CatSper channels in sea urchin sperm

•The CatSper channel is expressed in the flagellum of swollen sea urchin sperm.•Electrophysiology reveals CatSper like currents in sea urchin sperm.•Speract increase the CatSper current in sea urchin sperm.•Sea urchin sperm have a Ca2+-activated Cl− current. Sea urchin sperm swimming is regulated by speract, a decapeptide released from egg jelly that induces chemotaxis and triggers membrane potential (Em) changes, intracellular increases in cyclic nucleotides (cGMP, cAMP), pH (pHi) and calcium concentration ([Ca2+]i). The identity of the ionic transporters associated with the [Ca2+]i changes required for chemotaxis is not fully known. CatSper, a sperm exclusive Ca2+ channel has been detected by proteomic analysis and immunofluorescence in sea urchin sperm and there is evidence for its involvement in chemotaxis. This work presents an electrophysiological characterization of a CatSper channel in sea urchin sperm. By swelling sperm suspending them in 10-fold diluted artificial sea water (ASW) we achieve on-cell patch-clamp recordings that document a mildly voltage and pHi dependent Na+ permeable channel (in absence of divalent ions in the pipette), sensitive to speract, and blocked by Mibefradil (Mibe), NNC55–0396 (NNC) and RU1968 (RU) resembling CatSper. We also recorded a voltage dependent Cl− channel inhibited by Niflumic Acid and the TMEM16A blocker. [Display omitted]