CHARACTERIZATION OF MICROTUBULE-ASSOCIATED PROTEINS AT THE SYNAPSE - ABSENCE OF MAP-2

Abstract

The high-MW microtubule-associated proteins MAP 1 and MAP 2 are major components of [rat] brain cytosol and can be readily identified using polyacrylamide gel electrophoresis on the basis of heat stability and co-sedimentation with microtubules. An examination of synaptosomal cytosol, synaptic plasma membrane and postsynaptic density fractions showed that MAP 2 is absent from these fractions and from both pre- and postsynaptic sites. All of the fractions contained polypeptides that comigrated with MAP 1 and a MAP 1 like polypeptide was identified in a microtubule preparation from synaptosomal cytosol. The absence of MAP 2 from synaptosomal cytosol was confirmed by immunoblotting using an antibody directed against MAP 2. Immunocytochemistry using this antibody showed that MAP 2 was present in cell bodies and dendrites but absent from axons.