1
|
Effect of IGFBP2 Overexpression on the Expression of Fatty Acid Synthesis Genes in Primary Cultured Chicken Hepatocytes. J Poult Sci 2019; 56:177-185. [PMID: 32055212 PMCID: PMC7005387 DOI: 10.2141/jpsa.0180114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The effects of insulin-like growth factor binding protein 2 (IGFBP2) on the expression of fatty acid synthesis regulators and triglyceride production were investigated in primary cultured chicken hepatocytes. The full-length chicken IGFBP2 coding region was synthesized by overlap extension PCR and cloned into the pcDNA3.1 vector. An in situ digestion method was used to prepare the chicken hepatocytes. Primary chicken hepatocytes were maintained in monolayer culture. Real-time PCR was used to detect changes in the expression of IGFBP2, PPARG, IGF1, IGF1R, APOAI, and LFABP, after the overexpression of IGFBP2 in chicken hepatocytes. Triglyceride production and glucose content were also evaluated using triglyceride and glucose analysis methods. The expression level of IGFBP2 increased after transfection of the IGFBP2-containing vector. The expression levels of PPARG, IGF1, and IGF1R also increased in cultured chicken hepatocytes after the overexpression of IGFBP2, whereas the expression of LFABP and APOAI decreased. Triglyceride production in primary cultured chicken hepatocytes increased after the overexpression of IGFBP2. These results suggest that IGFBP2 is involved in lipogenesis, increasing both the expression of fatty acid synthesis regulators, and triglyceride production in primary cultured chicken hepatocytes.
Collapse
|
2
|
Qie Y, Nian X, Liu X, Hu H, Zhang C, Xie L, Han R, Wu C, Xu Y. Polymorphism in IGFBP3 gene is associated with prostate cancer risk: an updated meta-analysis. Onco Targets Ther 2016; 9:4163-71. [PMID: 27462171 PMCID: PMC4940022 DOI: 10.2147/ott.s102452] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE Insulin-like growth factor-binding protein-3 (IGFBP3) is the major protein that binds with insulin-like growth factor-1 (IGF-1) and is considered to be involved in the development and progression of various cancers. We aimed to examine the association between prostate cancer (PCa) and the IGFBP3 gene-202A/C polymorphism. METHODS A comprehensive search within PubMed, EMBASE, and Cochrane Library was conducted to identify all case-control studies up to October 30, 2015, for a meta-analysis. Pooled odds ratios (ORs) and the 95% confidence intervals (CIs) were calculated using the fixed or random effects model. RESULTS Eighteen studies including 10,538 cases and 10,078 controls were identified. Overall, the CC genotype of IGFBP3-202A/C polymorphism was associated with increased risk of PCa in homozygote comparison (CC vs AA - OR =1.16, 95% CI: 1.08-1.25) and in recessive model (CC vs AA+AC - OR =1.11, 95% CI: 1.04-1.17). In dominant model, the CC/AC genotypes also implicated an increased risk of PCa (CC+AC vs AA - OR =1.11, 95% CI: 1.05-1.19). The C allele of IGFBP3-202A/C polymorphism was the risk allele for PCa relative to the A allele (OR =1.09, 95% CI: 1.05-1.14). Further stratification analysis revealed that the association between -202A/C polymorphism and PCa risk among Caucasians, but not in other ethnicities, was statistically significant (recessive model, OR =1.10, 95% CI: 1.02-1.19). In addition, the IGFBP3-202A/C polymorphism was associated with PCa risk in both population-based and hospital-based studies in homozygote comparison, recessive model, and allele model. CONCLUSION Our meta-analysis indicates that the IGFBP3-202A/C polymorphism is associated with the risk of PCa, particularly in Caucasians, with the C allele being the risk allele for PCa.
