The pumps that fuel a sperm's journey

The sole purpose of a sperm cell is to carry genetic information from a male to a female egg. In order to accomplish this quest, the sperm cell must travel a long distance through a constantly changing environment. The success of this journey depends on membrane proteins that are uniquely expressed in sperm cells. One of these proteins is the alpha 4 isoform of the sodium pump. This pump is optimized to cope with the ionic environment characteristic of the female reproductive tract, and its activity may be tightly coupled with secondary transporters that maintain cytoplasmic pH. Pharmacological inhibition of alpha 4 is sufficient to inhibit sperm motility, and significant differences around the inhibitor-binding site compared with the ubiquitous alpha 1 isoform, make alpha 4 a feasible target in rational drug development.