Poster Topical Area: Vitamins and Minerals
Location: Hall D
Poster Board Number: 534
Using sodium-dependent vitamin C transporter (SVCT) family, we found peptide signals that can dictate the final presence of SVCT in apical or basolateral membrane of epithelial MDCK cells. However, the cellular route for SVCT or membrane transporters in general to go to the apical or basolateral membrane is largely unknown. A major question is whether the route is shared among nutrient transporters. We use various cell lines to test the hypothesis of a common route in epithelial cells.
METHODS: Flavone and glucose transport across the apical and basolateral membranes are measured in MDCK cell lines overexpressing various exogenous transporters. To control for the potential effect of G418 (200 µg/ml) that are used to maintain the overexpression, we also examine glucose transport in other cells that are naturally resistant to G418.
RESULTS: Flavone was shown to transport across cell membrane through passive diffusion and as expected, overexpression of various SVCT constructs does not affect flavone movement across apical or basolateral membrane. In contrast, the transport of glucose as measured by deoxyglucose (DOG) movement uniformly declined in cells that overexpress different SVCT constructs. Overexpression of SVCT constructs that are directed to the apical membrane can affect both the apical and basolateral transport of DOG. Similarly, overexpression of SVCT constructs that are directed to the basolateral membrane can affect both the apical and basolateral transport of DOG. MDCK cells expressing SVCT constructs that are trapped on the cellular protein trafficking route due to signal defect show further decline in DOG transport activity (apical and basolateral). Primary or immortalized embryonic fibroblasts treated with the 200 µg/ml G418 grow normally and do not show decreased DOG transport. The cells that overexpress non-membrane proteins need to be examined in the future to exclude the possible general effect of protein overexpression.
CONCLUSIONS: The overexpression of various SVCT constructs in MDCK cells all decrease the apical and basolateral glucose transport activity. This is consistent with the hypothetical presence of a common cellular route for nutrient transporters to go to the cell membrane.
University at Buffalo
Buffalo, New York