Collapse
Affiliation(s)
- Yunkai Qie
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Xuewu Nian
- Department of Urology, Tianjin Nankai Hospital, Tianjin, People's Republic of China
| | - Xuesen Liu
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Hailong Hu
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Changwen Zhang
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Linguo Xie
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Ruifa Han
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Changli Wu
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| | - Yong Xu
- Department of Urology, The Second Hospital of Tianjin Medical University, Tianjin Institute of Urology
| |
Collapse
|
3
|
Clemmons DR. Metabolic actions of insulin-like growth factor-I in normal physiology and diabetes. Endocrinol Metab Clin North Am 2012; 41:425-43, vii-viii. [PMID: 22682639 PMCID: PMC3374394 DOI: 10.1016/j.ecl.2012.04.017] [Citation(s) in RCA: 185] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Insulin-like growth factor-I (IGF-I) is closely related to insulin but has distinct metabolic actions. IGF-I is an important stimulant of protein synthesis in muscle, but it also stimulates free fatty acid use. The administration of IGF-I to patients with extreme insulin resistance results in improvement in glycemic control, and IGF-I is associated with lowering glucose and enhancing insulin sensitivity in Type 1 and Type 2 diabetes. However, patients with diabetes are also sensitive to stimulation of side effects in response to IGF-I. IGF-I coordinately links growth hormone and insulin actions and has direct effects on intermediary metabolism.
Collapse
Affiliation(s)
- David R Clemmons
- Division of Endocrinology, Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7170, USA.
| |
Collapse
|
4
|
Morales T. The quantitative and functional relation between insulin-like growth factor-I (IGF) and IGF-binding proteins during human osteoarthritis. J Orthop Res 2008; 26:465-74. [PMID: 18050312 PMCID: PMC2988493 DOI: 10.1002/jor.20549] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A previous hypothesis stated that during osteoarthritis (OA) increased insulin-like growth factor (IGF) binding proteins (IGFBPs) sequester IGFs and limit their access to the cell. The objective of this article was to test this by: (1) quantifying IGF and IGFBP-3 as well as their ratios in human OA cartilages, and (2) measuring the metabolic responses of diseased cartilage to IGF-I and its IGFBP-insensitive analogs. Knee or hip OA cartilages were staged for OA by histology. Cartilage slices were either extracted for assays of IGF proteins, or maintained intact as organ cultures. Proteoglycan (PG) metabolism +/- IGFs was measured by use of the (35)S-sulfate precursor. IGFBP-3 (ng/mg protein) was weakly correlated with OA score by regression analysis (R(2) = 0.122; p = 0.040; n = 35). IGF-I (ng/mg protein) was constant across all OA groups (ANOVA; p = .428, n = 18) and the IGF-I/IGFBP-3 ratios were > 1 in most samples. All OA cartilages responded to hrIGF-I by increasing PG synthesis [average 2.29-fold +/- 0.55 (+/-SD) at saturation, n = 12] irrespective of OA score. The des (1-3) IGF-I analog (which lacks the three N-terminal amino acids) had similar maximal effects (average 2.23-fold stimulation +/- 0.71, n = 10), but it was more effective in two out of three samples at suboptimal doses. The effect of hrIGF-I, des (1-3) IGF-I, or the B-chain analog on degradation was minimal. In summary, catabolism was insensitive to IGF-I, and this was probably not due to IGFBPs. By contrast, IGF-I exerted a robust stimulation of anabolism at sufficiently high doses, even though IGFBPs could tone down the ligand effect at low doses.
Collapse
Affiliation(s)
- T.I. Morales
- Harvard Medical School and Massachusetts General Hospital, Boston, MA. USA
| |
Collapse
|
5
|
Shin SY, Lee JR, Noh GW, Kim HJ, Kang WJ, Kim SH, Chung JK. Analysis of serum levels of anti-Mullerian hormone, inhibin B, insulin-like growth factor-I, insulin-like growth factor binding protein-3, and follicle-stimulating hormone with respect to age and menopausal status. J Korean Med Sci 2008; 23:104-10. [PMID: 18303208 PMCID: PMC2526482 DOI: 10.3346/jkms.2008.23.1.104] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study was undertaken to investigate age-dependent and postmenopausal changes in the serum levels of anti-Mullerian hormone (AMH), inhibin B, insulin-like growth factor (IGF)-I, IGF-binding protein-3 (IGFBP-3), and follicle-stimulating hormone (FSH), and to determine which of these markers best reflects the aging process in women. A total of 144 women aged 20-59 yr were enrolled in this cross-sectional study. Blood samples were obtained on cycle day 3 of regularly menstruating women (n=111), or at random in postmenopausal women (n=33). Data were analyzed with respect to premenopausal women age groups and compared in pre- and postmenopausal women. Area under the receiver operating characteristic curve (ROCAUC) analyses were performed to assess the ability of each marker to discriminate between the pre- and postmenopausal status. Serum levels of AMH, IGF-I, and IGFBP-3 decreased and serum levels of FSH increased significantly with age in premenopausal women. Serum luteinizing hormone (LH) was higher and inhibin B was lower in women in their 20-30's than in 40's. Serum levels of AMH and IGF-I showed a consistent decrease with all age groups. ROCAUC analysis showed that the diagnostic accuracy of AMH for menopausal status was similar to those of FSH, LH, and inhibin B, and was better than that of IGF-I. In conclusion, the serum AMH level appears to be the best marker of the aging process in premenopausal women.
