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

• Autores: Vilas, Gonzalo L.; Morgan, Patricio Eduardo; Loganathan, Sampath K.; Quon, Anita; Casey, Joseph R.
• Año de publicación: 2011
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Slc4a11; Eye; Distrophy; Structure
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Mutations in the SLC4A11 protein, reported as a sodium-coupled 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 H2DIDS, 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 [H2DIDS]  required for resin displacement and the fraction of protein bindingH2DIDS, 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.
Fil: Vilas, Gonzalo L.. University of Alberta; Canadá
Fil: Morgan, Patricio Eduardo. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares ; Argentina
Fil: Loganathan, Sampath K.. University of Alberta; Canadá
Fil: Quon, Anita. University of Alberta; Canadá
Fil: Casey, Joseph R.. University of Alberta; Canadá