Ezrin immunoreactivity in neuron subpopulations: cellular distribution in relation to cytoskeletal proteins in sensory neurons.

Ezrin was first identified as a low-abundance phosphoprotein associated with the cytoskeletal core of microvilli, where it may function as a regulatory protein. We report immunocytochemical evidence for expression of ezrin, or an ezrin-like protein of molecular mass near 80 KD, confined to select populations of neurons, including sensory, motor, and autonomic, during chick embryonic development. We have compared the distribution of anti-ezrin staining with that of other major cytoskeletal proteins in sensory neurons in an effort to identify a possible association of the neural homologue of ezrin with the neuronal cytoskeleton. The diffuse distribution of anti-ezrin staining in the cell soma bore little resemblance to the filamentous staining observed with antibodies to the 68 KD neurofilament protein and alpha-tubulin. F-actin staining with fluorescein-conjugated phalloidin was indistinguishable from the anti-ezrin staining pattern in the soma of cultured neurons, including a peak in staining intensity around the periphery of the cell. Microfilaments in growth cones did not stain with the ezrin antibody. A close correspondence between the anti-ezrin and anti-spectrin staining patterns was found on cryostat sections of dorsal root ganglia, but the anti-spectrin staining was weak and could not be demonstrated in culture. Our findings, primarily from cultured neurons, are not inconsistent with ezrin associating with F-actin, although not with microfilaments found in motile structures such as growth cones.