Expression, localization and functions in acrosome reaction and sperm motility of Ca_V3.1 and Ca_V3.2 channels in sperm cells: An evaluation from Ca_V3.1 and Ca_V3.2 deficient mice

Abstract

In spermatozoa, voltage-dependent calcium channels (VDCC) have been involved in different cellular functions like acrosome reaction (AR) and sperm motility. Multiple types of VDCC are present and their relative contribution is still a matter of debate. Based mostly on pharmacological studies, low-voltage-activated calcium channels (LVA-CC), responsible of the inward current in spermatocytes, were described as essential for AR in sperm. The development of Ca(V)3.1 or Ca(V)3.2 null mice provided the opportunity to evaluate the involvement of such LVA-CC in AR and sperm motility, independently of pharmacological tools. The inward current was fully abolished in spermatogenic cells from Ca(V)3.2 deficient mice. This current is thus only due to Ca(V)3.2 channels. We showed that Ca(V)3.2 channels were maintained in sperm by Western-blot and immunohistochemistry experiments. Calcium imaging experiments revealed that calcium influx in response to KCl was reduced in Ca(V)3.2 null sperm in comparison to control cells, demonstrating that Ca(V)3.2 channels were functional. On the other hand, no difference was noticed in calcium signaling induced by zona pellucida. Moreover, neither biochemical nor functional experiments, suggested the presence of Ca(V)3.1 channels in sperm. Despite the Ca(V)3.2 channels contribution in KCl-induced calcium influx, the reproduction parameters remained intact in Ca(V)3.2 deficient mice. These data demonstrate that in sperm, besides Ca(V)3.2 channels, other types of VDCC are activated during the voltage-dependent calcium influx of AR, these channels likely belonging to high-voltage activated Ca(2+) channels family. The conclusion is that voltage-dependent calcium influx during AR is due to the opening of redundant families of calcium channels.

Flagellar ion channels of sperm: similarities and differences between species

“…Specific ion channels mediate the rise in [Ca 2+ ] i within sperm, and many candidates for the principle Ca 2+ channel in sperm, including various voltagegated Ca 2+ channels, were proposed based primarily on studies using Ca 2+ imaging, immunolabeling, and patch-clamp experiments from sperm precursors [61][62][63]. However, genetic ablation studies suggested that these candidate proteins were not functionally necessary for male fertility or some compensatory mechanism for their loss may be present [64][65][66][67][68]. The molecular identity of the first sperm specific ion channel required for male fertility in mice was determined in 2001 with the cloning of CatSper1 [24].…”

Cl− Channels and Transporters in Sperm Physiology

“…However, Ca V 3.1 and 3.2 knockout mice are fertile (Stamboulian et al 2004 ), and Ca V currents, although recorded in testicular sperm, were not detected in epididymal sperm (Martinez-Lopez et al 2009 ;Ren and Xia 2010 ). These results raised doubts about the participation of Ca V 3 channels in the mouse sperm AR, although solid immunological data demonstrate their presence (Escoffi er et al 2007 ;Trevino et al 2004 ).…”

“…Early on it was thought that voltage-dependent Ca 2+ (Ca V ) channels were involved in the initial [Ca 2+ ] i increase detected during the AR induced by ZP in mouse sperm, taking into account their pharmacology and that of this reaction . Ca V 3.2 was the most likely Ca V candidate to participate in the mouse AR (Arnoult et al 1996 ;Escoffi er et al 2007 ;Lievano et al 1996 ;Trevino et al 2004 ). However, Ca V 3.1 and 3.2 knockout mice are fertile (Stamboulian et al 2004 ), and Ca V currents, although recorded in testicular sperm, were not detected in epididymal sperm (Martinez-Lopez et al 2009 ;Ren and Xia 2010 ).…”

Sperm Epidermal Growth Factor Receptor (EGFR) Mediates α7 Acetylcholine Receptor (AChR) Activation to Promote Fertilization

“…ZP3 triggers the elevation of [Ca 2ϩ ] i by activating voltage-gated Ca 2ϩ channel, possibly a member of the Cav3 family (6). Two members of this family, Cav3.1 and 3.2, are present in the sperm head and may mediate the acrosome reaction (7)(8)(9)(10)(11). However, disruption of the genes that encode for these channels does not affect fertility (11,12), suggesting that neither of these channels alone is essential for sperm function.…”

“…Two members of this family, Cav3.1 and 3.2, are present in the sperm head and may mediate the acrosome reaction (7)(8)(9)(10)(11). However, disruption of the genes that encode for these channels does not affect fertility (11,12), suggesting that neither of these channels alone is essential for sperm function. It also has been suggested that ZP3 activates TRPC2 (canonical transient receptor potential) via a store-operated mechanism (13,14), although Ca 2ϩ entry is not inhibited by blocking TRPC2 (13) suggesting that other channels may contribute to Ca 2ϩ influx.…”