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#calcium channels

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Regeneration -ll

Calcium channels activated by resact in sea urchin sperm are encoded by:

Chemotactic calcium signaling in sea urchin sperm relies on specific ion channels opened downstream of resact binding. Resact activates receptor guanylate cyclase raising cGMP, opening tetraKCNG channels causing hyperpolarization, then depleting cGMP leading to depolarization that activates voltage-dependent calcium entry. Electrophysiology and molecular cloning identified entry path as CatSper channel complex encoded by four homologous CatSper1-4 genes forming heterotetramer in principal piece of flagellum, associated with auxiliary subunits. CatSper null sperm lack calcium pulses and chemotaxis. Bindin, resact, or hyalin genes encode structural adhesion proteins or chemoattractants, not calcium channel subunits responsible for chemosensation.

Ref: EMBO Journal, Seifert et al., The CatSper channel controls chemosensation in sea urchin sperm.

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Sea urchin -l

Calcium channels activated by resact in sea urchin sperm are encoded by:

Resact peptide binding to receptor guanylate cyclase on sperm flagellum activates cGMP synthesis opening K+ channels and triggering Ca2+ oscillations critical for chemotactic steering. Electrophysiology and genomics identified cation channel of sperm, CatSper, as major Ca2+ entry route mediating oscillations. CatSper genes encode four homologous subunits forming pH-sensitive channel enriched in flagellar principal piece. Sea urchin genome contains CatSper orthologs; blocking pore abolishes Ca2+ influx and turning. Bindin, resact and hyalin encode adhesion proteins unrelated to conductance. Thus calcium channels activated by resact are encoded by CatSper genes.

Ref: Seifert et al., Nature 2015, CatSper channelosome in sperm; Kaupp Lab - resact/CatSper signaling.

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