Localization of Na/K-ATPase in developing and adult Drosophila melanogaster photoreceptor

Drosophila melanogaster photoreceptors are highly polarized cells and their plasma membrane is organized into distinct domains. Zonula adherens juncti ons separate a smooth peripheral surface, the equivalent of the basolateral surface in other epithelial cells, from the central surface (congruent to apical surface). The latter consists of the microvillar rhabdomere and the juxtarhabdomeric domain, a nonmicrovillar area between the rhabdomere and t he zonulae adherens. The distribution of Na/K-ATPase over these domains was examined by immunocytochemical, developmental, and genetic approaches. Imm unofluorescence and immunogold labeling of adult compound eyes reveal that the distribution of Na/K-ATPase is concentrated at the peripheral surface i n the photoreceptors R1-R6, but extends over the juxtarhabdomeric domain to the rhabdomere in the photoreceptors R7/R8. Developmental analysis demonst rates further that Na/K-ATPase is localized over the entire plasma membrane in all photoreceptors in early pupal eyes. Redistribution of Na/K-ATPase i n R1-R6 occurs at about 78% of pupal life, coinciding with the onset of Rh l-rhodopsin expression on the central surface of these cells. Despite the e ssential role of Rh1 in structural development and intracellular traffickin g, Rh1 mutations do not affect the distribution of Na/K-ATPase. These resul ts suggest that Na/K-ATPase and rhodopsin are involved in distinct intracel lular localization mechanisms, which are maintained independent of each oth er.