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bioRxiv · 10.1101/2023.06.15.545112

DIRECT REGULATION OF THE VOLTAGE-SENSING DOMAIN OF HCN CHANNELS BY MEMBRANE LIPID COMPARTMENTALIZATION

Handlin, L. J.·Dai, G.
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Abstract

Ion channels function within a membrane environment characterized by dynamic lipid compartmentalization. Limited knowledge exists regarding the response of voltage-gated ion channels to transmembrane potential within distinct membrane compartments. By leveraging fluorescence lifetime imaging microscopy (FLIM) and Forster resonance energy transfer (FRET), we visualized the localization of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in membrane domains. HCN4 exhibits a greater propensity for incorporation into ordered lipid domains compared to HCN1. To investigate the conformational changes of the S4 helix voltage sensor of HCN channels, we used dual stop-codon suppression to incorporate different noncanonical amino acids, orthogonal click chemistry for site-specific fluorescence labeling, and transition metal FLIM-FRET. Remarkably, altered FRET levels were observed between VSD sites within HCN channels upon disruption of membrane domains. We propose that the voltage-sensor rearrangements, directly influenced by membrane lipid domains, can explain the heightened activity of pacemaker HCN channels when localized in cholesterol-poor, disordered lipid domains, leading to membrane hyperexcitability and diseases.

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Handlin, L. J., Dai, G.. 2023-06-15. DIRECT REGULATION OF THE VOLTAGE-SENSING DOMAIN OF HCN CHANNELS BY MEMBRANE LIPID COMPARTMENTALIZATION. https://doi.org/10.1101/2023.06.15.545112

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