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Estudo do gene do fator de crescimento insulina-símile 1 (IGF1) e de receptor (IGF1R) em crianças nascidas pequenas para a idade gestacional; Study of insuline-like growth factor gene (IGF1) and its receptor in children born small for gestational age

Coutinho, Debora Cabral
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/04/2009 PT
Relevância na Pesquisa
76.08%
Crianças nascidas pequenas para a idade gestacional (PIG) apresentam maior risco de permanecerem com baixa estatura na vida adulta. Os fatores de crescimento insulina-símile 1 e 2 (IGF-1 e IGF-2) são os principais fatores endócrinos determinantes do crescimento fetal. Na vida pós-natal o GH, principal hormônio promotor de crescimento, exerce a maior parte de seus efeitos por meio do IGF-1. A grande maioria das ações conhecidas do IGF-1 e IGF-2 são mediadas via receptor tirosina quinase conhecido como receptor tipo 1 de IGFs (IGF-1R). Os objetivos deste trabalho foram estudar os genes IGF1 e IGF1R em crianças nascidas pequenas para a idade gestacional que não recuperaram o crescimento na vida pós-natal. Foram selecionados 145 pacientes nascidos PIG, 72 sem catch up e 73 com catch up. Em 54 PIG sem catch up foi estudado toda a seqüência codificadora do gene IGF1 por meio de PCR e seqüenciamento direto, nos demais PIG sem catch up e nos 73 PIG com catch up foi estudado apenas o exon 6 do IGF-1 por PCR e seqüenciamento direto para avaliação de um polimorfismo encontrado nesta região. Nos pacientes que apresentavam concentração sérica de IGF-1 e IGFBP-3 acima da média para idade e sexo e seqüência do IGF1 normal (n=23) foi realizada coleta de sangue periférico com posterior separação de leucócitos mononucleares pelo gradiente de ficoll seguido por extração de RNA pelo método de Trizol® Posteriormente...

Estudo in vitro da sensibilidade ao IGF-1 de fibroblastos de crianças nascidas pequenas para a idade gestacional sem recuperação estatural pós-natal; In vitro study of sensitivity to IGF-1 of fibroblasts of children born small for gestational age without postnatal statural recovery

Montenegro, Luciana Ribeiro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/05/2009 PT
Relevância na Pesquisa
76.03%
Introdução: Crianças nascidas pequenas para a idade gestacional (PIG) apresentam maior risco de permanecerem com baixa estatura na vida adulta. Os fatores de crescimento insulino-símile tipo 1 e 2 (IGF-1 e IGF-2) são os principais fatores endócrinos determinantes do crescimento fetal. A maioria das ações conhecidas do IGF-1 e 2 é mediada via um receptor tirosina quinase, conhecido como IGF-1R. Recentemente, a insensibilidade ao IGF-1 foi identificada como uma das causas de retardo de crescimento em crianças nascidas PIG que não apresentaram recuperação espontânea do crescimento na vida pós-natal. Crianças afetadas apresentavam níveis elevados de IGF-1, IGFBP-3 além de microcefalia. O papel de defeitos pósreceptor na sinalização do IGF-1 como causa de retardo de crescimento pré e pós-natal ainda não foi investigado. Objetivo: Analisar in vitro a ação do IGF-1 em fibroblastos de crianças nascidas PIG. Material e métodos: Desenvolvemos cultura de fibroblastos de 2 controles (C1 e C2) e de 4 pacientes nascidos PIG (SGA1, SGA2, SGA3 e SGA4) com suspeita de insensibilidade ao IGF-1 por ausência de recuperação do crescimento na vida pós natal, resposta insatisfatória ao tratamento com hGH apesar de níveis normais/elevados de IGF-1. Foi confirmado do ponto de vista molecular que um dos pacientes (SGA1) apresenta Síndrome de Sílver- Russell com perda da metilação do alelo paterno da região ICR1 (imprinting center region 1) importante para a expressão do IGF-2. Defeitos no gene do IGF1 e IGF1R foram afastados por sequenciamento direto. As ações do IGF- 1 foram determinadas por ensaios de proliferação...

