title: Cell surface rescue of kidney anion exchanger 1 mutants by disruption of chaperone interactions.
abstract: Mutations in the human kidney anion exchanger 1 (kAE1) membrane glycoprotein cause impaired urine acidification resulting in distal renal tubular acidosis (dRTA). Dominant and recessive dRTA kAE1 mutants exhibit distinct trafficking defects with retention in the endoplasmic reticulum (ER), Golgi, or mislocalization to the apical membrane in polarized epithelial cells. We examined the interaction of kAE1 with the quality control system responsible for the folding of membrane glycoproteins and the retention and degradation of misfolded mutants. Using small molecule inhibitors to disrupt chaperone interactions, two functional, dominant kAE1 mutants (R589H and R901stop), retained in the ER and targeted to the proteasome for degradation by ubiquitination, were rescued to the basolateral membrane of Madin-Darby canine kidney cells. In contrast, the Golgi-localized, recessive G701D and the severely misfolded, ER-retained dominant Southeast Asian ovalocytosis (SAO) mutants were not rescued. These results show that functional dRTA mutants are retained in the ER due to their interaction with molecular chaperones, particularly calnexin, and that disruption of these interactions can promote their escape from the ER and cell surface rescue.
authors.affiliation: From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Sian T
authors.initials: ST
authors.lastname: Patterson
authors.affiliation: From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada. Electronic address: r.reithmeier@utoronto.ca.
authors.forename: Reinhart A F
authors.initials: RAF
authors.lastname: Reithmeier
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics / Q000378:metabolism*; D037281:Calnexin / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D004612:Elliptocytosis, Hereditary / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D005799:Genes, Dominant; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D020125:Mutation, Missense; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D018832:Molecular Chaperones; C454201:SLC4A1 protein, human; D037281:Calnexin; D046988:Proteasome Endopeptidase Complex