Targeted screening of small molecules for chemical chaperone activity

Inherited retinal dystrophies (IRDs) are the major cause of incurable familial blindness in the western world. Bestrophinopathies are a group of IRDs caused by mutations in bestrophin-1, a Cl- channel in the retinal pigment epithelium, which lead to vision loss and blindness. There is currently no treatment available for these orphan diseases. More than 120 missense mutations in bestrophin-1 cause a bestrophinopathy, and are predicted to cause protein misfolding and a loss of protein function. We have described several forms of bestrophinopathy and their molecular pathogenesis [1, 2]. Mutant bestrophin-1 proteins are mislocalised, degraded by the proteasome, and lose Cl- conductance [3]. We have recently demonstrated that sodium 4-phenylbutyrate (4PBA) restores the expression, localisation, and function to mutant bestrophin-1 proteins [4].

4PBA is an FDA-approved drug for the long-term treatment of urea cycle disorders; it also acts as a chemical chaperone and has been trialled for the treatment of several diseases. The concentration used to restore function to mutant bestrophin-1 was much higher than is typical for therapeutic drugs. 4PBA has a complex and rapid metabolism [5], the major pathway being through a beta-oxidation to phenylacetate, which may be the reason why such high concentrations of 4PBA are required.

Using whole-cell patch-clamp to measure the Cl- conductance of different mutant bestrophin-1 proteins we will screen whether commercially available molecules with related chemical properties or structures to 4PBA have a similar, or improved, function.
It is unclear whether 4PBA’s role as a chaperone is attributed to this molecule or a metabolite, and this will also be investigated by evaluating key metabolites. In addition, we will also make the beta-monofluoro and beta, beta-difluoro analogues of 4PBA, which should show resistance to beta-oxidative metabolism.

The successful candidate will be trained in the all the necessary techniques, including cell culture, immunofluorescent and confocal microscopy, western blotting, whole-cell patch-clamp, chemical synthesis and analytical characterisation.

Applicants should hold (or expect to obtain) a minimum upper-second honours degree (or equivalent) in a relevant subject area such as pharmacology, biochemistry, cell biology, medicinal chemistry, pharmacy. Knowledge of protein synthesis, quality control, and chaperones would be advantageous, as would relevant research experience.