THE MEMBRANE PROXIMAL REGION OF THE INTEGRIN BETA-CYTOPLASMIC DOMAIN CAN MEDIATE OLIGOMERIZATION

Integrin-ligand binding generates many intracellular signals, includin g signals to initiate focal contact formation and to regulate cellular decisions concerning growth and differentiation. Oligomerization of t he beta subunit cytoplasmic domain appears to be required for many of these events. In order to study these processes, we have generated a n ovel chimeric protein, consisting of the chicken integrin beta(1) cyto plasmic domain connected to the central rod domain of a neuronal inter mediate filament, alpha-internexin. This chimeric protein, when expres sed transiently in 293T cells, oligomerizes in a beta cytoplasmic doma in-dependent manner. This oligomerization requires the membrane proxim al amino acids LLMII of the beta(1) cytoplasmic domain, as demonstrate d by deletion analysis. Therefore, the integrin beta cytoplasmic domai n in this system contains an oligomerization function, which may provi de some insight as to the function of intact integrins in vivo.