The NH2-terminal domain of rat CD2 binds rat CD48 with a low affinity and binding does not require glycosylation of CD2.
CD2, CD48 and CD58 are structurally similar cell adhesion-molecules forming a subset of the immunoglobulin superfamily (IgSF). In humans CD58 is a ligand for CD2 while in mice CD2 binds CD48. We constructed a soluble chimeric molecule comprising the extracellular portion of rat CD48 and domains 3 and 4 of rat CD4 (sCD48-CD4) and used it to examine whether CD2 is a ligand for CD48 in rats. sCD48-CD4-coated polystyrene Dynabeads formed rosettes on rat CD2-transfected COS-7 cells, and this rosetting was blocked by anti-CD2 (OX34) and anti-CD48 (OX45) monoclonal antibodies. We used sucrose-gradient ultracentrifugation to show that sCD48-CD4 binds, in solution, to soluble forms of rat CD2 including the single NH2-terminal IgSF domain of rat CD2 expressed in bacteria. The upper limit of the affinity of the rat CD48-CD2 interaction is 4 x 10(5) M-1, lower than the published affinity of human CD2 for CD58. These results show that rat CD48 binds CD2 on its NH2-terminal IgSF domain with a low affinity and that binding is independent of glycosylation.
van der Merwe
P A
PA
MRC Cellular Immunology Unit, Sir William Dunn School of Pathology, University of Oxford, GB.
McPherson
D C
DC
Brown
M H
MH
Barclay
A N
AN
Cyster
J G
JG
Williams
A F
AF
Davis
S J
SJ
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D018801:CD2 Antigens; D000071178:CD48 Antigen; D002448:Cell Adhesion; D006031:Glycosylation; D008024:Ligands; D011485:Protein Binding; D051381:Rats; D011971:Receptors, Immunologic / Q000378:metabolism*; D012397:Rosette Formation; D013329:Structure-Activity Relationship
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D000071178:CD48 Antigen; C000604065:CD48 protein, human; C000604066:Cd48 protein, mouse; C000604067:Cd48 protein, rat; D008024:Ligands; D011971:Receptors, Immunologic