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Varma Shrivastav S, Bhardwaj A, Pathak KA, Shrivastav A. Insulin-Like Growth Factor Binding Protein-3 (IGFBP-3): Unraveling the Role in Mediating IGF-Independent Effects Within the Cell. Front Cell Dev Biol 2020; 8:286. [PMID: 32478064 PMCID: PMC7232603 DOI: 10.3389/fcell.2020.00286] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Accepted: 04/02/2020] [Indexed: 12/22/2022] Open
Abstract
Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3), one of the six members of the IGFBP family, is a key protein in the IGF pathway. IGFBP-3 can function in an IGF-dependent as well as in an IGF-independent manner. The IGF-dependent roles of IGFBP-3 include its endocrine role in the delivery of IGFs from the site of synthesis to the target cells that possess IGF receptors and the activation of associated downstream signaling. IGF-independent role of IGFBP-3 include its interactions with the proteins of the extracellular matrix and the proteins of the plasma membrane, its translocation through the plasma membrane into the cytoplasm and into the nucleus. The C-terminal domain of IGFBP-3 has the ability to undergo cell penetration therefore, generating a short 8-22-mer C-terminal domain peptides that can be conjugated to drugs or genes for effective intracellular delivery. This has opened doors for biotechnological applications of the molecule in molecular medicine. The aim of this this review is to summarize the complex roles of IGFBP-3 within the cell, including its mechanisms of cellular uptake and its translocation into the nucleus, various molecules with which it is capable of interacting, and its ability to regulate IGF-independent cell growth, survival and apoptosis. This would pave way into understanding the modus operandi of IGFBP-3 in regulating IGF-independent processes and its pleiotropic ability to bind with potential partners thus regulating several cellular functions implicated in metabolic diseases, including cancer.
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Affiliation(s)
- Shailly Varma Shrivastav
- VastCon Inc., Winnipeg, MB, Canada.,Department of Biology, University of Winnipeg, Winnipeg, MB, Canada
| | - Apurva Bhardwaj
- Department of Biology, University of Winnipeg, Winnipeg, MB, Canada
| | - Kumar Alok Pathak
- Research Institute of Oncology and Hematology, CancerCare Manitoba, Winnipeg, MB, Canada.,Department of Surgery, University of Manitoba, Winnipeg, MB, Canada
| | - Anuraag Shrivastav
- Department of Biology, University of Winnipeg, Winnipeg, MB, Canada.,Research Institute of Oncology and Hematology, CancerCare Manitoba, Winnipeg, MB, Canada
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IGF1 Knockdown Hinders Myocardial Development through Energy Metabolism Dysfunction Caused by ROS-Dependent FOXO Activation in the Chicken Heart. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2019; 2019:7838754. [PMID: 31949883 PMCID: PMC6948330 DOI: 10.1155/2019/7838754] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 11/16/2019] [Accepted: 11/20/2019] [Indexed: 12/15/2022]
Abstract
Insulin-like growth factor 1 (IGF1) is a multifunctional cellular regulatory factor that can regulate cell growth and development by mediating growth hormone stimulation. However, the mechanism of IGF1 dysfunction in cardiomyocyte development is seldom reported. To study this, we employed the models of IGF1 knockdown in chicken embryo in vivo and in cardiomyocytes in vitro. We detected the antioxidant capacity, PI3K/Akt pathway, energy metabolism-related genes, and myocardial development-related genes. Our results revealed that the low expression of IGF1 can significantly suppress the antioxidant capacity and increase the ROS (P < 0.05) levels, activating the AMPK and PI3K pathway by inhibiting the expression of IRS1. We also found that myocardial energy metabolism is blocked through IGF1, GLUT, and IGFBP inhibition, further inducing myocardial developmental disorder by inhibiting Mesp1, GATA, Nkx2.5, and MyoD expression. Altogether, we conclude that low IGF1 expression can hinder myocardial development through the dysfunction of energy metabolism caused by ROS-dependent FOXO activation.
