Membrane Topology of Trafficking Regulator of GLUT4 1 (TRARG1)

• Published in: Biochemistry (Easton) Vol. 57; no. 26; pp. 3606 - 3615
• Main Authors: Duan, Xiaowen, Krycer, James R, Cooke, Kristen C, Yang, Guang, James, David E, Fazakerley, Daniel J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 03.07.2018
• Subjects: 3T3-L1 Cells; Animals; Cell Membrane - chemistry; Cell Membrane - metabolism; Glucose Transporter Type 4 - metabolism; HEK293 Cells; Humans; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Mice; Protein Conformation; Protein Transport; Tumor Suppressor Proteins - chemistry; Tumor Suppressor Proteins - metabolism
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/acs.biochem.8b00361

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.