Journal Article

Structure of the chemokine receptor CXCR1 in phospholipid bilayers

Kiefer, Hans, Casagrande, Fabio, Maier, Klaus, De Angelis, Anna A., Chu, Mignon, Das, Bibhuti B., Tian, Ye, Nothnagel, Henry J., Park, Sang Ho, Marassi, Francesca M., Opella, Stanley J.

2012

Overview

NMR spectroscopy is used to determine the three-dimensional structure of the full-length human chemokine receptor CXCR1 in phospholipid bilayers under physiological conditions. CXCR1 structure in a membrane G-protein-coupled receptors (GPCRs) are ubiquitous membrane proteins that transduce chemical signals from the outside of a cell, and many of them are drug targets. Sang Ho Park et al . present a new nuclear magnetic resonance spectroscopy method for the study of membrane proteins in phospholipid bilayers and use it to determine the structure of human CXCR1, a high-affinity GPCR for interleukin-8, a major mediator of immune and inflammatory responses. CXCR1 is one of two high-affinity receptors for the CXC chemokine interleukin-8 (IL-8), a major mediator of immune and inflammatory responses implicated in many disorders, including tumour growth 1 , 2 , 3 . IL-8, released in response to inflammatory stimuli, binds to the extracellular side of CXCR1. The ligand-activated intracellular signalling pathways result in neutrophil migration to the site of inflammation 2 . CXCR1 is a class A, rhodopsin-like G-protein-coupled receptor (GPCR), the largest class of integral membrane proteins responsible for cellular signal transduction and targeted as drug receptors 4 , 5 , 6 , 7 . Despite its importance, the molecular mechanism of CXCR1 signal transduction is poorly understood owing to the limited structural information available. Recent structural determination of GPCRs has advanced by modifying the receptors with stabilizing mutations, insertion of the protein T4 lysozyme and truncations of their amino acid sequences 8 , as well as addition of stabilizing antibodies and small molecules 9 that facilitate crystallization in cubic phase monoolein mixtures 10 . The intracellular loops of GPCRs are crucial for G-protein interactions 11 , and activation of CXCR1 involves both amino-terminal residues and extracellular loops 2 , 12 , 13 . Our previous nuclear magnetic resonance studies indicate that IL-8 binding to the N-terminal residues is mediated by the membrane, underscoring the importance of the phospholipid bilayer for physiological activity 14 . Here we report the three-dimensional structure of human CXCR1 determined by NMR spectroscopy. The receptor is in liquid crystalline phospholipid bilayers, without modification of its amino acid sequence and under physiological conditions. Features important for intracellular G-protein activation and signal transduction are revealed. The structure of human CXCR1 in a lipid bilayer should help to facilitate the discovery of new compounds that interact with GPCRs and combat diseases such as breast cancer.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/45/287/1192 / 631/45/535 / 631/57/2272 / Amino acids / Analytical, structural and metabolic biochemistry / Biological and medical sciences / Chemokine receptors / Chemokines / Crystallization / Disulfides - chemistry / Disulfides - metabolism / Enzyme Activation / Fundamental and applied biological sciences. Psychology / G proteins / Health aspects / Heterotrimeric GTP-Binding Proteins - metabolism / Humanities and Social Sciences / Humans / Interleukin-8 - chemistry / Interleukin-8 - metabolism / letter / Ligands / Lipid Bilayers - chemistry / Lipid Bilayers - metabolism / Magnetic studies / Methods / Models, Molecular / Molecular and cellular biology / Molecular Conformation / multidisciplinary / Mutation / NMR / Nuclear magnetic resonance / Nuclear Magnetic Resonance, Biomolecular / Phospholipids / Phospholipids - chemistry / Phospholipids - metabolism / Physiological aspects / Physiology / Proteins / Receptors, Interleukin-8A - chemistry / Receptors, Interleukin-8A - metabolism / Science / Signal Transduction / Structure