in capacitating sperm, inhibition of motility by W7 was independent of external Ca2+. Treatment of reactivated sperm with a synthetic calmodulin inhibitor peptide decreased VCL and ALH in a Ca(2+)-dependent manner (p < .05). Ca2+ exhibited a dramatic influence on motility within a narrow concentration range (0.7 to 1.0 microM) in reactivated sperm. A calmodulin-dependent protein phosphatase (PP2B) was identified by activity assay, immunoblotting, and dephosphorylation of endogenous phosphoproteins. The sperm enzyme, unlike bovine brain PP2B, was inhibited by 1 microM okadaic acid (OA) in the presence of Mn2+, suggesting that the sperm enzyme is unique. In reactivated sperm, inhibition of endogenous PP2B-like activity with anti-PP2B antibodies altered ALH, whereas OA altered both VCL and ALH and also inhibited a subset of Ca(2+)-dependent dephosphorylations of cAMP-dependent phosphoproteins in capacitating sperm. These results suggest (1) an important role for calmodulin and PP2B in Ca(2+)-regulated motility parameters, particularly ALH, and (2) that modulation of human sperm motility, including hyperactivation by cAMP-dependent phosphorylation, requires calmodulin-dependent as well as other protein dephosphorylations.
Ahmad
K
K
Department of Obstetrics and Gynecology, Albert Einstein College of Medicine, Bronx, New York, USA.
Bracho
G E
GE
Wolf
D P
DP
Tash
J S
JS
D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008969:Molecular Sequence Data; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000502:physiology*; D012710:Serum Albumin, Bovine / Q000276:immunology / Q000494:pharmacology; D013075:Sperm Capacitation / Q000187:drug effects / Q000502:physiology; D013081:Sperm Motility / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology
D000906:Antibodies; D002147:Calmodulin; D004988:Ethers, Cyclic; D013449:Sulfonamides; D019319:Okadaic Acid; D012710:Serum Albumin, Bovine; D004533:Egtazic Acid; C017967:W 7; C034700:N-(6-aminohexyl)-1-naphthalenesulfonamide; D000242:Cyclic AMP; D010749:Phosphoprotein Phosphatases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium