Antisera against a channel-forming 16 kDa protein inhibit dye-coupling and bind to cell membranes in Drosophila ovarian follicles

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Abstract
In Drosophila ovarian follicles, communication via gap junctions can be observed between the oocyte and its surrounding follicular epithelium. In the present study, the intercellular exchange of the fluorescent tracer Lucifer Yellow was analysed following pressure-injections of five different sera or protein solutions into the oocyte of stage-10 follicles. Three of the tested sera are directed against a channel-forming 16 kDa protein, which is a component of the vacuolar H+-ATPase and of Nephrops norvegicus gap junctions. When one of these antisera was injected 5-10 min prior to the dye, the percentage of follicles showing dye-coupling between oocyte and follicle cells was extremely small. On the other hand, injections of non-immune serum or of bovine serum albumin solution had only minor inhibitory effects. With indirect immunofluorescence, the three Nephrops antisera revealed a discrete punctate pattern at the membranes between neighbouring follicle cells as well as between follicle cells and oocyte. Most likely, this fluorescent pattern represents the distribution of gap junctions in the follicular epithelium. On immunoblots, the Nephrops antisera recognized a 29 kDa Drosophila ovary protein with high specificity. Affinity purification of one of these antisera against the 29 kDa protein revealed that this protein of Drosophila and the 16 kDa membrane-channel protein of Nephrops are immuno-logically related. Thus, the Nephrops antisera might help to reveal, in future injection experiments, the functional role of gap-junction mediated communication in Drosophila.

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