ANTIBODIES DIRECTED AGAINST MICROTUBULE PROTEINS FROM DROSOPHILA-MELANOGASTER CROSS-REACT WITH SIMILAR PROTEINS IN THE RAT-BRAIN

Monoclonal antibodies (Mabs) were used to delineate the localization o f three proteins in rat cerebral cortex, hippocampus and cerebellum. T he proteins were identified by Mabs directed against Drosophila melano gaster microtubule proteins (MTP). We have provisionally designated th ese proteins as Drosophila microtubule-associated proteins (DMAPs). Th e corresponding monoclonal antibodies are designated Mab DMAP-45, -55 and -66 indicating the molecular weights of each protein. All three Ma bs cross-react with proteins of similar molecular weights in the rat b rain. Correspondingly, these rat proteins are designated DMAPRs. DMAP- 45 binds microtubules in an ATP-dependent manner. The molecular weight and subcellular localization of DMAP-45R differs significantly from p reviously described mammalian brain MAPs suggesting that it represents a novel MAP. Biochemical evidence suggests it may be an actin-related protein. DMAP-55R co-purifies stoichiometrically with rat brain micro tubules and appears to be a previously undescribed isoform of tubulin. DMAP-66, which co-purifies stoichiometrically with Drosophila microtu bles, does not do so in the rat brain. Immunohistochemistry performed with all three Mabs revealed a general pattern of staining of cell som ata and dendrites in the cortex, hippocampus and cerebellum. Mab DMAP- 55 also stained axons. In cerebral cortex all three Mabs preferentiall y, but not exclusively, stained layer V neuronal somata and dendrites. In hippocampus, Mabs DMAP-45 and -66 stained cell somata and dendrite s in all hippocampal subfields, particularly the subiculum and CA3, wh ereas Mab DMAP-55 was most prevalent in messy fibers. All three Mabs s tain Purkinje cells in cerebellum with additional staining of cerebell ar basket cells and Golgi cells observed with Mab DMAP-66.