FWO-SB-Beurs: Unraveling the structure, function and molecular mechanisms of TBCID24, a new target for drug development against epilepsy and related disorders (FWOSB16)

Epilepsy is the third most common neurological disorder that affects around 50 million people worldwide of all ages and origins. Although in a large percentage of cases the symptoms can be suppressed through existing anti-epileptics, they do not cure the disease. In addition, about 30 to 40% of the patients will not respond to these agents over time. Therefore, it is necessary to look for new targets for the development of medicines. Recently, in various studies in epileptic patients, mutations in the gene encoding the TBC1D24 protein were directly linked to the onset of the disease. In addition, mutations in the same gene were subsequently linked to other neurological disorders such as DOORS syndrome and non-syndrome deafness. TBC1D24 contains an atypical TBC domain, a protein module that usually acts as an activator of the GTPase activity of small G proteins belonging to the Rab family (RabGAP). In 2011, in the lab of Prof. Patrik Verstreken (Laboratory of Neuronal Communication, KU Leuven) a homologue of the TBC1D24 protein characterized in Drosophila, namely Skywalker (or Sky). Sky is a regulator of synaptic aging and its loss of function leads to a more effective functioning of synapses and increased release of neurotransmitters, a phenotype that is parallel to the etiology of epilepsy in humans. In addition, the residues in TBC1D24, which are mutated in epilepsy, DOORS and non-syndrome deafness, are largely conserved in Sky. Although the cellular pathways linking TBC1D24 with epilepsy are not yet known, initial studies suggest a link with the small G proteins Rab35 and Arf6. In addition, very recent data from our lab also indicate an interaction with phosphoinositides. This project is part of a joint effort with the group of Prof. Patrik Verstreken, to map both the molecular mechanisms of TBC1D24 / Sky and the cellular pathways that lead to disease phenotypes. Ultimately, we hope to validate and use this pathway as a target for the development of new anti-epileptic drugs. Within this doctoral project, the interaction of TBC1D24 / Sky with its potential substrate proteins and / or interactors (Rab35 / Arf6 / phosphoinositides) will be investigated using various biophysical methods. Next, atomic resolution structures of these complexes will also be determined by X-ray crystallography. To further unravel the molecular mechanism of TBC1D24 / Sky and the mechanisms that lead to the disease phenotypes, we will review the effect of clinical mutations and rationally designed mutations on these interactions and on increasing the GTPase activity of Rab35 and Arf6. These in vitro results will be linked to in vivo data in fruitflies, by generating fruit flies expressing mutant Sky proteins. Finally, a first step towards drug design will be made by using these insights and high resolution structures of TBC1D24 / Sky to search for chemical chaperones that can be used as new anti-epileptics. This project will not only provide us with information about the molecular mechanism of TBC1D24 / Sky, but will also provide the opportunity to develop a new in vivo epilepsy model and use this model for the development of new drugs

Keywords:Epilepsy

Disciplines:Biomedical modelling

Project type:Collaboration project