Collapse
Affiliation(s)
- Sun Young Shin
- Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea
| | - Jung Ryeol Lee
- Department of Obstetrics and Gynecology, College of Medicine, Seoul National University, Seoul, Korea
| | - Gyung Woon Noh
- Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea
| | - Hyun Joo Kim
- Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea
| | - Won Jun Kang
- Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea
- Tumor Immunity Medical Research Center, College of Medicine, Seoul National University, Seoul, Korea
| | - Seok Hyun Kim
- Department of Obstetrics and Gynecology, College of Medicine, Seoul National University, Seoul, Korea
| | - June-Key Chung
- Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea
- Tumor Immunity Medical Research Center, College of Medicine, Seoul National University, Seoul, Korea
| |
Collapse
|
6
|
Oh SH, Kim WY, Kim JH, Younes MN, El-Naggar AK, Myers JN, Kies M, Cohen P, Khuri F, Hong WK, Lee HY. Identification of insulin-like growth factor binding protein-3 as a farnesyl transferase inhibitor SCH66336-induced negative regulator of angiogenesis in head and neck squamous cell carcinoma. Clin Cancer Res 2006; 12:653-61. [PMID: 16428512 DOI: 10.1158/1078-0432.ccr-05-1725] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The farnesyl transferase inhibitor (FTI) SCH66336 has been shown to have antitumor activities in head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo. However, its mechanism of action has not been well defined. Here, we report that the insulin-like growth factor (IGF) binding protein (IGFBP)-3 mediates antitumor activities of SCH66336 in HNSCC by inhibiting angiogenesis. SCH66336 significantly suppressed HNSCC tumor growth and angiogenesis via mechanisms that are independent of H-Ras and RhoB. By inducing IGFBP-3 secretion from HNSCC cells, this compound suppresses angiogenic activities of endothelial cells, including vessel formation in chorioallantoic membranes of chick, endothelial cell sprouting from chick aorta, and capillary tube formation of human umbilical vascular endothelial cells (HUVEC). Knockdown of IGFBP-3 expression in HNSCC cells by RNA interference or depletion of IGFBP-3 in HUVECs by neutralizing antibody effectively blocked the effects of IGFBP-3 secreted from SCH66336-treated HNSCC cells on HUVECs. These findings suggest that IGFBP-3 could be a primary target for antitumor activities of FTIs and that IGFBP-3 is an effective therapeutic approach against angiogenesis in HNSCC.
