Structural Basis of Native CXCL7 Monomer Binding to CXCR2 Receptor N-Domain and Glycosaminoglycan Heparin

Abstract

CXCL7, a chemokine highly expressed in platelets, orchestrates neutrophil recruitment during thrombosis and related pathophysiological processes by interacting with CXCR2 receptor and sulfated glycosaminoglycans (GAG). CXCL7 exists as monomers and dimers, and dimerization (~50 μM) and CXCR2 binding (~10 nM) constants indicate that CXCL7 is a potent agonist as a monomer. Currently, nothing is known regarding the structural basis by which receptor and GAG interactions mediate CXCL7 function. Using solution nuclear magnetic resonance (NMR) spectroscopy, we characterized the binding of CXCL7 monomer to the CXCR2 N-terminal domain (CXCR2Nd) that constitutes a critical docking site and to GAG heparin. We found that CXCR2Nd binds a hydrophobic groove and that ionic interactions also play a role in mediating binding. Heparin binds a set of contiguous basic residues indicating a prominent role for ionic interactions. Modeling studies reveal that the binding interface is dynamic and that GAG adopts different binding geometries. Most importantly, several residues involved in GAG binding are also involved in receptor interactions, suggesting that GAG-bound monomer cannot activate the receptor. Further, this is the first study that describes the structural basis of receptor and GAG interactions of a native monomer of the neutrophil-activating chemokine family.

Transcriptional, epigenetic and metabolic signatures in cardiometabolic syndrome defined by extreme phenotypes

“…The former two showed that vascular integrity, compromised by obesity (Shah et al, 2015), was restored, as also observed by Albrechtsen and colleagues (Wewer Albrechtsen et al, 2018). Almost half (6/13) of the blood specific DAP were also DEG in at least one cell type; SIRPB1 is known to be involved in impaired immune response and leptin resistance (Rendo-Urteaga et al, 2015), RAC2 plays a role in immune pathways (Das, Ma and Sharma, 2015), PPBP (also known as CXCL7) is a chemokine involved in neutrophils recruitment during thrombosis (Brown, Sepuru and Rajarathnam, 2017) while ADGRE2 mediates macrophage differentiation and inflammatory response (Kuan-Yu et al, 2017). This showed that some of the changes that occurred at transcriptional level are directly involved in the reduction of the proinflammatory environment but also that other levels of regulation are involved.…”

Glycosaminoglycan Interactions Fine-Tune Chemokine-Mediated Neutrophil Trafficking: Structural Insights and Molecular Mechanisms

“…22,[28][29][30] The molecular basis of CXCL1, CXCL5, CXCL7, and CXCL8 binding to heparin oligosaccharides has been characterized using solution nuclear magnetic resonance (NMR) spectroscopy. [31][32][33][34] In particular, binding-induced NMR chemical shift changes have been shown to be quite useful for describing the molecular basis of the binding process. These studies have shown that the dimer binds heparin with higher affinity, and cellular studies have also shown that chemokine dimerization and GAG binding are coupled.…”

“…Furthermore, these studies show not only basic residues that are conserved but also those that are unique to a given chemokine mediate binding. [30][31][32][33][34] Most interestingly, these chemokines show a diversity of GAG-binding surfaces, indicating chemokine-specific residues play an important role in dictating the binding interactions, and that location and distribution of both conserved and chemokine-specific residues in the context of three-dimensional structure determine binding geometry. Residues implicated in binding are highlighted, and those that are conserved (in at least five out of seven sequences) are in red and shaded in gray and are labeled from B1 to B8.…”

“…We have characterized the binding interactions of CXCL7 monomer and dimer to heparin using NMR spectroscopy. 30,34 Binding interactions of the native monomer were characterized by exploiting the weak propensity of CXCL7 to form dimers. This is the only structural characterization of GAG interactions of a native monomer in the NAC family.…”

“…Such studies for CXCL1, CXCL5, CXCL7, and CXCL8 have shown several residues that are involved in CXCR2 binding are also involved in GAG interactions. 28,[30][31][32]34,56 A schematic of the GAG and receptor-binding residues and the extent of overlap are shown (Fig. 6).…”