HIV-1 transgene expression altered the expression of two key components of alveolar epithelial tight junctions, occludin and zonula occludens-1 (ZO-1). Alveolar epithelial cells from HIV-1 Tg rats had significantly decreased (* P < 0.05) gene expression of both occludin and ZO-1 (Panel A; each value represents the mean ± of 6 determinations). In parallel, alveolar epithelial cells from HIV-1 Tg rats had significantly decreased (* P < 0.05) protein expression of occludin and ZO-1 in both the membrane/cytoskeleton (Triton X-100 insoluble) and the cytosol (Triton X-100 soluble) fractions (Panel B; shown are the summary data expressed as the mean ± SEM of 6 determinations as well as representative immunoblots for each group). Panel C shows representative fluorescent immunocytochemistry images, and illustrates that the relative distribution of ZO-1 and occludin was less uniform in the plasma membranes of alveolar epithelial monolayers derived from HIV-1 Tg rats when compared to monolayers from WT rats, and also showed more granular staining for each protein within the cytoplasm of the cells. These findings were particularly striking for ZO-1 (upper two panels). The magnification bar in the lower right image = 100 microns.