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Neurite Growth and Polarization on Vitronectin Substrate after in Vitro Trauma is not Enhanced after IGF Treatment. Brain Sci 2018; 8:brainsci8080151. [PMID: 30103517 PMCID: PMC6119911 DOI: 10.3390/brainsci8080151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 07/31/2018] [Accepted: 08/08/2018] [Indexed: 11/23/2022] Open
Abstract
Following traumatic brain injuries (TBI), insulin-like growth factor (IGF) is cortically widely upregulated. This upregulation has a potential role in the recovery of neuronal tissue, plasticity, and neurotrophic activity, though the molecular mechanisms involved in IGF regulation and the exact role of IGF after TBI remain unclear. Vitronectin (VN), an extracellular matrix (ECM) molecule, has recently been shown to be of importance for IGF-mediated cellular growth and migration. Since VN is downregulated after TBI, we hypothesized that insufficient VN levels after TBI impairs the potential beneficial activity of IGF. To test if vitronectin and IGF-1/IGFBP-2 could contribute to neurite growth, we cultured hippocampal neurons on ± vitronectin-coated coverslips and them treated with ± IGF-1/IGF binding protein 2 (IGFBP-2). Under same conditions, cell cultures were also subjected to in vitro trauma to investigate differences in the posttraumatic regenerative capacity with ± vitronectin-coated coverslips and with ± IGF-1/IGFBP-2 treatment. In both the control and trauma situations, hippocampal neurons showed a stronger growth pattern on vitronectin than on the control substrate. Surprisingly, the addition of IGF-1/IGFBP-2 showed a decrease in neurite growth. Since neurite growth was measured as the number of neurites per area, we hypothesized that IGF-1/IGFBP-2 contributes to the polarization of neurons and thus induced a less dense neurite network after IGF-1/IGFBP-2 treatment. This hypothesis could not be confirmed and we therefore conclude that vitronectin has a positive effect on neurite growth in vitro both under normal conditions and after trauma, but that addition of IGF-1/IGFBP-2 does not have a positive additive effect.
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Kashyap AS, Shooter GK, Shokoohmand A, McGovern J, Sivaramakrishnan M, Croll TI, Cane G, Leavesley DI, Söderberg O, Upton Z, Hollier BG. Antagonists of IGF:Vitronectin Interactions Inhibit IGF-I-Induced Breast Cancer Cell Functions. Mol Cancer Ther 2016; 15:1602-13. [PMID: 27196774 DOI: 10.1158/1535-7163.mct-15-0907] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 04/28/2016] [Indexed: 11/16/2022]
Abstract
We provide proof-of-concept evidence for a new class of therapeutics that target growth factor:extracellular matrix (GF:ECM) interactions for the management of breast cancer. Insulin-like growth factor-I (IGF-I) forms multiprotein complexes with IGF-binding proteins (IGFBP) and the ECM protein vitronectin (VN), and stimulates the survival, migration and invasion of breast cancer cells. For the first time we provide physical evidence for IGFBP-3:VN interactions in breast cancer patient tissues; these interactions were predominantly localized to tumor cell clusters and in stroma surrounding tumor cells. We show that disruption of IGF-I:IGFBP:VN complexes with L(27)-IGF-II inhibits IGF-I:IGFBP:VN-stimulated breast cancer cell migration and proliferation in two- and three-dimensional assay systems. Peptide arrays screened to identify regions critical for the IGFBP-3/-5:VN and IGF-II:VN interactions demonstrated IGFBP-3/-5 and IGF-II binds VN through the hemopexin-2 domain, and VN binds IGFBP-3 at residues not involved in the binding of IGF-I to IGFBP-3. IGFBP-interacting VN peptides identified from these peptide arrays disrupted the IGF-I:IGFBP:VN complex, impeded the growth of primary tumor-like spheroids and, more importantly, inhibited the invasion of metastatic breast cancer cells in 3D assay systems. These studies provide first-in-field evidence for the utility of small peptides in antagonizing GF:ECM-mediated biologic functions and present data demonstrating the potential of these peptide antagonists as novel therapeutics. Mol Cancer Ther; 15(7); 1602-13. ©2016 AACR.
