The membrane proximal region of the integrin β cytoplasmic domain can mediate oligomerization

Integrin-ligand binding generates many intracellular signals, including signals to initiate focal contact formation and to regulate cellular decisions concerning growth and differentiation. Oligomerization of the beta subunit cytoplasmic domain appears to be required for many of these events. In order to study these processes, we have generated a novel chimeric protein, consisting of the chicken integrin beta(1) cytoplasmic domain connected to the central rod domain of a neuronal intermediate filament, alpha-internexin. This chimeric protein, when expressed transiently in 293T cells, oligomerizes in a beta cytoplasmic domain-dependent manner. This oligomerization requires the membrane proximal amino acids LLMII of the beta(1) cytoplasmic domain, as demonstrated by deletion analysis. Therefore, the integrin beta cytoplasmic domain in this system contains an oligomerization function, which may provide some insight as to the function of intact integrins in vivo.