Role of carbonic anhydrase IV in the bicarbonate-mediated activation of murine and human sperm.
HCO(3) (-) is the signal for early activation of sperm motility. In vivo, this occurs when sperm come into contact with the HCO(3) (-) containing fluids in the reproductive tract. The activated motility enables sperm to travel the long distance to the ovum. In spermatozoa HCO(3) (-) stimulates the atypical sperm adenylyl cyclase (sAC) to promote the cAMP-mediated pathway that increases flagellar beat frequency. Stimulation of sAC may occur when HCO(3) (-) enters spermatozoa either directly by anion transport or indirectly via diffusion of CO(2) with subsequent hydration by intracellular carbonic anhydrase (CA). We here show that murine sperm possess extracellular CA IV that is transferred to the sperm surface as the sperm pass through the epididymis. Comparison of CA IV expression by qRT PCR analysis confirms that the transfer takes place in the corpus epididymidis. We demonstrate murine and human sperm respond to CO(2) with an increase in beat frequency, an effect that can be inhibited by ethoxyzolamide. Comparing CA activity in sperm from wild-type and CA IV(-/-) mice we found a 32.13% reduction in total CA activity in the latter. The CA IV(-/-) sperm also have a reduced response to CO(2). While the beat frequency of wild-type sperm increases from 2.86±0.12 Hz to 6.87±0.34 Hz after CO(2) application, beat frequency of CA IV(-/-) sperm only increases from 3.06±0.20 Hz to 5.29±0.47 Hz. We show, for the first time, a physiological role of CA IV that supplies sperm with HCO(3) (-), which is necessary for stimulation of sAC and hence early activation of spermatozoa.
Department of Anatomy and Cell Biology, Saarland University, Homburg, Saar, Germany.
Petra M
PM
Wandernoth
Michael
M
Raubuch
Nadja
N
Mannowetz
Holger M
HM
Becker
Joachim W
JW
Deitmer
William S
WS
Sly
Gunther
G
Wennemuth
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000494:pharmacology; D030741:Carbonic Anhydrase IV / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004822:Epididymis / Q000166:cytology / Q000201:enzymology; D005016:Ethoxzolamide / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000201:enzymology; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013081:Sperm Motility / Q000187:drug effects* / Q000502:physiology; D013082:Sperm Tail / Q000187:drug effects / Q000502:physiology; D013094:Spermatozoa / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D013997:Time Factors
D001639:Bicarbonates; D002245:Carbon Dioxide; D030741:Carbonic Anhydrase IV; D000262:Adenylyl Cyclases; D005016:Ethoxzolamide