Localization of 4.1 related proteins in cerebellar neurons.

Localization of 4.1 related proteins in neurons was studied with immunofluorescence microscopy and with immunoelectron microscopy on ultrathin cryosections. In rat cerebellum, 4.1 immunoreactive proteins were demonstrated in Purkinje cell bodies, dendrites and other neurons in the cerebellar cortex. Some glial cells showed staining, but no labeling was found in myelinated axons of the white matter and of the glomeruli in the granule cell layer. At the ultrastructural level, the 4.1 related proteins were localized mainly in the cytoplasmic matrix, while some labeling was found underneath the plasma membrane. To determine whether 4.1 related proteins in neuronal cytoplasm exist as part of the cytoskeleton or not, PC12 cells cultured in the presence of nerve growth factor were stained with the anti-4.1 antibody. Since cytoplasmic staining was retained after detergent treatment, the 4.1 related proteins seem to exist as a component of the neural cell cytoskeleton. Localization of 4.1 related proteins during the postnatal development of the cerebellum was also studied. In Purkinje cells, localization of 4.1 related proteins changed according to the stages of the postnatal development. The present data suggest that 4.1 related proteins in neurons localized mainly in the cytoplasm and may play some role in organizing cytoskeletal networks in the cytomatrix. Their distribution is developmentally regulated in some neurons, possibly in relationship to their maturation in the cytoskeleton.