Regulation and roles of Ca ²⁺ stores in human sperm

Abstract

[Ca ^{2 +}] _i signalling is a key regulatory mechanism in sperm function. In mammalian sperm the Ca ^{2 +}-permeable plasma membrane ion channel CatSper is central to [Ca ^{2 +}] _i signalling, but there is good evidence that Ca ^{2 +} stored in intracellular organelles is also functionally important. Here we briefly review the current understanding of the diversity of Ca ^{2 +} stores and the mechanisms for the regulation of their activity. We then consider the evidence for the involvement of these stores in [Ca ^{2 +}] _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 Ca ^{2 +} channels and stored Ca ^{2 +} may play discrete roles in the regulation of sperm activities and propose a mechanism by which these different components of the sperm Ca ^{2 +}-signalling apparatus may interact to generate complex and spatially diverse [Ca ^{2 +}] _i signals.