Growth hormone-dependent insulin-like growth factor (IGF) binding protein both inhibits and potentiates IGF-I-stimulated DNA synthesis in human skin fibroblasts

doi:10.1016/S0006-291X(88)80824-6

Biochemical and Biophysical Research Communications

Volume 156, Issue 1, 14 October 1988, Pages 199-204

https://doi.org/10.1016/S0006-291X(88)80824-6 Get rights and content

Summary

This study investigates the effects of BP-53, the acid-stable IGF-binding subunit of the circulating 150 kDa IGF-binding protein complex, on IGF-I-stimulated thymidine incorporation by neonatal human skin fibroblasts. When cells were incubated for 24 h with IGF-I in serum-free medium, and thymidine incorporation studied over the final 4-h period, maximal stimulation (4- to 7-fold) was seen with 30 ng/ml IGF-I, with a half-maximal effect at 6.8±1.2 ng/ml (SD, n=4). Co-incubation of IGF-I with increasing concentrations of pure BP-53 caused dose-dependent inhibition of IGF-I-stimulated thymidine incorporation, which was complete when IGF-I and BP-53 were equimolar. In contrast, preincubation of cells with BP-53 for 8–48 h before adding IGF-I resulted in a potentiation of the subsequent IGF-I effect. The potentiation was maximal (2-fold) at a BP-53 concentration of 150 ng/ml, and appeared to act by increasing the maximal rate of thymidine incorporation rather than the sensitivity of this process to IGF-I. Since neonatal fibroblasts produce a protein which is identical to BP-53 in size and immunoreactivity, these results suggest an autocrine role for BP-53 in regulating fibroblast responsiveness to IGF-I.

