Conformational changes in the human Cx43/GJA1 gap junction channel visualized using cryo-EM
Hyuk-Joon Lee1, Hyung Jin Cha1, Hyeongseop Jeong1,2
1Department of Life Sciences, Korea University, Seoul, 02841, Korea.
Nature Communications
|February 22, 2023
Summary
Connexin 43 (Cx43) gap junction intercellular channels (GJIChs) adopt dynamic conformations. These structures reveal how N-terminal helix arrangements influence channel gating and pore size, impacting cellular communication.
Area of Science:
- Structural biology
- Molecular biophysics
- Cell biology
Background:
- Connexin proteins form gap junction intercellular channels (GJIChs) essential for cell-to-cell communication.
- Understanding Cx43 GJICh structure is crucial for elucidating its function and regulation.
Purpose of the Study:
- To determine the cryo-electron microscopy structures of Cx43 GJICh.
- To identify and characterize different conformational states of Cx43 GJICh.
- To investigate the factors influencing Cx43 GJICh conformation and gating.
Main Methods:
- Cryo-electron microscopy (cryo-EM) of purified Cx43 GJICh.
- Analysis of channel conformations in detergents and lipid nanodiscs.
- Investigating effects of cholesteryl hemisuccinates, C-terminal truncations, and pH on conformation.
Main Results:
- Identified three N-terminal helix conformations: gate-covering (GCN), pore-lining (PLN), and flexible intermediate (FIN).
- Observed shifts in conformational equilibrium influenced by specific chemical and structural modifications.
- Demonstrated a link between protomer conformation, lipid occlusion, and varying pore sizes.
- Revealed an α-to-π-helix transition in the first transmembrane helix, creating membrane side openings in FIN and PLN states.
Conclusions:
- Cx43 GJICh exists in a dynamic equilibrium of multiple conformations.
- N-terminal helix conformation and its transitions are key determinants of Cx43 channel gating and function.
- Structural insights provide a basis for understanding Cx43 GJICh regulation and potential therapeutic targeting.
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