Four-year fellowships for a PhD student : Contribution to the development of new specific blockers...

SK channels (small conductance calcium-activated potassium channels) are expressed in various tissues and organs e.g. nervous system, smooth muscle and heart. These channels play an important role in modulating the firing rate and the firing pattern of different types of neurons. They are selective for K+ ions and are gated by Ca2+ via calmodulin molecules. SK2 is mostly expressed in the cortex and hippocampus while the SK3 expression is higher in the monoamine cell regions. They represent potential targets for central and peripheral nervous system disorders. Recently, new possibilities for treating diseases such as atrial fibrillation, schizophrenia (SK3), breast cancer (SK3) or mood disorders were proposed.
The development of new non-peptidic blockers combining high affinity and selectivity towards SK2 or SK3 channels requires a better knowledge of the structural features essential to the affinity of these ligands.
In this project, we will prepare new labelled ligands for in vitro high throughput binding assay using selective modifications of SK2/3 inhibitory toxins like tamapin to attach a biotin or a fluorescent molecule. The labelled toxins will be compared to determine the most appropriate and accurate one for the competition assay with SK2 and SK3 containing membrane preparations. In parallel to this approach, we will adapt to SK2 and SK3 the recently described liposome flux assay (LFA) that enables the screening of molecules modifying the K+ flux across the membrane. This very powerful assay is performed using purified channels reconstituted in proteoliposomes.
The project will also involve a high throughput mutagenesis of tamapin, a 31 amino acid toxin, and the selection of the most potent and specific blockers of SK2 or SK3 channels.
The project is part of a larger program (at least 5 PhD students) studying the SK2 and SK3 channels that involves structural study of the proteins, medicinal chemistry, mass spectrometry for the screening of toxins from venom of different origins, and development of new in vivo biological models to further advance the potential therapeutic use of such blockers.