In neurodegenerative diseases, a low-molecular-weight protein named "ubiquitin" colocalizes intracellular inclusions, which causes protein toxicity (proteinopathy). We have identified a novel type of ubiquitin chain that correlates with inflammatory responses in the nerve cells of patients with amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD). Moreover, we have developed a specific inhibitor against the enzyme that produces the ubiquitin chain. In this research and development, we will use model mice of ALS and AD to elucidate the cellular basis of ubiquitination and the inhibitor's efficacy and develop new drug seeds for ALS and AD.