Caracterização da insensibilidade ao fator de crescimento insulina-símile tipo 1 em pacientes com defeitos no receptor tipo 1 de IGFs (IGF-1R); Characterization of an insensitivity to type 1 insulin-like growth factor in patients with defects in the type 1 IGF receptor (IGF-1R)

Leal, Andréa de Castro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/09/2012 PT
Relevância na Pesquisa
86.09%
Introdução: Crianças nascidas pequenas para a idade gestacional (PIG) apresentam maior risco de permanecerem com baixa estatura na vida adulta. Os fatores de crescimento insulino-símile tipo 1 e 2 (IGF-1 e IGF-2) são os principais fatores endócrinos determinantes do crescimento fetal. A maioria das ações conhecidas destes hormônios é mediada via um receptor tirosina quinase, conhecido como IGF-1R. As mutações inativadoras e deleções do gene do IGF1R em heterozigose vêm sendo relatadas de forma crescente nos últimos 9 anos em pacientes com história de déficit de crescimento pré e pós-natal. Postula-se que pelo menos 2 a 3% das crianças nascidas PIG poderiam apresentar defeitos no IGF1R. O quadro clínico destes pacientes apresenta grande variabilidade quanto à gravidade do retardo de crescimento pré- e pós-natal e aos parâmetros hormonais. Objetivo: Caracterizar in vitro a resistência ao IGF-1 de pacientes com defeitos no IGF1R, identificados em nosso ambulatório. Material e métodos: Desenvolvemos cultura de fibroblastos de 2 controles (C1 e C2) e de 4 pacientes nascidos PIG (SGA1, SGA2, SGA3 e SGA4) com suspeita de insensibilidade ao IGF-1 por ausência de recuperação do crescimento na vida pós natal. Destes pacientes...

Análise da expressão e do silenciamento do receptor tipo 1 do fator de crescimento semelhante à insulina em tumores adrenocorticais humanos; Analysis of expression and silencing of insulin-like growth factor 1 receptor in human adrenocortical tumors

Ribeiro, Tamaya Castro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/01/2015 PT
Relevância na Pesquisa
66%
Introdução O sistema dos fatores de crescimento semelhantes à insulina (IGF) desempenha importante papel no crescimento e desenvolvimento celular normal. Hiperexpressão do gene IGF1R tem sido demonstrada em diversos tumores, sugerindo que a expressão deste receptor represente um pré-requisito fundamental para transformação celular. Nosso grupo de pesquisa demonstrou o aumento de expressão de IGF1R em tumores adrenocorticais pediátricos. Objetivos: Induzir o silenciamento do gene IGF1R por siRNA na linhagem de tumor adrenocortical humano NCI H295R, bem como avaliar os efeitos in vitro por meio da análise de proliferação celular e apoptose desta linhagem celular. Adicionalmente, avaliar a expressão de IGF-1R e de microRNAs relacionados a sua transcrição em tumores adrenocorticais humanos. Pacientes e métodos: A linhagem celular de carcinoma adrenocortical humano NCI H295R foi cultivada e submetida ao tratamento com 2 siRNAs específicos para IGF-1R. Todos os experimentos foram realizados em quatro grupos: (1) células não tratadas com siRNA, (2) células tratadas com siRNA # 1, (3) células tratadas com siRNA # 2 e (4) células tratadas com o siRNA controle negativo. A expressão gênica e proteica de IGF-1R foram determinadas por meio das técnicas de PCR em tempo real e Western Blot...

Decreased IGF Type 1 Receptor Signaling in Mammary Epithelium during Pregnancy Leads to Reduced Proliferation, Alveolar Differentiation, and Expression of Insulin Receptor Substrate (IRS)-1 and IRS-2

