The purified myxoma virus gamma interferon receptor homolog M-T7 interacts with the heparin-binding domains of chemokines.
The myxoma virus T7 protein M-T7 is a functional soluble gamma interferon receptor homolog that has previously been shown to bind gamma interferon and inhibit its antiviral activities in a species-specific manner, but gene knockout analysis has suggested a further role for M-T7 in blocking leukocyte influx into infected lesions. We purified M-T7 to apparent homogeneity and showed that M-T7 is an N-linked glycoprotein that appears to be a stable homotrimer with a molecular mass of approximately 113 kDa in solution. M-T7, in addition to forming inhibitory complexes with rabbit gamma interferon, was also shown to bind to human interleukin-8, a prototypic member of the chemokine superfamily. Moreover, M-T7 was able to interact promiscuously with all members of the CXC, CC, and C chemokine subfamilies tested. Binding of human RANTES to M-T7 can be competed by rabbit gamma interferon and also by cold RANTES competitor with a 50% inhibitory concentration of 900 nM. Although M-T7 retains binding to a number of interleukin-8 N-terminal (ELR) deletion mutants, binding to mutants containing deletions in the C-terminal heparin-binding domain of interleukin-8 is abrogated. Furthermore, heparin effectively competes the interaction of M-T7 with the chemokine RANTES but not with rabbit gamma interferon. We propose that this novel M-T7 interaction with members of the chemokine superfamily may be facilitated through the conserved heparin-binding domains found in a wide spectrum of chemokines and that M-T7 may function by modulating chemokine-glycosaminoglycan interactions in virus-infected tissues.
Lalani
A S
AS
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Graham
K
K
Mossman
K
K
Rajarathnam
K
K
Clark-Lewis
I
I
Kelvin
D
D
McFadden
G
G
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D018946:Chemokine CCL5 / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism*; D002522:Chlorocebus aethiops; D006493:Heparin / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D009233:Myxoma virus / Q000378:metabolism*; D011485:Protein Binding; D017471:Receptors, Interferon / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins; D014764:Viral Proteins / Q000302:isolation & purification / Q000378:metabolism*; D000096743:Interferon gamma Receptor
D018946:Chemokine CCL5; D018925:Chemokines; D006493:Heparin; D007371:Interferon-gamma; D016209:Interleukin-8; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D014764:Viral Proteins; D000096743:Interferon gamma Receptor; C091989:M-T7 protein, Myxoma virus