Collapse
MESH Headings
- Animals
- Aorta/drug effects
- Aorta/metabolism
- Carcinoma, Non-Small-Cell Lung
- Carcinoma, Squamous Cell/drug therapy
- Carcinoma, Squamous Cell/metabolism
- Carcinoma, Squamous Cell/pathology
- Cell Proliferation/drug effects
- Chickens
- Chorioallantoic Membrane/drug effects
- Chorioallantoic Membrane/metabolism
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Enzyme Inhibitors/pharmacology
- Farnesyltranstransferase/antagonists & inhibitors
- Farnesyltranstransferase/metabolism
- Female
- Gene Expression Regulation, Neoplastic/drug effects
- Genes, ras/physiology
- Head and Neck Neoplasms/drug therapy
- Head and Neck Neoplasms/metabolism
- Head and Neck Neoplasms/pathology
- Humans
- Insulin-Like Growth Factor Binding Protein 3/metabolism
- Mice
- Mice, Nude
- Neovascularization, Pathologic/drug therapy
- Piperidines/pharmacology
- Pyridines/pharmacology
- Tumor Cells, Cultured
- Umbilical Veins/cytology
- Umbilical Veins/drug effects
- Umbilical Veins/metabolism
- Vascular Endothelial Growth Factor A/metabolism
- rhoB GTP-Binding Protein/metabolism
Collapse
Affiliation(s)
- Seung-Hyun Oh
- Department of Thoracic/Head and Neck Medical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Ramsey MM, Adams MM, Ariwodola OJ, Sonntag WE, Weiner JL. Functional characterization of des-IGF-1 action at excitatory synapses in the CA1 region of rat hippocampus. J Neurophysiol 2005; 94:247-54. [PMID: 15985695 DOI: 10.1152/jn.00768.2004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Insulin-like growth factor-1 (IGF-1) and growth hormone play a major role in the growth and development of tissues throughout the mammalian body. Plasma IGF-1 concentrations peak during puberty and decline with age. We have determined that chronic treatments to restore plasma IGF-1 concentrations to adult levels attenuate spatial learning deficits in aged rats, but little is known of the acute actions of IGF-1 in the brain. To this end, we utilized hippocampal slices from young Sprague-Dawley rats to characterize the acute effects of des-IGF-1 on excitatory synaptic transmission in the CA1 region. We observed a 40% increase in field excitatory postsynaptic potential (fEPSP) slope with application of des-IGF-1 (40 ng/ml) and used whole cell patch-clamp recordings to determine that this enhancement was due to a postsynaptic mechanism involving alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) but not N-methyl-D-aspartate receptors. Furthermore, the enhancement was completely blocked by the broad-spectrum tyrosine kinase inhibitor, genistein (220 microM), and significantly reduced by the PI3K blockers wortmannin (1 microM) and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (10 microM), suggesting that the effect was predominantly dependent on PI3K activation. This characterization of the acute actions of des-IGF-1 at hippocampal excitatory synapses may provide insight into the mechanism by which long-term increases in plasma IGF-1 impart cognitive benefits in aged rats. Increases in AMPA receptor-mediated synaptic transmission may contribute directly to cognitive improvement or initiate long-term changes in synthesis of proteins such as brain-derived neurotrophic factor that are important to learning and memory.
Collapse
Affiliation(s)
- Melinda M Ramsey
- Department of Physiology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1083, USA
| | | | | | | | | |
Collapse
|
8
|
Catrina SB, Lewitt M, Massambu C, Dricu A, Grünler J, Axelson M, Biberfeld P, Brismar K. Insulin-like growth factor-I receptor activity is essential for Kaposi's sarcoma growth and survival. Br J Cancer 2005; 92:1467-74. [PMID: 15812560 PMCID: PMC2362008 DOI: 10.1038/sj.bjc.6602408] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Kaposi's sarcoma (KS) is a highly vascular tumour and is the most common neoplasm associated with human immunodeficiency virus (HIV-1) infection. Growth factors, in particular vascular endothelial growth factor (VEGF), have been shown to play an important role in its development. The role of insulin-like growth factors (IGFs) in the pathophysiology of different tumours led us to evaluate the role of IGF system in KS. The IGF-I receptors (IGF-IR) were identified by immunohistochemistry in biopsies taken from patients with different AIDS/HIV-related KS stages and on KSIMM cells (an established KS-derived cell line). Insulin-like growth factor-I is a growth factor for KSIMM cells with a maximum increase of 3H-thymidine incorporation of 130±27.6% (P<0.05) similar to that induced by VEGF and with which it is additive (281±13%) (P<0.05). Moreover, specific blockade of the receptor (either by α IR3 antibody or by picropodophyllin, a recently described selective IGF-IR tyrosine phosphorylation inhibitor) induced KSIMM apoptosis, suggesting that IGF-IR agonists (IGF-I and -II) mediate antiapoptotic signals for these cells. We were able to identify an autocrine loop essential for KSIMM cell survival in which IGF-II is the IGF-IR agonist secreted by the cells. In conclusion, IGF-I pathway inhibition is a promising therapeutical approach for KS tumours.
