Article

Egg Coat Proteins Activate Calcium Entry into Mouse Sperm via CATSPER Channels

Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Biology of Reproduction (Impact Factor: 3.45). 03/2009; 80(6):1092-8. DOI: 10.1095/biolreprod.108.074039
Source: PubMed

ABSTRACT During mammalian fertilization, the contact between sperm and egg triggers increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in sperm. Voltage-gated Ca(2+) channels (Ca(V)s) are believed to mediate the initial phase of [Ca(2+)](i) increases in sperm induced by egg coat (zona pellucida [ZP]) glycoproteins, while store depletion-activated Ca(2+) entry is thought to mediate the sustained phase. Using patch-clamp recording and Ca(2+) imaging, we show herein that Ca(V) channel currents, while found in spermatogenic cells, are not detectable in epididymal sperm and are not essential for the ZP-induced [Ca(2+)](i) changes. Instead, CATSPER channels localized in the distal portion of sperm (the principal piece) are required for the ZP-induced [Ca(2+)](i) increases. Furthermore, the ZP-induced [Ca(2+)](i) increase starts from the sperm tail and propagates toward the head.

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    • "Ca 2+ channels and Ca 2+ stores are present in mammalian sperm (Publicover et al., 2007; Costello et al., 2009; Darszon et al., 2011) and both play important roles in sperm function. CatSper, a sperm-specific cation channel localized to the flagellum, is the primary Ca 2+ -influx channel in mammalian sperm, is central to the regulation of [Ca 2+ ] i and experiments in CatSper-null mice have shown that the channels play a key role in both regulation of motility and the early phase of zona pellucida-induced acrosome [Ca 2+ ] i signalling (Carlson et al., 2003; Xia and Ren, 2009). Intriguingly, 'late' [Ca 2+ ] i responses persisted in the mutant mice and the zona pellucida-induced acrosome reaction was not inhibited (Xia and Ren, 2009). "
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    ABSTRACT: Previous work has provided evidence for involvement of store operated channels (SOCs) in [Ca(2+)]i signalling of human sperm, including a contribution to the transient [Ca(2+)]i elevation that occurs upon activation of CatSper, a sperm-specific cation channel localised to the flagellum, by progesterone . To further investigate the potential involvement of SOCs in the generation of [Ca(2+)]i signals in human sperm we have used cell-penetrating peptides containing the important basic sequence KIKKK, part of the STIM-Orai activating region/CRAC activation domain (SOAR/CAD) of the regulatory protein stromal interaction molecule 1 (STIM1). SOAR/CAD plays a key role in controlling the opening of SOCs, which occurs upon mobilisation of stored Ca(2+). Resting [Ca(2+)]i temporarily decreased upon application of KIKKK peptide (3-4 min) but scrambled KIKKK peptide had a similar effect, indicating that this action was not sequence specific. However, in cells pre-treated with KIKKK the transient [Ca(2+)]i elevation induced by stimulation with progesterone decayed significantly more slowly than in parallel controls and in cells pre-treated with scrambled KIKKK peptide. Examination of single cell responses showed that this effect was due, at least in part, to an increase in the proportion of cells in which the initial transient was maintained for an extended period, lasting up to 10 minutes in a sub-population of cells. We hypothesise that SOCs contribute to the progesterone-induced [Ca(2+)]i transient and that interference with the regulatory mechanisms of SOC delays their closure, causing a prolongation of the [Ca(2+)]i transient. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology.
    Molecular Human Reproduction 04/2015; DOI:10.1093/molehr/gav019 · 3.48 Impact Factor
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    • "Finally, CatSper is the only voltage-activated Ca 2 þ channel that can be detected by patch-clamp recordings from ejaculated human and epididymal mouse sperm (Kirichok et al, 2006; Navarro et al, 2008; Xia and Ren, 2009; Lishko et al, 2010, 2011; Kirichok and Lishko, 2011; Strü nker et al, 2011). Currents carried by other Ca v channels have only been recorded from precursor cells or testicular sperm (Martinez-Lopez et al, 2009; Xia and Ren, 2009). The only other Ca 2 þ -permeable ion channel that has been functionally characterized is a purinergic P2X2 receptor present in mouse sperm (Navarro et al, 2011). "
