Expression of the intermediate filament-associated protein related to beta-amyloid precursor protein is developmentally regulated in cultured cells

It was previously reported that a monoclonal antibody to beta-amyloid precursor protein (mab22C11; Boehringer Mannheim, Indianapolis, IN) labels an intermediate filament-associated protein (beta APP-IFAP) in cultured human skin fibroblasts (Dooley et al.: J Neurosci Res 33:60-67, 1992). The time course of its expression and association with different classes of intermediate filaments has been assessed in neurons, Schwann cells, and astrocytes in dissociated cultures of murine brain and spinal cord-dorsal root ganglia; in primary cultures of human muscle; and in the epithelial cell line PtK1. beta APP-IFAP was expressed in all non-neuronal cell types examined. Mab22C11 immunoreactivity was minimal or absent following dissociation or subculture, but gradually increased with time. In fibroblasts, myoblasts, and epithelial cells, the distribution eventually resembled that of vimentin. With the exception of glial fibrillary acidic protein (GFAP), beta APP-IFAP was not associated with the intermediate filament proteins characteristically found in differentiated cells, i.e., desmin, the cytokeratins, and neurofilament proteins. No labeling of neurons by mab22C11 was observed at any stage of in vitro maturation. In sections of Alzheimer's brain, the antibody labeled a subpopulation of reactive astrocytes. It is suggested that beta APP-IFAP may be the product of a member of the beta APP multigene family expressed developmentally in non-neuronal cells.