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Ron G Rosenfeld - One of the best experts on this subject based on the ideXlab platform.
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the insulin like growth factor binding protein igfbp superfamily
Endocrine Reviews, 1999Co-Authors: Vivian Hwa, Ron G RosenfeldAbstract:Over the last decade, the concept of an IGFBP family has been well accepted, based on structural similarities and on functional abilities to bind IGFs with high affinities. The existence of other potential IGFBPs was left open. The discovery of proteins with N-terminal domains bearing striking structural similarities to the N terminus of the IGFBPs, and with reduced, but demonstrable, affinity for IGFs, raised the question of whether these proteins were "new" IGFBPs (22, 23, 217). The N-terminal domain had been uniquely associated with the IGFBPs and has long been considered to be critical for IGF binding. No other function has been confirmed for this domain to date. Thus, the presence of this important IGFBP domain in the N terminus of other proteins must be considered significant. Although these other proteins appear capable of binding IGF, their relatively low affinity and the fact that their major biological actions are likely to not directly involve the IGF peptides suggest that they probably should not be classified within the IGFBP family as provisionally proposed (22, 23). The conservation of this single domain, so critical to high-affinity binding of IGF by the six IGFBPs, in all of the IGFBP-rPs, as well, speaks to its biological importance. Historically, and perhaps, functionally, this has led to the designation of an "IGFBP superfamily". The classification and nomenclature for the IGFBP superfamily, are, of course, arbitrary; what is ultimately relevant is the underlying biology, much of which still remains to be deciphered. The nomenclature for the IGFBP related proteins was derived from a consensus of researchers working in the IGFBP field (52). Obviously, a more general consensus on nomenclature, involving all groups working on each IGFBP-rP, has yet to be reached. Further understanding of the biological functions of each protein should help resolve the nomenclature dilemma. For the present, redesignating these proteins IGFBP-rPs simplifies the multiple names already associated with each IGFBP related protein, and reinforces the concept of a relationship with the IGFBPs. Beyond the N-terminal domain, there is a lack of structural similarity between the IGFBP-rPs and IGFBPs. The C-terminal domains do share similarities to other internal domains found in numerous other proteins. For example, the similarity of the IGFBP C terminus to the thyroglobulin type-I domain shows that the IGFBPs are also structurally related to numerous other proteins carrying the same domain (87). Interestingly, the functions of the different C-terminal domains in members of the IGFBP superfamily include interactions with the cell surface or ECM, suggesting that, even if they share little sequence similarities, the C-terminal domains may be functionally related. The evolutionary conservation of the N-terminal domain and functional studies support the notion that IGFBPs and IGFBP-rPs together form an IGFBP superfamily. A superfamily delineates between closely related (classified as a family) and distantly related proteins. The IGFBP superfamily is therefore composed of distantly related families. The modular nature of the constituents of the IGFBP superfamily, particularly their preservation of an highly conserved N-terminal domain, seems best explained by the process of exon shuffling of an ancestral gene encoding this domain. Over the course of evolution, some members evolved into high-affinity IGF binders and others into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means (Fig. 10). A final word, from Stephen Jay Gould (218): "But classifications are not passive ordering devices in a world objectively divided into obvious categories. Taxonomies are human decisions imposed upon nature--theories about the causes of nature's order. The chronicle of historical changes in classification provides our finest insight into conceptual revolutions
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identification of a family of low affinity insulin like growth factor binding proteins igfbps characterization of connective tissue growth factor as a member of the igfbp superfamily
Proceedings of the National Academy of Sciences of the United States of America, 1997Co-Authors: Hoseong Kim, Srinivasa R Nagalla, Elizabeth M Wilson, Charles Roberts, Ron G RosenfeldAbstract:The insulin-like growth factor (IGF) binding proteins (IGFBPs) modulate the actions of the insulin-like growth factors in endocrine, paracrine, and autocrine settings. Additionally, some IGFBPs appear to exhibit biological effects that are IGF independent. The six high-affinity IGFBPs that have been characterized to date exhibit 40–60% amino acid sequence identity overall, with the most conserved sequences in their NH2 and COOH termini. We have recently demonstrated that the product of the mac25/IGFBP-7 gene, which shows significant conservation in the NH2 terminus, including an “IGFBP motif” (GCGCCXXC), exhibits low-affinity IGF binding. The closely related mammalian genes connective tissue growth factor (CTGF) gene, nov, and cyr61 encode secreted proteins that also contain the conserved sequences and IGFBP motifs in their NH2 termini. To ascertain if these genes, along with mac25/IGFBP-7, encode a family of low-affinity IGFBPs, we assessed the IGF binding characteristics of recombinant human CTGF (rhCTGF). The ability of baculovirus-synthesized rhCTGF to bind IGFs was demonstrated by Western ligand blotting, affinity cross-linking, and competitive affinity binding assays using 125I-labeled IGF-I or IGF-II and unlabeled IGFs. CTGF, like mac25/IGFBP-7, specifically binds IGFs, although with relatively low affinity. On the basis of these data, we propose that CTGF represents another member of the IGFBP family (IGFBP-8) and that the CTGF gene, mac25/IGFBP-7, nov, and cyr61 are members of a family of low-affinity IGFBP genes. These genes, along with those encoding the high-affinity IGFBPs 1–6, together constitute an IGFBP superfamily whose products function in IGF-dependent or IGF-independent modes to regulate normal and neoplastic cell growth.
