Nucleocytoplasmic transport in human astrocytes: decreased nuclear uptake of the HIV Rev shuttle protein

Astrocytes are cellular targets for the human immunodeficiency virus (HIV) that limit virus production, owing, at least in part, to the diminished fun ctionality of the viral post-transcriptional stimulatory factor Rev. To und erstand the trafficking process in astrocytes, we compared nucleocytoplasmi c transport of Rev and various proteins with well-characterized nucleocytop lasmic transport features in human astrocytes and control cells (HeLa), Loc alization and trafficking characteristics of several cellular and viral pro teins, as well as nuclear trafficking of classical peptide signals upon mic roinjection were similar in both cell types, indicating maintenance of gene ral features of nucleocytoplasmic transport in astrocytes, Quantification o f fluorescence in living cells expressing Rev fused to green fluorescent pr otein (GFP) indicated a strong shift in intracellular distribution of Rev i n astrocytes, with 50-70% of Rev in the cytoplasm, whereas the cytoplasmic proportion of Rev in HeLa cells is around 10%, The dynamics of nucleocytopl asmic trafficking of Rev were compared in astrocytes and Rev-permissive cel ls by monitoring migration of Rev-GFP in cell fusions using highly sensitiv e time-lapse imaging. Nuclear uptake of Rev was dramatically retarded in ho mo-polykaryons of astrocytes compared with control cells. Diminished nuclea r uptake of Rev was also observed in hetero-polykaryons of Rev-permissive c ells and astrocytes, These results indicate that astrocytes contain a cytop lasmic activity that interferes with nuclear uptake of Rev. Our studies sug gest a model in which Rev is prevented from functioning efficiently in astr ocytes by specific alterations of its nucleocytoplasmic trafficking propert ies.