Sun, Zhaoyu; Shushanov, Sain; LeRoith, Derek; Wood, Teresa L.
Fonte: Endocrine Society Publicador: Endocrine Society
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
65.98%
The IGFs and the IGF type 1 receptor (IGF-1R) are essential mediators of normal mammary gland development in mice. IGF-I and the IGF-1R have demonstrated functions in formation and proliferation of terminal end buds and in ductal outgrowth and branching during puberty. To study the functions of IGF-1R during pregnancy and lactation, we established transgenic mouse lines expressing a human dominant-negative kinase dead IGF-1R (dnhIGF-1R) under the control of the whey acidic protein promoter. We provide evidence that the IGF-1R pathway is necessary for normal epithelial proliferation and alveolar formation during pregnancy. Furthermore, we demonstrate that the whey acidic protein-dnhIGF-1R transgene causes a delay in alveolar differentiation including lipid droplet formation, lumen expansion, and β-casein protein expression. Analysis of IGF-1R signaling pathways showed a decrease in P-IGF-1R and P-Akt resulting from expression of the dnhIGF-1R. We further demonstrate that disruption of the IGF-1R decreases mammary epithelial cell expression of the signaling intermediates insulin receptor substrate (IRS)-1 and IRS-2. No alterations were observed in downstream signaling targets of prolactin and progesterone, suggesting that activation of the IGF-1R may directly regulate expression of IRS-1/2 during alveolar development and differentiation. These data show that IGF-1R signaling is necessary for normal alveolar proliferation and differentiation...

Production and characterization of monoclonal antibodies against insulin-like growth factor type 1 receptor

Keyhanfar, M.; Forbes, B.; Cosgrove, L.; Wallace, J.; Booker, G.
Fonte: Mary Ann Liebert, Inc. Publishers Publicador: Mary Ann Liebert, Inc. Publishers
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
86.03%
The type 1 insulin-like growth factor receptor (IGF-1R) has been extensively reported to play an important role in cancer. Activation of the IGF-1R by IGF-I and IGF-II binding to the extracellular domains of the receptor induces mitogenic and anti-apoptotic effects, which are important events in tumor growth and survival. Several cancer cell types overexpress IGF-1R, suggesting a possible use of monoclonal antibodies (MAbs) against IGF-1R as diagnostic reagents. Here, we report the production and characterization of two independent MAbs, namely 7C2 and 9E11, generated by immunizing mice with the soluble extracellular part of this receptor (amino acids 1-906). Both MAbs bind to membrane bound IGF-1R and do not cross-react with insulin receptor isoforms, IR-A and IR-B expressed on IGF-1R() cells. MAbs 7C2 and 9E11 stained the IGF- 1R on frozen or paraffin-embedded tissue sections or frozen cells. The MAbs 7C2 and 9E11 immunoprecipitated the IGF-1R from P6 cell lysates (cells overexpressing human IGF-1R) and could detect non-reduced intact IGF-1R on immunoblots. However, the MAbs were not able to detect reduced and denatured receptor alpha and beta chains. Sequencing of the heavy- and light-chain variable regions revealed that the 7C2 and 9E11 CDR amino acid sequences are different but result in antibodies with similar properties. MAbs 7C2 and 9E11 are therefore potentially useful diagnostic tools and could be of therapeutic use for humans in the future.; http://www.liebertonline.com/doi/abs/10.1089/hyb.2006.25.230; Mehrnaz Keyhanfar...

Structural and functional characteristics of the Val44Met insulin-like growth factor I missense mutation: Correlation with effects on growth and development

Denley, A.; Wang, C.; McNeil, K.; Walenkamp, M.; van Duyvenvoorde, H.; Wit, J.; Wallace, J.; Norton, R.; Karperien, M.; Forbes, B.
Fonte: Endocrine Soc Publicador: Endocrine Soc
Tipo: Artigo de Revista Científica
Publicado em //2005 EN
Relevância na Pesquisa
65.99%
We have previously described the phenotype resulting from a missense mutation in the IGF-I gene, which leads to expression of IGF-I with a methionine instead of a valine at position 44 (Val44Met IGF-I). This mutation caused severe growth and mental retardation as well as deafness evident at birth and growth retardation in childhood, but is relatively well tolerated in adulthood. We have conducted a biochemical and structural analysis of Val44Met IGF-I to provide a molecular basis for the phenotype observed. Val44Met IGF-I exhibits a 90-fold decrease in type 1 IGF receptor (IGF-1R) binding compared with wild-type human IGF-I and only poorly stimulates autophosphorylation of the IGF-1R. The ability of Val44Met IGF-I to signal via the extracellular signal-regulated kinase 1/2 and Akt/protein kinase B pathways and to stimulate DNA synthesis is correspondingly poorer. Binding or activation of both insulin receptor isoforms is not detectable even at micromolar concentrations. However, Val44Met IGF-I binds IGF-binding protein-2 (IGFBP-2), IGFBP-3, and IGFBP-6 with equal affinity to IGF-I, suggesting the maintenance of overall structure, particularly in the IGFBP binding domain. Structural analysis by nuclear magnetic resonance confirms retention of near-native structure with only local side-chain disruptions despite the significant loss of function. To our knowledge...