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insulin like growth factor binding proteins igfbps and their regulatory dynamics
The International Journal of Biochemistry & Cell Biology, 1996Co-Authors: Kevin M Kelley, Sharron E Gargosky, Zoran Gucev, Tomoko Matsumoto, Vivian Hwa, Diane M Simpson, Ron G RosenfeldAbstract:The IGFBPs are a family of homologous proteins that have co-evolved with the IGFs and that confer upon the IGF regulatory system both functional and tissue specificity. IGFBPs are not merely carrier proteins for IGFs, but hold a central position in IGF ligand-receptor interactions through influences on both the bioavailability and distribution of IGFs in the extracellular environment. In addition, IGFBPs appear to have intrinsic biological activity independent of IGFs. The current status of research on IGFBPs is reviewed herein. Following a brief introduction to the entire IGF/IGFBP system, separate sections for each of the six cloned mammalian IGFBPs, the most extensive for IGFBP3, cover selected topics that emphasize the dynamics of IGFBPs—that is, their regulation in cells, their functionally important post-translational modifications, and their interactions in the cellular microenvironment—and how these dynamics influence physiological function.
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insulin like growth factors and their binding proteins in the term and preterm human fetus and neonate with normal and extremes of intrauterine growth
The Journal of Clinical Endocrinology and Metabolism, 1995Co-Authors: Linda C Giudice, Sharron E Gargosky, F De Zegher, B A Dsupin, L De Las Fuentes, R A Crystal, Raymond L Hintz, Ron G RosenfeldAbstract:Insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs), and insulin are believed to be important in the regulation of fetal and neonatal growth. We previously reported that the profiles of IGFBPs in fetal cord serum (FCS) were dependent on the growth/metabolic status of the fetus. The goals of the current study were to examine the IGF system in FCS from term fetuses with normal growth, those with intrauterine growth retardation (IUGR), and those who were large for gestational age (LGA) and in FCS from normal weight preterm (25-37 weeks) and term fetuses in the neonatal period from the day of birth (day 0) until 7 days of age (day 7). Western ligand blotting (WLB) of term FCS revealed IGFBPs with mol wt of 43 and 38 kilodaltons (kDa; IGFBP-3), 34 kDa (IGFBP-2), 28 kDa (IGFBP-1 and glycosylated IGFBP-4), and 24 kDa (IGFBP-4). In IUGR FCS, there was a 50% decrease in IGFBP-3 detected by WLB, which was shown not to be due to an IGFBP-3 protease in IUGR sera. In LGA FCS, IGFBP-3 levels were elevated...
