Arima H et al. (2018), Conservation of the Ca2+-permeability through t...

XB-ART-55101

Channels (Austin) 2018 Jan 01;121:240-248. doi: 10.1080/19336950.2018.1476791.

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Conservation of the Ca2+-permeability through the voltage sensor domain of mammalian CatSper subunit.

Arima H , Tsutsui H , Okamura Y .

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Cation channel of Spermatozoa (CatSper) is one of the voltage-gated ion channels consisting of voltage sensor domains (VSDs) and pore-gate domains. CatSper is exclusively expressed in spermatozoa and indispensable for Ca2+ influx into cytosol. Recently, we have reported that the VSD of ascidian CatSper induces Ca2+-permeable pathways in heterologous expression systems. However, it is not known whether ion permeability through the VSD of CatSper is conserved in mammals. In the present study, electrophysiology and fluorometry in Xenopus oocytes revealed that Ca2+-permeable paths are also formed by expressing the VSD of murine CatSper. We also examined the permeability to monovalent cations other than Na+ in the VSD of ascidian CatSper.

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	Figure 1. Permeability of CiCS3 VSD to monovalent cations (A-D) Current traces and I-V relationships of the recordings (mean ± SEM) for examining K+ (A), Li+ (B), Cs+ (C) and NMDG (D) permeability. The same cells were recorded in the solutions with two different concentrations of cations. Voltage steps were from + 50 mV to −150 mV by 10 mV decrement. Holding potential (Vh) was at −10 mV. The current evoked by a step pulse to −150 mV is colored by red. (E) Test of proton permeability. Currents and fluorescence changes of iR-pHluorin were recorded from an oocyte expressing CiCS3 VSD-iR-pHluorin (left) or iR-pHluorin-CiHv1/VSOP (right) in the pH6 solution. Voltage steps for CiCS3 VSD-iR-pHluorin were from −150 mV to −10 mV. Vh was −10 mV. The voltage steps for iR-pHluorin-CiHv1/VSOP expressing cells were from −20 mV to + 100 mV. Vh was −80 mV.
	Figure 2. Inward currents are elicited in cells expressing the voltage-sensor domain of murine CatSper3. (A) Alignment of the amino acid sequence of the mCS3 VSD and the CiCS3 VSD (LC329335 in DDBJ). Negatively and positively charged amino acids are colored by red and blue, respectively. The putative trans-membrane regions are indicated by green lines. (B) Representative current traces from Xenopus oocytes injected with the cRNA of the mCS3 VSD (left upper) and the MT-mCS3 VSD (left lower), and an uninjected oocyte (right upper). The bath solution was ND69 solution. Voltage steps were from + 50 mV to −150 mV by 10 mV decrement (right lower). Vh was at −10 mV. The current evoked by a step pulse to −150 mV is colored by red. (C) Current-Voltage relationships of the recordings (mean ± SEM).
	Figure 3. The ion permeation paths induced by the MT-mCS3 VSD are permeable to Ca2+ [2]+ . (A) Representative current traces and fluorescence changes from oocytes expressing the MT-mCS3 VSD bathed in ND96 (Left) or Ca2+ free solution (Right). The voltage steps were from −150 mV to −10 mV by 20 mV increment. Vh was at −10 mV. The traces evoked by a step pulse to −150 mV are colored by red. The recordings in ND96 and Ca2+ free solution were from different cells. (B) Fluorescence-Voltage relationships (upper) and Current-Voltage relationships (lower) of the recordings (mean ± SEM).

References [+] :

Arima, Induction of divalent cation permeability by heterologous expression of a voltage sensor domain. 2018, Pubmed, Xenbase