Satoshi Ninagawa

Glycoproteins misfolded in the endoplasmic reticulum (ER) are subjected to ER-associated glycoprotein degradation (gpERAD) in which Htm1-mediated mannose trimming from the oligosaccharide Man8GlcNAc2 to Man7GlcNAc2 is the rate-limiting step in yeast. In contrast, the roles of the three Htm1 homologues (EDEM1/2/3) in mammalian gpERAD have remained elusive, with a key controversy being whether EDEMs function as mannosidases or as lectins. We therefore conducted transcription activator-like effecto

The introduction of innovative genome editing technology into analysis of the mechanisms of mammalian ERAD, as exemplified here, will provide new insights into the pathogenesis of various diseases.

Glycoproteins and non-glycoproteins possessing unfolded/misfolded parts in their luminal regions are cleared from the endoplasmic reticulum (ER) by ER-associated degradation (ERAD)-L with distinct mechanisms. Two-step mannose trimming from Man9GlcNAc2 is crucial in the ERAD-L of glycoproteins. We recently showed that this process is initiated by EDEM2 and completed by EDEM3/EDEM1. Here, we constructed chicken and human cells simultaneously deficient in EDEM1/2/3 and analyzed the fates of four ER

Second-generation antipsychotics are widely used to medicate patients with schizophrenia, but may cause metabolic side effects such as diabetes, which has been considered to result from obesity-associated insulin resistance. Olanzapine is particularly well known for this effect. However, clinical studies have suggested that olanzapine-induced hyperglycemia in certain patients cannot be explained by such a generalized mechanism. Here, we focused on the effects of olanzapine on insulin biosynthesi

Proteins misfolded in the endoplasmic reticulum (ER) are degraded in the cytosol by a ubiquitin-dependent proteasome system, a process collectively termed ER-associated degradation (ERAD). Unraveling the molecular mechanisms of mammalian ERAD progresses more slowly than that of yeast ERAD due to the laborious procedures required for gene targeting and the redundancy of components. Here, we utilized the chicken B lymphocyte-derived DT40 cell line, which exhibits an extremely high homologous recom

This protocol aims to evaluate folding status of proteins, utilizing trypsin sensitivity. Unfolded/misfolded proteins are more susceptible to trypsin than folded proteins, because trypsin easily accesses and cleaves loosely folded parts of proteins. This method is especially useful to compare tightness of the folding among wild-type and mutant proteins. As trypsin generally cleaves a peptide bond at the carboxyl-terminal side of the amino acids lysine or arginine, this method can be used to anal

This protocol aims to evaluate folding status of proteins, utilizing peptide:N-glycanase (PNGase) sensitivity. In the cytosol, PNGase works as a deglycosylation-enzyme. N-glycans on unfolded/misfolded proteins are more susceptible to PNGase than N-glycans on folded proteins because of the preference of PNGase to non-native proteins. PNGase is endogenously expressed in various cell types, including HCT116 cells, DT40 cells and mouse embryonic fibroblast cells. Partial deglycosylation by PNGase ca

How the fate (folding versus degradation) of glycoproteins is determined in the endoplasmic reticulum (ER) is an intriguing question. Monoglucosylated glycoproteins are recognized by lectin chaperones to facilitate their folding, whereas glycoproteins exposing well-trimmed mannoses are subjected to glycoprotein ER-associated degradation (gpERAD); we have elucidated how mannoses are sequentially trimmed by EDEM family members (George et al., 2020; 2021 eLife). Although reglucosylation by UGGT was

How the fate (folding versus degradation) of glycoproteins is determined in the endoplasmic reticulum (ER) is an intriguing question. Monoglucosylated glycoproteins are recognized by lectin chaperones to facilitate their folding, whereas glycoproteins exposing well-trimmed mannoses are subjected to glycoprotein ER-associated degradation (gpERAD); we have elucidated how mannoses are sequentially trimmed by EDEM family members (George et al., 2020; 2021 eLife). Although reglucosylation by UGGT was

Abstract How the fate (folding versus degradation) of glycoproteins is determined in the endoplasmic reticulum (ER) is an intriguing question. Monoglucosylated glycoproteins are recognized by lectin chaperones to facilitate their folding, whereas glycoproteins exposing well-trimmed mannoses are subjected to glycoprotein ER-associated degradation (gpERAD); we have elucidated how mannoses are sequentially trimmed by EDEM family members (George et al., 2020, 2021 eLife). Although reglucosylation by

Here we investigated how the fate (folding versus degradation) of glycoproteins is determined in the endoplasmic reticulum (ER). Monoglucosylated glycoproteins are recognized by lectin chaperones to facilitate their folding, whereas glycoproteins with well-trimmed mannoses are subjected to glycoprotein ER-associated degradation (gpERAD). Previously we elucidated how mannoses are trimmed by EDEM family members (, eLife). Though reglucosylation by UGGTs (UGGT1 and UGGT2) was reported to have no ef

ABSTRACT How the fate (folding versus degradation) of glycoproteins is determined in the endoplasmic reticulum (ER) is an intriguing question. Monoglucosylated glycoproteins are recognized by lectin chaperones to facilitate their folding, whereas glycoproteins exposing well-trimmed mannoses are subjected to glycoprotein ER-associated degradation (gpERAD); we have elucidated how mannoses are sequentially trimmed by EDEM family members (George et al., 2020, 2021 eLife). Although reglucosylation by