Trafficking Defects of a Novel Autosomal Recessive Distal Renal Tubular Acidosis Mutant (S773P) of the Human Kidney Anion Exchanger (kAE1)

Distal renal tubular acidosis (dRTA) is an inherited disease characterized by the failure of the kidneys to appropriately acidify urine and is associated with mutations in the anion exchanger (AE)1 gene. The effect of the R589H dRTA mutation on the expression of the human erythroid AE1 and the truncated kidney form (kAE1) was examined in transfected human embryonic kidney 293 cells. AE1, AE1 R589H, and kAE1 were present at the cell surface, whereas kAE1 R589H was located primarily intracellularly as shown by immunofluorescence, cell surface biotinylation, N-glycosylation, and anion transport assays. Coexpression of kAE1 R589H reduced the cell surface expression of kAE1 and AE1 by a dominant-negative effect, due to heterodimer formation. The mutant AE1 and kAE1 bound to an inhibitor affinity resin, suggesting that they were not grossly misfolded. Other mutations at R589 also prevented the formation of the cell surface form of kAE1, indicating that this conserved arginine residue is important for proper trafficking. The R589H dRTA mutation creates a severe trafficking defect in kAE1 but not in erythroid AE1.

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Impaired trafficking of human kidney anion exchanger (kAE1) caused by hetero-oligomer formation with a truncated mutant associated with distal renal tubular acidosis

Biochemical Journal ◽

10.1042/bj20020574 ◽

2002 ◽

Vol 368 (3) ◽

pp. 895-903 ◽

Cited By ~ 46

Author(s):

Janne A. QUILTY ◽

Emmanuelle CORDAT ◽

Reinhart A.F. REITHMEIER

Keyword(s):

Renal Tubular Acidosis ◽

Anion Exchanger ◽

Human Kidney ◽

Distal Renal Tubular Acidosis ◽

Dominant Negative ◽

Dominant Negative Effect ◽

Wild Type ◽

Hek 293 ◽

Oligomer Formation ◽

Renal Tubular

Autosomal dominant distal renal tubular acidosis (dRTA) has been associated with several mutations in the anion exchanger AE1 gene. The effect of an 11-amino-acid C-terminal dRTA truncation mutation (901 stop) on the expression of kidney AE1 (kAE1) and erythroid AE1 was examined in transiently transfected HEK-293 cells. Unlike the wild-type proteins, kAE1 901 stop and AE1 901 stop mutants exhibited impaired trafficking from the endoplasmic reticulum to the plasma membrane as determined by immunolocalization, cell-surface biotinylation, oligosaccharide processing and pulse—chase experiments. The 901 stop mutants were able to bind to an inhibitor affinity resin, suggesting that these mutant membrane proteins were not grossly misfolded. Co-expression of wild-type and mutant kAE1 or AE1 resulted in intracellular retention of the wild-type proteins in a pre-medial Golgi compartment. This dominant negative effect was due to hetero-oligomer formation of the mutant and wild-type proteins. Intracellular retention of kAE1 in the α-intercalated cells of the kidney would account for the impaired acid secretion into the urine characteristic of dRTA.

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