Collapse
Affiliation(s)
- S-B Catrina
- Department of Molecular Medicine, Diabetes Center Karolinska, Karolinska Hospital, M1:02, Karolinska Institutet, Stockholm, Sweden.
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Loughran G, Huigsloot M, Kiely PA, Smith LM, Floyd S, Ayllon V, O'Connor R. Gene expression profiles in cells transformed by overexpression of the IGF-I receptor. Oncogene 2005; 24:6185-93. [PMID: 15940254 DOI: 10.1038/sj.onc.1208772] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To identify genes associated with insulin-like growth factor-I receptor (IGF-IR)-mediated cellular transformation, we isolated genes that are differentially expressed in R- cells (derived from the IGF-IR knockout mouse) and R+ cells (R- cells that overexpress the IGF-IR). From these, 45 genes of known function were expressed at higher levels in R+ cells and 22 were expressed at higher levels in R- cells. Differential expression was confirmed by Northern blot analysis of R+ and R- cells. Genes expressed more abundantly in R+ cells are associated with (1) tumour growth and metastasis including, betaigH3, mts1, igfbp5 protease, and mystique; (2) cell division, including cyclin A1 and cdk1; (3) signal transduction, including pkcdeltabp and lmw-ptp; and (4) metabolism including ATPase H+ transporter and ferritin. In MCF-7 cells IGF-I induced expression of two genes, lasp-1 and mystique, which could contribute to metastasis. Lasp-1 expression required activity of the PI3-kinase signalling pathway. Mystique was highly expressed in metastatic but not in androgen-dependent prostate cancer cell lines and Mystique overexpression in MCF-7 cells promoted cell migration and invasion. We conclude that genes identified in this screen may mediate IGF-IR function in cancer progression.
Collapse
Affiliation(s)
- Gary Loughran
- Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | | | | | | | | | | | | |
Collapse
|
10
|
Galiano RD, Zhao LL, Clemmons DR, Roth SI, Lin X, Mustoe TA. Interaction between the insulin-like growth factor family and the integrin receptor family in tissue repair processes. Evidence in a rabbit ear dermal ulcer model. J Clin Invest 1996; 98:2462-8. [PMID: 8958208 PMCID: PMC507703 DOI: 10.1172/jci119064] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have determined previously that IGF-I is dependent on the presence of IGF binding protein-1 (IGFBP-1) to act as a wound healing agent. We sought to determine the mechanism whereby IGFBP-1 is able to enhance IGF-I bioactivity. As IGFBP-1 binds both the alpha5beta1 integrin as well as IGF-I in vitro, we asked which of the following interactions were important: (a) the ability of IGFBP-1 to interact with an integrin receptor, and/or (b) the binding of IGF-I by IGFBP-1. We used an IGF-1 analogue (des(1-3)IGF-I) with a > 100-fold reduction in affinity for IGFBP-1 as well as an IGFBP-1 mutant (WGD-IGFBP-1) which does not associate with the alpha5beta1 integrin to selectively abrogate each of these interactions. We also tested the ability of IGFBP-2, a related binding protein which has an arginine-glycine-aspartate sequence but does not associate with integrin family members, to enhance IGF-I bioactivity. Full-thickness dermal wounds were created on rabbit ears; various combinations of native IGF-I, native IGFBP-1, native IGFBP-2, and their respective analogues/mutants were applied to each wound. Wounds were harvested 7 d later for analysis. Only native IGF-I in combination with native IGFBP-1 was effective as a wound healing agent, enhancing reepithelialization and granulation tissue deposition by 64+/-5 and 83+/-12% over controls (P = 0.008 and 0.016, respectively). The same doses of IGF-I/WGD-IGFBP-1, des(1-3)IGF-I/IGFBP-1, and IGF-I/IGFBP-2 were ineffective. We propose that IGF-I physically interacts with IGFBP-1 and that IGFBP-1 also binds to an integrin receptor, most likely the alpha5beta1 integrin. This interaction is unique to IGFBP-1 as the closely related IGFBP-2 had no effect, a finding consistent with its inability to bind to integrin receptors. Our results suggest that activation of both the IGF-I receptor and the alpha5beta1 integrin is required for IGF-I to stimulate wound healing.
