Palmitoylated TMX and calnexin target to the mitochondria-associated membrane.

Publication Type:

Journal Article

Source:

The EMBO journal, Volume 31, Issue 2, p.457-70 (2012)

Keywords:

2012, Amino Acid Sequence, Animals, Calnexin, Cell Line, Tumor, Center-Authored Paper, Cysteine, Dogs, Electron Microscopy Core Facility, Endoplasmic Reticulum, Hela Cells, Heme Oxygenase-1, Humans, Intracellular Membranes, Lipoylation, MELANOMA, Membrane Glycoproteins, Membrane Proteins, MICE, mitochondria, Molecular Sequence Data, Mutagenesis, Site-Directed, Protein Disulfide Reductase (Glutathione), Protein Disulfide-Isomerases, Protein Processing, Post-Translational, Protein Structure, Tertiary, Protein Transport, Shared Resources, Thioredoxins

Abstract:

The mitochondria-associated membrane (MAM) is a domain of the endoplasmic reticulum (ER) that mediates the exchange of ions, lipids and metabolites between the ER and mitochondria. ER chaperones and oxidoreductases are critical components of the MAM. However, the localization motifs and mechanisms for most MAM proteins have remained elusive. Using two highly related ER oxidoreductases as a model system, we now show that palmitoylation enriches ER-localized proteins on the MAM. We demonstrate that palmitoylation of cysteine residue(s) adjacent to the membrane-spanning domain promotes MAM enrichment of the transmembrane thioredoxin family protein TMX. In addition to TMX, our results also show that calnexin shuttles between the rough ER and the MAM depending on its palmitoylation status. Mutation of the TMX and calnexin palmitoylation sites and chemical interference with palmitoylation disrupt their MAM enrichment. Since ER-localized heme oxygenase-1, but not cytosolic GRP75 require palmitoylation to reside on the MAM, our findings identify palmitoylation as key for MAM enrichment of ER membrane proteins.