Letter | Published:

Progesterone activates the principal Ca2+ channel of human sperm

Nature volume 471, pages 387391 (17 March 2011) | Download Citation

Abstract

Steroid hormone progesterone released by cumulus cells surrounding the egg is a potent stimulator of human spermatozoa. It attracts spermatozoa towards the egg and helps them penetrate the egg’s protective vestments1. Progesterone induces Ca2+ influx into spermatozoa1,2,3 and triggers multiple Ca2+-dependent physiological responses essential for successful fertilization, such as sperm hyperactivation, acrosome reaction and chemotaxis towards the egg4,5,6,7,8. As an ovarian hormone, progesterone acts by regulating gene expression through a well-characterized progesterone nuclear receptor9. However, the effect of progesterone upon transcriptionally silent spermatozoa remains unexplained and is believed to be mediated by a specialized, non-genomic membrane progesterone receptor5,10. The identity of this non-genomic progesterone receptor and the mechanism by which it causes Ca2+ entry remain fundamental unresolved questions in human reproduction. Here we elucidate the mechanism of the non-genomic action of progesterone on human spermatozoa by identifying the Ca2+ channel activated by progesterone. By applying the patch-clamp technique to mature human spermatozoa, we found that nanomolar concentrations of progesterone dramatically potentiate CatSper, a pH-dependent Ca2+ channel of the sperm flagellum. We demonstrate that human CatSper is synergistically activated by elevation of intracellular pH and extracellular progesterone. Interestingly, human CatSper can be further potentiated by prostaglandins, but apparently through a binding site other than that of progesterone. Because our experimental conditions did not support second messenger signalling, CatSper or a directly associated protein serves as the elusive non-genomic progesterone receptor of sperm. Given that the CatSper-associated progesterone receptor is sperm specific and structurally different from the genomic progesterone receptor, it represents a promising target for the development of a new class of non-hormonal contraceptives.

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Acknowledgements

This work was funded by the UCSF Program for Breakthrough Biomedical Research.

Author information

Affiliations

  1. Department of Physiology, University of California San Francisco, UCSF Mail Code 2140, Genentech Hall Room N272F, 600 16th Street, San Francisco, California 94158, USA

    • Polina V. Lishko
    • , Inna L. Botchkina
    •  & Yuriy Kirichok

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Contributions

P.V.L. and Y.K. conceived the project, designed the experiments and wrote the manuscript. P.V.L. performed most of the experiments. I.L.B. helped with pilot experiments for the project. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Yuriy Kirichok.

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DOI

https://doi.org/10.1038/nature09767

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