Transactivation of CXCR4 by the insulin-like growth factor-1 receptor (IGF-1R) in human MDA-MB-231 breast cancer epithelial cells

Akekawatchai, C.; Holland, J.; Kochetkova, M.; Wallace, J.; McColl, S.
Fonte: Amer Soc Biochemistry Molecular Biology Inc Publicador: Amer Soc Biochemistry Molecular Biology Inc
Tipo: Artigo de Revista Científica
Publicado em //2005 EN
Relevância na Pesquisa
75.94%
In the multimolecular environment in tissues and organs, crosstalk between growth factor and G protein-coupled receptors is likely to play an important role in both normal and pathological responses. In this report, we demonstrate transactivation of the chemokine receptor CXCR4 by the growth factor insulin-like growth factor (IGF)-1 is required for IGF-1-induced cell migration in metastatic MDA-MB-231 cells. The induction of chemotaxis in MDAMB- 231 cells by IGF-1 was inhibited by pretreatment of the cells with pertussis toxin (PTX) and by RNAi-mediated knockdown of CXCR4. Transactivation of the CXCR4 pathway by IGF-1 occurred independently of CXCL12, the chemokine ligand of CXCR4. Neither CXCR4 knockdown nor PTX had any effect on the ability of IGF-1 to activate IGF-1R, suggesting thatCXCR4andGproteins are activated subsequent to, or independently of, phosphorylation of IGF-1R by IGF-1. Coprecipitation studies revealed the presence of a constitutive complex containing IGF-1R, CXCR4, and theGprotein subunits, Giα2 and Gß, and stimulation of MDA-MB-231 cells with IGF-1 led to the release of Giα2 and Gß from CXCR4. Based on our findings, we propose that CXCR4 constitutively forms a complex with IGF-1R in MDA-MB-231 cells, and that this interaction allows IGF-1 to activate migrational signaling pathways through CXCR4...

Contribution of residues A54 and L55 of the human insulin-like growth factor-II (IGF-II) A domain to Type 2 IGF receptor binding specificity

Forbes, B.; McNeil, K.; Scott, C.; Surinya, K.; Cosgrove, L.; Wallace, J.
Fonte: Harwood Acad Publ GMBH Publicador: Harwood Acad Publ GMBH
Tipo: Artigo de Revista Científica
Publicado em //2001 EN
Relevância na Pesquisa
66%
The underlying specificity of the interaction between insulin-like growth factor-II (IGF-II) and mammalian Type 2 insulin-like growth factor/cation-independent mannose 6 phosphate receptor (IGF2R) is not understood. We have mutated residues A54 and L55 of IGF-II in the second A domain helix to arginine (found in the corresponding positions of IGF-I) and measured IGF2R binding. There is a 4- and 3.3-fold difference in dissociation constants for A54R IGF-II and L55R IGF-II, respectively, and a 6.6-fold difference for A54R L55R IGF-II compared with IGF-II as measured by BlAcore analysis using purified rat IGF2R. This is also confirmed using cross-linking and soluble rat placental membrane receptor binding assays. Binding to the type I IGF receptor (IGF1R) and IGF binding protein-2 (IGFBP-2) is not altered. We can, therefore, conclude that residues at positions 54 and 55 in IGF-II are important for and equally contribute to IGF2R binding.

