title: Ligand-regulated transport of the Menkes copper P-type ATPase efflux pump from the Golgi apparatus to the plasma membrane: a novel mechanism of regulated trafficking.
abstract: The Menkes P-type ATPase (MNK), encoded by the Menkes gene (MNK; ATP7A), is a transmembrane copper-translocating pump which is defective in the human disorder of copper metabolism, Menkes disease. Recent evidence that the MNK P-type ATPase has a role in copper efflux has come from studies using copper-resistant variants of cultured Chinese hamster ovary (CHO) cells. These variants have MNK gene amplification and consequently overexpress MNK, the extents of which correlate with the degree of elevated copper efflux. Here, we report on the localization of MNK in these copper-resistant CHO cells when cultured in different levels of copper. Immunofluorescence studies demonstrated that MNK is predominantly localized to the Golgi apparatus of cells in basal medium. In elevated copper conditions there was a rapid trafficking of MNK from the Golgi to the plasma membrane. This shift in steady-state distribution of MNK was reversible and not dependent on new protein synthesis. In media containing basal copper, MNK accumulated in cytoplasmic vesicles after treatment of cells with a variety of agents that inhibit endosomal recycling. We suggest that MNK continuously recycles between the Golgi and the plasma membrane and elevated copper shifts the steady-state distribution from the Golgi to the plasma membrane. These data reveal a novel system of regulated protein trafficking which ultimately leads to the efflux of an essential yet potentially toxic ligand, where the ligand itself appears directly and specifically to stimulate the trafficking of its own transporter.
authors.affiliation: Department of Genetics, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Petris
authors.forename: J F
authors.initials: JF
authors.lastname: Mercer
authors.forename: J G
authors.initials: JG
authors.lastname: Culvenor
authors.forename: P
authors.initials: P
authors.lastname: Lockhart
authors.forename: P A
authors.initials: PA
authors.lastname: Gleeson
authors.forename: J
authors.initials: J
authors.lastname: Camakaris
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001324:Autoantigens; D015152:Blotting, Northern; D015153:Blotting, Western; D020126:Brefeldin A; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism*; D027682:Cation Transport Proteins; D002462:Cell Membrane / Q000378:metabolism; D003300:Copper / Q000378:metabolism / Q000494:pharmacology; D000073840:Copper-Transporting ATPases; D006224:Cricetinae; D003513:Cycloheximide / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D018942:Macrolides; D008565:Membrane Proteins / Q000378:metabolism; D007706:Menkes Kinky Hair Syndrome / Q000235:genetics*; D019216:Metals, Heavy / Q000494:pharmacology; D008854:Microscopy, Electron; D015739:Nocodazole / Q000494:pharmacology; D011993:Recombinant Fusion Proteins
chemical_list: D000900:Anti-Bacterial Agents; D001324:Autoantigens; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D003517:Cyclopentanes; C098772:GOLGA4 protein, human; D018942:Macrolides; D008565:Membrane Proteins; D019216:Metals, Heavy; D011993:Recombinant Fusion Proteins; D020126:Brefeldin A; D003300:Copper; C040929:bafilomycin A1; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D000251:Adenosine Triphosphatases; C081184:ATP7A protein, human; D000073840:Copper-Transporting ATPases; D015739:Nocodazole