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differential effects of insulin like growth factor igf i and igf ii on the expression of igf binding proteins igfbps in a rat neuroblastoma cell line isolation and characterization of two forms of igfbp 4
Endocrinology, 1991Co-Authors: Paolo G Ceda, Paul J Fielder, William J Henzel, Andrea Louie, Sharon M Donovan, Andrew R Hoffman, Ron G RosenfeldAbstract:The isolation and hormonal regulation of two low molecular weight insulin-like growth factor binding proteins (IGFBPs) present in the conditioned medium (CM) of the rat neuroblastoma cell line B104 cells has been performed. IGFBPs were purified by ZnSO4 precipitation, insulin-like growth factor- I 1IGF-I) affinity chromatography, and reverse phase HPLC. Final isolation and N-terminal analysis was accomplished by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electroblotting to polyvinylidene difluoride membranes, and sequencing of the bound proteins. Two IGFBPs, with apparent Mr of 28K and 24K were coisolated and sequenced. Both proteins had identical N-terminal sequences and appear to be two forms of IGFBP-4. Treatment of the IGFBPs with endoglycosidase-F caused a shift in the apparent Mr of the 28K IGFBP to 24K. However, there was no change in the apparent Mr of the 24K IGFBP. The data from this study suggest that the IGFBP-4 exists as both a glycosylated and nonglycosylated protein. Treatme...
David R Clemmons - One of the best experts on this subject based on the ideXlab platform.
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insulin like growth factor igf binding protein 2 functions coordinately with receptor protein tyrosine phosphatase β and the igf i receptor to regulate igf i stimulated signaling
Molecular and Cellular Biology, 2012Co-Authors: Xinchun Shen, Clifford J Rosen, Laura A Maile, Christine Wai, David R ClemmonsAbstract:Insulin-like growth factor I (IGF-I) is a mitogen for vascular smooth muscle cells (VSMC) and has been implicated in the development and progression of atherosclerosis. IGF binding proteins (IGFBPs) modify IGF-I actions independently of IGF binding, but a receptor-based mechanism by which they function has not been elucidated. We investigated the role of IGFBP-2 and receptor protein tyrosine phosphatase β (RPTPβ) in regulating IGF-I signaling and cellular proliferation. IGFBP-2 bound RPTPβ, which led to its dimerization and inactivation. This enhanced PTEN tyrosine phosphorylation and inhibited PTEN activity. Utilization of substrate trapping and phosphatase-dead mutants showed that RPTPβ bound specifically to PTEN and dephosphorylated it. IGFBP-2 knockdown led to decreased PTEN tyrosine phosphorylation and decreased AKT Ser473 activation. IGFBP-2 enhanced IGF-I-stimulated VSMC migration and proliferation. Analysis of aortas obtained from IGFBP-2−/− mice showed that RPTPβ was activated, and this was associated with inhibition of IGF-I stimulated AKT Ser473 phosphorylation and VSMC proliferation. These changes were rescued following administration of IGFBP-2. These findings present a novel mechanism for coordinate regulation of IGFBP-2 and IGF-I signaling functions that lead to stimulation of VSMC proliferation. The results have important implications for understanding how IGFBPs modulate the cellular response to IGF-I.
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insulin like growth factor binding protein 2 is required for osteoclast differentiation
Journal of Bone and Mineral Research, 2012Co-Authors: Victoria E Demambro, Clifford J Rosen, Masanobu Kawai, Laura A Maile, Christine Wai, Teresa Cascella, David R ClemmonsAbstract:Global deletion of the Igfbp2 gene results in the suppression of bone turnover. To investigate the role of insulin-like growth factor-binding protein-2 (IGFBP-2) in regulating osteoclast differentiation, we cultured Igfbp2−/− bone marrow cells and found a reduction in the number of osteoclasts and impaired resorption. Addition of full-length IGFBP-2 restored osteoclast differentiation, fusion, and resorption. To determine the molecular domains of IGFBP-2 that were required for this effect to be manifest, Igfbp2−/− bone marrow cells were transfected with constructs in which the heparin-binding (HBD) or the IGF-binding domains of IGFBP-2 were mutated. We found that both domains were necessary for osteoclastogenesis because expression of the mutated forms of either domain failed to support the formation of functionally mature osteoclasts. To discern the mechanism by which IGFBP-2 regulates osteoclast formation, PTEN abundance and phosphorylation status as well as AKT responsiveness to IGF-I were analyzed. Igfbp2−/− cells had elevated levels of PTEN and phospho-PTEN compared with controls. Expression of wild-type IGFBP-2 reduced the level of PTEN to that of wild-type cells. Cells expressing the IGF-binding mutant