Structural basis of GIRK2 channel modulation by cholesterol and PIP₂

Abstract

Significance/Impact:• GIRK2 is one of the primary GIRK channels in brain. Characterization of cholesterol binding in GIRK2 provides new therapeutic sites for modulating these channels.• Many ion channels are modulated by cholesterol, but the molecular basis of this modulation has been elusive.• First cryoEM structures of pore-forming Kir alpha subunit. Word counts: Abstract (136) -Main text (3048)ABSTRACT 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 2 . The structures and their comparison reveal that CHS binds near PIP 2 in lipid-facing hydrophobic pockets of the transmembrane domain (TMD). CHS potentiates the effects of PIP 2 , 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.* is shown with a dashed square.

Structural insights into GIRK2 channel modulation by cholesterol and PIP2

“…An earlier version of this manuscript was uploaded on bioRxiv (Mathiharan et al, 2020). This work was supported in part by the National Institute on Alcohol Abuse and Alcoholism (AA018734) to P.A.S.…”

Upregulated GIRK2 counteracts ethanol-induced changes in excitability & respiration in human neurons

“…The top two upregulated genes in our 7-day ethanol exposure paradigm (ANGPTL4 and PDK4) (Figure 3B) are also key players in lipid metabolism; PDK4 in particular, has been associated with a loss of metabolic flexibility (Zhang et al, 2014;Jeon et al, 2020) and disrupted mitochondrial homeostasis (Ma et al, 2019). Notably, GIRK channel activity is potentiated by cholesterol (Glaaser and Slesinger, 2017;Mathiharan et al, 2020), suggesting that changes in membrane cholesterol could impact GIRK function.…”

“…Despite a much lower concentration of ethanol in our paradigm (17mM vs. 50mM in Jensen et al, 2019 57 ), our results are similar: the top two upregulated genes in our 7-day ethanol exposure paradigm ( ANGPTL4 and PDK4 ) ( Figure 3B ) are also key players in lipid metabolism; PDK4 in particular, has been associated with a loss of metabolic flexibility 40, 41 and disrupted mitochondrial homeostasis 38 . Interestingly, GIRK channel activity is potentiated by cholesterol 12, 58 , suggesting that changes in membrane cholesterol could impact GIRK function.…”