Medical College of Wisconsin
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A C-terminal region dictates the apical plasma membrane targeting of the human sodium-dependent vitamin C transporter-1 in polarized epithelia. J Biol Chem 2004 Jun 25;279(26):27719-28 PMID: 15084584

Abstract

The human sodium-dependent vitamin C transporter (hSVCT1) mediates sodium-dependent cellular uptake of the essential micronutrient l-ascorbic acid (vitamin C). However, the molecular determinants that control the cell surface expression, subcellular distribution, and dynamics of hSVCT1 remain undefined. To identify molecular determinants involved in hSVCT1 targeting in polarized epithelia, we used live cell imaging approaches to resolve the targeting and trafficking dynamics of hSVCT1 truncation mutants in renal and intestinal cells. Confocal imaging demonstrated that hSVCT1 was expressed at the apical cell surface and video rate measurements revealed hSVCT1 also resided in a heterogeneous population of intracellular organelles with discrete dynamic properties. By progressive truncation of the cytoplasmic C-terminal tail of hSVCT1, we delimited an essential role for an embedded ten amino acid sequence PICPVFKGFS (amino acids 563-572) in defining the physiological targeting of hSVCT1. Intriguingly, this sequence bears significant homology to recently identified apical targeting motifs in two other sodium-dependent transporters, and we suggest this conservation is reflected topologically through the adoption of a beta-turn confirmation in the cytoplasmic C-tail of each transporter. Our results provide the first direct resolution of functional hSVCT1 expression at the apical cell surface of polarized epithelia and define an apical targeting signal of relevance to transporters of diverse substrate specificity.

Author List

Subramanian VS, Marchant JS, Boulware MJ, Said HM

Author

Jonathan S. Marchant PhD Chair, Professor in the Cell Biology, Neurobiology and Anatomy department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amino Acid Motifs
Amino Acid Sequence
Animals
Caco-2 Cells
Cell Line
Cell Membrane
Cell Polarity
Cellular Structures
Dogs
Epithelial Cells
Humans
Kidney
Luminescent Proteins
Microscopy, Confocal
Organic Anion Transporters, Sodium-Dependent
Protein Transport
Recombinant Fusion Proteins
Symporters



View this publication's entry at the Pubmed website PMID: 15084584
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