The Glycosphingolipid GM3 Modulates Conformational Dynamics of the Glucagon Receptor

Abstract

The extracellular domain (ECD) of class B1 G-protein-coupled receptors (GPCRs) plays a central role in signal transduction and is uniquely positioned to sense both the extracellular and membrane environments. Although recent studies suggest a role for membrane lipids in the modulation of class A and class F GPCR signaling properties, little is known about the effect of lipids on class B1 receptors. In this study, we employed multiscale molecular dynamics simulations to access the dynamics of the glucagon receptor (GCGR) ECD in the presence of native-like membrane bilayers. Simulations showed that the ECD could move about a hinge region formed by residues Q122–E126 to adopt both closed and open conformations relative to the transmembrane domain. ECD movements were modulated by binding of the glycosphingolipid GM3. These large-scale fluctuations in ECD conformation may affect the ligand binding and receptor activation properties. We also identify a unique phosphatidylinositol (4,5)-bisphosphate (PIP 2 ) interaction profile near intracellular loop (ICL) 2/TM3 at the G-protein-coupling interface, suggesting a mechanism of engaging G-proteins that may have a distinct dependence on PIP 2 compared with class A GPCRs. Given the structural conservation of class B1 GPCRs, the modulatory effects of GM3 and PIP 2 on GCGR may be conserved across these receptors, offering new insights into potential therapeutic targeting.

In Silico Identification of Cholesterol Binding Motifs in the Chemokine Receptor CCR3

“…Coarse-grained (CG) MD facilitates the analysis of dynamic interactions on timescales that are typically too computationally demanding to perform on atomistic systems. Such approaches have been implemented to good effect in defining lipid–protein binding sites [ 30 , 31 , 32 , 33 , 34 , 35 ]. Computation approaches are not, however, limited to defining the locus of lipid–protein interactions.…”

The Interplay of Glucagon-Like Peptide-1 Receptor Trafficking and Signalling in Pancreatic Beta Cells

“…Moreover, the GLP-1R undergoes agonistdependent palmitoylation at its C-terminus, providing a mechanism for altered interaction and targeting of active receptors to these cholesterol-rich membrane regions (71). As well as a role in concentrating active GPCRs in particular membrane nanodomains enriched in signalling and trafficking proteins, direct interactions with cholesterol may alter the binding affinity of GPCRs (84,85), suggesting that this lipid might allosterically modulate receptors by limiting their conformational flexibility, a possibility that remains to be investigated for the GLP-1R.…”

Structures and Dynamics of Native-State Transmembrane Protein Targets and Bound Lipids

“…An exogenous PtdIns(4,5)P 2 molecule is seen to bridge the complexed structure of NTSR1 and β-arrestin, stabilizing their active conformation [ 47 ] and suggesting that such ternary states are viable targets. The interactions of lipids including gangliosides in the outer leaflet and PIs in the inner leaflet can be modelled and reveal multiple potential binding sites in GPCRs of either class A [ 48 ] or class B [ 49 ], illustrating such multivalent interactions ( Figure 3 ). NTSR1 complexes have been expressed in insect cells and solubilized using polymethacrylate (PMA) co-polymer, yielding nanodiscs with higher levels of stimulation of both G q and G i1 heterotrimers than detergent micelle preparations [ 50 ].…”

“…Cross-grain molecular dynamics simulation of this class B GPCR (light blue) in an asymmetric lipid bilayer reveals a variety of binding poses of PI(4,5)P 2 molecules (red) in the inner leaflet, showing the juxtaposition of phosphate groups (black) and Arg and Lys residues (blue spheres). Taken from [ 49 ].…”