A K+-selective CNG channel orchestrates Ca2+ signalling in zebrafish sperm
- Center of Advanced European Studies and Research, United States
- Center of Advanced European Studies and Research, Germany
- Ruhr-Universität Bochum, Germany
- Forschungszentrum Jülich, Germany
- University of Massachusetts Boston, United States
- Helmholtz-Zentrum München, Germany
Abstract
Calcium in the flagellum controls sperm navigation. In sperm of marine invertebrates and mammals, Ca2+ signalling has been intensely studied, whereas for fish little is known. In sea urchin sperm, a cyclic nucleotide-gated K+ channel (CNGK) mediates a cGMP-induced hyperpolarization that evokes Ca2+ influx. Here, we identify in sperm of the freshwater fish Danio rerio a novel CNGK family member featuring non-canonical properties. It is located in the sperm head rather than the flagellum and is controlled by intracellular pH, but not cyclic nucleotides. Alkalization hyperpolarizes sperm and produces Ca2+ entry. Ca2+ induces spinning-like swimming, different from swimming of sperm from other species. The 'spinning' mode probably guides sperm into the micropyle, a narrow entrance on the surface of fish eggs. A picture is emerging of sperm channel orthologues that employ different activation mechanisms and serve different functions. The channel inventories probably reflect adaptations to species-specific challenges during fertilization.
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© 2015, Fechner et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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A K+-selective CNG channel orchestrates Ca2+ signalling in zebrafish sperm
eLife 4:e07624.
https://doi.org/10.7554/eLife.07624
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