Nature Cell Biology
- 8, 1149 - 1154 (2006)
Published online: 10 September 2006; | doi:10.1038/ncb1473
A K+-selective cGMP-gated ion channel controls chemosensation of spermTimo Strünker1, 2, Ingo Weyand1, 2, Wolfgang Bönigk1, Qui Van1, Astrid Loogen1, Joel E. Brown2, Nachiket Kashikar1, Volker Hagen3, Eberhard Krause3 & U.Benjamin Kaupp1, 21
Institut für Neurowissenschaft und Biophysik, Abteilung Zelluläre Signalverarbeitung, INB-1, Forschungszentrum Jülich, 52425 Jülich, Germany. 2
Marine Biological Laboratory, Woods Hole, MA 02543, USA. 3
Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str., 13125 Berlin, Germany.
Correspondence should be addressed to U.Benjamin Kaupp a.eckert@fz-juelich.de Eggs attract sperm by chemical factors, a process called chemotaxis. Sperm from marine invertebrates use cGMP signalling to transduce incident chemoattractants into changes in the Ca2+ concentration in the flagellum, which control the swimming behaviour during chemotaxis1,
2,
3. The signalling pathway downstream of the synthesis of cGMP by a guanylyl cyclase is ill-defined. In particular, the ion channels that are involved in Ca2+ influx and their mechanisms of gating are not known4. Using rapid voltage-sensitive dyes and kinetic techniques, we record the voltage response that is evoked by the chemoattractant in sperm from the sea urchin Arbacia punctulata. We show that the chemoattractant evokes a brief hyperpolarization followed by a sustained depolarization. The hyperpolarization is caused by the opening of K+-selective cyclic-nucleotide-gated (CNG) channels in the flagellum. Ca2+ influx commences at the onset of recovery from hyperpolarization. The voltage threshold of Ca2+ entry indicates the involvement of low-voltage-activated Cav channels. These results establish a model of chemosensory transduction in sperm whereby a cGMP-induced hyperpolarization opens Cav channels by a 'recovery-from-inactivation' mechanism and unveil an evolutionary kinship between transduction mechanisms in sperm and photoreceptors.
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