Localization Of Human Sperm Pmca4b Which Is Required For Normal Motility In Mouse Sperm

Progressive and hyperactivated motility in sperm are both dependent on Ca2+ and ATP to effect fertilization, with hyperactivated motility utilizing more ATP than progressive motility. The ATP‐driven enzyme Plasma Membrane Calcium/calmodulin‐dependent ATPase isoform 4b (PMCA4b) is the principal calcium efflux pump in mouse sperm, and its absence results in the loss of hyperactivated motility and fertility. Thus, PMCA4b plays an important role in murine sperm function. Protein BLAST analysis illustrates 84% identity and 91% similarity between the mouse and human PMCA4b sequences. Analysis of the functional domains suggests conservation of PMCA4b's activity in human sperm. The objective of this investigation is to characterize the presence of PMCA4b in human sperm by Western blotting, as well as to determine its subcellular localization by immunocytochemistry (ICC). Flow cytometric analysis serves to confirm the presence of PMCA4b on the membrane. ICC studies should elucidate whether or not localization of human PMCA4b is present on the principal piece of the flagellum, which would coincide with findings in the mouse and suggest its involvement in human sperm motility. This work was supported by the Charles Peter White Fellowship and the NIH‐COBRE grant #5P20RR015588‐07.