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Effect of Lipid Composition on the Membrane Orientation of the G Protein-Coupled Receptor Kinase 2-G?1?2 Complex.

ABSTRACT: Interactions between proteins and cell membranes are critical for biological processes such as transmembrane signaling, and specific components of the membrane may play roles in helping to organize or mandate particular conformations of both integral and peripheral membrane proteins. One example of a signaling enzyme whose function is dependent on membrane binding and whose activity is affected by specific lipid components is G protein-coupled receptor (GPCR) kinase 2 (GRK2). Efficient GRK2-mediated phosphorylation of activated GPCRs is dependent not only on its recruitment to the membrane by heterotrimeric G?? subunits but also on the presence of highly negatively charged lipids, in particular phosphatidylinositol 4',5'-bisphosphate (PIP2). We hypothesized that PIP2 may favor a distinct orientation of the GRK2-G?? complex on the membrane that is more optimal for function. In this study, we compared the possible orientations of the GRK2-G?? complex and G?? alone on model cell membranes prepared with various anionic phospholipids as deduced from sum frequency generation vibrational and attenuated total reflectance Fourier transform infrared spectroscopic methods. Our results indicate that PIP2 affects the membrane orientation of the GRK2-G?1?2 complex but not that of complexes formed with anionic phospholipid binding deficient mutations in the GRK2 pleckstrin homology (PH) domain. G?1?2 exhibits a similar orientation on the lipid bilayer regardless of its lipid composition. The PIP2-induced orientation of the GRK2-G?1?2 complex is therefore most likely caused by specific interactions between PIP2 and the GRK2 PH domain. Thus, PIP2 not only helps recruit GRK2 to the membrane but also "fine tunes" the orientation of the GRK2-G?? complex so that it is better positioned to phosphorylate activated GPCRs.

SUBMITTER: Yang P

PROVIDER: S-EPMC4886744 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Effect of Lipid Composition on the Membrane Orientation of the G Protein-Coupled Receptor Kinase 2-Gβ1γ2 Complex.

Yang Pei P Homan Kristoff T KT Li Yaoxin Y Cruz-Rodríguez Osvaldo O Tesmer John J G JJ Chen Zhan Z

Biochemistry 20160506 20

Interactions between proteins and cell membranes are critical for biological processes such as transmembrane signaling, and specific components of the membrane may play roles in helping to organize or mandate particular conformations of both integral and peripheral membrane proteins. One example of a signaling enzyme whose function is dependent on membrane binding and whose activity is affected by specific lipid components is G protein-coupled receptor (GPCR) kinase 2 (GRK2). Efficient GRK2-medi ...[more]

PMID: 27088923

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Project description:Some lipid mixtures form membranes containing submicroscopic (nanodomain) ordered lipid domains (rafts). Some of these nanodomains are so small (radius <5 nm) that they cannot be readily detected with Förster resonance energy transfer (FRET)-labeled lipid pairs with large Ro. We define such domains as ultrananodomains. We studied the effect of lipid structure/composition on the formation of ultrananodomains in lipid vesicles using a dual-FRET-pair approach in which only one FRET pair had Ro values that were sufficiently small to detect the ultrananodomains. Using this approach, we measured the temperature dependence of domain and ultrananodomain formation for vesicles composed of various mixtures containing a high-Tm lipid (brain sphingomyelin (SM)) or dipalmitoyl phosphatidylcholine (DPPC)), low-Tm lipid (dioleoylphosphatidylcholine (DOPC) or 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC)), and a lower (28 mol %) or higher (38 mol %) cholesterol concentration. For every lipid combination tested, the thermal stabilities of the ordered domains were similar, in agreement with our prior studies. However, the range of temperatures over which ultrananodomains formed was highly lipid-type dependent. Overall, vesicles that were closest to mammalian plasma membrane in lipid composition (i.e., with brain SM, POPC, and/or higher cholesterol) formed ultrananodomains in preference to larger domains over the widest temperature range. Relative to DPPC, the favorable effect of SM on ultrananodomain formation versus larger domains was especially large. In addition, the favorable effect of a high cholesterol concentration, and of POPC versus DOPC, on the formation of ultrananodomains versus larger domains was greater in vesicles containing SM than in those containing DPPC. We speculate that it is likely that natural mammalian lipids are tuned to maximize the tendency to form ultrananodomains relative to larger domains. The observation that domain size is more sensitive than domain formation to membrane composition has implications for how membrane domain properties may be regulated in vivo.

Dataset Information

Effect of Lipid Composition on the Membrane Orientation of the G Protein-Coupled Receptor Kinase 2-G?1?2 Complex.

Publications

Effect of Lipid Composition on the Membrane Orientation of the G Protein-Coupled Receptor Kinase 2-Gβ1γ2 Complex.

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