Ion occupancy of the selectivity filter controls opening of a cytoplasmic gate in the K2P channel TALK-2

Lea C. Neelsen, Elena B. Riel, Susanne Rinné, Freya-Rebecca Schmid, Björn C. Jürs, Mauricio Bedoya, Jan P. Langer, Bisher Eymsh, Aytug K. Kiper, Sönke Cordeiro, Niels Decher (), Thomas Baukrowitz () and Marcus Schewe ()
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Lea C. Neelsen: Christian-Albrechts University of Kiel
Elena B. Riel: Christian-Albrechts University of Kiel
Susanne Rinné: Philipps-University of Marburg
Freya-Rebecca Schmid: Weill Cornell Medical College
Björn C. Jürs: Christian-Albrechts University of Kiel
Mauricio Bedoya: Universidad Católica del Maule
Jan P. Langer: Christian-Albrechts University of Kiel
Bisher Eymsh: Christian-Albrechts University of Kiel
Aytug K. Kiper: Philipps-University of Marburg
Sönke Cordeiro: Christian-Albrechts University of Kiel
Niels Decher: Philipps-University of Marburg
Thomas Baukrowitz: Christian-Albrechts University of Kiel
Marcus Schewe: Christian-Albrechts University of Kiel

Nature Communications, 2024, vol. 15, issue 1, 1-14

Abstract: Abstract Two-pore domain K+ (K2P) channel activity was previously thought to be controlled primarily via a selectivity filter (SF) gate. However, recent crystal structures of TASK-1 and TASK-2 revealed a lower gate at the cytoplasmic pore entrance. Here, we report functional evidence of such a lower gate in the K2P channel K2P17.1 (TALK-2, TASK-4). We identified compounds (drugs and lipids) and mutations that opened the lower gate allowing the fast modification of pore cysteine residues. Surprisingly, stimuli that directly target the SF gate (i.e., pHe., Rb+ permeation, membrane depolarization) also opened the cytoplasmic gate. Reciprocally, opening of the lower gate reduced the electric work to open the SF via voltage driven ion binding. Therefore, it appears that the SF is so rigidly locked into the TALK-2 protein structure that changes in ion occupancy can pry open a distant lower gate and, vice versa, opening of the lower gate concurrently promote SF gate opening. This concept might extent to other K+ channels that contain two gates (e.g., voltage-gated K+ channels) for which such a positive gate coupling has been suggested, but so far not directly demonstrated.

Date: 2024
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DOI: 10.1038/s41467-024-51812-w

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