Functional Rescue of a Kidney Anion Exchanger 1 Trafficking Mutant in Renal Epithelial Cells

Abstract

Mutations in the SLC4A1 gene encoding the anion exchanger 1 (AE1) can cause distal renal tubular acidosis (dRTA), a disease often due to mis-trafficking of the mutant protein. In this study, we investigated whether trafficking of a Golgi-retained dRTA mutant, G701D kAE1, or two dRTA mutants retained in the endoplasmic reticulum, C479W and R589H kAE1, could be functionally rescued to the plasma membrane of Madin-Darby Canine Kidney (MDCK) cells. Treatments with DMSO, glycerol, the corrector VX-809, or low temperature incubations restored the basolateral trafficking of G701D kAE1 mutant. These treatments had no significant rescuing effect on trafficking of the mis-folded C479W or R589H kAE1 mutants. DMSO was the only treatment that partially restored G701D kAE1 function in the plasma membrane of MDCK cells. Our experiments show that trafficking of intracellularly retained dRTA kAE1 mutants can be partially restored, and that one chemical treatment rescued both trafficking and function of a dRTA mutant. These studies provide an opportunity to develop alternative therapeutic solutions for dRTA patients.

Intercalated Cell Depletion and Vacuolar H+-ATPase Mistargeting in an Ae1 R607H Knockin Model

“…These results resemble half-lives of the human wild-type and mutant proteins in HEK-293 cells 11 but differ greatly from the kAE1-R598H half-life of 1-2 hours measured in polarized MDCK monolayers. 7,12 Taken together, the preceding experiments suggest that even though intrinsic anion transport activities (i.e., the activity per AE1 molecule) of mouse kAe1 R607H and human kAE1 R589H measured in transfected cell models are normal, basolateral anion-exchange activity in renal A-ICs might be severely compromised by a dramatic decrease of kAe1 expression in Ae1 +/R607H and Ae1 R607H/R607H mice.…”

A novel mutant Na+/HCO3− cotransporter NBCe1 in a case of compound‐heterozygous inheritance of proximal renal tubular acidosis

“…Whole-body pH in proximal renal tubular acidosis patients can be controlled by alkali therapy, relieving growth defects if administered from an early age (Shiohara et al 2000) but this treatment does not address those pathologies that are related to defects in control of intracellular pH caused by NBCe1 loss from non-renal cells. Importantly in this regard, both R510H and Q913R-mutant proteins exhibit a per molecule Na/HCO 3 cotransport activity that similar to wild-type, suggesting that some signs could be corrected by increasing the plasma membrane abundance of these mutants (Chu et al 2013;Chiu et al 2015). This may be a valuable therapy for R510H homozygotes.…”

Structure, Function, and Trafficking of SLC4 and SLC26 Anion Transporters

“…Thus, some dominant dRTA mutants are retained in the ER of polarized MDCK by their interaction with calnexin. It has been shown (Chu, King, Berrini, Alexander, & Cordat, 2013) that it is possible to rescue the trafficking and partially the function of the recessive G701D mutant to the BLM of MDCK cells using a chemical chaperone, while the dominant R589H or C479W mutants were not rescued. It would be worthwhile to perform high-throughput screens of chemical libraries to identify small molecules that can perform a similar rescue function (Romisch, 2004), without the toxic properties of drugs like castanospermine.…”