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Affiliation(s)
- Abhishek S Kashyap
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia. Cancer Immunology, Department of Biomedicine, University Hospital Basel, Basel, Switzerland.
| | - Gary K Shooter
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia
| | - Ali Shokoohmand
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia
| | - Jacqui McGovern
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia
| | | | - Tristan I Croll
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia
| | - Gaëlle Cane
- Department of Immunology, Genetics and Pathology Science for Life Laboratory, BMC, Uppsala University, Uppsala, Sweden
| | - David I Leavesley
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia
| | - Ola Söderberg
- Department of Immunology, Genetics and Pathology Science for Life Laboratory, BMC, Uppsala University, Uppsala, Sweden
| | - Zee Upton
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia
| | - Brett G Hollier
- Queensland University of Technology, Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Brisbane, Queensland, Australia. Australian Prostate Cancer Research Centre - Queensland, Institute of Health and Biomedical Innovation, Translational Research Institute, Brisbane, Queensland, Australia.
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Johnson MA, Firth SM. IGFBP-3: a cell fate pivot in cancer and disease. Growth Horm IGF Res 2014; 24:164-173. [PMID: 24953254 DOI: 10.1016/j.ghir.2014.04.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 04/21/2014] [Indexed: 12/19/2022]
Abstract
One of the hallmarks in the advancement of cancer cells is an ability to overcome and acquire resistance to adverse conditions. There has been a large amount of cancer research on IGFBP-3 as a pro-apoptotic molecule in vitro. These pro-apoptotic properties, however, do not correlate with several studies linking high IGFBP-3 levels in breast cancer tissue to rapid growth and poor prognosis. Evidence is emerging that IGFBP-3 also exhibits pro-survival and growth-promoting properties in vitro. How IGFBP-3 pivots cell fate to either death or survival, it seems, comes down to a complex interplay between cells' microenvironments and the presence of cellular IGFBP-3 binding partners and growth factor receptors. The cytoprotective actions of IGFBP-3 are not restricted to cancer but are also observed in other disease states, such as retinopathy and brain ischaemia. Here we review the literature on this paradoxical nature of IGFBP-3, its pro-apoptotic and growth-inhibitory actions versus its cytoprotective and growth-potentiating properties, and discuss the implications of targeting IGFBP-3 for treatment of disease.
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Affiliation(s)
- Michael A Johnson
- Hormones and Cancer, Kolling Institute of Medical Research, The University of Sydney, Royal North Shore Hospital, St Leonards, NSW 2065, Australia
| | - Sue M Firth
- Hormones and Cancer, Kolling Institute of Medical Research, The University of Sydney, Royal North Shore Hospital, St Leonards, NSW 2065, Australia
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Güllü G, Peker I, Haholu A, Eren F, Küçükodaci Z, Güleç B, Baloglu H, Erzik C, Özer A, Akkiprik M. Clinical significance of miR-140-5p and miR-193b expression in patients with breast cancer and relationship to IGFBP5. Genet Mol Biol 2014; 38:21-9. [PMID: 25983620 PMCID: PMC4415571 DOI: 10.1590/s1415-475738120140167] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 10/06/2014] [Indexed: 01/01/2023] Open
Abstract
The functional role of IGFBP5 in breast cancer is complicated. Experimental and
bioinformatics studies have shown that IGFBP5 is targeted by miR-140-5p and miR-193b,
although this has not yet been proven in clinical samples. The aim of this study was
to evaluate the expression of miR-140-5p and miR-193b in breast cancer and adjacent
normal tissue and assess its correlation with IGFBP5 and the clinicopathological
characteristics of the tumors. IGFBP5 protein expression was analyzed
immunohistochemically and IGFBP5, miR-140 and miR-193b mRNA expression levels were
analyzed with real-time RT-PCR. Tumor tissue had higher miR-140-5p expression than
adjacent normal tissue (p = 0.015). Samples with no immunohistochemical staining for
IGFBP5 showed increased miR-140-5p expression (p = 0.009). miR-140-5p expression was
elevated in invasive ductal carcinomas (p = 0.002), whereas basal-like tumors had
decreased expression of miR-140-5p compared to other tumors (p = 0.008). Lymph
node-positive samples showed an approximately 13-fold increase in miR-140-5p
expression compared to lymph node-negative tissue (p = 0.049). These findings suggest
that miR-140-5p, but not miR-193b, could be an important determinant of IGFBP5
expression and clinical phenotype in breast cancer patients. Further studies are
needed to clarify the expressional regulation of IGFBP5 by miR-140-5p.
