Roles of the Na,K-ATPase alpha4 isoform and the Na+/H+ exchanger in sperm motility.
The Na,K-ATPase generates electrochemical gradients that are used to drive the coupled transport of many ions and nutrients across the plasma membrane. The functional enzyme is comprised of an alpha and beta subunit and families of isoforms for both subunits exist. Recent studies in this laboratory have identified a biological role for the Na,K-ATPase alpha4 isoform in sperm motility. Here we further investigate the role of the Na,K-ATPase carrying the alpha4 isoform, showing again that ouabain eliminates sperm motility, and in addition, that nigericin, a H+/K+ ionophore, and monensin, a H+/Na+ ionophore, reinitiate motility. These data, along with the observation that the K+ ionophore valinomycin has no effect on the motility of ouabain-inhibited sperm, suggest that ouabain may change intracellular H+ levels in a manner that is incompatible with sperm motility. We have also localized NHE1 and NHE5, known regulators of intracellular H+ content, to the same region of the sperm as the Na,K-ATPase alpha4 isoform. These data highlight the important role of the Na,K-ATPase alpha4 isoform in regulating intracellular H(+) levels, and provide evidence suggesting the involvement of the Na+/H+ exchanger, which is critical for maintaining normal sperm motility.
Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA.
Alison L
AL
Woo
Paul F
PF
James
Jerry B
JB
Lingrel
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D007476:Ionophores / Q000494:pharmacology; D007527:Isoenzymes / Q000502:physiology; D008297:Male; D008565:Membrane Proteins; D008985:Monensin / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D013081:Sperm Motility / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D014634:Valinomycin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007476:Ionophores; D007527:Isoenzymes; D008565:Membrane Proteins; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; C117561:sodium-hydrogen exchanger 5; D014634:Valinomycin; D010042:Ouabain; D008985:Monensin; C485720:Atp1a4 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase; D009550:Nigericin