title: DNAJB4 molecular chaperone distinguishes WT from mutant E-cadherin, determining their fate in vitro and in vivo.
abstract: E-cadherin (Ecad) is a well-known invasion suppressor and its loss of expression is common in invasive carcinomas. Germline Ecad mutations are the only known genetic cause of hereditary diffuse gastric cancer (HDGC), demonstrating the causative role of Ecad impairment in gastric cancer. HDGC-associated Ecad missense mutations can lead to folding defects and premature proteasome-dependent endoplasmic reticulum-associated degradation (ERAD), but the molecular determinants for this fate were unidentified. Using a Drosophila-based genetic screen, we found that Drosophila DnaJ-1 interacts with wild type (WT) and mutant human Ecad in vivo. DnaJ (Hsp40) homolog, subfamily B, member 4 (DNAJB4), the human homolog of DnaJ-1, influences Ecad localization and stability even in the absence of Ecad endogenous promoter, suggesting a post-transcriptional level of regulation. Increased expression of DNAJB4 leads to stabilization of WT Ecad in the plasma membrane, while it induces premature degradation of unfolded HDGC mutants in the proteasome. The interaction between DNAJB4 and Ecad is direct, and is increased in the context of the unfolded mutant E757K, especially when proteasome degradation is inhibited, suggesting that DNAJB4 is a molecular mediator of ERAD. Post-translational regulation of native Ecad by DNAJB4 molecular chaperone is sufficient to influence cell adhesion in vitro. Using a chick embryo chorioallantoic membrane assay with gastric cancer derived cells, we demonstrate that DNAJB4 stimulates the anti-invasive function of WT Ecad in vivo. Additionally, the expression of DNAJB4 and Ecad is concomitantly decreased in human gastric carcinomas. Altogether, we demonstrate that DNAJB4 is a sensor of Ecad structural features that might contribute to gastric cancer progression.
authors.affiliation: IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Porto 4200-465, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Simões-Correia
authors.forename: Diana I
authors.initials: DI
authors.lastname: Silva
authors.forename: Soraia
authors.initials: S
authors.lastname: Melo
authors.forename: Joana
authors.initials: J
authors.lastname: Figueiredo
authors.forename: Joana
authors.initials: J
authors.lastname: Caldeira
authors.forename: Marta T
authors.initials: MT
authors.lastname: Pinto
authors.forename: Henrique
authors.initials: H
authors.lastname: Girão
authors.forename: Paulo
authors.initials: P
authors.lastname: Pereira
authors.forename: Raquel
authors.initials: R
authors.lastname: Seruca
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015153:Blotting, Western; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D002642:Chick Embryo; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005434:Flow Cytometry; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D018832:Molecular Chaperones / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009361:Neoplasm Invasiveness; D059748:Proteolysis; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: D015820:Cadherins; C494650:DNAJB4 protein, human; C494637:DnaJ-1 protein, Drosophila; D029721:Drosophila Proteins; D050956:HSP40 Heat-Shock Proteins; D018832:Molecular Chaperones