Precise mapping of an IGF-I-binding site on the IGF-1R

Keyhanfar, M.; Booker, G.; Whittaker, J.; Wallace, J.; Forbes, B.
Fonte: Portland Press Publicador: Portland Press
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
65.99%
The IGF-1R [type 1 IGF (insulin-like growth factor) receptor] is activated upon binding to IGF-I and IGF-II leading to cell growth, survival and migration of both normal and cancerous cells. We have characterized the binding interaction between the IGF-1R and its ligands using two high-affinity mouse anti-IGF-1R mAbs (monoclonal antibodies), 7C2 and 9E11. These mAbs both block IGF-I binding to the IGF-1R but have no effect on IGF-II binding. Epitope mapping using chimaeras of the IGF-1R and insulin receptor revealed that the mAbs bind to the CR (cysteine-rich) domain of IGF-1R. The epitope was finely mapped using single point mutations in the IGF-1R. Mutation of Phe241, Phe251 or Phe266 completely abolished 7C2 and 9E11 binding. The three-dimensional structure showed that these residues cluster on the surface of the CR-domain. BIAcore analyses revealed that IGF-I and a chimaeric IGF-II with the IGF-I C-domain competed for the binding of both mAbs with the IGF-1R, whereas neither IGF-II nor a chimaeric IGF-I with the IGF-II C-domain affected antibody binding. We therefore conclude the IGF-I C-domain interacts with the CR (cysteine-rich) domain of the receptor at the cluster of residues Phe241, Phe251 and Phe266. These results allow precise orientation of IGF-I within the IGF-I–IGF-1R complex involving the IGF-I C-domain binding to the IGF-1R CR domain. In addition...

An investigation of the ligand binding properties and negative cooperatively of soluble insulin-like growth factor receptors

Surinya, K.; Forbes, B.; Occhiodoro, F.; Booker, G.; Francis, G.; Siddle, K.; Wallace, J.; Cosgrove, L.
Fonte: Amer Soc Biochemistry Molecular Biology Inc Publicador: Amer Soc Biochemistry Molecular Biology Inc
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
66.02%
To investigate the interaction of the insulin-like growth factor (IGF) ligands with the insulin-like growth factor type 1 receptor (IGF-1R), we have generated two soluble variants of the IGF-1R. We have recombinantly expressed the ectodomain of IGF-1R or fused this domain to the constant domain from the Fc fragment of mouse immunoglobulin. The ligand binding properties of these soluble IGF-1Rs for IGF-I and IGF-II were investigated using conventional ligand competition assays and BIAcore biosensor technology. In ligand competition assays, the soluble IGF-1Rs both bound IGF-I with similar affinities and a 5-fold lower affinity than that seen for the wild type receptor. In addition, both soluble receptors bound IGF-II with similar affinities to the wild type receptor. BIAcore analyses showed that both soluble IGF-1Rs exhibited similar ligand-specific association and dissociation rates for IGF-I and for IGF-II. The soluble IGF-1R proteins both exhibited negative cooperativity for IGF-I, IGF-II, and the 24-60 antibody, which binds to the IGF-1R cysteine-rich domain. We conclude that the addition of the self-associating Fc domain to the IGF-1R ectodomain does not affect ligand binding affinity, which is in contrast to the soluble ectodomain of the IR. This study highlights some significant differences in ligand binding modes between the IGF-1R and the insulin receptor...

Differential activation of insulin receptor substrates 1 and 2 by insulin-like growth factor-activated insulin receptors

Denley, A.; Carroll, J.; Brierley, G.; Cosgrove, L.; Wallace, J.; Forbes, B.; Roberts, C.
Fonte: Amer Soc Microbiology Publicador: Amer Soc Microbiology
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
75.95%
The insulin-like growth factors (insulin-like growth factor I [IGF-I] and IGF-II) exert important effects on growth, development, and differentiation through the IGF-I receptor (IGF-IR) transmembrane tyrosine kinase. The insulin receptor (IR) is structurally related to the IGF-IR, and at high concentrations, the IGFs can also activate the IR, in spite of their generally low affinity for the latter. Two mechanisms that facilitate cross talk between the IGF ligands and the IR at physiological concentrations have been described. The first of these is the existence of an alternatively spliced IR variant that exhibits high affinity for IGF-II as well as for insulin. A second phenomenon is the ability of hybrid receptors comprised of IGF-IR and IR hemireceptors to bind IGFs, but not insulin. To date, however, direct activation of an IR holoreceptor by IGF-I at physiological levels has not been demonstrated. We have now found that IGF-I can function through both splice variants of the IR, in spite of low affinity, to specifically activate IRS-2 to levels similar to those seen with equivalent concentrations of insulin or IGF-II. The specific activation of IRS-2 by IGF-I through the IR does not result in activation of the extracellular signal-regulated kinase pathway but does induce delayed low-level activation of the phosphatidylinositol 3-kinase pathway and biological effects such as enhanced cell viability and protection from apoptosis. These findings suggest that IGF-I can function directly through the IR and that the observed effects of IGF-I on insulin sensitivity may be the result of direct facilitation of insulin action by IGF-I costimulation of the IR in insulin target tissues.; Adam Denley...

