title: Adaptor Protein-1 Complex Affects the Endocytic Trafficking and Function of Peptidylglycine α-Amidating Monooxygenase, a Luminal Cuproenzyme.
abstract: The adaptor protein-1 complex (AP-1), which transports cargo between the trans-Golgi network and endosomes, plays a role in the trafficking of Atp7a, a copper-transporting P-type ATPase, and peptidylglycine α-amidating monooxygenase (PAM), a copper-dependent membrane enzyme. Lack of any of the four AP-1 subunits impairs function, and patients with MEDNIK syndrome, a rare genetic disorder caused by lack of expression of the σ1A subunit, exhibit clinical and biochemical signs of impaired copper homeostasis. To explore the role of AP-1 in copper homeostasis in neuroendocrine cells, we used corticotrope tumor cells in which AP-1 function was diminished by reducing expression of its μ1A subunit. Copper levels were unchanged when AP-1 function was impaired, but cellular levels of Atp7a declined slightly. The ability of PAM to function was assessed by monitoring 18-kDa fragment-NH2 production from proopiomelanocortin. Reduced AP-1 function made 18-kDa fragment amidation more sensitive to inhibition by bathocuproine disulfonate, a cell-impermeant Cu(I) chelator. The endocytic trafficking of PAM was altered, and PAM-1 accumulated on the cell surface when AP-1 levels were reduced. Reduced AP-1 function increased the Atp7a presence in early/recycling endosomes but did not alter the ability of copper to stimulate its appearance on the plasma membrane. Co-immunoprecipitation of a small fraction of PAM and Atp7a supports the suggestion that copper can be transferred directly from Atp7a to PAM, a process that can occur only when both proteins are present in the same subcellular compartment. Altered luminal cuproenzyme function may contribute to deficits observed when the AP-1 function is compromised.
authors.affiliation: From the Departments of Molecular Biology and Biophysics and.
authors.forename: Mathilde L
authors.initials: ML
authors.lastname: Bonnemaison
authors.affiliation: the Department of Anatomy, Faculty of Medicine, University of Helsinki, FIN-00014 Helsinki, Finland, and.
authors.forename: Nils
authors.initials: N
authors.lastname: Bäck
authors.affiliation: the Department of Molecular and Medical Genetics, Oregon Health and Sciences University, Portland, Oregon 97239.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Duffy
authors.affiliation: the Department of Molecular and Medical Genetics, Oregon Health and Sciences University, Portland, Oregon 97239.
authors.forename: Martina
authors.initials: M
authors.lastname: Ralle
authors.affiliation: Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Mains
authors.affiliation: From the Departments of Molecular Biology and Biophysics and Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030, eipper@uchc.edu.
authors.forename: Betty A
authors.initials: BA
authors.lastname: Eipper
mesh_terms: D033961:Adaptor Protein Complex 1 / Q000032:analysis / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000032:analysis / Q000378:metabolism; D000818:Animals; D027682:Cation Transport Proteins / Q000032:analysis / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D003300:Copper / Q000378:metabolism*; D000073840:Copper-Transporting ATPases; D004705:Endocytosis; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D006899:Mixed Function Oxygenases / Q000032:analysis / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000032:analysis / Q000378:metabolism*; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism; D021381:Protein Transport; D051381:Rats
chemical_list: D033961:Adaptor Protein Complex 1; C486201:Atp7a protein, mouse; D027682:Cation Transport Proteins; D009097:Multienzyme Complexes; D003300:Copper; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase; D000251:Adenosine Triphosphatases; C486202:Atp7a protein, rat; D000073840:Copper-Transporting ATPases
keywords: AtT-20; Atp7a; PAM; adaptor protein; amidation; copper; peptide biosynthesis; pituitary gland; secretion