sas [Search on AGR]
Drosophila melanogaster stranded at second (sas) encodes a single-pass transmembrane protein that localizes to the apical cell surface in polarized epithelia, such as the embryonic/larval salivary gland (SG). Overexpression of sas in the developing SG leads to all membrane domains taking on apical membrane character, with the exception of the region where septate junctions form.