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Affiliation(s)
- Gökçe Güllü
- Department of Medical Biology, School of Medicine, Marmara University, Istanbul, Turkey
| | - Irem Peker
- Department of Medical Biology, School of Medicine, Marmara University, Istanbul, Turkey
| | - Aptullah Haholu
- Department of Pathology, Haydarpasa Training Hospital, Gülhane Military Medical Academy, Istanbul, Turkey
| | - Fatih Eren
- Department of Medical Biology, School of Medicine, Marmara University, Istanbul, Turkey
| | - Zafer Küçükodaci
- Department of Pathology, Haydarpasa Training Hospital, Gülhane Military Medical Academy, Istanbul, Turkey
| | - Bülent Güleç
- Department of General Surgery, Haydarpasa Training Hospital, Gülhane Military Medical Academy, Istanbul, Turkey
| | - Hüseyin Baloglu
- Department of Pathology, Anadolu Medical Center, Istanbul, Turkey
| | - Can Erzik
- Department of Medical Biology, School of Medicine, Marmara University, Istanbul, Turkey
| | - Ayse Özer
- Department of Medical Biology, School of Medicine, Marmara University, Istanbul, Turkey
| | - Mustafa Akkiprik
- Department of Medical Biology, School of Medicine, Marmara University, Istanbul, Turkey
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Lysine residues of IGF-I are substrates for transglutaminases and modulate downstream IGF-I signalling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3176-3185. [DOI: 10.1016/j.bbamcr.2013.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 09/02/2013] [Accepted: 09/03/2013] [Indexed: 01/20/2023]
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Leavesley DI, Kashyap AS, Croll T, Sivaramakrishnan M, Shokoohmand A, Hollier BG, Upton Z. Vitronectin--master controller or micromanager? IUBMB Life 2013; 65:807-18. [PMID: 24030926 DOI: 10.1002/iub.1203] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 07/18/2013] [Indexed: 11/07/2022]
Abstract
The concept that the mammalian glycoprotein vitronectin acts as a biological 'glue' and key controller of mammalian tissue repair and remodelling activity is emerging from nearly 50 years of experimental in vitro and in vivo data. Unexpectedly, the vitronectin-knockout (VN-KO) mouse was found to be viable and to have largely normal phenotype. However, diligent observation revealed that the VN-KO animal exhibits delayed coagulation and poor wound healing. This is interpreted to indicate that VN occupies a role in the earliest events of thrombogenesis and tissue repair. VN is the foundation upon which the thrombus grows in an organised structure. In addition to sealing the wound, the thrombus also serves to protect the underlying tissue from oxidation, is a reservoir of mitogens and tissue repair mediators, and provides a provisional scaffold for the repairing tissue. In the absence of VN (e.g., VN-KO animal), this cascade is disrupted before it begins. A wide variety of biologically active species associate with VN. Although initial studies were focused on mitogens, other classes of bioactives (e.g., glycosaminoglycans and metalloproteinases) are now also known to specifically interact with VN. Although some interactions are transient, others are long-lived and often result in multi-protein complexes. Multi-protein complexes provide several advantages: prolonging molecular interactions, sustaining local concentrations, facilitating co-stimulation of cell surface receptors and thereby enhancing cellular/biological responses. We contend that these, or equivalent, multi-protein complexes facilitate VN polyfunctionality in vivo. It is also likely that many of the species demonstrated to associate with VN in vitro, also associate with VN in vivo in similar multi-protein complexes. Thus, the predominant biological function of VN is that of a master controller of the extracellular environment; informing, and possibly instructing cells 'where' to behave, 'when' to behave and 'how' to behave (i.e., appropriately for the current circumstance).
