Cholesterol-induced suppression of Kir2 channels is mediated by decoupling at the inter-subunit interfaces
Nicolas Barbera,
Sara T. Granados,
Carlos Guillermo Vanoye,
Tatiana V. Abramova,
Danielle Kulbak,
Sang Joon Ahn,
Alfred L. George, Jr.,
Belinda S. Akpa,
Irena Levitan
Affiliations
Nicolas Barbera
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA; Corresponding author
Sara T. Granados
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
Carlos Guillermo Vanoye
Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
Tatiana V. Abramova
Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
Danielle Kulbak
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
Sang Joon Ahn
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
Alfred L. George, Jr.
Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
Belinda S. Akpa
Division of Biosciences, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA; Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA; Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27695, USA; Corresponding author
Irena Levitan
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA; Corresponding author
Summary: Cholesterol is a major regulator of multiple types of ion channels. Although there is increasing information about cholesterol binding sites, the molecular mechanisms through which cholesterol binding alters channel function are virtually unknown. In this study, we used a combination of Martini coarse-grained simulations, a network theory-based analysis, and electrophysiology to determine the effect of cholesterol on the dynamic structure of the Kir2.2 channel. We found that increasing membrane cholesterol reduced the likelihood of contact between specific regions of the cytoplasmic and transmembrane domains of the channel, most prominently at the subunit-subunit interfaces of the cytosolic domains. This decrease in contact was mediated by pairwise interactions of specific residues and correlated to the stoichiometry of cholesterol binding events. The predictions of the model were tested by site-directed mutagenesis of two identified residues—V265 and H222—and high throughput electrophysiology.
