Expression and differential cell distribution of low‐threshold Ca²⁺ channels in mammalian male germ cells and sperm

Abstract

Numerous sperm functions including the acrosome reaction (AR) are associated with Ca 2+ in£ux through voltage-gated Ca 2+ (Ca V ) channels. Although the electrophysiological characterization of Ca 2+ currents in mature sperm has proven di⁄cult, functional studies have revealed the presence of lowthreshold (Ca V 3) channels in spermatogenic cells. However, the molecular identity of these proteins remains unde¢ned. Here, we identi¢ed by reverse transcription polymerase chain reaction the expression of Ca V 3.3 mRNA in mouse male germ cells, an isoform not previously described in these cells. Immunoconfocal microscopy revealed the presence of the three Ca V 3 channel isoforms in mouse spermatogenic cells. In mature mouse sperm only Ca V 3.1 and Ca V 3.2 were detected in the head, suggesting its participation in the AR. Ca V 3.1 and Ca V 3.3 were found in the principal and the midpiece of the £agella. All Ca V 3 channels are also present in human sperm, but only to a minor extent in the head. These ¢ndings were corroborated by immunogold transmission electron microscopy. Tail localization of Ca V 3 channels suggested they may participate in motility, however, mibefradil and gossypol concentrations that inhibit Ca V 3 channels did not signi¢cantly a¡ect human sperm motility. Only higher mibefradil doses that can block high-threshold (HVA) Ca V channels caused small but signi¢cant motility alterations. Antibodies to HVA channels detected Ca V 1.3 and Ca V 2.3 in human sperm £agella. ß 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

Involvement of Cystic Fibrosis Transmembrane Conductance Regulator in Mouse Sperm Capacitation

“…We examined if CFTR is present in mouse and human sperm. First, the presence of CFTR transcripts was analyzed using reverse transcription-PCR; cDNA was synthesized from total RNA extracted from human sperm ejaculates and purified mouse spermatogenic cells (33). Specific primers for CFTR were designed using the reported human and mouse nucleotide sequences for these genes.…”

Expression of Pkd2l2 in Testis Is Implicated in Spermatogenesis

“…14-16) These channels include high voltage-gated calcium channels (CaV1.2, 2.1/2/3) 17) ; cyclic nucleotide-gated channels 18) ; the T-, N-, R-type, and L-type voltage operated Ca 2ϩ channels 19,20) ; and the transient receptor potential (TRP) channel. 21) Moreover, three members of TRP channel family (Trp2, TRPC and pkd2) have been identified to be associated with sperm biological functions.…”

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 ).…”