CatSper4

CatSper4 is a sperm-specific subunit of the CatSper calcium channel complex, encoded by the CATSPER4 gene in humans. The CatSper channel is a sperm-tail calcium channel that mediates calcium influx required for sperm hyperactivation, a specialized motility pattern that enables successful fertilization. CatSper4 is part of the core pore-forming subunits together with CatSper1, CatSper2, and CatSper3, assembling into a functional channel that is activated by intracellular alkalization and other sperm-specific signals.

Structurally, CatSper4 is a transmembrane protein predicted to contribute to the pore-forming region of the CatSper channel. It localizes predominantly to the flagellum of mature sperm where the CatSper complex resides, and it works in concert with other CatSper subunits and auxiliary components to regulate calcium entry.

Expression and conservation of CatSper4 are restricted largely to the male germ line in mammals. The gene is part of a conserved CatSper gene family, and its product shows tissue- and species-specific expression consistent with a role in fertilization. The CatSper channel complex, including CatSper4, is essential for normal sperm function in many species.

Clinical relevance and research interest follow from its role in fertility. Disruption or mutation of CatSper4 can impair CatSper channel function and reduce calcium signaling in sperm, contributing to male infertility in model organisms and associated human cases. Because of its sperm-specific expression and essential role in motility, CatSper4 remains a focus in studies of reproductive biology and as a potential target for new forms of contraception.