showed suppression of PTEN and phospho-PTEN equivalent to the wild-type protein, whereas those expressing the IGFBP-2 HBD mutant showed no PTEN suppression. When the ability of IGF-I to stimulate AKT activation, measured by Thr308 and Ser473 phosphorylation, was analyzed, stimulation of Ser473 in response to IGF-I in preosteoclasts required the presence of intact IGFBP-2. This effect was duplicated by the addition of a CK2 inhibitor that prevents the phosphorylation of PTEN. In contrast, in fully differentiated osteoclasts, stimulation of Thr308 phosphorylation required the presence of intact IGFBP-2. We conclude that IGFBP-2 is an important regulator of osteoclastogenesis and that both the heparin- and the IGF-binding domains of IGFBP-2 are essential for the formation of fully differentiated and functional osteoclasts. © 2012 American Society for Bone and Mineral Research
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the heparin binding domain of igfbp 2 has insulin like growth factor binding independent biologic activity in the growing skeleton
Journal of Biological Chemistry, 2011Co-Authors: Masanobu Kawai, Victoria E Demambro, David R Clemmons, Mary L Bouxsein, Wesley G Beamer, Ernesto Canalis, Anne Breggia, Xinchun Shen, Clifford J RosenAbstract:Insulin-like growth factor-binding protein 2 (IGFBP-2) is a member of a family of six highly conserved IGFBPs that are carriers for the insulin-like growth factors (IGFs). IGFBP-2 levels rise during rapid neonatal growth and at the time of peak bone acquisition. In contrast, Igfbp2−/− mice have low bone mass accompanied by reduced osteoblast numbers, low bone formation rates, and increased PTEN expression. In the current study, we postulated that IGFBP-2 increased bone mass partly through the activity of its heparin-binding domain (HBD). We synthesized a HBD peptide specific for IGFBP-2 and demonstrated in vitro that it rescued the mineralization phenotype of Igfbp2−/− bone marrow stromal cells and calvarial osteoblasts. Consistent with its cellular actions, the HBD peptide ex vivo stimulated metacarpal periosteal expansion. Furthermore, administration of HBD peptide to Igfbp2−/− mice increased osteoblast number, suppressed marrow adipogenesis, restored trabecular bone mass, and reduced bone resorption. Skeletal rescue in the Igfbp2−/− mice was characterized by reduced PTEN expression followed by enhanced Akt phosphorylation in response to IGF-I and increased β-catenin signaling through two mechanisms: 1) stimulation of its cytosolic accumulation and 2) increased phosphorylation of serine 552. We conclude that the HBD peptide of IGFBP-2 has anabolic activity by activating IGF-I/Akt and β-catenin signaling pathways. These data support a growing body of evidence that IGFBP-2 is not just a transport protein but rather that it functions coordinately with IGF-I to stimulate growth and skeletal acquisition.
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gender specific changes in bone turnover and skeletal architecture in igfbp 2 null mice
Endocrinology, 2008Co-Authors: Victoria E Demambro, David R Clemmons, Lindsay G Horton, Mary L Bouxsein, Teresa L Wood, Wesley G Beamer, Ernesto Canalis, Clifford J RosenAbstract:IGF-binding protein-2 (IGFBP-2) is a 36-kDa protein that binds to the IGFs with high affinity. To determine its role in bone turnover, we compared Igfbp2−/− mice with Igfbp2+/+ colony controls. Igfbp2−/− males had shorter femurs and were heavier than controls but were not insulin resistant. Serum IGF-I levels in Igfbp2−/− mice were 10% higher than Igfbp2+/+ controls at 8 wk of age; in males, this was accompanied by a 3-fold increase in hepatic Igfbp3 and Igfbp5 mRNA transcripts compared with Igfbp2+/+ controls. The skeletal phenotype of the Igfbp2−/− mice was gender and compartment specific; Igfbp2−/− females had increased cortical thickness with a greater periosteal circumference compared with controls, whereas male Igfbp2−/− males had reduced cortical bone area and a 20% reduction in the trabecular bone volume fraction due to thinner trabeculae than Igfbp2+/+ controls. Serum osteocalcin levels were reduced by nearly 40% in Igfbp2−/− males, and in vitro, both CFU-ALP+ preosteoblasts, and tartrate-resistant acid phosphatase-positive osteoclasts were significantly less abundant than in Igfbp2+/+ male mice. Histomorphometry confirmed fewer osteoblasts and osteoclasts per bone perimeter and reduced bone formation in the Igfbp2−/− males. Lysates from both osteoblasts and osteoclasts in the Igfbp2−/− males had phosphatase and tensin homolog (PTEN) levels that were significantly higher than Igfbp2+/+ controls and were suppressed by addition of exogenous IGFBP-2. In summary, there are gender- and compartment-specific changes in Igfbp2−/− mice. IGFBP-2 may regulate bone turnover in both an IGF-I-dependent and -independent manner.