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Role of IGF Binding Proteins in Regulating Metabolism
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Insulin-like growth factors (IGFs) circulate in extracellular fluids bound to a family of binding proteins. Although they function in a classical manner to limit the access of the IGFs to their receptors they also have a multiplicity of actions that are independent of this property; they bind to their own receptors or are transported to intracellular and intranuclear sites to influence cellular functions that may directly or indirectly modify IGF actions. The availability of genetically modified animals has helped to determine their functions in a physiological context. These results show that many of their actions are cell type- and context-specific, and have led to a broader understanding of how these proteins function coordinately with IGF-I and -II to regulate growth and metabolism.
The coordinate cellular response to insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding protein-2 (IGFBP-2) is regulated through vimentin binding to receptor tyrosine phosphatase β (RPTPβ)
2015, Journal of Biological Chemistry
Insulin-like growth factor-binding protein-2 (IGFBP-2) functions coordinately with IGF-I to stimulate cellular proliferation and differentiation. IGFBP-2 binds to receptor tyrosine phosphatase β (RPTPβ), and this binding in conjunction with IGF-I receptor stimulation induces RPTPβ polymerization leading to phosphatase and tensin homolog inactivation, AKT stimulation, and enhanced cell proliferation. To determine the mechanism by which RPTPβ polymerization is regulated, we analyzed the protein(s) that associated with RPTPβ in response to IGF-I and IGFBP-2 in vascular smooth muscle cells. Proteomic experiments revealed that IGF-I stimulated the intermediate filament protein vimentin to bind to RPTPβ, and knockdown of vimentin resulted in failure of IGFBP-2 and IGF-I to stimulate RPTPβ polymerization. Knockdown of IGFBP-2 or inhibition of IGF-IR tyrosine kinase disrupted vimentin/RPTPβ association. Vimentin binding to RPTPβ was mediated through vimentin serine phosphorylation. The serine threonine kinase PKCζ was recruited to vimentin in response to IGF-I and inhibition of PKCζ activation blocked these signaling events. A cell-permeable peptide that contained the vimentin phosphorylation site disrupted vimentin/RPTPβ association, and IGF-I stimulated RPTPβ polymerization and AKT activation. Integrin-linked kinase recruited PKCζ to SHPS-1-associated vimentin in response to IGF-I and inhibition of integrin-linked kinase/PKCζ association reduced vimentin serine phosphorylation. PKCζ stimulation of vimentin phosphorylation required high glucose and vimentin/RPTPβ-association occurred only during hyperglycemia. Disruption of vimetin/RPTPβ in diabetic mice inhibited RPTPβ polymerization, vimentin serine phosphorylation, and AKT activation in response to IGF-I, whereas nondiabetic mice showed no difference. The induction of vimentin phosphorylation is important for IGFBP-2-mediated enhancement of IGF-I-stimulated proliferation during hyperglycemia, and it coordinates signaling between these two receptor-linked signaling systems.
Background: IGFBP-2 binding to RPTPβ is required for IGF-I-stimulated AKT activation.
Results: IGF-I stimulates PKCζ recruitment and serine phosphorylation of vimentin leading to vimentin/RPTPβ association, RPTPβ polymerization, and enhanced AKT activation.
Conclusion: Vimentin phosphorylation stimulates vimentin/RPTPβ association, which mediates RPTPβ polymerization in response to IGF-I and IGFBP-2.
Significance: This study demonstrates how these two receptor systems collaborate to obtain optimal IGF-I signal transduction.
Single nucleotide polymorphism in Egyptian cattle insulin-like growth factor binding protein-3 gene
2014, Journal of Genetic Engineering and Biotechnology
Citation Excerpt :
On the other hand, twenty-six animals (56.52%) are genotyped as AC heterozygous patterns with 9 digested fragments whereas the allele frequencies for A and C allele are identical and equal 50% for each of them. As one of six related proteins that modify IGF bioactivity in complex [14,30,34], both inhibiting and enhancing effects of IGFBP3 on IGF-I action have been reported [6,8,9,23]. Therefore concentrations of IGFBPs are potential indicators of IGF-I status and may provide insight into an animal’s growth or carcass potential.
Insulin-like growth factor binding protein-3 (IGFBP-3) gene is a structural gene responsible for the multiple influences of insulin-like growth factors (IGFs) system. It is considered as a candidate gene for growth and production traits. In the present study, we aimed to determine the genetic polymorphism of Egyptian cattle IGFBP-3 gene.
The amplified fragment of cattle IGFBP-3 gene at 651-bp was digested with three different endonucleases; HaeIII, MspI and TaqI. The digestion of the PCR products with MspI and TaqI endonucleases revealed similar restriction patterns in all tested animals.
Digestion of the PCR product with HaeIII restriction enzyme revealed three different genotypes in Egyptian cattle due to the presence of two alleles; allele A with 7 digested fragments resulting from the presence of 6 restriction sites and allele C with 8 digested fragments resulting from the presence of 7 restriction sites; six sites as allele A in the addition of another restriction site at position 298^299 as a result of SNP (A → C) in C allele at position 299. The restriction patterns of IGFBP-3/HaeIII showed that forty-six examined animals are genotyped as AA, CC and AC with frequencies of 21.74%, 21.74% and 56.52%, respectively.
It is concluded that the IGFBP-3/HaeIII polymorphism may be utilized as a good marker for genetic differentiation between cattle animals for different body functions such as growth, metabolism, reproduction, immunity and energy balance. The nucleotide sequences of Egyptian cattle IGFBP-3 A and C alleles were submitted to GenBank with the accession numbers KF899893 and KF899894, respectively.
Attenuation of IGF-I receptor signaling inhibits serum-induced proliferation of prostate cancer cells