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Affiliation(s)
- David I Leavesley
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, QLD, Australia
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Sampson N, Zenzmaier C, Heitz M, Hermann M, Plas E, Schäfer G, Klocker H, Berger P. Stromal insulin-like growth factor binding protein 3 (IGFBP3) is elevated in the diseased human prostate and promotes ex vivo fibroblast-to-myofibroblast differentiation. Endocrinology 2013; 154:2586-99. [PMID: 23720424 DOI: 10.1210/en.2012-2259] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Dysregulation of the IGF axis is implicated in the development of benign prostatic hyperplasia (BPH) and prostate cancer (PCa), 2 of the most common diseases affecting elderly males. PCa is the second leading cause of male-related cancer death in Western societies. Although distinct pathologies, BPH and PCa are both characterized by extensive stromal remodeling, in particular fibroblast-to-myofibroblast differentiation, thought to be induced by elevated local production of TGFβ1. We previously showed that TGFβ1-mediated fibroblast-to-myofibroblast differentiation of primary human prostatic stromal cells resulted in the dsyregulation of several components of the IGF axis, including the induction of IGF binding protein 3 (IGFBP3). Using isoform-specific lentiviral-mediated knockdown, we demonstrate herein that IGFBP3 is essential for TGFβ1-mediated differentiation. Although recombinant human IGFBP3 alone was not sufficient to induce differentiation, IGFBP3 synergistically potentiated TGFβ1-mediated stromal remodeling predominantly via an IGF-independent mechanism. Consistent with these in vitro findings, IGFBP3 immunohistochemistry revealed elevated levels of IGFBP3 in the hyperplastic fibromuscular stroma of BPH specimens and in the tumor-adjacent stroma of high-grade PCa. Collectively these data indicate that the dysregulation of the stromal IGF axis, in particular elevated IGFBP3, plays a crucial role in fibroblast-to-myofibroblast differentiation in the diseased prostatic stroma and indicate the therapeutic potential of inhibiting stromal remodeling and the resulting dysregulation of the stromal IGF axis as a novel strategy for the treatment of advanced PCa and BPH.
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Sivaramakrishnan M, Kashyap AS, Amrein B, Saenger S, Meier S, Staudenmaier C, Upton Z, Metzger F. PEGylation of lysine residues reduces the pro-migratory activity of IGF-I. Biochim Biophys Acta Gen Subj 2013; 1830:4734-42. [PMID: 23800578 DOI: 10.1016/j.bbagen.2013.06.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Revised: 05/17/2013] [Accepted: 06/13/2013] [Indexed: 01/15/2023]
Abstract
BACKGROUND The insulin-like growth factor (IGF) system is composed of ligands and receptors which regulate cell proliferation, survival, differentiation and migration. Some of these functions involve regulation by the extracellular milieu, including binding proteins and other extracellular matrix proteins. However, the functions and exact nature of these interactions remain incomplete. METHODS IGF-I variants PEGylated at lysines K27, K65 and K68, were assessed for binding to IGFBPs using BIAcore, and for phosphorylation of the IGF-IR. Furthermore, functional consequences of PEGylation were investigated using cell viability and migration assays. In addition, downstream signaling pathways were analyzed using phospho-AKT and phospho-ERK1/2 assays. RESULTS IGF-I PEGylated at lysines 27 (PEG-K27), 65 (PEG-K65) or 68 (PEG-K68) was employed. Receptor phosphorylation was similarly reduced 2-fold with PEG-K65 and PEG-K68 in 3T3 fibroblasts and MCF-7 breast cancer cells, whereas PEG-K27 showed a more than 10- and 3-fold lower activation for 3T3 and MCF-7 cells, respectively. In addition, all PEG-IGF-I variants had a 10-fold reduced association rate to IGF binding proteins (IGFBPs). Functionally, all PEG variants lost their ability to induce cell migration in the presence of IGFBP-3/vitronectin (VN) complexes, whereas cell viability was fully preserved. Analysis of downstream signaling revealed that AKT was preferentially affected upon treatment with PEG-IGF-I variants whereas MAPK signaling was unaffected by PEGylation. CONCLUSION PEGylation of IGF-I has an impact on cell migration but not on cell viability. GENERAL SIGNIFICANCE PEG-IGF-I may differentially modulate IGF-I mediated functions that are dependent on receptor interaction as well as key extracellular proteins such as VN and IGFBPs.
