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Membrane targeting and intracellular trafficking of the human sodium-dependent multivitamin transporter in polarized epithelial cells. Am J Physiol Cell Physiol 2009 Apr;296(4):C663-71

Date

02/13/2009

Pubmed ID

19211916

Pubmed Central ID

PMC2670647

DOI

10.1152/ajpcell.00396.2008

Scopus ID

2-s2.0-65649091395   24 Citations

Abstract

The human sodium-dependent multivitamin transporter (hSMVT) mediates sodium-dependent uptake of biotin in renal and intestinal epithelia. To date, however, there is nothing known about the structure-function relationship or targeting sequences in the hSMVT polypeptide that control its polarized expression within epithelia. Here, we focused on the role of the COOH-terminal tail of hSMVT in the targeting and functionality of this transporter. A full-length hSMVT-green fluorescent protein (GFP) fusion protein was functional and expressed at the apical membrane in renal and intestinal cell lines. Microtubule disrupting agents disrupted the mobility of trafficking vesicles and impaired cell surface delivery of hSMVT, which was also prevented in cells treated with dynamitin (p50), brefeldin, or monensin. Progressive truncation of the COOH-terminal tail impaired the functionality and targeting of the transporter. First, biotin transport decreased by approximately 20-30% on deletion of up to 15 COOH-terminal amino acids of hSMVT, a decrease mimicked solely by deletion of the terminal PDZ motif (TSL). Second, deletions into the COOH-terminal tail (between residues 584-612, containing a region of predicted high surface accessibility) resulted in a further drop in hSMVT transport (to approximately 40% of wild-type). Third, apical targeting was lost on deletion of a helical-prone region between amino acids 570-584. We conclude that the COOH tail of hSMVT contains several determinants important for polarized targeting and biotin transport.

Author List

Subramanian VS, Marchant JS, Boulware MJ, Ma TY, 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

Animals
Biotin
Brefeldin A
Caco-2 Cells
Cell Membrane
Cell Polarity
Cytoplasm
Dogs
Dynactin Complex
Dyneins
Epithelial Cells
Green Fluorescent Proteins
Humans
Intestinal Mucosa
Kidney
Microtubule-Associated Proteins
Microtubules
Monensin
Protein Structure, Tertiary
Protein Transport
Recombinant Fusion Proteins
Symporters
Time Factors
Transfection
Transport Vesicles
Tubulin Modulators
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a