公募シンポジウム

公募シンポジウム神経病理と神経化学の接点としての"液ー液相分離"

7月7日（金）　16:00-18:00　Room F 2SY⑧-1 神経変性疾患におけるタンパク質凝集と液―液相分離（LLPS） Protein aggregation and its liquid-liquid phase separation (LLPS) in neurodegenerative diseases 永井　義隆^1,2 1. 近畿大学　医学部　脳神経内科, 2. 近畿大学　ライフサイエンス研究所 Yoshitaka Nagai^1,2 1. Dept. of Neurology, Kindai Univ. Faculty of Med., 2. Life Science Res. Inst., Kindai Univ. Misfolding and aggregation of disease-causing proteins have been recognized as a common molecular pathogenesis of various neurodegenerative diseases including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and the polyglutamine (polyQ) diseases. Many of these proteins such as TDP-43, FUS, tau, α-synuclein, and polyQ have been found to separate into liquid droplets by liquid-liquid phase separation (LLPS), and to physiologically assemble into biomolecular condensates, called membraneless organelles (MLOs) within the cell, such as nucleolus, nuclear speckle, and stress granules. Recent evidence suggests that dysregulation of LLPS and MLO formation of these disease-causing proteins would trigger their pathological aggregation in neurodegenerative diseases. Especially, TDP-43 and FUS, ALS-linked RNA-binding proteins, are known to physiologically assemble into stress granules upon various stressed conditions. We hypothesize that qualitative alterations (mutations, post-translational modifications, etc) as well as quantitative alterations (autoregulation, intracellular trafficking, etc) of TDP-43 and FUS would trigger their irreversible pathological aggregation, leading to neurodegeneration. In this symposium, I will provide an overview of LLPS in neurodegenerative diseases and introduce our ongoing research on stress granule formation of TDP-43.		7月7日（金）　16:00-18:00　Room F 2SY⑧-2 FUSの相分離性のインビトロ解析 Molecular analysis of phase separating protein FUS. 吉澤　拓也中外製薬 Takuya Yoshizawa Chugai pharmaceutical co., ltd. Fused in Sarcoma (FUS) is a 526 amino acid RNA binding protein that is believed to be involved in trancription, RNA processing and DNA repair. FUS consists of large low-complexity sequence (LC), which is an intrinsically disordered region that does not have a ternary structure. Recent studies have revealed that the weak and transient interactions between LCs are important for the formation of droplets via phase separation. In addition, aberrant phase separation of FUS has been implicated in serious neurodegenerative diseases, so proper regulation is required. FUS has been studied as a model protein for LLPS both in vitro and in vivo. In this talk, I will describe how we perform in vitro analysis using purified proteins. We have identified the karyopherinβ family as regulators of FUS phase separation. The mechanism of FUS regulation by karyopherinβ2 will be also discussed.

7月7日（金）　16:00-18:00　Room F 2SY⑧-3 ユビキチン鎖依存的なプロテアソームの液-液相分離 ubiquitylation dependent phase separation of the proteasome 土屋　光, 佐伯　泰東京都医学総合研究所　蛋白質代謝研究室 Hikaru Tsuchiya, Yasushi Saeki Laboratory of Protein Metabolism Tokyo Metropolitan Institute of Medical Science The proteasome is a major proteolytic machine that regulates cellular proteostasis through selective degradation of ubiquitylated proteins. Recently, a number of ubiquitin-related molecules emerged to be involved in the regulation of biomolecular condensates or membrane-less organelles, which arise by liquid liquid phase separation of specific biomolecules, including stress granules, nuclear speckles, and autophagosomes, but it remains unclear whether the proteasome also participates in such regulation. In this study, we found that proteasome-containing nuclear foci form under acute hyperosmotic stress. These foci are transient structures that contain not only ubiquitylated proteins, but also p97, as well as multiple proteasome-interacting proteins, which collectively constitute a proteolytic center. The major substrates for degradation by these foci were ribosomal proteins that failed to properly assemble. Notably, the proteasome foci exhibited liquid-droplet properties. RAD23B, a substrate shuttling factor for the proteasome, and ubiquitylated proteins were necessary for formation of proteasome foci. Collectively, our results suggest that ubiquitin chain dependent phase separation induces the formation of a nuclear proteolytic compartment that promotes proteasomal degradation.		7月7日（金）　16:00-18:00　Room F 2SY⑧-4 ALSにおける液ー液相分離 Liquid-liquid phase separation in ALS 須貝　章弘新潟大学　脳神経内科 Akihiro Sugai Dept. of Neurology, Univ. of Niigata, Japan Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons. Despite extensive research, the underlying mechanisms of ALS pathogenesis remain largely unknown. However, recent studies have suggested that abnormal phase separation of RNA-binding proteins (RBPs) plays a crucial role in the disease. RBPs undergo liquid-liquid phase separation (LLPS) to form membrane-less organelles that regulate RNA metabolism. Mutations in ALS-related genes, such as C9orf72, FUS, and TDP-43, lead to aberrant RBP phase separation, promoting pathological aggregation, impaired RNA metabolism, and toxicity. Pathological aggregates in ALS patients contain not only RBPs but also other proteins and RNA molecules, which interact with each other. In this talk, I will discuss these relationships, focusing on TDP-43, the accumulating protein in both sporadic and many familial cases of ALS. Understanding the molecular mechanisms underlying the phase separation of these RBPs will provide new insights into the pathogenesis of ALS and guide the development of effective therapies.