Oral Presentation 2014 International Biophysics Congress

Unravelling the Glycosaminoglycan regulated structural integrity of a dimeric Chemokine (#506)

Krishna Mohan Poluri 1
  1. Indian Institute of Technology Roorkee, Roorkee, UK, India

Chemokines constitute the largest subfamily of cytokines that provide important regulatory cues in trafficking leukocytes. Glycosaminoglycans (GAGs) such as heparan sulfate are highly negatively charged linear polysaccharides. They are ubiquitously found on cell surfaces, and mediate a wide variety of biological functions. Though it is now well established that chemokine-heparan sulfate interactions regulate leukocyte recruitment, the structural basis and molecular mechanisms underlying these interactions are not well understood. CXCL1 (mKC) is a proinflammatory neutrophil activating chemokine, and exists in equilibrium between monomers and dimers (Kd = 36 mM). NMR and mutational studies using an engineered disulfide trapped CXCL1 dimer (dCXCL1) showed that GAGs bind orthogonal to the helical axis spanning the dimer interface. Residue level dynamics and stability measurements of apo- and GAG-bound dCXCL1 demonstrated GAGs enhanced chemokine’s structural integrity. Further, the generated quadruple mutant (H20A/K22A/K62A/K66A) on the basis of the binding data failed to bind heparin octasaccharide, validating our derived structural model. These data together indicate GAG-bound dimers regulate in-vivo neutrophil trafficking by multiple mechanisms including, defining the gradient formation and increasing the life time of ‘active’ chemokines on the endothelial cell surface for sustained recruitment.

  1. Poluri KM, Joseph PR, Sawant KR and Rajarathnam K, “Molecular Basis for Glycosaminoglycan binding to Chemokine CXCL1 Dimer”. ”, J Biol Chem., 278(22), 19980-19985, 2013.