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    ABSTRACT: The sperm-specific CatSper channel controls the intracellular Ca(2+) concentration ([Ca(2+)](i)) and, thereby, the swimming behaviour of sperm. In humans, CatSper is directly activated by progesterone and prostaglandins-female factors that stimulate Ca(2+) influx. Other factors including neurotransmitters, chemokines, and odorants also affect sperm function by changing [Ca(2+)](i). Several ligands, notably odorants, have been proposed to control Ca(2+) entry and motility via G protein-coupled receptors (GPCRs) and cAMP-signalling pathways. Here, we show that odorants directly activate CatSper without involving GPCRs and cAMP. Moreover, membrane-permeable analogues of cyclic nucleotides that have been frequently used to study cAMP-mediated Ca(2+) signalling also activate CatSper directly via an extracellular site. Thus, CatSper or associated protein(s) harbour promiscuous binding sites that can host various ligands. These results contest current concepts of Ca(2+) signalling by GPCR and cAMP in mammalian sperm: ligands thought to activate metabotropic pathways, in fact, act via a common ionotropic mechanism. We propose that the CatSper channel complex serves as a polymodal sensor for multiple chemical cues that assist sperm during their voyage across the female genital tract.
    The EMBO Journal 02/2012; 31(7):1654-65. DOI:10.1038/emboj.2012.30 · 10.75 Impact Factor
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    • "Finally, all attempts to identify voltagegated Ca 2+ currents electrophysiologically in mature mouse or human spermatozoa have failed. T-type Ca 2+ channels could be recorded from mouse testicular sperm (Darszon et al., 2006b), but they seemed to be silenced via an unknown mechanism and are undetectable in the epididymal mouse sperm (Xia and Ren, 2009b). Ejaculated human spermatozoa do not posses functional Ca v channels as recorded with the patch-clamp technique (Lishko and Kirichok, unpublished data). "
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    ABSTRACT: Upon ejaculation, mammalian spermatozoa have to undergo a sequence of physiological transformations within the female reproductive tract that will allow them to reach and fertilize the egg. These include initiation of motility, hyperactivation of motility and perhaps chemotaxis toward the egg, and culminate in the acrosome reaction that permits sperm to penetrate the protective vestments of the egg. These physiological responses are triggered through the activation of sperm ion channels that cause elevations of sperm intracellular pH and Ca(2+) in response to certain cues within the female reproductive tract. Despite their key role in sperm physiology and their absolute requirement for the process of fertilization, sperm ion channels remain poorly understood due to the extreme difficulty in application of the patch-clamp technique to spermatozoa. This review covers the topic of sperm ion channels in the following order: first, we discuss how the intracellular Ca(2+) and pH signaling mediated by sperm ion channels controls sperm behavior during the process of fertilization. Then, we briefly cover the history of the methodology to study sperm ion channels, which culminated in the recent development of a reproducible whole-cell patch-clamp technique for mouse and human cells. We further discuss the main approaches used to patch-clamp mature mouse and human spermatozoa. Finally, we focus on the newly discovered sperm ion channels CatSper, KSper (Slo3) and HSper (H(v)1), identified by the sperm patch-clamp technique. We conclude that the patch-clamp technique has markedly improved and shifted our understanding of the sperm ion channels, in addition to revealing significant species-specific differences in these channels. This method is critical for identification of the molecular mechanisms that control sperm behavior within the female reproductive tract and make fertilization possible.
    Molecular Human Reproduction 06/2011; 17(8):478-99. DOI:10.1093/molehr/gar044 · 3.48 Impact Factor
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