SYNAPTIC AND GLIAL LOCALIZATION OF THE INTEGRIN ALPHA-V-BETA-8 IN MOUSE AND RAT-BRAIN

Integrins are a large family of cell adhesion receptors mediating cell -extracellular matrix (ECM) interactions and are widely distributed in tissues. The beta 8 integrin subunit mRNA has been shown to be expres sed at higher levels in the central nervous system (CNS) than in other organs [M. Moyle, M.A. Napier, J.W. McLean, Cloning and expression of a divergent integrin subunit beta 8, J. Biol. Chem, 266 (29) (1991) 1 9650-19658] but its cellular and subcellular localization in the CNS a re unknown. In this report, we demonstrate that beta 8 pairs exclusive ly with the alpha v subunit in the CNS to form the alpha v beta 8 hete rodimer. Immunohistochemical analysis of the distribution of beta 8 in adult mouse and rat brains revealed that the protein is expressed in several regions of the hippocampal formation and in the molecular laye r and glomeruli of the granular cell layer of the cerebellum. Punctate and diffuse immunolabeling was observed occasionally surrounding neur onal pericarya and extensively throughout dendritic fields suggesting both pre-and post-synaptic localization and/or expression in non-neuro nal cells. By immunoelectron microscopy, beta 8 immunoreactivity was d etected in dendritic spines where it was often localized at post-synap tic densities, occasionally in axon terminals and in glial processes. Association of beta 8 with synaptic membranes was further supported by its enrichment in synaptosomal preparations as detected by immunoblot ting. These results demonstrate that alpha v beta 8 is present in matu re synapses and therefore may play a role in synaptic function. (C) 19 98 Elsevier Science B.V.