A biochemical framework for SLC4A11, the plasma membrane protein defective in corneal dystrophies.

Abstract

Mutations in the SLC4A11 protein, reported as a sodium-coup-led borate transporter of the human plasma membrane, are responsible for three corneal dystrophies (CD): congenital hereditary endothelial dystrophy type 2, Harboyan syndrome, and late-onset Fuch's CD. To develop a rational basis to understand these diseases, whose point mutations are found throughout the SLC4A11 sequence, we analyzed the protein biochemically. Hydropathy analysis and an existing topology model for SLC4A1 (AE1), a bicarbonate transporter with the lowest evolutionary sequence divergence from SLC4A11, formed the basis to propose an SLC4A11 topology model. Immunofluorescence studies revealed the cytosolic orientation of N- and C-termini of SLC4A11. Limited trypsinolysis of SLC4A11 partially mapped the folding of the membrane and cytoplasmic domains of the protein. The binding of SLC4A11 to a stilbenedisulfonate inhibitor resin (SITS-Affi-Gel) was prevented by preincubation with H(2)DIDS, with a significantly higher half-maximal effective concentration than AE1. We conclude that stilbenedisulfonates interact with SLC4A11 but with a lower affinity than other SLC4 proteins. Disease-causing mutants divided into two classes on the basis of the half-maximal [H(2)DIDS] required for resin displacement and the fraction of protein binding H(2)DIDS, likely representing mildly misfolded and grossly misfolded proteins. Disease-causing SLC4A11 mutants are retained in the endoplasmic reticulum of HEK 293 cells. This phenotype could be partially rescued in some cases by growing the cells at 30 °C.

• Authors: Gonzalo L Vilas, Patricio E Morgan, Sampath K Loganathan, Anita Quon, Joseph R Casey
• Journal: Biochemistry (Biochemistry) Vol. 50 Issue 12 Pg. 2157-69 (Mar 29 2011) ISSN: 1520-4995 [Electronic] United States
• PMID: 21288032 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Anion Transport Proteins
• Antiporters
• Cell Extracts
• Epitopes
• SLC4A11 protein, human
• 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid
• Trypsin

Topics

• 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid (metabolism, pharmacology)
• Alleles
• Amino Acid Sequence
• Anion Transport Proteins (antagonists & inhibitors, chemistry, genetics, metabolism)
• Antiporters (antagonists & inhibitors, chemistry, genetics, metabolism)
• Cell Extracts
• Cell Membrane (metabolism)
• Corneal Dystrophies, Hereditary (genetics, metabolism)
• Endoplasmic Reticulum (metabolism)
• Epitopes (metabolism)
• HEK293 Cells
• Humans
• Molecular Sequence Data
• Mutation
• Protein Folding
• Protein Structure, Tertiary
• Sequence Analysis, DNA
• Temperature
• Trypsin (metabolism)