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Whole-cell patch-clamp measurements of spermatozoa reveal an alkaline-activated Ca2+ channel

Abstract

In mammals, sperm cells become motile during ejaculation and swim up the female reproductive tract. Before fertilization and to overcome various barriers, their motility must be hyperactivated, a motion that is characterized by vigorous asymmetric tail beating1. Hyperactivation requires an increase in calcium in the flagella, a process that probably involves plasmalemmal ion channels2,3,4,5,6,7,8. Numerous attempts in the past two decades to understand sperm cell channels have been frustrated by the difficulty of measuring spermatozoan transmembrane ion currents2,3,9,10,11,12,13,14,15,16. Here, by using a simple approach to patch-clamp spermatozoa and to characterize whole-spermatozoan currents, we describe a constitutively active flagellar calcium channel that is strongly potentiated by intracellular alkalinization. This current is not present in spermatozoa lacking the sperm-specific putative ion channel protein, CatSper1. This plasma membrane protein of the six transmembrane-spanning ion channel superfamily is specifically localized to the principal piece of the sperm tail and is required for sperm cell hyperactivation and male fertility4,5. Our results identify CatSper1 as a component of the key flagellar calcium channel, and suggest that intracellular alkalinization potentiates CatSper current to increase intraflagellar calcium and induce sperm hyperactivation.

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Figure 1: Whole-cell patch-clamp recordings from intact spermatozoa.
Figure 2: I CatSper originates from the principal piece of the sperm cell flagellum.
Figure 3: I CatSper is Ca 2+ selective.
Figure 4: pH and voltage-dependence of ICatSper.

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Acknowledgements

We thank H. Qi for help in preparation of sperm cells and for discussion.

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Competing interests

D.E.C. has a patent pending on the use of CatSper1 as a contraception target.

Supplementary information

Supplementary Figure 1.

Monovalent ICatSper is potentiated by intracellular alkalinization. (PDF 272 kb)

Supplementary Figure 2.

CatSper conducts inward and outward Ba2+ current in response to a voltage ramp in symmetrical 50 mM [Ba2+]. (PDF 279 kb)

Supplementary Figure 3.

ICatSper is insensitive to cyclic nucleotides. (PDF 676 kb)

Supplementary Movie

Application of the patch pipette to the small cytoplasmic droplet of the sperm, a remnant of the precursor germ cell cytoplasm located on the midpiece of a mature sperm cell that is shed around the time of ejaculation. (AVI 7515 kb)

Supplementary Legends

Legends to accompany the above Supplementary Figures and Supplementary Movie. (DOC 26 kb)

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Kirichok, Y., Navarro, B. & Clapham, D. Whole-cell patch-clamp measurements of spermatozoa reveal an alkaline-activated Ca2+ channel. Nature 439, 737–740 (2006). https://doi.org/10.1038/nature04417

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  • DOI: https://doi.org/10.1038/nature04417

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