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differential expression and biological effects of insulin like growth factor binding protein 4 and 5 in vascular smooth muscle cells
Journal of Biological Chemistry, 1998Co-Authors: Cunming Duan, David R ClemmonsAbstract:Abstract Insulin-like growth factor-I (IGF-I) plays an important role in regulating vascular smooth muscle cell (VSMC) proliferation, migration, and apoptosis. The bioactivity of IGF-I is modulated by a group of high affinity, specific binding proteins (IGF-binding proteins; IGFBPs) that are present in the interstitial fluid. Previously, we have reported that porcine VSMCs synthesize and secrete IGF-I and several forms of IGFBPs, including IGFBP-2, IGFBP-4, and IGFBP-5. In this study, we examined the role of autocrine/paracrine secreted IGF-I in controlling the expression of IGFBP-4 and IGFBP-5 as well as the effects of these IGFBPs in modulating the cellular replication response to IGF-I. The concentrations of IGFBP-4 in the conditioned medium increased significantly from <50 ng/ml to 742 ± 105 ng/ml. This increase was associated with a decrease in the activity of an IGF-I-regulated IGFBP-4 protease. In contrast, the synthesis of IGFBP-5 was inversely correlated with culture density, and its concentration decreased from 792 ± 91 to 44 ± 14 ng/ml. IGFBP-5 mRNA in sparse cultures was 3-fold higher compared with those in confluent cultures. This culture density-dependent change in IGFBP-5 mRNA correlated closely with endogenous IGF-I levels. Since treatment of VSMC with exogenous IGF-I increased IGFBP-5 mRNA levels, we neutralized the effect of endogenously secreted IGF-I with an anti-IGF-I antibody to determine if it would alter IGFBP-5 mRNA abundance. This resulted in a 4.4-fold decrease in IGFBP-5 mRNA levels. When added together with IGF-I, exogenous IGFBP-4 inhibited IGF-I-induced DNA synthesis in a concentration-dependent manner. IGFBP-5, on the other hand, potentiated the effect of IGF-I. Therefore, IGFBP-4 and IGFBP-5 appear to be differentially regulated by autocrine/paracrine IGF-I through distinct mechanisms. These two proteins, in turn, play opposing roles in modulating IGF-I action in stimulating VSMC proliferation.
Linda C Giudice - One of the best experts on this subject based on the ideXlab platform.
