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Dominant and Recessive Distal Renal Tubular Acidosis Mutations of Kidney Anion Exchanger 1 Induce Distinct Trafficking Defects in MDCK Cells
Author(s) -
Cordat Emmanuelle,
Kittanakom Saranya,
Yenchitsomanus Pathai,
Li Jing,
Du Kai,
Lukacs Gergely L.,
Reithmeier Reinhart A. F.
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2005.00366.x
Subject(s) - biology , distal renal tubular acidosis , mutant , intercalated cell , epithelial polarity , apical membrane , endoplasmic reticulum , golgi apparatus , microbiology and biotechnology , renal tubular acidosis , kidney , biochemistry , genetics , epithelium , gene , endocrinology , metabolic acidosis , acidosis
Distal renal tubular acidosis (dRTA), a kidney disease resulting in defective urinary acidification, can be caused by dominant or recessive mutations in the kidney Cl – /HCO 3 – anion exchanger (kAE1), a glycoprotein expressed in the basolateral membrane of α‐intercalated cells. We compared the effect of two dominant (R589H and S613F) and two recessive (S773P and G701D) dRTA point mutations on kAE1 trafficking in Madin‐Darby canine kidney (MDCK) epithelial cells. In contrast to wild‐type (WT) kAE1 that was localized to the basolateral membrane, the dominant mutants (kAE1 R589H and S613F) were retained in the endoplasmic reticulum (ER) in MDCK cells, with a few cells showing in addition some apical localization. The recessive mutant kAE1 S773P, while misfolded and largely retained in the ER in non‐polarized MDCK cells, was targeted to the basolateral membrane after polarization. The other recessive mutants, kAE1 G701D and designed G701E, G701R but not G701A or G701L mutants, were localized to the Golgi in both non‐polarized and polarized cells. The results suggest that introduction of a polar mutation into a transmembrane segment resulted in Golgi retention of the recessive G701D mutant. When coexpressed, the dominant mutants retained kAE1 WT intracellularly, while the recessive mutants did not. Coexpression of recessive G701D and S773P mutants in polarized cells showed that these proteins could interact, yet no G701D mutant was detected at the basolateral membrane. Therefore, compound heterozygous patients expressing both recessive mutants (G701D/S773P) likely developed dRTA due to the lack of a functional kAE1 at the basolateral surface of α‐intercalated cells.