Approximately one-third of newly synthesized proteins are inserted into the endoplasmic reticulum, one of organelle, where they undergo disulfide bond formation and glycosylation. These chemical modifications are essential elements for protein folding, and cells have highly conserved sophisticated protein quality control mechanisms. Our laboratory aims to achieve a comprehensive understanding of protein behavior in living cells. We also hope to elucidate the mechanisms of various misfolding diseases, such as Parkinson's disease, Alzheimer's disease, and diabetes, which are caused by dysfunction of protein quality control system.