title: Multiple post-translational modifications regulate E-cadherin transport during apoptosis.
abstract: E-cadherin is synthesized as a precursor and then undergoes cleavage by proprotein convertases. This processing is essential for E-cadherin maturation and cell adhesion. Loss of cell adhesion causes detachment-induced apoptosis, which is called anoikis. Anoikis can be inhibited despite loss of cell-matrix interactions by preserving E-cadherin-mediated cell-cell adhesion. Conversely, acute loss of E-cadherin sensitizes cells to apoptosis by unknown post-translational mechanisms. After treatment of breast cancer cells with drugs, we found that two independent modifications of E-cadherin inhibit its cell surface transport. First, O-linked β-N-acetylglucosamine (O-GlcNAc) modification of the cytoplasmic domain retains E-cadherin in the endoplasmic reticulum. Second, incomplete processing by proprotein convertases arrests E-cadherin transport late in the secretory pathway. We demonstrated these E-cadherin modifications (detected by specific lectins and antibodies) do not affect binding to α-catenin, β-catenin or γ-catenin. However, binding of E-cadherin to Type I gamma phosphatidylinositol phosphate kinase (PIPKIγ), a protein required for recruitment of E-cadherin to adhesion sites, was blocked by O-GlcNAc glycosylation (O-GlcNAcylation). Consequently, E-cadherin trafficking to the plasma membrane was inhibited. However, deletion mutants that cannot be O-GlcNAcylated continued to bind PIPKIγ, trafficked to the cell surface and delayed apoptosis, confirming the biological significance of the modifications and PIPKIγ binding. Thus, O-GlyNAcylation of E-cadherin accelerates apoptosis. Furthermore, cell-stress-induced inactivation of proprotein convertases, inhibited E-cadherin maturation, further exacerbating apoptosis. The modifications of E-cadherin by O-GlcNAcylation and lack of pro-region processing represent novel mechanisms for rapid regulation of cell surface transport of E-cadherin in response to intoxication.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Fei
authors.initials: F
authors.lastname: Geng
authors.forename: Weijia
authors.initials: W
authors.lastname: Zhu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Anderson
authors.forename: Brian
authors.initials: B
authors.lastname: Leber
authors.forename: David W
authors.initials: DW
authors.lastname: Andrews
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD; D017209:Apoptosis / Q000187:drug effects; D015820:Cadherins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D061986:MCF-7 Cells; D061985:Madin Darby Canine Kidney Cells; D008954:Models, Biological; D010455:Peptides / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D017384:Sequence Deletion / Q000235:genetics; D013312:Stress, Physiological / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
chemical_list: D015703:Antigens, CD; C513384:CDH1 protein, human; D015820:Cadherins; D010455:Peptides; C027794:polyserine; D019284:Thapsigargin; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D000117:Acetylglucosamine