The integrin chains beta 1 and alpha 6 associate with the chaperone calnexin prior to integrin assembly.

Integrins are alpha beta heterodimers that mediate cell-cell adhesion, as well as cell-substrate adhesion. The largest subclass is formed by 10 heterodimers (the very late antigens) that all share the beta 1-chain. We have found a 90-kDa protein that co-isolates with mouse integrin beta 1-chain. This 90-kDa protein was identified ...
as the mouse homolog of calnexin, a membrane-bound chaperone and resident protein of the endoplasmic reticulum. First, the sequence of the 15 NH2-terminal amino acids of the 90-kDa protein is 80% and 87% identical to the corresponding sequences of canine and human calnexin, respectively. Second, the 90-kDa protein was recognized by a monoclonal antibody against calnexin/IP90. Association of calnexin with the integrin beta 1-chain was directly demonstrated by chemical cross-linking. As pulse-chase experiments revealed, the association of the beta 1-chain with calnexin occurred prior to the assembly with integrin alpha 6-chain. Additionally, the alpha 6-chain bound to calnexin before integrin assembly and dissociated again at the time of integrin-assembly. Our data suggest that calnexin is involved in the assembly of beta 1 integrins, as well as in the retention of a pool of immature integrin beta 1-chains in the ER.
Mesh Terms:
Amino Acid Sequence, Animals, Calcium-Binding Proteins, Calnexin, Cell Line, Cysteine, Electrophoresis, Polyacrylamide Gel, Endothelium, Vascular, Humans, Integrin alpha6beta1, Integrins, Kidney, Kinetics, Membrane Proteins, Methionine, Mice, Molecular Sequence Data, Molecular Weight, Rats, Receptors, Laminin, Sequence Homology, Amino Acid, Sulfur Radioisotopes
J. Biol. Chem.
Date: Apr. 22, 1994
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