Alanine scanning of a putative receptor binding surface of insulin-like growth factor-I

Gauguin, L.; Delaine, C.; Alvino, C.; McNeil, K.; Wallace, J.; Forbes, B.; De Meyts, P.
Fonte: Amer Soc Biochemistry Molecular Biology Inc Publicador: Amer Soc Biochemistry Molecular Biology Inc
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
65.99%
Current evidence supports a binding model in which the insulin molecule contains two binding surfaces, site 1 and site 2, which contact the two halves of the insulin receptor. The interaction of these two surfaces with the insulin receptor results in a high affinity cross-linking of the two receptor alpha subunits and leads to receptor activation. Evidence suggests that insulin-like growth factor-I (IGF-I) may activate the IGF-I receptor in a similar mode. So far IGF-I residues structurally corresponding to the residues of the insulin site 1 together with residues in the C-domain of IGF-I have been found to be important for binding of IGF-I to the IGF-I receptor (e.g. Phe(23), Tyr(24), Tyr(31), Arg(36), Arg(37), Val(44), Tyr(60), and Ala(62)). However, an IGF-I second binding surface similar to site 2 of insulin has not been identified yet. In this study, we have analyzed whether IGF-I residues corresponding to the six residues of the insulin site 2 have a role in high affinity binding of IGF-I to the IGF-I receptor. Six single-substituted IGF-I analogues were produced, each containing an alanine substitution in one of the following positions (corresponding insulin residues in parentheses): Glu(9) (His(B10)), Asp(12) (Glu(B13)), Phe(16) (Leu(B17))...

Keeping IGF-II under control: Lessons from the IGF-II-IGF2R crystal structure

Brown, J.; Jones, E.; Forbes, B.
Fonte: Elsevier Science London Publicador: Elsevier Science London
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
65.96%
Insulin-like growth factor-II (IGF-II) is a key regulator of cell growth, survival, migration and differentiation. Its pivotal role in these processes requires tight regulation of both expression and activity. The type 1 IGF receptor tyrosine kinase (IGF-1R) mediates IGF-II actions, and a family of six high affinity IGF binding proteins (IGFBPs) regulates IGF-II circulating half-life and its availability to bind IGF-1R. In addition, the type 2 IGF receptor (IGF2R; also called the cation-independent mannose-6-phosphate receptor) modulates the circulating and tissue levels of IGF-II by targeting it to lysosomes for degradation. The recently elucidated crystal structure of IGFII– IGF2R complex provides new insight into IGF-II regulation, and reveals a common binding surface on IGF-II for the regulatory proteins, IGF2R and the IGFBPs.; James Brown, E. Yvonne Jones and Briony E. Forbes

Silencing of the insulin receptor isoform A favors formation of type 1 insulin-like growth factor receptor (IGF-IR) homodimers and enhances ligand-induced IGF-IR activation and viability of human colon carcinoma cells

Brierley, G.; Macaulay, S.; Forbes, B.; Wallace, J.; Cosgrove, L.; Macaulay, V.
Fonte: Endocrine Soc Publicador: Endocrine Soc
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
86.04%
Insulin receptor (IR) overexpression is common in cancers, with expression of the A isoform (IR-A, exon 11–) predominating over the B isoform. The IR-A signals a proliferative, antiapoptotic response to IGF-II, which itself can be secreted by tumors to establish an autocrine proliferative loop. Therefore, IGF-II signaling via the IR-A could mediate resistance to type 1 IGF receptor (IGF-IR) inhibitory drugs that are currently in development. This study addressed the role of the IR-A, using a small interfering RNA-based approach in SW480 human colon adenocarcinoma cells that coexpress the IGF-IR. Clonogenic survival was inhibited by depletion of the IGF-IR but not the IR-A, and dual receptor depletion had no greater effect than IGF-IR knockdown alone, suggesting that the IR-A could not compensate for IGF-IR loss. IGF-IR knockdown also resulted in a decrease in viability, whereas IR-A depletion resulted in increased viability. Consistent with this, upon IR-A depletion, we found a concomitant enhancement of IGF-IR activation by IGF-I and IGF-II, reduced formation of IGF-IR:IR-A hybrid receptors and increased IGF-IR homodimer formation. Together, these results suggest that IGF bioactivity is mediated more effectively by the IGF-IR than by the IR-A or receptor hybrids and that signaling via the IGF-IR is dominant to the IR-A in colon cancer cells that express both receptors.; G.V. Brierley...

