Cloning, expression, and vesicular localization of zinc transporter Dri 27/ZnT4 in intestinal tissue and cells

We have identified the Dri 27 cDNA on the basis of its upregulated expressi on during rat intestinal development. it encodes a hydrophobic protein of 4 30 amino acids that shares significant homology with members of the mammali an zinc transporter family ZnT. The murine homologue of Dri 27 (named ZnT4) was recently associated with the mouse mutation "lethal milk." The primary sequence of Dri 27/ZnT4 displays features characteristic of polytopic memb rane proteins. In this paper, we show that Dri 27/ZnT4 is localized in the membrane of intracellular vesicles, the majority of which concentrate in th e basal cytoplasmic region of polarized enterocytes. A Dri 27/ZnT4 myc-tagg ed construct, transiently transfected in intestinal Caco-2 cells, partially colocalizes with the transferrin receptor and with the beta-subunits of th e clathrin adaptor complexes AP-1 and AP-2 in a subpopulation of endosomal vesicles. By subcloning distinct portions of the protein in frame with glut athione-S-transferase, we also provide experimental. evidence of their func tion as zinc-binding and protein-protein-interaction domains.