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the insulin related ovarian regulatory system in health and disease
Endocrine Reviews, 1999Co-Authors: Leonid Poretsky, Nicholas A Cataldo, Z Rosenwaks, Linda C GiudiceAbstract:I. Introduction II. Insulin and Insulin Receptor A. Structures of insulin and insulin receptor B. Presence of insulin and insulin receptor in the ovary C. Insulin action and the ovary D. Summary III. IGFs and Their Receptors A. IGF peptides and receptors B. Expression of IGFs and IGF receptors in the ovary C. Role of IGFs in ovulatory function and steroidogenesis D. Summary IV. IGF-Binding Proteins (IGFBPs) and Proteases A. Structural relationships among IGFBPs B. IGFBP expression in the ovary C. IGFBP proteases in the ovary D. IGFBP actions in the ovary E. Role of IGFBPs in follicular development and atresia F. Summary V. Polycystic Ovary Syndrome (PCOS) A. Clinical features B. Theories of pathogenesis C. Insulin resistance in PCOS D. Alterations of IGFs and IGFBPs in PCOS E. Summary VI. The Insulin-Related Ovarian Regulatory System: Implications for Therapy A. Treatment of PCOS B. Therapeutic use of IGF-I and IGF-II C. Use of GH in ovulation induction VII. Summary and Conclusions
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insulin like growth factors and their binding proteins in the term and preterm human fetus and neonate with normal and extremes of intrauterine growth
The Journal of Clinical Endocrinology and Metabolism, 1995Co-Authors: Linda C Giudice, Sharron E Gargosky, F De Zegher, B A Dsupin, L De Las Fuentes, R A Crystal, Raymond L Hintz, Ron G RosenfeldAbstract:Insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs), and insulin are believed to be important in the regulation of fetal and neonatal growth. We previously reported that the profiles of IGFBPs in fetal cord serum (FCS) were dependent on the growth/metabolic status of the fetus. The goals of the current study were to examine the IGF system in FCS from term fetuses with normal growth, those with intrauterine growth retardation (IUGR), and those who were large for gestational age (LGA) and in FCS from normal weight preterm (25-37 weeks) and term fetuses in the neonatal period from the day of birth (day 0) until 7 days of age (day 7). Western ligand blotting (WLB) of term FCS revealed IGFBPs with mol wt of 43 and 38 kilodaltons (kDa; IGFBP-3), 34 kDa (IGFBP-2), 28 kDa (IGFBP-1 and glycosylated IGFBP-4), and 24 kDa (IGFBP-4). In IUGR FCS, there was a 50% decrease in IGFBP-3 detected by WLB, which was shown not to be due to an IGFBP-3 protease in IUGR sera. In LGA FCS, IGFBP-3 levels were elevated...
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characterization of the steroid dependence of insulin like growth factor binding protein 2 synthesis and mrna expression in cultured human endometrial stromal cells
Human Reproduction, 1991Co-Authors: Linda C Giudice, Paul J Fielder, Deborah A Milkowski, J C IrwinAbstract:The insulin-like growth factors (IGF-I and -II) are believed to be important in endometrial differentiation and blastocyst nidation, and proteins that regulate IGF action (IGF-binding proteins, IGFBPs) are hormonally regulated in endometrium during the menstrual cycle. To characterize further steroid-dependence of the IGFBPs, we established endometrial stromal cells in culture in the absence and presence of oestradiol (E2) and progesterone (P) and examined the conditioned medium for IGFBPs by Western ligand blot analysis. Stromal cells constitutively synthesized IGFBP-3, IGFBP-2, a 27 kd, and a 24 kd IGFBP. In the presence of E2 and P, a 10- to 15-fold increase in IGFBP-2 was detected in the conditioned medium beginning after about 7 days in culture, when cells decidualized and steroid-mediated prolactin secretion began. Withdrawal of steroids resulted in a marked decrease in IGFBP-2, comparable to control levels, and cells increased their IGFBP-2 production when rechallenged with E2 and P. Total RNA was isolated from stromal cells, and Northern blot analysis using a cDNA probe specific for IGFBP-2 revealed differential expression of a 1.4 kb mRNA transcript in steroid-treated compared to control cells. The effects of progestational agents alone on IGFBP synthesis was also examined. Progesterone, medroxyprogesterone acetate and norethindrone all stimulated IGFBP-2 synthesis 12- to 15-fold compared to controls, and a progesterone receptor antagonist, RU 486, blocked the stimulatory effect of progesterone. IGFBP-2 synthesis was increased two-fold above controls by 17-alpha-hydroxyprogesterone, and RU 486 alone and hydrocortisone were without effect. Identification of IGFBP-2 in conditioned medium was made using IGFBP-specific antiserum. These data show that (a) endometrial stromal cells synthesize and secrete IGFBP-2, (b) IGFBP-2 protein synthesis is controlled by steroid hormones, (c) P, by interacting with its receptor, modulates IGFBP-2 synthesis and (d) expression of IGFBP-2 mRNA is controlled by sex steroids.
