Ubiquitylation and degradation of postsynaptic scaffold proteins

一系列多结构域蛋白构成了哺乳动物大脑兴奋性突触突触后密度（PSD）的支架，包括Shank和SAPAP家族的不同成员。PSD分子组成的变化是突触发育和可塑性的基础。神经元活动通过泛素/蛋白酶体系统（UPS）诱导几种选定的PSD成分的降解，包括Shank和SAPAP亚型。使用体内刺激方案，我们打算分析突触后部位UPS活性的动力学和底物特异性。在细胞和体外实验中，我们将研究Shank和SAPAP家族成员泛素化和蛋白酶体靶向的分子机制。在这种情况下，我们将特别关注sharpin，一种通过不同基序与Shank和泛素相互作用的蛋白质。在细胞中，Shank/sharpin相互作用通过蛋白酶体抑制而稳定，这表明Shank/sharpin复合物可以快速降解。我们将研究sharpin是否作为突触后蛋白E3连接酶复合体的一部分，或者它是否在将泛素化底物靶向到蛋白酶体中发挥作用。概述的研究将有助于揭示UPS在活动诱导的突触调节中的作用，这可能有助于学习和记忆。

A series of multi-domain proteins constitute the scaffold of the postsynaptic density (PSD) in excitatory synapses of the mammalian brain, including different members of the Shank and SAPAP families. Changes in the molecular composition of the PSD are fundamental to synaptic development and plasticity. Neuronal activity induces degradation of several selected PSD components by the ubiquitin/proteasome system (UPS), including Shank and SAPAP subtypes. Using in vivo stimulation protocols, we intend to analyze the kinetics and substrate specificity of UPS activity at the postsynaptic site. In cellular and in vitro assays, we will investigate the molecular mechanisms contributing to ubiquitylation and proteasomal targeting of Shank and SAPAP family members. In this context, we will particularly focus on sharpin, a protein that interacts with both Shank and ubiquitin through different motifs. In cells, the Shank/sharpin interaction is stabilized by proteasome inhibition, indicating that Shank/sharpin complexes are subject to rapid degradation. We will investigate whether sharpin acts as part of an E3 ligase complex for postsynaptic proteins, or if it plays a role in targeting ubiquitylated substrates to proteasomes. The outlined research will help to unravel the role of the UPS in activity-induced modulation of the synapse, which may contribute to learning and memory.