THE POLARIZED SORTING OF MEMBRANE-PROTEINS EXPRESSED IN CULTURED HIPPOCAMPAL-NEURONS USING VIRAL VECTORS

One model of neuronal polarity (Dotti and Simons, 1990) proposes that neurons and polarized epithelia use similar mechanisms to sort membran e proteins. To explore this hypothesis, we used viral vectors to expre ss proteins in cultured neurons and assessed their distribution using quantitative immunofluorescence microscopy. Basolateral epithelial pro teins were polarized to dendrites; more significantly, mutations of se quences required for their basolateral targeting in epithelia also dis rupted dendritic targeting. Unexpectedly, apical proteins were not pol arized to axons but were expressed at roughly equal amounts in dendrit es and axons. These data provide strong evidence that targeting of bas olateral and dendritic proteins depends on common mechanisms. In contr ast, the sorting of proteins to the axon requires signals that are not present in apical proteins.