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insulin like growth factor binding proteins in human endometrium steroid dependent messenger ribonucleic acid expression and protein synthesis
The Journal of Clinical Endocrinology and Metabolism, 1991Co-Authors: Linda C Giudice, Ron G Rosenfeld, Deborah A Milkowski, George Lamson, Juan C IrwinAbstract:The insulin-like growth factor (IGF) autocrine/paracrine system is believed to play a role in endometrial differentiation and trophoblast growth. The IGFs bind with high affinity to a family of binding proteins (IGFBPs) that regulate the actions of the IGFs at their target cells. IGFBP-1, one of three well-characterized IGFBPs in humans, has been shown by numerous investigators to be present in secretory but not proliferative endometrium; however, no information is available with regard to two other human IGFBPs, IGFBP-2 and IGFBP-3, in normal human endometrium. We have examined expression of the messenger RNAs (mRNAs) encoding IGFBP-2 and IGFBP-3 in human proliferative endometrium [under the influence of estradiol (E2)] compared to secretory endometrium (under the influence of E2 and progesterone). Using a complementary DNA probe specific for IGFBP-2, by Northern analysis, expression of a 1.4 kilobase mRNA was found to be differentially expressed in secretory compared to proliferative phase endometrium. ...
Michael R Green - One of the best experts on this subject based on the ideXlab platform.
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efficacy of IGFBP7 for treatment of metastatic melanoma and other cancers in mouse models and human cell lines
Molecular Cancer Therapeutics, 2009Co-Authors: Narendra Wajapeyee, Varun N Kapoor, Meera Mahalingam, Michael R GreenAbstract:We recently identified the secreted protein IGFBP7 as a factor required for an activated BRAF oncogene to induce senescence or apoptosis in primary human cells. In human melanomas containing an activating BRAF mutation (BRAF-positive melanomas), IGFBP7 is epigenetically silenced, which seems to be a critical step in melanoma genesis. Restoration of IGFBP7 function by the addition of recombinant IGFBP7 (rIGFBP7) induces apoptosis in BRAF-positive human melanoma cell lines, and systemically administered rIGFBP7 markedly suppresses the growth of BRAF-positive primary tumors in xenografted mice. Here we further evaluate the role of IGFBP7 in the treatment of BRAF-positive melanoma and other malignancies. We find that in human metastatic melanoma samples IGFBP7 is epigenetically silenced and at an even higher frequency than that found in primary melanomas. Using a murine experimental metastasis assay, we show that systemic administration of rIGFBP7 markedly suppresses the growth of metastatic disease and prolongs survival. An analysis of the NCI60 panel of human cancer cell lines reveals that in addition to melanoma, IGFBP7 induces apoptosis in several other cancer types, in particular colorectal cancer cell lines. In general, IGFBP7 induces apoptosis in human cancer cell lines that have an activating mutation in BRAF or RAS, and that are sensitive to chemical inhibition of BRAF-MEK-ERK signaling. Significantly, systemically administered rIGFBP7 blocks the growth of colorectal tumors containing an activating RAS or BRAF mutation in mouse xenografts. The results presented here, in conjunction with those from previous studies, justify the further development of IGFBP7 as an anticancer agent.
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oncogenic braf induces senescence and apoptosis through pathways mediated by the secreted protein IGFBP7
Cell, 2008Co-Authors: Narendra Wajapeyee, Meera Mahalingam, Ryan W Serra, Xiaochun Zhu, Michael R GreenAbstract:SUMMARY Expression of an oncogene in a primary cell can, paradoxically, block proliferation by inducing senescence or apoptosis through pathways that remain to be elucidated. Here we perform genome-wide RNAinterference screening to identify 17 genes required for an activated BRAF oncogene (BRAFV600E) to block proliferation of human primary fibroblasts and melanocytes. Surprisingly, we find a secreted protein, IGFBP7, has a central role in BRAFV600E-mediated senescence and apoptosis. Expression of BRAFV600E in primary cells leads to synthesis and secretion of IGFBP7, which acts through autocrine/ paracrine pathways to inhibit BRAF-MEK-ERK signaling and induce senescence and apoptosis. Apoptosis results from IGFBP7-mediated upregulation of BNIP3L, a proapoptotic BCL2 family protein. Recombinant IGFBP7 (rIGFBP7) induces apoptosis in BRAFV600E-positive human melanoma cell lines, and systemically administered rIGFBP7 markedly suppresses growth of BRAFV600E-positive tumors in xenografted mice. Immunohistochemical analysis of human skin, nevi, and melanoma samples implicates loss of IGFBP7 expression as a critical step in melanoma genesis.
