Structural basis of GIRK2 channel modulation by cholesterol and PIP 2

G protein-gated inwardly rectifying potassium (GIRK) channels play important roles in controlling cellular excitability in the heart and brain. While structural data begin to unravel the molecular basis for G protein and alcohol dependent activation of GIRK channels, little is known about the modulation by cholesterol. Here, we present cryo-electron microscopy (cryoEM) structures of GIRK2 in the presence and absence of the cholesterol analog cholesteryl hemisuccinate (CHS), and PIP. The structures and their comparison reveal that CHS binds near PIP in lipid-facing hydrophobic pockets of the transmembrane domain (TMD). CHS potentiates the effects of PIP, which stabilizes the inter-domain region and promotes the engagement of the cytoplasmic domain (CTD) onto the transmembrane region. The results suggest that CHS acts as a positive allosteric modulator and identify novel therapeutic sites for modulating GIRK channels in the brain.