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Forbes BE, McCarthy P, Norton RS. Insulin-like growth factor binding proteins: a structural perspective. Front Endocrinol (Lausanne) 2012; 3:38. [PMID: 22654863 PMCID: PMC3356058 DOI: 10.3389/fendo.2012.00038] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Accepted: 02/16/2012] [Indexed: 11/13/2022] Open
Abstract
Insulin-like growth factor binding proteins (IGFBP-1 to -6) bind insulin-like growth factors-I and -II (IGF-I and IGF-II) with high affinity. These binding proteins maintain IGFs in the circulation and direct them to target tissues, where they promote cell growth, proliferation, differentiation, and survival via the type 1 IGF receptor. IGFBPs also interact with many other molecules, which not only influence their modulation of IGF action but also mediate IGF-independent activities that regulate processes such as cell migration and apoptosis by modulating gene transcription. IGFBPs-1 to -6 are structurally similar proteins consisting of three distinct domains, N-terminal, linker, and C-terminal. There have been major advances in our understanding of IGFBP structure in the last decade and a half. While there is still no structure of an intact IGFBP, several structures of individual N- and C-domains have been solved. The structure of a complex of N-BP-4:IGF-I:C-BP-4 has also been solved, providing a detailed picture of the structural features of the IGF binding site and the mechanism of binding. Structural studies have also identified features important for interaction with extracellular matrix components and integrins. This review summarizes structural studies reported so far and highlights features important for binding not only IGF but also other partners. We also highlight future directions in which structural studies will add to our knowledge of the role played by the IGFBP family in normal growth and development, as well as in disease.
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Affiliation(s)
- Briony E Forbes
- The School of Molecular and Biomedical Science, The University of Adelaide Adelaide, SA, Australia
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12
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Current World Literature. Curr Opin Nephrol Hypertens 2012; 21:106-18. [DOI: 10.1097/mnh.0b013e32834ee42b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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Kashyap AS, Hollier BG, Manton KJ, Satyamoorthy K, Leavesley DI, Upton Z. Insulin-like growth factor-I:vitronectin complex-induced changes in gene expression effect breast cell survival and migration. Endocrinology 2011; 152:1388-401. [PMID: 21303956 DOI: 10.1210/en.2010-0897] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Recent studies have demonstrated that IGF-I associates with vitronectin (VN) through IGF-binding proteins (IGFBP), which in turn modulate IGF-stimulated biological functions such as cell proliferation, attachment, and migration. Because IGFs play important roles in transformation and progression of breast tumors, we aimed to describe the effects of IGF-I:IGFBP:VN complexes on breast cell function and to dissect mechanisms underlying these responses. In this study we demonstrate that substrate-bound IGF-I:IGFBP:VN complexes are potent stimulators of MCF-7 breast cell survival, which is mediated by a transient activation of ERK/MAPK and sustained activation of phosphoinositide 3-kinase/AKT pathways. Furthermore, use of pharmacological inhibitors of the MAPK and phosphoinositide 3-kinase pathways confirms that both pathways are involved in IGF-I:IGFBP:VN complex-mediated increased cell survival. Microarray analysis of cells stimulated to migrate in response to IGF-I:IGFBP:VN complexes identified differential expression of genes with previously reported roles in migration, invasion, and survival (Ephrin-B2, Sharp-2, Tissue-factor, Stratifin, PAI-1, IRS-1). These changes were not detected when the IGF-I analogue ([L(24)][A(31)]-IGF-I), which fails to bind to the IGF-I receptor, was substituted; confirming the IGF-I-dependent differential expression of genes associated with enhanced cell migration. Taken together, these studies have established that IGF-I:IGFBP:VN complexes enhance breast cell migration and survival, processes central to facilitating metastasis. This study highlights the interdependence of extracellular matrix and growth factor interactions in biological functions critical for metastasis and identifies potential novel therapeutic targets directed at preventing breast cancer progression.
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Affiliation(s)
- Abhishek S Kashyap
- Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, 4059, Queensland, Australia.
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