Distinct Roles for the α and β Subunits in the Functions of Integrin αMβ2*

By D. A. Solovjov, E. Pluskota, E. Plow. Journal of Biological Chemistry, 2004

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Integrin αMβ2 (Mac-1, CD11b/CD18) is a noncovalently linked heterodimer of αM and β2 subunits on the surface of leukocytes, where it plays a pivotal role in the adhesion and migration of these cells. Using HEK293 cells expressing αMβ2 or the individual constituent chains on their surface, we analyzed the contributions of the αM or β2 subunits to functional responses mediated by the integrin. In cells expressing only αM or β2, the individual subunits were not associated with the endogenous integrins of the cells, and other partners for the subunits were not detected by surface labeling and immunoprecipitation under a variety of conditions. The αM cells mediated adhesion and spreading on a series of αMβ2 ligands (fibrinogen, Factor X, iC3b, ICAM-1 (intercellular adhesion molecule-1), and denatured ovalbumin) but could not support cell migration to any of these. The spreading of the αM cells suggested an unanticipated linkage of this subunit to the cytoskeleton. The β2 cells supported migration and attachment but not spreading on a subset of the αMβ2 ligands. The heterodimeric receptor and its individual subunits were purified from the cells by affinity chromatography and recapitulated the ligand binding properties of the corresponding cell lines. These data indicate that each subunit of αMβ2 contributes distinct properties to αMβ2 and that, in most but not all cases, the response of the integrin is a composite of the functions of its individual subunits.

Subfields: Hematology, Immunology and Allergy, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/780503777d2a77ae3a33d52fde229d6e01057752