ABSTRACT
The C-X-C motif chemokine CXCL8 (interleukin-8, IL-8) and its receptor chemokine receptor 2 (CXCR2) mediate neutrophil migration during cell development and inflammatory responses and thus are related to numerous inflammatory diseases and cancers. We have determined the cryo-electron microscopy structure of CXCL8 bound CXCR2 coupled to Gi protein, as well as the crystal structure of inactive CXCR2 in complex with a designed allosteric antagonist. These results reveal the binding modes between CXCL8 and CXCR2, CXCR2 and G protein, and the detailed binding pattern of the allosteric antagonist, 00767013. Further structural analysis of the inactive- and active- states of CXCR2 reveals the unique shallow-pocket activation mechanism of C-X-C chemokine receptors and promotes our understanding on how a G protein-coupled receptor (GPCR) is activated by an endogenous protein molecule. In addition, the cholesterol molecule is observed in the activated CXCR2 structure, providing the structural basis of the potential allosteric modulation role of cholesterol in chemokine receptors.
Subject(s)
GTP-Binding Proteins/genetics , Inflammation/genetics , Interleukin-8/genetics , Receptors, Interleukin-8B/genetics , Allosteric Regulation/genetics , Cell Movement/genetics , GTP-Binding Proteins/ultrastructure , Humans , Inflammation/pathology , Interleukin-8/ultrastructure , Neutrophils/metabolism , Protein Binding/genetics , Protein Conformation , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/ultrastructure , Receptors, Interleukin-8B/ultrastructure , Signal Transduction/geneticsABSTRACT
The study aimed to explore the role of interleukin 8 (IL-8) in atherosclerotic plaques and develop a new method for the evaluation of endothelial function by assessing the interactions between the injured endothelial cells and the targeted ultrasound agent that carried anti-human IL-8 monoclonal antibody. Anti-human IL-8 monoclonal antibodies were associated to the shells of SonoVue microbubbles by covalent conjugation technology. The specific interaction between the microbubbles and the normal or injured endothelial cells was observed using an inverted microscope. The microbubble adherence was quantified by calculating the ratio of the adherent microbubbles to endothelial cells. The results were compared with the control microbubbles. There were rare adherences of control microbubbles to the normal or injured endothelial cells, whereas the targeted microbubbles could adhere to endothelial cells well. Importantly, compared with the normal endothelial cells, a significantly higher number of targeted microbubbles bound to the injured endothelial cells. The ultrasound agents with anti-human IL-8 monoclonal antibody can specifically bind to the injured endothelial cell, which provides a new insight to the noninvasive detection of endothelial dysfunction using ultrasound imaging techniques.
