Membrane Topology of Trafficking Regulator of GLUT4 1 (TRARG1)

• DOI: 10.1021/acs.biochem.8b00361
• Publication Date: 2018-05-22T19:37:48Z
• Authors: Xiaowen Duan; James R. Krycer; Kristen C. Cooke; Guang Yang; David E. James; Daniel J. Fazakerley
• Keywords: 0303 health sciences; Glucose Transporter Type 4; Protein Conformation; Tumor Suppressor Proteins; Cell Membrane; Membrane Proteins; Mice; Protein Transport; 03 medical and health sciences; HEK293 Cells; 3T3-L1 Cells; Animals; Humans

Trafficking regulator of GLUT4 1 (TRARG1) was recently identified to localize to glucose transporter type 4 (GLUT4) storage vesicles (GSVs) and to positively regulate GLUT4 trafficking. Our knowledge of TRARG1 structure and membrane topology is limited to predictive models, hampering efforts to further our mechanistic understanding of how it carries out its functions. Here, we use a combination of bioinformatics prediction tools and biochemical assays to define the membrane topology of the 173-amino acid mouse TRARG1. These analyses revealed that, contrary to the consensus prediction, the N-terminus is cytosolic and that a short segment at the C-terminus resides in the luminal/extracellular space. Based on our biochemical analyses including membrane association and antibody accessibility assays, we conclude that TRARG1 has one transmembrane domain (TMD) (145-172) and a re-entrant loop between residues 101 and 127.