High-throughput Screening for Chaperones of R138Q Podocin Mutant

Our increasing understanding of the pathophysiology of nephrotic syndrome caused by genetically determined defects in podocyte structure and function opens an avenue of experimental research towards novel, non-immunological therapeutic approaches. In particular, the frequent mutations leading to defective intracellular trafficking of podocin may be amenable to treatment with small-molecular compounds stimulating the translocation of mutated protein into the plasma membrane and/or increase the membrane residency time. Such strategies are being pursued with preliminary success in experimental models of other genetic diseases, and may hold promise in podocin-related SRNS. The project comprises the following steps:

• Set-up of an appropriate cellular model which will allow the rapid testing for mutant podocin localization, and verification of the validity of the model by testing drugs already shown to be effective on mutant podocin targeting rescue (such as TMAO);
• Miniaturization of the assay and medium-throughput screening

The assay will be miniaturized and validated in partnership with the Strasbourg academic screening platform in order to allow a medium-throughput screening in 96 well microtiter plates (collaboration with M. Hibert and J. Haiech, Strasbourg, France). The aim in the mean term is to screen two compound libraries: the Prestwick Chemical library and the Strasbourg academic library. If necessary, the screening could eventually be extended to the 35.000 molecules of the French Academic Compound Library (http://chimiotheque-nationale. enscm.fr). The Prestwick Chemical Library® is of particular interest. It contains 1.120 small molecules, 90% being marketed drugs and 10% bioactive alkaloids or related substances, thus it presents the greatest possible degree of drug-likelihood. The active compounds were selected for their high chemical and pharmacological diversity as well as for their known bioavailability and safety in humans. Hits will be analysed and optimised in collaboration with medicinal chemists. Once efficient lead compounds have been found (provided their safety has been proven in animals), they will be tested in the Nphs2Flox/R138Q, Cre+ mice.