Regulation and roles of Ca2+ stores in human sperm

Abstract

[Ca2+]i signalling is a key regulatory mechanism in sperm function. In mammalian sperm the Ca2+-permeable plasma membrane ion channel CatSper is central to [Ca2+]i signalling, but there is good evidence that Ca2+ stored in intracellular organelles is also functionally important. Here we briefly review the current understanding of the diversity of Ca2+ stores and the mechanisms for the regulation of their activity. We then consider the evidence for the involvement of these stores in [Ca2+]i signalling in mammalian (primarily human) sperm, the agonists that may activate these stores and their role in control of sperm function. Finally we consider the evidence that membrane Ca2+ channels and stored Ca2+ may play discrete roles in the regulation of sperm activities and propose a mechanism by which these different components of the sperm Ca2+-signalling apparatus may interact to generate complex and spatially diverse [Ca2+]i signals.