Rediscovering sperm ion channels with the patch-clamp technique.

Department of Physiology, University of California San Francisco UCSF Mail Code 2140, Genentech Hall Room N272F 600 16th Street, San Francisco, CA 94158, USA.
Molecular Human Reproduction (Impact Factor: 3.48). 06/2011; 17(8):478-99. DOI: 10.1093/molehr/gar044
Source: PubMed

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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sperm intracellular pH, membrane voltage and calcium concentration [Ca2+]i are all important for sperm activity within the female reproductive tract.•Ion homeostasis and membrane voltage are under control of sperm ion channels and transporters. They regulate sperm motility and ability to locate and fertilize an egg.•Sperm ion channels are diverse and could differ between species in respect to their regulation.•Here we discuss the current knowledge about flagellar ion channels of mammalian sperm and concentrate our attention on calcium channel CatSper, proton channel Hv1, potassium channels of Slo family, and several new emerging ion channels.
    Cell Calcium 10/2014; DOI:10.1016/j.ceca.2014.10.009 · 4.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Molecular cascades of calcium homeostasis and signalling (Ca2+ pumps, channels, cation exchangers, and Ca2 + -binding proteins) emerged in prokaryotes and further developed at the unicellular stage of eukaryote evolution. With progressive evolution, mechanisms of signalling became diversified reflecting multiplication and specialisation of Ca2+ -regulated cellular activities. Recent genomic analysis of organisms from different systematic positions, combined with proteomic and functional probing invigorated expansion in our understanding of the evolution of Ca2+ signalling. Particularly impressive is the consistent role of Ca2 + -ATPases/pumps, calmodulin and calcineurin from very early stages of eukaryotic evolution, although with interspecies differences. Deviations in Ca2+ handling and signalling are observed between vertebrates and flowering plants as well as between protists at the basis of the two systematic categories, Unikonta (for example choanoflagellates) and Bikonta (for example ciliates). Only the B-subunit of calcineurin, for instance, is maintained to regulate highly diversified protein kinases for stress defence in flowering plants, whereas the complete dimeric protein, in vertebrates up to humans, regulates gene transcription, immune-defence and plasticity of the brain. Calmodulin is similarly maintained throughout evolution, but in plants a calmoldulin-like domain is integrated into protein kinase molecules. The eukaryotic cell has inherited and invented many mechanisms to exploit the advantages of signalling by Ca2+, and there is considerable overall similarity in basic processes of Ca2+ regulation and signalling during evolution, although some details may vary.
    Cell Calcium 03/2015; 57(3):123-132. DOI:10.1016/j.ceca.2014.12.004 · 4.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Following entry into the female reproductive tract, mammalian sperm undergo a maturation process termed capacitation that results in competence to fertilize ova. Associated with capacitation is an increase in membrane conductance to both Ca(2+) and K(+), leading to an elevation in cytosolic Ca(2+) critical for activation of hyperactivated swimming motility. In mice, the Ca(2+) conductance (alkalization-activated Ca(2+)-permeable sperm channel, CATSPER) arises from an ensemble of CATSPER subunits, whereas the K(+) conductance (sperm pH-regulated K(+) current, KSPER) arises from a pore-forming ion channel subunit encoded by the slo3 gene (SLO3) subunit. In the mouse, both CATSPER and KSPER are activated by cytosolic alkalization and a concerted activation of CATSPER and KSPER is likely a common facet of capacitation-associated increases in Ca(2+) and K(+) conductance among various mammalian species. The properties of heterologously expressed mouse SLO3 channels differ from native mouse KSPER current. Recently, a potential KSPER auxiliary subunit, leucine-rich-repeat-containing protein 52 (LRRC52), was identified in mouse sperm and shown to shift gating of SLO3 to be more equivalent to native KSPER. Here, we show that genetic KO of LRRC52 results in mice with severely impaired fertility. Activation of KSPER current in sperm lacking LRRC52 requires more positive voltages and higher pH than for WT KSPER. These results establish a critical role of LRRC52 in KSPER channels and demonstrate that loss of a non-pore-forming auxiliary subunit results in severe fertility impairment. Furthermore, through analysis of several genotypes that influence KSPER current properties we show that in vitro fertilization competence correlates with the net KSPER conductance available for activation under physiological conditions.
    Proceedings of the National Academy of Sciences 02/2015; DOI:10.1073/pnas.1423869112 · 9.81 Impact Factor

Full-text (2 Sources)

Available from
Jun 1, 2014