A sperm-specific Na+/H+ exchanger (sNHE) is critical for expression and in vivo bicarbonate regulation of the soluble adenylyl cyclase (sAC).
We previously identified a sperm-specific Na(+)/H(+) exchanger (sNHE) principally localized to the flagellum. Disruption of the sNHE gene in mice resulted in absolute male infertility associated with a complete loss of sperm motility. Here, we show that the sNHE-null spermatozoa fail to develop the cAMP-dependent protein tyrosine phosphorylation that coincides with the functional maturation occurring upon incubation in capacitating conditions in vitro. Both the sperm motility defect and the lack of induced protein tyrosine phosphorylation are rescued by the addition of cell-permeable cAMP analogs, suggesting that cAMP metabolism is impaired in spermatozoa lacking sNHE. Our analyses of the bicarbonate-dependent soluble adenylyl cyclase (sAC) signaling pathway in sNHE-null sperm cells reveal that sNHE is required for the expression of full-length sAC, and that it is important for the bicarbonate stimulation of sAC activity in spermatozoa. Furthermore, both codependent expression and coimmunoprecipitation experiments indicate that sNHE and sAC associate with each other. Thus, these two proteins appear to be components of a signaling complex at the sperm flagellar plasma membrane. We propose that the formation of this complex efficiently modulates intracellular pH and bicarbonate levels through the rapid and effective control of sAC and sNHE activities to facilitate sperm motility regulation.
Wang
Dan
D
Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9051, USA. dan.wang@utsouthwestern.edu
Hu
Jie
J
Bobulescu
I Alexandru
IA
Quill
Timothy A
TA
McLeroy
Paul
P
Moe
Orson W
OW
Garbers
David L
DL
D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002457:Cell Extracts; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D012680:Sensitivity and Specificity; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D013081:Sperm Motility; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*
D001639:Bicarbonates; D002457:Cell Extracts; D017923:Sodium-Hydrogen Exchangers; D019000:Phosphotyrosine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases