Twisting and Protonation of Retinal Chromophore Regulate Channel Gating of Channelrhodopsin C1C2

Channelrhodopsins (ChRs) are light-gated ion channels and central optogenetic tools that can control neuronal activity with high temporal resolution at the single-cell level. Although their application in optogenetics has rapidly progressed, it is unsolved how their channels open and close. ChRs transport ions through a series of interlocking elementary processes that occur over a broad time scale of subpicoseconds to seconds. During these processes, the retinal chromophore functions as a channel regulatory domain and transfers the optical input as local structural changes to the channel operating domain, the helices, leading to channel gating. Thus, the core question on channel gating dynamics is how the retinal chromophore structure changes throughout the photocycle and what rate-limits the kinetics. Here, we investigated the structural changes in the retinal chromophore of canonical ChR, C1C2, in all photointermediates using time-resolved resonance Raman spectroscopy. Moreover, to reveal the rate-limiting factors of the photocycle and channel gating, we measured the kinetic isotope effect of all photoreaction processes using laser flash photolysis and laser patch clamp, respectively. Spectroscopic and electrophysiological results provided the following understanding of the channel gating: the retinal chromophore highly twists upon the retinal Schiff base (RSB) deprotonation, causing the surrounding helices to move and open the channel. The ion-conducting pathway includes the RSB, where inflowing water mediates the proton to the deprotonated RSB. The twisting of the retinal chromophore relaxes upon the RSB reprotonation, which closes the channel. The RSB reprotonation rate-limits the channel closing.

Medienart:

E-Artikel

Erscheinungsjahr:

2023

Erschienen:

2023

Enthalten in:

Zur Gesamtaufnahme - volume:145

Enthalten in:

Journal of the American Chemical Society - 145(2023), 19 vom: 17. Mai, Seite 10779-10789

Sprache:

Englisch

Beteiligte Personen:

Shibata, Keisei [VerfasserIn]
Oda, Kazumasa [VerfasserIn]
Nishizawa, Tomohiro [VerfasserIn]
Hazama, Yuji [VerfasserIn]
Ono, Ryohei [VerfasserIn]
Takaramoto, Shunki [VerfasserIn]
Bagherzadeh, Reza [VerfasserIn]
Yawo, Hiromu [VerfasserIn]
Nureki, Osamu [VerfasserIn]
Inoue, Keiichi [VerfasserIn]
Akiyama, Hidefumi [VerfasserIn]

Links:

Volltext

Themen:

Channelrhodopsins
Ion Channels
Journal Article
Protons
Research Support, Non-U.S. Gov't

Anmerkungen:

Date Completed 18.05.2023

Date Revised 18.05.2023

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1021/jacs.3c01879

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM356328333