Structural Basis of GIRK2 Channel Modulation by Cholesterol and PIP 2

G protein-gated inwardly rectifying potassium (GIRK) channels are important for determining neuronal excitability and have been implicated in a number of neurological diseases. In addition to G proteins, GIRK channels are also regulated by membrane cholesterol, which is elevated in the brain for neurodegenerative diseases like Alzheimer’s Dementia and Parkinson’s Disease.  The structural mechanism of cholesterol modulation of GIRK channels is not well understood.  Here, we present cryo-electron microscopy (cryoEM) structures of GIRK2 in the presence and absence of the cholesterol analog cholesteryl hemisuccinate (CHS) and PIP2. The structures reveal that CHS binds near PIP2 in lipid-facing hydrophobic pockets of the transmembrane domain. Our analysis suggests that CHS stabilizes PIP2 interaction with the channel and promotes the engagement of the cytoplasmic domain onto the transmembrane region. Mutagenesis of residues in one CHS binding pocket occludes cholesterol-dependent potentiation. Elucidating the cholesterol-binding site and characterizing the structural mechanisms underlying modulation of neuronal GIRK channels could facilitate the development of novel therapeutics for treating human diseases.