The invention relates to polarized cell tubulo-vesicular structure localization signals. The localization signals are utilized as research tools or are linked to polypeptides of interest or therapeutic molecules. Disclosed are methods of making and using polypeptides and modified polypeptides as signals to localize therapeutics, experimental compounds, peptides, proteins and/or other macromolecules to the tubulo-vesicular structures of polarized cells. The polypeptides of the invention optionally include linkage to reporters, epitopes and/or other experimental or therapeutic molecules. The invention also encompasses polynucleotides encoding the localization signals and vectors comprising these polynucleotides.