The neoglycoprotein mannose-bovine serum albumin, but not progesterone, activates T-type calcium channels in human spermatozoa.
The neoglycoproteins alpha-D-mannose-bovine serum albumin (mannose-BSA) and N-acetyl-alpha-D-glucosamine-BSA (glucNAc-BSA) were shown to rapidly increase intracellular free calcium ([Ca2+]i) in human spermatozoa. The increase in [Ca2+]i induced by these neoglycoproteins accounts for the known ability of these compounds to induce the acrosome reaction in human spermatozoa. Our data support the hypothesis that mannose-BSA, but not progesterone, activates T-type Ca2+ channels in human spermatozoa for the following reasons: (i) the capacity of mannose-BSA to increase [Ca2+]i was inhibited by the specific T-type Ca2+ channel blocker mibefradil (IC50 = 10(-6) mol/l) while progesterone was not inhibited by 10(-5) M mibefradil; (ii) the effect of mannose-BSA to elevate [Ca2+]i was inhibited more potently by Ni2+ (IC50 = 0.1 mmol/l) than Cd2+ (IC50 = 0.5 mmol/l), whereas the effect of progesterone to elevate [Ca2+]i was inhibited equally by Ni2+ and Cd2+ (IC50 = 0.25 mmol/l); (iii) the effects of mannose-BSA and progesterone to increase [Ca2+]i were greater than additive. These data support the idea that mannose-BSA and progesterone were activating distinct Ca2+ channels, one of which was a T-type Ca2+ channel activated by mannose-BSA whereas the Ca2+ channel that was activated by progesterone has yet to be defined at the molecular level.
Blackmore
P F
PF
Department of Physiological Sciences, Eastern Virginia Medical School, P.O. Box 1980, Norfolk, VA 23501, USA.
Eisoldt
S
S
D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling; D016764:Cell Polarity; D006023:Glycoproteins / Q000494:pharmacology; D006801:Humans; D008297:Male; D008358:Mannose / Q000494:pharmacology*; D020748:Mibefradil; D009532:Nickel / Q000494:pharmacology; D011189:Potassium Chloride / Q000737:chemistry; D011374:Progesterone / Q000378:metabolism / Q000494:pharmacology*; D012709:Serum Albumin / Q000494:pharmacology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology*; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D013764:Tetrahydronaphthalenes / Q000494:pharmacology
D001562:Benzimidazoles; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D006023:Glycoproteins; C050080:N-acetylglucosamine-bovine serum albumin conjugate; D012709:Serum Albumin; D013764:Tetrahydronaphthalenes; C023840:mannose-bovine serum albumin conjugate; D002104:Cadmium; D012710:Serum Albumin, Bovine; D020748:Mibefradil; D011374:Progesterone; D011189:Potassium Chloride; D009532:Nickel; D008358:Mannose; D000117:Acetylglucosamine