title: Overexpression of the nucleolar protein nucleophosmin/B23 in collagen lattice-cultured fibroblasts: potential role in the control of protein synthesis.
abstract: Fibroblasts cultivated in tridimensional collagen lattices exhibit a downregulation of protein synthesis, related to decreased ribosomal RNA (rRNA) content and half life, when compared to monolayer cultivated cells. The involvement in this process of nucleophosmin/B23, a nucleolar phosphoprotein with ribonuclease properties, was checked. We compared production of nucleophosmin/B23 in monolayer and collagen lattice cultured fibroblasts. A significant increase of nucleophosmin/B23 mRNA levels was noticed in lattice-cultured fibroblasts vs monolayers (+154%, p < 0.05). A concomitant enhancement of nucleolar nucleophosmin/B23 content was found (+112%, p < 0.001). Simultaneously, ribonuclease activity contained in nucleolar extracts from collagen lattice-cultured fibroblasts was significantly increased (+54%, p < 0.01). These data demonstrate that extracellular collagen matrix induces the overexpression of nucleophosmin/B23, and suggest that the regulation of protein syntheses in collagen lattice cultures may be explained, at least partly, by an increased degradation of neosynthesized rRNAs dependent on nucleophosmin.
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Faculty of Medicine, University of Reims Champagne-Ardenne, Reims, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Lefèvre
authors.forename: Roselyne
authors.initials: R
authors.lastname: Garnotel
authors.forename: Nadine
authors.initials: N
authors.lastname: Georges
authors.forename: Philippe
authors.initials: P
authors.lastname: Gillery
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000090243:Nucleophosmin; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism
chemical_list: C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D000090243:Nucleophosmin; D003094:Collagen