Characterization of the cell surface heterodimer VLA-4 and related peptides

• Published in: The Journal of biological chemistry 1987-08, Vol.262 (24), p.11478-11485
• Main Authors: Hemler, M E, Huang, C, Takada, Y, Schwarz, L, Strominger, J L, Clabby, M L
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antibodies, Monoclonal; antigens; Antigens, Surface - analysis; Biological and medical sciences; Cholic Acids; Electrophoresis, Polyacrylamide Gel; Flow Cytometry; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Immunobiology; lymphocytes T; Lymphoid cells: ontogeny, maturation, markers, receptors, circulation and recirculation; man; Molecular Weight; Octoxynol; Peptides - analysis; Polyethylene Glycols; Receptors, Very Late Antigen; Solubility; Trypsin - metabolism; VLA-4
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)60831-2

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.