Thomas E Spencer - One of the best experts on this subject based on the ideXlab platform.
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insulin like growth factor binding protein 1 in the ruminant uterus potential endometrial marker and regulator of conceptus elongation
Endocrinology, 2009Co-Authors: Rebecca M Simmons, David W Erikson, Jinyoung Kim, Robert C Burghardt, Fuller W Bazer, Greg A Johnson, Thomas E SpencerAbstract:Establishment of pregnancy in ruminants requires conceptus elongation and production of interferon-tau (IFNT), the pregnancy recognition signal that maintains ovarian progesterone (P4) production. These studies determined temporal and spatial alterations in IGF binding protein (IGFBP)-1 and IGFBP3 in the ovine and bovine uterus; effects of P4 and IFNT on their expression in the ovine uterus; and effects of IGFBP1 on ovine trophectoderm cell proliferation, migration, and attachment. IGFBP1 and IGFBP3 were studied because they are the only IGFBPs specifically expressed by the endometrial luminal epithelia in sheep. In sheep, IGFBP1 and IGFBP3 expression was coordinate with the period of conceptus elongation, whereas only IGFBP1 expression was coordinate with conceptus elongation in cattle. IGFBP1 mRNA in the ovine endometria was between 5- and 29-fold more abundant between d 12 and 16 of pregnancy compared with the estrous cycle and greater on d 16 of pregnancy than nonpregnancy in the bovine uterus. In sheep, P4 induced and IFNT stimulated expression of IGFBP1 but not IGFBP3; however, the effect of IFNT did not mimic the abundant increase observed in pregnant ewes. Therefore, IGFBP1 expression in the endometrium is regulated by another factor from the conceptus. IGFBP1 did not affect the proliferation of ovine trophectoderm cells in vitro but did stimulate their migration and mediate their attachment. These studies reveal that IGFBP1 is a common endometrial marker of conceptus elongation in sheep and cattle and most likely regulates conceptus elongation by stimulating migration and attachment of the trophectoderm.
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progesterone regulates fgf10 met igfbp1 and igfbp3 in the endometrium of the ovine uterus
Biology of Reproduction, 2008Co-Authors: Carey M Satterfield, Fuller W Bazer, Kanako Hayashi, Gwonhwa Song, Sarah G Black, Thomas E SpencerAbstract:Progesterone (P4) is unequivocally required to maintain a uterine environment conducive to pregnancy. This study investigated the effects of P4 treatment on expression of selected growth factors (fibroblast growth factor 7 [FGF7], FGF10, hepatocyte growth factor [HGF], and insulin-like growth factors [IGF1 and IGF2]), their receptors (MET, FGFR2(IIIB), and IGF1R), and IGF binding proteins (IGFBPs) in the ovine uterus. Ewes received daily injections of corn oil vehicle (CO) or 25 mg of P4 in vehicle from 36 h after mating (Day 0) to hysterectomy on Day 9 or Day 12. Another group received P4 to Day 8 and 75 mg of mifepristone (RU486, a P4 receptor antagonist) from Day 8 through Day 12. Endometrial FGF10 mRNA levels increased between Day 9 and Day 12 and in response to P4 on Day 9 in CO-treated ewes, which had larger blastocysts, and were substantially reduced in P4+RU486-treated ewes, which had no blastocysts on Day 12. Endometrial FGF7 or HGF mRNA levels were not affected by day or reduced by RU486 treatment, but MET mRNA levels were higher in P4-treated ewes on Day 9 and Day 12. Levels of IGF1, IGF2, and IGF1R mRNA in the endometria were not affected by early P4 treatment. Although stromal IGFBPs were unaffected by P4, levels of IGFBP1 and IGFBP3 mRNA in uterine luminal epithelia were increased substantially between Day 9 and Day 12 of pregnancy in CO-treated ewes and on Day 9 in early P4-treated ewes. Therefore, FGF10, MET, IGFBP1, and IGFBP3 are P4-regulated factors within the endometrium of the ovine uterus that have potential effects on endometrial function and peri-implantation blastocyst growth and development.
