title: Unglycosylation at Asn-633 made extracellular domain of E-cadherin folded incorrectly and arrested in endoplasmic reticulum, then sequentially degraded by ERAD.
abstract: The human E-cadherin is a single transmembrane domain protein involved in Ca(2+)-dependent cell-cell adhesion. In a previous study, we demonstrated that all of four potential N-glycosylation sites in E-cadherin are occupied by N-glycans in human breast carcinoma cells in vivo and the elimination of N-glycan at Asn-633 dramatically affected E-cadherin expression and made it degraded. In this study we investigated the molecular mechanism of E-cadherin, which lacks N-glycosylation at Asn-633 (M4), degradation and the role of the N-glycan at Asn-633 in E-cadherin folding. We treated cells stably expressed M4 E-cadherin with MG123, DMM, respectively. Either MG132 or DMM could efficiently block degradation of M4 E-cadherin. M4 E-cadherin was recognized as the substrate of ERAD and was retro-translocated from ER lumen to cytoplasm by p97. It was observed that the ration of M4 E-cadherin binding to calnexin was significantly increased compared with that of other variants, suggesting that it was a misfolded protein, though cytoplasmic domain of M4 E-cadherin could associate with beta-catenin. Furthermore, we found that N-glycans of M4 E-cadherin were modified in immature high mannose type, suggesting that it could not depart to Golgi apparatus. In conclusion, this study revealed that N-glycosylation at Asn-633 is essential for E-cadherin expression, folding and trafficking.
authors.affiliation: Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
authors.forename: Jianmin
authors.initials: J
authors.lastname: Su
authors.forename: Le
authors.initials: L
authors.lastname: Fu
authors.forename: Yong
authors.initials: Y
authors.lastname: Yang
authors.forename: Lineng
authors.initials: L
authors.lastname: Zhang
authors.forename: Liying
authors.initials: L
authors.lastname: Wang
authors.forename: Hongbo
authors.initials: H
authors.lastname: Zhao
authors.forename: Diancai
authors.initials: D
authors.lastname: Zhang
authors.forename: Zengxia
authors.initials: Z
authors.lastname: Li
authors.forename: Xiliang
authors.initials: X
authors.lastname: Zha
mesh_terms: D001216:Asparagine / Q000737:chemistry; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015820:Cadherins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D017931:DNA Primers / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005260:Female; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D015820:Cadherins; D017931:DNA Primers; D011994:Recombinant Proteins; D025801:Ubiquitin; D001216:Asparagine; D046988:Proteasome Endopeptidase Complex