Published in:
01-03-2014 | Original Article
Association of TM4SF4 with the Human Thiamine Transporter-2 in Intestinal Epithelial Cells
Published in: Digestive Diseases and Sciences | Issue 3/2014
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Background
The human thiamine transporter-2 (hTHTR-2) is involved in the intestinal absorption of thiamine. Recent studies with membrane transporters of other nutrients/substrates have shown that they have associated proteins that affect different aspects of their physiology and cell biology. Nothing is known about protein(s) that interact with hTHTR-2 in intestinal epithelial cells and influence its physiological function and/or its cell biology.
Aims
The aim of this study was to identify protein partner(s) that interact with hTHTR-2 in human intestinal cells and determine the physiological/biological consequence of that interaction.
Methods
The yeast split-ubiquitin two-hybrid approach was used to screen a human intestinal cDNA library. GST-pull-down and cellular co-localization approaches were used to confirm the interaction between hTHTR-2 and the associated protein(s). The effect of such an interaction on hTHTR-2 function was examined by 3H-thiamine uptake assays.
Results
Our screening results identified the human TransMembrane 4 SuperFamily 4 (TM4SF4) as a potential interactor with hTHTR-2. This interaction was confirmed by an in vitro GST-pull-down assay, and by live-cell confocal imaging of HuTu-80 cells co-expressing hTHTR-2–GFP and mCherry–TM4SF4 (the latter displayed a significant overlap of these two proteins in intracellular vesicles and at the cell membrane). Co-expression of hTHTR-2 with TM4SF4 in HuTu-80 cells led to a significant induction in thiamine uptake. In contrast, silencing TM4SF4 with gene-specific siRNA led to a significant decrease in thiamine uptake.
Conclusions
These results show for the first time that the accessory protein TM4SF4 interacts with hTHTR-2 and influences the physiological function of the thiamine transporter.