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: 3.32). 03/2009; 80(6):1092-8. DOI: 10.1095/biolreprod.108.074039
Source: PubMed


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.
    Full-text · Article · Apr 2015 · Molecular Human Reproduction
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    • "The results of our experiment observed that the protein expression patterns of MMP-2, MMP-9, TIMP-2, and TIMP-3 differed when FSH, LH, and Lutalyse were added, which signifies that hormones affect the expression of these 4 proteins. The effects of hormones on normal acrosomal morphology and protein expression patterns varied based on the type of hormone added and the time of culture, demonstrating the differences in MMP activation (Siu et al., 2004; Xia, et al., 2007, 2009). "
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    ABSTRACT: Proteases and protease inhibitors play key roles in most physiological processes, including cell migration, cell signaling, and cell surface and tissue remodeling. Among these, the matrix metalloproteinase (MMPs) pathway is one of the most efficient biosynthetic pathways for controlling the activation of enzymes responsible for protein degradation. This also indicates the association of MMPs with the maturation of spermatozoa. In an attempt to investigate the effect of MMP activation and inhibitors in cultures with various hormones during sperm capacitation, we examined and monitored the localization and expression of MMPs (MMP-2 and MMP-9), tissue inhibitors of metalloproteinases (TIMP-2 and TIMP-3), as well as their expression profiles. Matured spermatozoa were collected from cultures with follicle-stimulating hormone (FSH), luteinizing hormone (LH), and Lutalyse at 1 h, 6 h, 18 h, and 24 h. ELISA detected the expression of MMP-2, MMP-9, TIMP-2, and TIMP-3 in all culture media, regardless of medium type (FSH-supplemented fertilization Brackett-Oliphant medium (FFBO), LH-supplemented FBO (LFBO), or Lutalyse-supplemented FBO (LuFBO)). TIMP-2 and TIMP-3 expression patterns decreased in LFBO and LuFBO. MMP-2 and MMP-9 activity in FBO and FFBO progressively increased from 1 h to 24 h but was not detected in LFBO and LuFBO. The localization and expression of TIMP-2 and TIMP-3 in sperm heads was also measured by immunofluorescence analysis. However, MMPs were not detected in the sperm heads. MMP and TIMP expression patterns differed according to the effect of various hormones. These findings suggest that MMPs have a role in sperm viability during capacitation. In conjunction with hormones, MMPs play a role in maintaining capacitation and fertilization by controlling extracellular matrix inhibitors of sperm.
    Full-text · Article · Mar 2013 · Asian Australasian Journal of Animal Sciences
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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.
    Full-text · Article · Feb 2012 · The EMBO Journal
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