Collapse
Affiliation(s)
- R D Galiano
- Division of Plastic and Reconstructive Surgery, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | | | | | | | | | | |
Collapse
|
11
|
Milner SJ, Francis GL, Wallace JC, Magee BA, Ballard FJ. Mutations in the B-domain of insulin-like growth factor-I influence the oxidative folding to yield products with modified biological properties. Biochem J 1995; 308 ( Pt 3):865-71. [PMID: 8948444 PMCID: PMC1136804 DOI: 10.1042/bj3080865] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The oxidative folding of human insulin-like growth factor (IGF)-I yields two major disulphide folding isomers. In the present study, B-domain analogues of IGF-I were used to investigate the effect of mutations on the folding reaction and to investigate the functional implications of misfolding. The analogues used were substitutions of the native Glu3 by Gly or Arg, or the native Glu9 by Lys. IGF-I and these analogues were also prepared attached to a hydrophobic 13-amino-acid N-terminal extension, Met-Phe-Pro-Ala-Met-Pro-Leu-Ser-Ser-Leu-Phe-Val-Asn, referred to as 'Long-IGF-I' analogues. Each IGF was fully reduced and refolded to yield native and misfolded isomers, which were subsequently purified for biological characterization. Analysis of the folding reaction at equilibrium revealed a distribution of folding isomers characteristic for each peptide. The yield of the native disulphide folding isomer was increased for the Glu3 substitutions, but not for the Glu9 substitution. The main alternative folding isomer was present in the IGF-I analogues in reduced proportions. Except for [Gly3]IGF-I the N-terminal extension increased the yield of the native isomer which was maximal for the analogue Long-[Arg3]IGF-I. A folding intermediate for the latter analogue was isolated and partially characterized. The biological assays showed that all the main alternative isomers bound poorly to IGF-binding proteins (IGFBPs) secreted by L6 myoblasts. Moreover, these isomers bound to the type 1 IGF receptor with 0.5-25% the affinity of the native isomer. In a rat L6 myoblast protein-synthesis assay, the observed biological activity of the native and main alternative isomers was explained by their modified IGFBP- and receptor-binding properties. We propose that the N-terminal extension imparts a steric constraint at a crucial point in folding, thus allowing native disulphide bonds to form efficiently.
Collapse
Affiliation(s)
- S J Milner
- Cooperative Research Centre for Tissue Growth and Repair, Adelaide, Australia
| | | | | | | | | |
Collapse
|
12
|
Baxter RC, Suikkari AM, Martin JL. Characterization of the binding defect in insulin-like growth factor binding protein-3 from pregnancy serum. Biochem J 1993; 294 ( Pt 3):847-52. [PMID: 7691057 PMCID: PMC1134539 DOI: 10.1042/bj2940847] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During pregnancy, insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) undergoes proteolysis, rendering it undetectable by radioligand binding techniques. This study examines the physical and functional defect in pregnancy IGFBP-3. Ternary complex formation has been measured by the binding of the acid-labile subunit of the circulating IGFBP-3 complex, which also requires IGF-I or IGF-II binding. IGF-depleted pregnancy IGFBP-3, prepared by size-exclusion chromatography at low pH, could not form a ternary complex in the presence of [Tyr60]IGF-I or of an IGF-I analogue extensively altered in the A-domain, whereas analogues altered in the C- or D-domains complexed as well as native IGF-I. After purification by immunoaffinity chromatography, non-pregnancy and pregnancy IGFBP-3 formed ternary complexes with IGF-I equally well, although the pregnancy-proteolysed protein appeared degraded to approximately 30 kDa. On analysis by affinity labelling, cross-linked ternary complexes containing non-pregnancy or pregnancy IGFBP-3 were predominantly 135-140 kDa, with an additional complex of 110-115 kDa in the pregnancy preparation. After reverse-phase h.p.l.c., affinity-isolated pregnancy IGFBP-3 was inactive, whereas the protein from non-pregnancy serum retained activity. Thus pregnancy-proteolysed IGFBP-3 is altered in its specificity for IGF analogues, and is more labile than non-pregnancy IGFBP-3, but shows little impairment in normal IGF binding or ternary complex formation.
Collapse
Affiliation(s)
- R C Baxter
- Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
| | | | | |
Collapse
|