TY - JOUR

T1 - A di-arginine motif contributes to the ER localization of the type I transmembrane ER oxidoreductase TMX4

AU - Roth, Doris

AU - Lynes, Emily

AU - Riemer, Jan

AU - Hansen, Henning Gram

AU - Althaus, Nils

AU - Simmen, Thomas

AU - Ellgaard, Lars

N1 - Keywords: Amino Acid Motifs; Amino Acid Sequence; Animals; Arginine; Blotting, Northern; Blotting, Western; Cell Line, Tumor; Cercopithecus aethiops; Endoplasmic Reticulum; Female; Gene Expression Profiling; Glycosylation; Hela Cells; Humans; Membrane Glycoproteins; Membrane Proteins; Microscopy, Fluorescence; Molecular Sequence Data; Mutation; Oxidation-Reduction; Phylogeny; Protein Disulfide Reductase (Glutathione); Protein Disulfide-Isomerases; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Vero Cells

PY - 2010

Y1 - 2010

N2 - The thiol-disulfide oxidoreductases of the PDI (protein disulfide isomerase) family assist in disulfide-bond formation in the ER (endoplasmic reticulum). In the present study, we have shown that the previously uncharacterized PDI family member TMX4 (thioredoxin-like transmembrane 4) is an N-glycosylated type I membrane protein that localizes to the ER. We also demonstrate that TMX4 contains a single ER-luminal thioredoxin-like domain, which, in contrast with similar domains in other PDIs, is mainly oxidized in living cells. The TMX4 transcript displays a wide tissue distribution, and is strongly expressed in melanoma cells. Unlike many type I membrane proteins, TMX4 lacks a typical C-terminal di-lysine retrieval signal. Instead, the cytoplasmic tail has a conserved di-arginine motif of the RXR type. We show that mutation of the RQR sequence in TMX4 to KQK interferes with ER localization of the protein. Moreover, whereas the cytoplasmic region of TMX4 confers ER localization to a reporter protein, the KQK mutant of the same protein redistributes to the cell surface. Overall, features not commonly found in other PDIs characterize TMX4 and suggest unique functional properties of the protein.

AB - The thiol-disulfide oxidoreductases of the PDI (protein disulfide isomerase) family assist in disulfide-bond formation in the ER (endoplasmic reticulum). In the present study, we have shown that the previously uncharacterized PDI family member TMX4 (thioredoxin-like transmembrane 4) is an N-glycosylated type I membrane protein that localizes to the ER. We also demonstrate that TMX4 contains a single ER-luminal thioredoxin-like domain, which, in contrast with similar domains in other PDIs, is mainly oxidized in living cells. The TMX4 transcript displays a wide tissue distribution, and is strongly expressed in melanoma cells. Unlike many type I membrane proteins, TMX4 lacks a typical C-terminal di-lysine retrieval signal. Instead, the cytoplasmic tail has a conserved di-arginine motif of the RXR type. We show that mutation of the RQR sequence in TMX4 to KQK interferes with ER localization of the protein. Moreover, whereas the cytoplasmic region of TMX4 confers ER localization to a reporter protein, the KQK mutant of the same protein redistributes to the cell surface. Overall, features not commonly found in other PDIs characterize TMX4 and suggest unique functional properties of the protein.

U2 - 10.1042/BJ20091064

DO - 10.1042/BJ20091064

M3 - Journal article

C2 - 19811453

VL - 425

SP - 195

EP - 205

JO - Biochemical Journal

JF - Biochemical Journal

SN - 0264-6021

IS - 1

ER -