Abstract
Purpose :
SLC4A11 is an integral membrane protein abundant in corneal endothelium. Point mutations of SLC4A11 protein cause genetic endothelial corneal dystrophies manifesting very early in life (congenital hereditary endothelial corneal dystrophy (CHED) and Harboyan syndrome (HS)) or in the fifth to sixth decade of life (Fuchs endothelial corneal dystrophy (FECD)). The molecular defect associated with these mutations include mis-folding of the protein, leading to its retention in endoplasmic reticulum (ER) and a loss of SLC4A11 water flux function. We aim to elucidate the effect of disease-causing SLC4A11 mutations on protein structure. This is a first attempt to classify SLC4A11 mutations into structural sub-categories, to provide a molecular explanation for SLC4A11- associated disease.
Methods :
A 3D homology model of the human SLC4A11 protein membrane domain was created on the basis of the crystal structure of human SLC4A1 structure at 3.5 Å. The homology modelling was performed, using the SWISS-MODEL server. To test the validity of the SLC4A11 homology model, mutations were made at positions corresponding to the protein’s predicted catalytic site. Functional activity of these mutants was assessed by whole cell swelling assay.
Results :
Amongst 29 disease-causing mutations of SLC4A11 membrane domain, 17 altered helix packing and two were in the dimeric interface. The other mutations mapped to the SLC4A11 transport catalytic site. Consistent with the homology model, protein-packing mutants were associated with protein mis-folding and ER retention. Catalytic site mutants affected SLC4A11 water flux activity.
Conclusions :
Missense mutants of SLC4A11 were categorized as disrupting 1. Helix packing, 2. Catalytic activity, or 3. Dimerization. The 3D SLC4A11 model provides the ability to predict pathogenicity of variants of this protein identified in the future.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.