title: Intracellular colocalization and interaction of IGF-binding protein-2 with the cyclin-dependent kinase inhibitor p21CIP1/WAF1 during growth inhibition.
abstract: It is presently unknown whether any member of the IGFBP (insulin-like growth factor binding protein) family directly participates in the control of cell proliferation. We have previously documented that induction of IGFBP-2 was associated with inhibition of DNA synthesis in lung alveolar epithelial cells. In the present study, we investigated the relationship between IGFBP-2 and the cell cycle inhibitor p21CIP1/WAF1 further. We used serum deprivation to inhibit the proliferation of MLE (mouse lung epithelial)-12 cells, and characterized the spatial localization of IGFBP-2. We found that growth inhibition, which was supported by the strong induction of p21CIP1/WAF1, was correlated with increased secretion of IGFBP-2 and, unexpectedly, with its increased localization in the nucleus and particularly in the cytoplasm. By coimmunoprecipitation, we discovered that IGFBP-2 is capable of binding to p21CIP1/WAF1. Interaction between these two proteins was further supported by colocalization of the proteins within growth-arrested cells, as visualized by confocal microscopy. Furthermore, this interaction increased with the duration of the stress, but was suppressed when proliferation was restimulated by the addition of serum. The recombinant expression of GFP (green fluorescent protein)-tagged IGFBP-2 in transfected MLE-12 cells demonstrated its ability to bind specifically to p21CIP1/WAF1. Taken together, these results provide a link between IGFBP-2 and p21CIP1/WAF1 in the regulation of alveolar lung cell proliferation.
authors.affiliation: INSERM U719, Université Pierre et Marie Curie, Hôpital St-Antoine, 75571 Paris Cedex 12, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Terrien
authors.forename: Elise
authors.initials: E
authors.lastname: Bonvin
authors.forename: Sophie
authors.initials: S
authors.lastname: Corroyer
authors.forename: Olivier
authors.initials: O
authors.lastname: Tabary
authors.forename: Annick
authors.initials: A
authors.lastname: Clement
authors.forename: Alexandra
authors.initials: A
authors.lastname: Henrion Caude
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D008168:Lung / Q000166:cytology; D051379:Mice; D011485:Protein Binding; D021381:Protein Transport; D051381:Rats
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018971:Insulin-Like Growth Factor Binding Protein 2