Influence of Lipid Mimetics on Gating of Ryanodine Receptor

• Published in: Structure (London) 2018-10, Vol.26 (10), p.1303-1313.e4
• Main Authors: Willegems, Katrien, Efremov, Rouslan G.
• Format: Article
• Language: English
• Subjects: calcium signaling; cryo-EM; ion channel gating; lipid mimetic; lipid nanodiscs; ryanodine receptor
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2018.06.010

Understanding gating principles of ion channels at high resolution is of great importance. Here we investigate the conformational transition from closed to open state in ryanodine receptor 1 (RyR1) reconstituted into lipid nanodiscs. RyR1 is a homotetrameric giant ion channel that couples excitation of muscle cells to fast calcium release from the sarcoplasmic reticulum. Using single-particle cryo-EM we show that RyR1 reconstituted into lipid nanodiscs is stabilized in the open conformation when bound to the plant toxin ryanodine, but not in the presence of its physiological activators, calcium and ATP. Further, using ryanodine binding assays we show that membrane mimetics influence RyR1 transition between closed and open-channel conformations. We find that all detergents, including fluorinated detergents added to nanodiscs, stabilize closed state of RyR1. Our biochemical results correlate with available structural data and suggest optimal conditions for structural studies of RyR1 gating. [Display omitted] •Structure of transmembrane domain of RyR1 is influenced by lipid mimetics•Structural changes associated with channel opening are similar in lipids and detergent•Detergent reduces open probability of RyR1•Detergent-lipid mixture or nanodiscs mimic closely RyR1 behavior in lipid bilayer By combining cryo-EM with biochemical assays, Willegems et al. show that the use of lipid bilayer mimetics influences closed-open transitions in ryanodine receptor 1 (RyR1), a calcium release channel. Lipids are essential for reproducing the native gating properties of RyR1 in structural studies using cryo-EM.