Characterization of the cell surface heterodimer VLA-4 and related peptides.
A monoclonal antibody (B-5G10) was produced which specifically recognizes the Mr 150,000/130,000 VLA-4 complex on the surface of human cells. Cross-linking studies indicated that the Mr 150,000 alpha 4 subunit of VLA-4 is in noncovalent 1:1 association with the Mr 130,000 VLA beta subunit. In the absence of cross-linking, the VLA-4 alpha 4 beta subunit complex was easily dissociated, especially in Nonidet P-40 detergent, or at elevated pH (above 8.0). Studies of dissociated subunits showed that B-5G10 recognizes an epitope on the Mr 150,000 alpha 4 subunit of VLA-4, whereas the beta subunit is immunologically identical to the Mr 130,000 beta subunit common to all VLA heterodimers. VLA-4 is widely distributed on hematopoietic cells, including thymocytes, peripheral blood lymphocytes, monocytes, activated T cells, T and B lymphoblastoid cell lines, and myeloid cell lines. However, VLA-4 is only weakly expressed on most adherent cell lines tested. Immunoprecipitates of VLA-4 often contain additional proteins of Mr 80,000 and Mr 70,000. These are probably derived from the Mr 150,000 alpha 4 subunit because: 1) they are both recognized by anti-alpha 4 sera, but not anti-beta sera; 2) the sum of their sizes is equal to the size of alpha 4; 3) they are selectively coexpressed with alpha 4 and not other VLA alpha subunits; 4) the Mr 80,000 protein has an identical NH2-terminal sequence to alpha 4; 5) like alpha 4, the Mr 70,000 and 80,000 peptides can variably associate with the VLA beta subunit; and 6) trypsin appears to cleave the Mr 150,000 alpha 4 subunit into products of Mr 70,000 and 80,000.
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis*; D002793:Cholic Acids; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006801:Humans; D008970:Molecular Weight; D017830:Octoxynol; D010455:Peptides / Q000032:analysis*; D011092:Polyethylene Glycols; D016029:Receptors, Very Late Antigen; D012995:Solubility; D014357:Trypsin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D002793:Cholic Acids; D010455:Peptides; D016029:Receptors, Very Late Antigen; D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40; D014357:Trypsin; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate