Conformational changes in the human Cx43/GJA1 gap junction channel visualized using cryo-EM.

Hyuk-Joon Lee, Hyung Jin Cha, Hyeongseop Jeong, Seu-Na Lee, Chang-Won Lee, Minsoo Kim, Jejoong Yoo, Jae-Sung Woo

Nature communications 2023 Feb 18

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Connexin family proteins assemble into hexameric hemichannels in the cell membrane. The hemichannels dock together between two adjacent membranes to form gap junction intercellular channels (GJIChs). We report the cryo-electron microscopy structures of Cx43 GJICh, revealing the dynamic equilibrium state of various channel conformations in detergents and lipid nanodiscs. We identify three different N-terminal helix conformations of Cx43-gate-covering (GCN), pore-lining (PLN), and flexible intermediate (FIN)-that are randomly distributed in purified GJICh particles. The conformational equilibrium shifts to GCN by cholesteryl hemisuccinates and to PLN by C-terminal truncations and at varying pH. While GJIChs that mainly comprise GCN protomers are occluded by lipids, those containing conformationally heterogeneous protomers show markedly different pore sizes. We observe an α-to-π-helix transition in the first transmembrane helix, which creates a side opening to the membrane in the FIN and PLN conformations. This study provides basic structural information to understand the mechanisms of action and regulation of Cx43 GJICh. © 2023. The Author(s).

Citation

Hyuk-Joon Lee, Hyung Jin Cha, Hyeongseop Jeong, Seu-Na Lee, Chang-Won Lee, Minsoo Kim, Jejoong Yoo, Jae-Sung Woo. Conformational changes in the human Cx43/GJA1 gap junction channel visualized using cryo-EM. Nature communications. 2023 Feb 18;14(1):931