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.

Role of Ion Channels in the Sperm Acrosome Reaction

“…There is evidence of Ca 2+ store mobilization consistent with the occurrence of store-operated Ca 2+ entry in sperm (Blackmore 1999;O'Toole et al 2000;González-Martínez et al 2001;Costello et al 2009;Correia et al 2015).…”

“…Interestingly, in human sperm NAADP induced Ca 2+ mobilization (Sánchez-Tusie et al 2014) and the AR (Arndt et al 2014) in the absence of extracellular Ca 2+ , a condition also observed by De Blas et al (2002) but implicating the IP3R instead of TPC. Since Arndt also observed colocalization of IP3R and TPC1 in lipid rafts, they proposed that acrosomal exocytosis may well fit the "NAADP trigger hypothesis" (Calcraft et al 2009), in which initial NAADP Ca 2+ release triggers further Ca 2+ release through IP3 or Ryanodine receptors located in adjacent Ca 2+ stores amplifying the signal (Correia et al 2015).…”

“…Progesterone evokes as well a two-component Ca 2+ rise: one fast and transient and another one slower and sustained. Due to the kinetics and nature of this dual response and since Ca 2+ levels are a balance between influx from the exterior and efflux from intracellular stores, intracellular Ca 2+ channels were also looked for and reported to be present in human sperm (reviewed in Darszon et al 2011;Correia et al 2015). These and other important findings (reviewed in Lishko et al 2011a;Buffone et al 2014;Darszon and Hernández-Cruz 2014) (Zeng et al 2013).…”

Penicillamine prevents ram sperm agglutination in media that support capacitation

“…Under in vitro conditions, fatty acid free albumin is included in capacitating media to fulfil this function. The final ingredient, calcium, is required for a variety of cellular functions including hyperactivation (Correia et al 2015) and induction of the acrosome reaction following binding of the spermatozoon to the zona pellucida (Jin et al 2011, Yanagimachi 2011.…”

Ketamine inhibits human sperm function by Ca2+-related mechanism

“…In the present study, ketamine caused a reduction in [Ca 2þ ] i that may explain the inhibited Ca 2þ -related sperm functions such as motility and the progesterone-induced acrosome reaction. Change in mammalian sperm [Ca 2þ ] i can be achieved by Ca 2þ flux into the cytoplasm from the extracellular fluid or by Ca 2þ release from stores within the cell [26,27]. In human sperm, Ca 2þ influx is predominantly controlled by CatSper [28], which is closely associated with human sperm functions.…”