Heterodimerization of integrin Mac-1 subunits studied by single-molecule imaging

Heterodimerization of integrin Mac-1 (αMβ2) subunits plays important role on regulating leukocytes adhesion to extracellular matrix or endothelial cells. Here, using total internal reflection microscopy, we investigated the heterodimerization of integrin Mac-1 subunits at the single-molecule level in live cells. Individual αM subunit fused to the enhanced yellow fluorescent protein (eYFP) was imaged at the basal plasma membrane of live Chinese hamster ovary (CHO) cells. Through analysis of mean square displacement (MSD), diffusion coefficient, the size of restricted domain and fraction of molecules undergoing restricted diffusion, we found that as compared with the diffusion in the absence of β2 subunit, the diffusion of single-molecule of αM-YFP was suppressed significantly in the presence of β2 subunit. Thus, based on the oligomerization-induced trapping model, we suggested that in the presence of β2 subunit, the αM subunit may form heterodimer with it.