Nuclear Localization of Insulin-Like Growth Factor Binding Protein 3 in a Lung Cancer Cell Line

Abstract

Considerable evidence exists that lung cancer cell lines produce large amounts of insulin-like growth factor-binding proteins (IGFBPs). In addition, these cells are subject to an autocrine or paracrine growth control by insulin-like growth factors (IGFs). We now demonstrate by immunocytochemistry with IGFBP-3 antibodies that nuclei of a lung cancer cell line distinctly immunostain for IGFBP-3. This finding led us to investigate in more detail the localization of this protein that, to date, had only been known to occur extracellularly. Ligand blotting revealed that purified nuclear extracts contain a 43,000-Da IGFBP which can bind [I125]IGF-I. By Western blot this protein was identified as IGFBP-3. Thus, our data are consistent with the results of a previous structural study predicting a nuclear localization for IGFBP-3. Moreover, our findings raise the possibility that nuclear IGFBP-3 is functional and involved in the pathogenesis of lung cancer.

Nuclear Import of Insulin-like Growth Factor-binding Protein-3 and -5 Is Mediated by the Importin β Subunit

“…These results support the proposal that, upon entry into the nucleus, IGFBP-3 accumulates through nuclear binding and suggest that residues 228 -232 are required for these nuclear interactions. The ability of IGFBP-3 to bind to structures within the nucleus supports the hypothesis that it may have a role in the nucleus, possibly in direct regulation of gene transcription (33)(34)(35)(36). This has been suggested for granzyme A and B (53,54) and parathyroid hormone-related protein (24), which can also accumulate in the nucleus even in the absence of an intact nuclear envelope.…”

“…In the presence of cytosolic factors and an ATP-regeneration system, full-length wildtype IGFBP-3 was capable of nuclear uptake in all cells where the plasma membrane had been permeabilized, but the nuclear envelope remained intact. Previous studies in intact cells have shown that nuclear transport of IGFBP-3 is detected only in a low percentage of cells in the monolayer (33)(34)(35)(36). Therefore, these data suggest that the plasma membrane is an important regulator of nuclear uptake of IGFBP-3 and consequently also of its subsequent function in the nucleus.…”

“…These include platelet-derived growth factor A (30), acidic fibroblast growth factor (31), and parathyroid hormone-related protein (32). We and others have described the nuclear transport of IGFBP-3 and IGFBP-5 in a number of cell lines (33)(34)(35)(36).…”

Identification of differentially expressed genes in pulmonary adenocarcinoma by using cDNA array

“…Table 1 presents these genes, their function and chromosomal location. Figure 1 shows all Bornslaeger et al, 1996, 4 Caligo et al, 1995 Lee et al, 1997, 6 Pines and Hunter, 1992, 7 Toyoshima-Morimoto et al, 2001, 8 Everett et al, 2001, 9 Nhung et al, 1999, 10 Smith, 1991, 11 Fassina et al, 2000 Laronga et al, 2000, 13 Nakanishi et al, 1997, 14 Smith et al, 1997, 15 Yu andRohan, 2000, 16 Jaques et al, 1997, 17 Nishihira, 1998 Sethi et al, 1999, 19 Zhou et al, 1998, 20 Ratziu et al, 1998, 21 Kojima et al, 2000, 22 Diviani and Scott, 2001, 23 Feliciello et al, 2001 Wilson et al, 2000, 25 Engelman et al, 1998 Razani andLisanti, 2001, 27 Tuder et al, 2001, 28 Hefferan et al, 2000, 29 Boot et al, 1998, 30 Dohr et al, 1997, 31 Matikainen et al, 2001, 32 Chu et al, 1995. a Clontech array gene-specification number Figure 1 The gene expression profile of the 25 most over-and under-expressed genes in 14 patients calculated with either PCA analysis or permutation test. Names of the genes appear on the right-hand side and the samples studied are listed at the top.…”

Cellular Internalization of Insulin-like Growth Factor Binding Protein-3

“…Nuclear localization of IGFBP-3 is a well described phenomenon and has been demonstrated in a variety of cellular models (5)(6)(7)(8). IGFBP-3 possesses a consensus bipartite nuclear localization sequence (9), and nuclear transport is facilitated by importin-␤ factor (10).…”