Understanding the mechanism of insulin and insulin-like growth factor (IGF) receptor activation by IGF-II

Alvino, C.; Ong, S.; McNeil, K.; Delaine, C.; Booker, G.; Wallace, J.; Forbes, B.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
75.96%
Background: Insulin-like growth factor-II (IGF-II) promotes cell proliferation and survival and plays an important role in normal fetal development and placental function. IGF-II binds both the insulin-like growth factor receptor (IGF-1R) and insulin receptor isoform A (IR-A) with high affinity. Interestingly both IGF-II and the IR-A are often upregulated in cancer and IGF-II acts via both receptors to promote cancer proliferation. There is relatively little known about the mechanism of ligand induced activation of the insulin (IR) and IGF-1R. The recently solved IR structure reveals a folded over dimer with two potential ligand binding pockets arising from residues on each receptor half. Site-directed mutagenesis has mapped receptor residues important for ligand binding to two separate sites within the ligand binding pocket and we have recently shown that the IGFs have two separate binding surfaces which interact with the receptor sites 1 and 2. Methodology/Principal Findings: In this study we describe a series of partial IGF-1R and IR agonists generated by mutating Glu12 of IGF-II. By comparing receptor binding affinities, abilities to induce negative cooperativity and potencies in receptor activation, we provide evidence that residue Glu12 bridges the two receptor halves leading to receptor activation. Conclusions/Significance: This study provides novel insight into the mechanism of receptor binding and activation by IGFII...

Molecular mechanisms underlying insulin-like growth factor action: How mutations in the GH: IGF axis lead to short stature

Forbes, B.
Fonte: YS Medical Media Ltd Publicador: YS Medical Media Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
75.99%
Insulin-like growth factors (IGFs) act via the Type 1 IGF receptor (IGF-1R) to promote growth and development. Recent structural and site-directed mutagenesis studies have provided detailed insight into the mechanism of interaction between the IGFs and the IGF-IR. Studies of the insulin: insulin receptor interaction have provided important additional understanding of the mechanisms underlying the IGF:IGF-1R interaction. The recent crystal structure of the insulin receptor ectodomain showed a folded over conformation accommodating two potential ligand binding pockets. The ligand interacts with the receptor at two different sites within a binding pocket to achieve high affinity binding and activation of the receptor. In this review the effect of mutations in the human IGF1 and IGF-1R genes so for reported are explained in terms of the effect on ligand binding and receptor activation. The severity of patient phenotype can generally be correlated to the effect of the mutation on protein structure and function.; B. E. Forbes

Maternal dietary restriction during the periconceptional period in normal-weight or obese ewes results in adrenocortical hypertrophy, an up-regulation of the JAK/STAT and down-regulation of the IGF1R signaling pathways in the adrenal of the postnatal lamb

Zhang, S.; Morrison, J.; Gill, A.; Rattanatray, L.; MacLaughlin, S.; Kleemann, D.; Walker, S.; McMillen, I.
Fonte: Endocrine Soc Publicador: Endocrine Soc
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
65.94%
Maternal dietary restriction during the periconceptional period results in an increase in adrenal growth and in the cortisol stress response in the offspring. The intraadrenal mechanisms that result in the programming of these changes are not clear. Activation of the IGF and the signal transducer and activator of transcription (STAT)/suppressors of cytokine signaling (SOCS) pathways regulate adrenal growth. We have used an embryo transfer model in sheep to investigate the impact of exposure to either dietary restriction in normal or obese mothers or to maternal obesity during the periconceptional period on adrenal growth and function in the offspring. We assessed the adrenal abundance of key signaling molecules in the IGF-I and Janus kinase/STAT/SOCS pathways including IGF-I receptor, IGF-II receptor, Akt, mammalian target of rapamycin, ribosomal protein S6, eukaryotic translation initiation factor 4E-binding protein 1, eukaryotic translation initiation factor 4E, STAT1, STAT3, STAT5, SOCS1, and SOCS3 in female and male postnatal lambs. Maternal dietary restriction in the periconceptional period resulted in the hypertrophy of the adrenocortical cells in the zona fasciculata-reticularis and an up-regulation in STAT1, phospho-STAT1, and phospho-STAT3 (Ser727) abundance and a down-regulation in IGF-I receptor...

