SPATIAL AND SUBCELLULAR-LOCALIZATION OF THE MEMBRANE CYTOSKELETON-ASSOCIATED PROTEIN ALPHA-ADDUCIN IN THE RAT-BRAIN

Studies on the identification and characterization of constituents of rat brain synaptic junctions have lead to the isolation of cDNA clones encoding segments of alpha-adducin. These and other studies suggest t hat adducin, a protein involved in promoting the assembly of actin and spectrin filaments at the plasma membrane, may play a role in dynamic assembly-disassembly processes underlying synaptic plasticity. In ord er to verify that brain alpha-adducin is indeed a constituent of synap tic structures, we have generated monoclonal antibodies against epitop es in the C-terminal region of alpha-adducin and have determined its s patial and sub-cellular distribution in postnatal day-30 rat brain. al pha-Adducin is found to be highly enriched in regions with high synaps e densities of the hippocampus, corpus striatum, cerebral cortex and c erebellum. Immune-electron microscopic analysis of peroxidase stained sections of the hippocampus and the cerebellum revealed that alpha-add ucin is localized at distinct sub-cellular structures. In the CA1 and CA3 regions of the hippocampus alpha-adducin immunoreactivity is found in a distinct subset of dendrites and dendritic spines. In the molecu lar layer of the cerebellum, a distinct fraction of pre-synaptic termi nals of parallel fiber terminals is labeled. In both cases the majorit y of synaptic structures does not contain adducin. Significant immunor eactivity is also detected in processes of glial cells both in the hip pocampus and the cerebellum.