Glycosaminoglycan binding properties of the myxoma virus CC-chemokine inhibitor, M-T1.
Poxviruses encode a number of secreted virulence factors that function to mitigate or modulate the host immune response. M-T1 is a secreted 43-kDa glycoprotein produced by the myxoma virus, a poxvirus pathogen of rabbits, that binds CC-chemokines with high affinity, blocks binding to their cognate G-protein coupled receptors, and thereby inhibits chemokine-induced leukocyte chemotaxis. The present study indicates that M-T1, but not the related vaccinia virus 35-kDa CC-chemokine-binding protein, can localize to cell surfaces through an interaction with glycosaminoglycan molecules. In addition to biochemically characterizing the nature of this interaction, we demonstrate that M-T1 can also simultaneously interact with CC-chemokines while bound to heparin, suggesting that the binding sites on M-T1 for chemokines and heparin are distinct. Furthermore, using recombinant baculovirus-expressed M-T1 truncation and internal deletion mutants, we localize the heparin-binding region of M-T1 to the C terminus of the protein, a region that contains a high abundance of basic residues and includes two clusters of basic amino acid residues that resemble Cardin and Weintraub heparin-binding consensus sequences. The ability of M-T1 to simultaneously interact with chemokines and glycosaminoglycans may enable M-T1 to tether to endothelial surfaces or extracellular matrix and capture host chemokines that are expressed close to sites of virus infection.
Seet
B T
BT
Departments of Microbiology and Immunology and Biochemistry, The University of Western Ontario, London, Ontario, Canada N6A 5C1.
Barrett
J
J
Robichaud
J
J
Shilton
B
B
Singh
R
R
McFadden
G
G
D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D002460:Cell Line; D018925:Chemokines / Q000037:antagonists & inhibitors; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000166:cytology / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D017353:Gene Deletion; D006025:Glycosaminoglycans / Q000737:chemistry* / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009233:Myxoma virus / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D020349:Surface Plasmon Resonance; D013552:Swine; D014616:Vaccinia virus / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry*
D018925:Chemokines; D006025:Glycosaminoglycans; C119017:M-T1 protein, myxoma virus; D011994:Recombinant Proteins; D014764:Viral Proteins; D012965:Sodium Chloride; D006493:Heparin