Co-Inhibition von epidermal growth factor receptor (EGFR) und insulin-like growth factor-I receptor (IGF-IR): Ein neuer Ansatz für die Reduktion der Zelltodresistenz humaner maligner Gliomzellen; Co-inhibition of epidermal growth factor receptor and type 1 insulin-like growth factor receptor: a new approach in reducing of restistance to apoptosis of human malignant glioma cells

Eisenmann, Christine
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
DE_DE
Relevância na Pesquisa
75.99%
In der vorliegenden Arbeit wurde zunächst der Effekt der Wachstumsfaktoren EGF, IGF-I, FGF-I und PDGF auf Wachstum und Überleben von zwölf humanen malignen Glioblastomzellinien bei Serumentzug untersucht. Dabei wurden bei den einzelnen Zelllinien unterschiedliche Abhängigkeit von individuellen Wachstumsfaktoren beobachtet, die als eine Art 'molekulare Signatur' Hinweise auf die Relevanz der zugehörigen Rezeptortyrosinkinase gelten können. Die Charakterisierung der Effekte einer Co-Inhibition von EGFR und IGF-IR auf den CD95L-induzierten Zelltod war der zentrale Bestandteil dieser Arbeit. Dabei konnte zunächst eine synergistische Sensitivierung gegenüber CD95 durch die Co-Inhibition bei den p53-Wildtyp-Zelllinien LNT-229 und U87MG nachgewiesen werden, nicht jedoch bei den p53-mutanten Zelllinien LN-18 und T98G. Experimente mit dem temperatursensitiven p53val135A zeigten jedoch, dass der sensitivierende Effekt der Co-Inhibition nicht p53-abhängig ist. Der Typ des durch die Co-Inhibition fazilitierten Zelltods war apoptotisch und begleitet von einer crmA-sensitiven Aktivierung von Caspase 8, den Effektorcaspasen 3 und 7, und dem Caspasesubstrat PARP. Da ein Effekt der Co-Inhibition auf das Expressionsniveau von CD95 ausgeschlossen wurde...

A Novel Approach to Identify Two Distinct Receptor Binding Surfaces of Insulin-like Growth Factor II

Alvino, C.; McNeil, K.; Ong, S.; Delaine, C.; Booker, G.; Wallace, J.; Whittaker, J.; Forbes, B.
Fonte: Amer Soc Biochemistry Molecular Biology Inc Publicador: Amer Soc Biochemistry Molecular Biology Inc
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
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Very little is known about the residues important for the interaction of insulin-like growth factor II (IGF-II) with the type 1 IGF receptor (IGF-1R) and the insulin receptor (IR). Insulin, to which IGF-II is homologous, is proposed to cross-link opposite halves of the IR dimer through two receptor binding surfaces, site 1 and site 2. In the present study we have analyzed the contribution of IGF-II residues equivalent to insulin's two binding surfaces toward the interaction of IGF-II with the IGF-1R and IR. Four "site 1" and six "site 2" analogues were produced and analyzed in terms of IGF-1R and IR binding and activation. The results show that Val(43), Phe(28), and Val(14) (equivalent to site 1) are critical to IGF-1R and IR binding, whereas mutation to alanine of Gln(18) affects only IGF-1R and not IR binding. Alanine substitutions at Glu(12), Asp(15), Phe(19), Leu(53), and Glu(57) analogues resulted in significant (>2-fold) decreases in affinity for both the IGF-1R and IR. Furthermore, taking a novel approach using a monomeric, single-chain minimized IGF-1R we have defined a distinct second binding surface formed by Glu(12), Phe(19), Leu(53), and Glu(57) that potentially engages the IGF-1R at one or more of the FnIII domains.; Clair L. Alvino...