Impaired trafficking and intracellular retention of mutant kidney anion exchanger 1 proteins (G701D and A858D) associated with distal renal tubular acidosis.
Novel compound heterozygous mutations, G701D, a recessive mutation, and A858D, a mild dominant mutation, of human solute carrier family 4, anion exchanger, member 1 (SLC4A1) were identified in two pediatric patients with distal renal tubular acidosis (dRTA). To examine the interaction, trafficking, and cellular localization of the wild-type and two mutant kidney AE1 (kAE1) proteins, we expressed the proteins alone or together in human embryonic kidney (HEK) 293T and Madin-Darby canine kidney (MDCK) epithelial cells. In individual expressions, wild-type kAE1 was localized at the cell surface of HEK 293T and the basolateral membrane of MDCK cells. In contrast, kAE1 G701D was mainly retained intracellularly, while kAE1 A858D was observed intracellularly and at the cell surface. In co-expression experiments, wild-type kAE1 formed heterodimers with kAE1 G701D and kAE1 A858D, and promoted the cell surface expression of the mutant proteins. The co-expressed kAE1 G701D and A858D could also form heterodimers but showed predominant intracellular retention in HEK 293T and MDCK cells. Thus impaired trafficking of the kAE1 G701D and A858D mutants would lead to a profound decrease in functional kAE1 at the basolateral membrane of alpha-intercalated cells in the distal nephron of the patients with dRTA.
Division of Medical Molecular Biology, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok.
Duangporn
D
Ungsupravate
Nunghathai
N
Sawasdee
Sookkasem
S
Khositseth
Wandee
W
Udomchaiprasertkul
Siri
S
Khoprasert
Jing
J
Li
Reinhart A F
RA
Reithmeier
Pa-Thai
PT
Yenchitsomanus
D000141:Acidosis, Renal Tubular / Q000378:metabolism*; D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D015153:Blotting, Western; D002457:Cell Extracts; D002460:Cell Line; D002648:Child; D004285:Dogs; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism*; D055503:Protein Multimerization; D021381:Protein Transport; D013347:Subcellular Fractions / Q000378:metabolism
D001457:Anion Exchange Protein 1, Erythrocyte; D002457:Cell Extracts; D050505:Mutant Proteins; C454201:SLC4A1 protein, human