Two splice variants of the human SLC30A5 Zn transporter gene have been reported in the literature (Cragg et al, 2002, Kambe et al, 2002). The sequences reported differ at their N- and C-terminal regions, corresponding with the use of different 5′ and 3′ exons (Jackson et al, 2007). The ZnT5 splice variants adopt different subcellular localizations when expressed as fusions to GFP from the corresponding transgenes introduced into Chinese hamster ovary cells. Variant A is expressed in the Golgi apparatus and variant B is expressed throughout the cell, including at the plasma membrane (Jackson et al, 2007). Plasma membrane localization of variant B, has also been observed in human intestinal Caco-2 cells (Cragg et al, 2002), and we have also reported previously localization of ZnT5 to the apical enterocyte membrane in human small intestine, using an antibody that may recognize both splice variants (Cragg et al, 2005), however the differential targeting sequences of the two variants has yet to be defined. Here we report differential localisation of ZnT5 in HeLa cells, when expressed as either an N- or C-terminal GFP fusion. Plasmid constructs from which one or other of the ZnT5 splice variants have been expressed with either a C-terminal or N-terminal GFP tag were transiently transfected into HeLa cells. Forty eight hours post transfection, cells were visualized by fluorescence microscopy. Dual labelling with markers of specific subcellular compartments was also carried out. Results for Variant A expressed with a C terminal GFP tag confirm localisation at the Golgi apparatus, as previously reported (Kambe at al, 2002), however the same variant expressed as an N-terminal GFP fusion was observed only at the endoplasmic reticulum (ER), confirmed by co-localisation with an ER marker. A potential cleavage site at the N-terminal region of variant A, identified through bioinformatics could explain this pattern of localisation and we hypothesise that the mature variant A peptide localises to the Golgi apparatus and the cleaved GFP N- terminal sequence is visualised at the ER. We will confirm this hypothesis with Western blotting. In transfected HeLa cells, Variant B is localised to the ER when expressed as either an N-terminal or C-terminal GFP fusion and analysis of the sequence at the N-terminal region does not predict the same cleavage site as observed with variant A, however an ER localisation signal is observed in the C-terminal region. The results from this study are beginning to elucidate the role of the different N- and C- termini of the two splice variants in intracellular localisation/targeting.