Preprint Article Version 1 This version is not peer-reviewed

Mutated Channelrhodopsins with Increased Sodium and Calcium Permeability

Version 1 : Received: 7 February 2019 / Approved: 8 February 2019 / Online: 8 February 2019 (09:41:15 CET)

A peer-reviewed article of this Preprint also exists.

Duan, X.; Nagel, G.; Gao, S. Mutated Channelrhodopsins with Increased Sodium and Calcium Permeability. Appl. Sci. 2019, 9, 664. Duan, X.; Nagel, G.; Gao, S. Mutated Channelrhodopsins with Increased Sodium and Calcium Permeability. Appl. Sci. 2019, 9, 664.

Journal reference: Appl. Sci. 2019, 9, 664
DOI: 10.3390/app9040664

Abstract

(1) Background: After the discovery and application of Chlamydomonas reinhardtii channelrhodopsins, the optogenetic toolbox has been greatly expanded with engineered and newly discovered natural channelrhodopsins. However, channelrhodopsins of higher Ca2+ conductance or more specific ion permeability are still in demand. (2) Methods: In this study, we mutated the conserved aspartate of the transmembrane helix 4 (TM4) within Chronos (Stigeoclonium helveticum channelrhodopsin = ShChR) and PsChR (Platymonas subcordiformis channelrhodopsin) and compared them with published ChR2 (C. reinhardtii channelrhodopsin-2) aspartate mutants. (3) Results: We found that the ChR2 D156H mutant (XXM) showed enhanced Na+ and Ca2+ conductance, which was not noticed before, while the D156C mutation (XXL) influenced the Na+ and Ca2+ conductance only slightly. Furthermore, the D173H mutant of PsChR showed a much improved photocurrent, compared to wildtype, and even higher Na+ selectivity to H+ than XXM. PsChR D173H also showed a strongly enhanced Ca2+ conductance, more than 2-fold that of the calcium translocating L132C of ChR2 (CatCh). (4) Conclusions: We found that mutating the aspartate of the TM4 to histidine influences the ion selectivity of channelrhodopsins. With the large photocurrent and enhanced Na+ selectivity and Ca2+ conductance, XXM and PsChR D139H are promising powerful optogenetic tools, especially for Ca2+ manipulation.

Subject Areas

optogenetics; channelrhodopsins; sodium; Calcium; DC gate

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