Secretion of insulin-like growth factor II (IGF-II) and igf-binding protein-2 by intestinal epithelial (IEC-6) cells: Implications for autocrine growth regulation

Jung H Y Park, Robert H. McCusker, Jon A. Vanderhoof, Hamid Mohammadpour, Richard F. Harty, Richard G MacDonald

Research output: Contribution to journalArticle

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Abstract

To identify the factors regulating the proliferation of intestinal epithelium, we examined the effects of various growth factors on [3H] thymidine incorporation into the DNA of IEC-6 cells, an intestinal epithelial cell line derived from rat jejunal crypts. Insulin-like growth factor-I (IGF-I), IGF-II, and insulin stimulated the DNA and protein synthesis of IEC-6 cells in serum-free medium supplemented with transferrin, dexamethasone, and BSA (basal medium). Concentration- response experiments demonstrated that IGF-I is approximately 10 times more potent than IGF-II or insulin in producing 2- to 3-fold stimulations of DNA and protein synthesis by IEC-6 cells. In addition, IEC-6 cells proliferated slowly in the basal medium without any added growth factors. Analysis of medium conditioned by IEC-6 cells by gel filtration chromatography, RIA, HPLC, and N-terminal sequencing revealed that IEC-6 cells synthesize and secrete mature, 7,500 mo wt (M,) IGF-II as well as high Mt forms of IGF-II. In addition, ligand blot, immunoblot, and N-terminal sequence analyses showed that IEC-6 cells produce the 34,000 M, IGF-binding protein-2 (IGFBP-2). To determine if IGFBP-2 modulates IGF responses in IEC-6 cells, the IGF-I analogs, Des-(l-3)-IGF-I and [Gln3, Ala4, Tyr15, Leu16]IGF-I, both of which have a reduced affinity for IGFBPs, were tested for their effects on IEC-6 cell proliferation. Both analogs exhibited 10-fold greater potency than IGF-I, presumably because endogenously secreted IGFBPs depress IGF-I binding to cell surface receptors. Finally, purified IGFBP-2 attenuated the DNA synthesis of IEC-6 cells in a dose- dependent manner. We conclude that IGFBP-2 secreted by intestinal epithelial cells is capable of limiting the mitogenic activity of both exogenous and endogenous IGFs by blocking the association of the growth factors with cell surface binding sites. These results further suggest that the growth of IEC-6 cells is modulated by autocrine mechanisms involving IGF-II and IGFBP-2.

Original languageEnglish (US)
Pages (from-to)1359-1368
Number of pages10
JournalEndocrinology
Volume131
Issue number3
DOIs
StatePublished - Sep 1992

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Insulin-Like Growth Factor II
Carrier Proteins
Insulin-Like Growth Factor I
Insulin-Like Growth Factor Binding Protein 2
Growth
Insulin-Like Growth Factor Binding Proteins
Intercellular Signaling Peptides and Proteins
DNA
Epithelial Cells
Insulin
Serum-Free Culture Media
Cell Surface Receptors
Intestinal Mucosa
Transferrin
Conditioned Culture Medium
Thymidine
Dexamethasone
Gel Chromatography
Sequence Analysis
Proteins

ASJC Scopus subject areas

  • Endocrinology

Cite this

Secretion of insulin-like growth factor II (IGF-II) and igf-binding protein-2 by intestinal epithelial (IEC-6) cells : Implications for autocrine growth regulation. / Park, Jung H Y; McCusker, Robert H.; Vanderhoof, Jon A.; Mohammadpour, Hamid; Harty, Richard F.; MacDonald, Richard G.

In: Endocrinology, Vol. 131, No. 3, 09.1992, p. 1359-1368.

Research output: Contribution to journalArticle

Park, Jung H Y ; McCusker, Robert H. ; Vanderhoof, Jon A. ; Mohammadpour, Hamid ; Harty, Richard F. ; MacDonald, Richard G. / Secretion of insulin-like growth factor II (IGF-II) and igf-binding protein-2 by intestinal epithelial (IEC-6) cells : Implications for autocrine growth regulation. In: Endocrinology. 1992 ; Vol. 131, No. 3. pp. 1359-1368.
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abstract = "To identify the factors regulating the proliferation of intestinal epithelium, we examined the effects of various growth factors on [3H] thymidine incorporation into the DNA of IEC-6 cells, an intestinal epithelial cell line derived from rat jejunal crypts. Insulin-like growth factor-I (IGF-I), IGF-II, and insulin stimulated the DNA and protein synthesis of IEC-6 cells in serum-free medium supplemented with transferrin, dexamethasone, and BSA (basal medium). Concentration- response experiments demonstrated that IGF-I is approximately 10 times more potent than IGF-II or insulin in producing 2- to 3-fold stimulations of DNA and protein synthesis by IEC-6 cells. In addition, IEC-6 cells proliferated slowly in the basal medium without any added growth factors. Analysis of medium conditioned by IEC-6 cells by gel filtration chromatography, RIA, HPLC, and N-terminal sequencing revealed that IEC-6 cells synthesize and secrete mature, 7,500 mo wt (M,) IGF-II as well as high Mt forms of IGF-II. In addition, ligand blot, immunoblot, and N-terminal sequence analyses showed that IEC-6 cells produce the 34,000 M, IGF-binding protein-2 (IGFBP-2). To determine if IGFBP-2 modulates IGF responses in IEC-6 cells, the IGF-I analogs, Des-(l-3)-IGF-I and [Gln3, Ala4, Tyr15, Leu16]IGF-I, both of which have a reduced affinity for IGFBPs, were tested for their effects on IEC-6 cell proliferation. Both analogs exhibited 10-fold greater potency than IGF-I, presumably because endogenously secreted IGFBPs depress IGF-I binding to cell surface receptors. Finally, purified IGFBP-2 attenuated the DNA synthesis of IEC-6 cells in a dose- dependent manner. We conclude that IGFBP-2 secreted by intestinal epithelial cells is capable of limiting the mitogenic activity of both exogenous and endogenous IGFs by blocking the association of the growth factors with cell surface binding sites. These results further suggest that the growth of IEC-6 cells is modulated by autocrine mechanisms involving IGF-II and IGFBP-2.",
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