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 of three proteins in rat cerebral cortex, hippocampus and cerebellum. The proteins were identified by Mabs directed against Drosophila melanogaster microtubule proteins (MTP). We have provisionally designated these proteins as Drosophila microtubule-associated proteins (DMAPs). The corresponding monoclonal antibodies are designated Mab DMAP-45, -55 and -66 indicating the molecular weights of each protein. All three Mabs cross-react with proteins of similar molecular weights in the rat brain. 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 previously 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 microtubules and appears to be a previously undescribed isoform of tubulin. DMAP-66, which co-purifies stoichiometrically with Drosophila microtubles, does not do so in the rat brain. Immunohistochemistry performed with all three Mabs revealed a general pattern of staining of cell somata and dendrites in the cortex, hippocampus and cerebellum. Mab DMAP-55 also stained axons. In cerebral cortex all three Mabs preferentially, but not exclusively, stained layer V neuronal somata and dendrites. In hippocampus, Mabs DMAP-45 and -66 stained cell somata and dendrites in all hippocampul subfields, particularly the subiculum and CA3, whereas Mab DMAP-55 was most prevalent in mossy fibers. All three Mahs stain Purkinje cells in cerebellum with additional staining of cerebella basket cells and Golgi cells observed with Mah DMAP-66.