Restoration of mutant bestrophin-1 expression, localisation and function in a polarised epithelial cell model

• Main Authors: Carolina Uggenti, Kit Briant, Anne-Kathrin Streit, Steven Thomson, Yee Hui Koay, Richard A. Baines, Eileithyia Swanton, Forbes D. Manson
• Format: Article
• Language: English
• Published: The Company of Biologists 2016-11-01
• Series: Disease Models & Mechanisms
• Subjects: Autosomal recessive bestrophinopathy; Bestrophin-1; Chemical chaperone; 4-phenylbutyrate
• Online Access: http://dmm.biologists.org/content/9/11/1317
• ISSN: 1754-8403; 1754-8411

Autosomal recessive bestrophinopathy (ARB) is a retinopathy caused by mutations in the bestrophin-1 protein, which is thought to function as a Ca2+-gated Cl− channel in the basolateral surface of the retinal pigment epithelium (RPE). Using a stably transfected polarised epithelial cell model, we show that four ARB mutant bestrophin-1 proteins were mislocalised and subjected to proteasomal degradation. In contrast to the wild-type bestrophin-1, each of the four mutant proteins also failed to conduct Cl− ions in transiently transfected cells as determined by whole-cell patch clamp. We demonstrate that a combination of two clinically approved drugs, bortezomib and 4-phenylbutyrate (4PBA), successfully restored the expression and localisation of all four ARB mutant bestrophin-1 proteins. Importantly, the Cl− conductance function of each of the mutant bestrophin-1 proteins was fully restored to that of wild-type bestrophin-1 by treatment of cells with 4PBA alone. The functional rescue achieved with 4PBA is significant because it suggests that this drug, which is already approved for long-term use in infants and adults, might represent a promising therapy for the treatment of ARB and other bestrophinopathies resulting from missense mutations in BEST1.