2011, Growth Hormone and IGF Research
Citation Excerpt :
Values are presented as the mean ± SEM. Since IGF-I is a known survival factor [4] that also stimulates cell cycling in many cell types [20–22], it is conceivable that IGF-I affects tumor growth via both mechanisms. To address the contribution of these mechanisms in the effects of IGF-I on the proliferation of Du145 cells, we assessed the effects of IGF-I on cell number, DNA synthesis and cell survival.
Several studies showed that high serum levels of insulin-like growth factor-I (IGF-I) correlate with an increased risk for prostate cancer, although the causal role of IGF-I remains to be established. In this study, we addressed the role of IGF-I as a serum factor on the growth of two androgen-independent cell lines (Du145 and PC3) and one androgen-dependent cell line (LNCaP).
We investigated the effects of a blocking antibody against the IGF-I receptor (αIR3) on DNA synthesis in prostate cancer cells cultured in the presence of recombinant human IGF-I or normal human serum (NHS).
We show that in all three prostate cancer cell lines, NHS exerts a markedly stronger stimulating effect on DNA synthesis than IGF-I, and that the effect of NHS can be completely abrogated by an antibody against the IGF-I receptor (αIR3). Using pharmacological inhibitors of the two canonical IGF-I receptor signaling pathways, we show that the phosphatidylinositol-3′-kinase (PI3K) and the Mek–Erk pathways are not required for the stimulating effect of NHS.
Our observations indicate that the stimulating effect of NHS is completely dependent on IGF-I receptor signaling transduction and that IGF-I stimulates DNA synthesis in prostate cancer cells in strong synergy with other serum factors. We speculate that the role of other serum factors could explain the discrepancy between the results observed in different animal models to study the function of IGF-I in prostate cancer.
Effect of dietary n-3 polyunsaturated fatty acid supplementation on bovine uterine endometrial and hepatic gene expression of the insulin-like growth factor system
2011, Theriogenology
Supplementation of cattle diets with n-3 polyunsaturated fatty acids (n-3 PUFA) has been suggested to have positive effects on fertility. In addition, the actions of the insulin-like growth factor (IGF) system both systemically and locally have been shown to influence reproductive processes. The objective of this study was to evaluate the effect of dietary n-3 PUFA supplementation on hepatic and endometrial expression of IGF signalling genes in cattle. Beef heifers were supplemented with a rumen protected source of either a saturated fatty acid (palmitic acid; CON) or high n-3 PUFA diet (n-3 PUFA) for 45 days before slaughter and tissue recovery. Transcription level of candidate IGF signalling genes was measured by reverse transcription quantitative real-time PCR (RT-qPCR) in total RNA isolated from uterine endometrial and liver tissue from seven CON and seven n-3 PUFA supplemented animals. Compared to controls, mRNA abundance in n-3 PUFA liver tissues was higher for IGF-2R, IGFBP-1 and IGFBP-5 (P < 0.05); lower for GHR-1A (P < 0.05); and unchanged for IGF-1, IGF-2, IGF-1R, IGFBP-2, IGFBP-3, IGFBP-4, IGFBP-6, ALS and GHR_total (P > 0.05). Compared to controls, mRNA abundance in n-3 PUFA endometrial tissues was higher for IGF-2, IGF-1R, IGF-2R and IGFBP-2 (P < 0.05); lower for IGF-1, IGFBP-3 and IGFBP-6 (P < 0.05); and unchanged for IGFBP-1, IGFBP-4, IGFBP-5 and GHR_total (P > 0.05). Thus, dietary supplementation of cattle with n-3 PUFA affects transcription of genes involved in IGF signalling, in a tissue dependent fashion.
Functional modulation of IGF-binding protein-3 expression in melanoma
2010, Journal of Investigative Dermatology
Citation Excerpt :
IGFBP3 is one member of this family, and has been shown to inhibit cell proliferation in breast, lung and prostrate cancer cells, and in some cell lines to reduce tumor growth (Hwa et al., 1999). IGFBP3 is reported to be a growth suppressor by virtue of its effects on multiple pathways (De Mellow and Baxter, 1988; Valentinis et al., 1995). In the IGF receptor-dependent pathways, IGFBP3 binds to IGF-1, 2 and suppresses its growth signal (De Mellow and Baxter, 1988).
IGF-binding protein-3 (IGFBP3) is a member of the IGFBP family, which regulates mitogenic and antiapoptotic effects of IGFs. In this report we evaluated the role of IGFBP3 in melanoma. Quantitative real-time PCR (qRT-PCR), western blot, and ELISA analyses indicated a significant downregulation of IGFBP3 expression in melanoma cell lines as compared with a normal melanocyte cell line. Melanoma cell lines treated with the demethylating agent 5-AZA-2′-deoxycytidine reexpressed IGFBP3 at the mRNA and protein levels. Chromatin immunoprecipitation assays revealed enrichment of acetylated histones H3 and H4, and H3 di- and tri-methylated lysine 4 on the unmethylated IGFBP3 promoter. The IGFBP3 promoter region was highly methylated in human melanoma samples as compared with normal nevi. Overexpression of IGFBP3 in melanoma cells in vitro suppressed tumor cell survival, induced apoptosis, reduced colony formation and invasion, and induced expression of the proapoptotic genes p21, PUMA, and BAX. IGFBP3 overexpression also resulted in cleavage of caspase 3 and reduced expression of phosphorylated AKT. Stable overexpression of IGFBP3 suppressed tumor cell growth in vivo. Our study results indicate that silencing of IGFBP3 in melanoma is due to the methylation of its promoter, and that overexpression of IGFBP3 induces apoptosis and suppresses cell survival and growth.

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Growth hormone-dependent insulin-like growth factor (IGF) binding protein both inhibits and potentiates IGF-I-stimulated DNA synthesis in human skin fibroblasts

Summary

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

J. Biol. Chem.

Molec. Cell. Endocrinol.

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

Analyt. Biochem.

Eur. J. Biochem.

J. Clin. Endocrinol. Metab.

Endocrinology

Endocrinology

J. Clin. Endocrinol. Metab.

J. Clin. Invest.

J. Clin. Endocrinol. Metab.