Splicing-Dependent Regulation of Oligomerization of SynGAP1

Abstract

Synaptic GTPase-activating protein 1 (SynGAP1) is enriched in the dendritic spines of excitatory neurons. It plays a crucial role in synaptic plasticity and neuronal connectivity. SynGAP1 forms complexes with PSD-95 (postsynaptic density protein 95) and NMDA (N-methyl-D-aspartate) receptors, contributing to calcium-dependent signaling cascades. Dysregulation or mutations in the SynGAP1 gene are associated with epilepsy, autism spectrum disorders, and other neurodevelopmental disorders (NDDs). The C-terminal region of SynGAP1 includes a predicted coiled-coil domain abundant with hydrophobic residues which are mainly responsible for forming parallel and asymmetric trimers in solution. Splicing-dependent insertion of specific amino acids valine and lysine (VK) in the 5' extension of exon 17 may cause structural changes in the coiled-coil domain, affecting hydrophobic interactions that influence protein stability and function. The aim of the thesis was to study whether the presence of VK insert effect the oligomerization.

The fluorescence-based assays provided an estimate of how protein interaction works using the BRET (Bioluminescence Resonance Energy Transfer) assay between donor and acceptor in close distance through dipole-dipole coupling.

From the experiments, SynGAP1 plasmid with the combinations of donor with VK (+VK) and acceptor without VK (-VK) show higher BRET signals than combinations with donor and acceptor both with VK (+VK), suggesting stronger or more stable interactions. This indicates the influence of VK insert in the structure dynamics of the coiled-coil domain.