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OL Posttranscriptional regulation of the insulin and IGF system
Growth Hormone & IGF Research 22S1 (2012) S1–S31
Contents lists available at SciVerse ScienceDirect
Growth Hormone & IGF Research journal homepage: www.elsevier.com/locate/ghir
Oral Presentations
Wednesday, 17 October 2012 OL Posttranscriptional regulation of the insulin and IGF system M. Gorospe1 . 1 Laboratory of Molecular Biology and Immunology, Baltimore, MD, United States Insulin and IGFs regulate glucose homeostasis. Acute and long-term alterations in glucose levels trigger changes in the concentration of insulin and IGF and modulate insulin and IGF signaling pathways. These processes are tightly regulated by posttranscriptional mechanisms that alter the stability and translation of mRNAs encoding insulin, IGF, and their receptors. The half-life and translation of mRNAs are governed by RNA-binding proteins and noncoding RNAs that interact with target mRNAs. RNA-binding proteins and microRNAs associate with mRNAs encoding insulin, IGFs, and their receptors in order to elicit timely, versatile, and tissue-specific changes in insulin and IGF function. To illustrate these regulatory events, I will discuss the recent discovery of HuD as an RNA-binding protein expressed in pancreatic b cells under control by the insulin receptor signaling pathway [1]. In mouse b cells, HuD associated with the 5 -untranslated region of preproinsulin (Ins2) mRNA and modulated HuD abundance without altering Ins2 mRNA levels. Specifically, HuD was found to repress Ins2 mRNA translation and insulin production. Following treatment with glucose, HuD rapidly dissociated from Ins2 mRNA and enabled insulin biosynthesis. Importantly, HuD knockout mice displayed higher insulin levels in pancreatic islets, while HuD-overexpressing mice exhibited lower levels of insulin in islets and in plasma. The identification of HuD as a key regulator of insulin translation in pancreatic b cells underscores the role of mRNA-binding factors in the control of glucose metabolism. Reference(s) [1] Lee, E.K., Kim, W., Tominaga, K., Martindale, J.L., Yang, X., Subaran, S.S., Carlson, O.D., Kulkarni, R. Akamatsu, W., Okano, H., PerroneBizzozero, N.I., de Cabo, R., Egan, J.M., and Gorospe, M.: RNA-binding protein HuD controls insulin translation. Molecular Cell 45(6): 826–35 (2012).
Thursday, 18 October 2012 PL01 Two years in GH K. Ho No abstract available. PL02 IGF receptor signalling and regulation in cancer R. O’Connor. Department of Biochemistry, University College Cork, Cork, Ireland The C terminal tail of the IGF-1R is only 48% similar to the Insulin Receptor and may mediate key differences in regulation and function between these two highly conserved Receptor Tyrosine 1096-6374/$ - see front matter © 2012 Elsevier Ltd. All rights reserved.
Kinases. This domain is essential for cooperation of IGF-1 signalling with adhesion and GPCR signalling in cancer cells and also participates in regulating receptor kinase activity, trafficking and degradation. In particular, mutation of the 1248-SFYYS-1252 motif has a profound impact on receptor tyrosine kinase activity, signalling, and trafficking. Crystallographic structures of the IGF-1R kinase domain demonstrate that the 1248-SFYYS-1252 motif is tightly packed against the kinase C-lobe, and this interaction would be modified by phosphorylation of either serine or tyrosine residues. However the phosphorylation status and mechanisms of action of this motif are poorly understood. To address this we have begun to investigate the phosphorylation, cellular kinases, interacting proteins and effects on IGF-1R kinase activity and signalling associated with the serine and tyrosine residues within the 1248-SFYYS-1252 motif.
OR01: GH secretion and excess OR01-1 Early postnatal nutrition programs the somatotropic axis through epigenetic mechanism L. Kappeler1,2 , E.C. Cottrell3 , A. Dahan1 , I. Hellstrom2 , C. Caldji2 , T. Zhang2 , J. Diorio2 , J.R. Seckl3 , Y. Le Bouc1 , M.J. Meaney2,4 . 1 Inserm, Centre De Recherche St Antoine, Paris, France; 2 Sackler Program for Epigenetics & Psychobiology of McGill University, Douglas Mental health Institute, Montr´eal, Canada; 3 Endocrinology Unit, the Queen’s Medical Research Institute, Edinburgh, United Kingdom; 4 Singapore Institute for Clinical Sciences, Singapore, Singapore Our previous findings suggest that differential activation of the IGF-1R programs the activity of GH secretion in adulthood. Such studies have used a transgenic mouse model carrying a brain specific igf-1r knockout, or a physiological one experiencing a decrease of circulating IGF-I by a transient decrease of nutrition during the early postnatal period. We studied GHRH and somatostatin (SRIH) neurons that demonstrate a persistent alteration in our models to determine molecular mechanisms involved in the programming of the GH axis activity. Effects occurring at the transcriptional level strongly suggest epigenetic influences in programming neuronal expression with changes of histones marks and DNA methylation. Accordingly, ChIP against histone H3 acetylated on the lysine 9 (H3K9ac) or histone H4 monomethylated on the lysine 20 (H4K20me1) highlight increased enrichment of the srih promoter in adult mice previously restricted during early postnatal period as compared with control. These changes are associated with a decreased frequency of cytosine methylation in the CpG island present in the srih promoter and correlate well with the persistent increased transcription. In contrast, no modifications were observed in the promoter of GHRH. We infused epigenetic modifiers intracerebroventrically (icv) for 14 days in order to understand implication of epigenetic mechanisms in the control of SRIH and GHRH expression. Icv infusion of deacetylase inhibitor Trichostatin A (TSA) in adult control mice was performed to mimic the restricted phenotype regarding epigenetic status. In agreement with our hypothesis, control mice infused with TSA show increased association of H3K9ac and H4K20me1 with the srih promoter. In contrast, restricted mice icv-infused with the
Contents lists available at SciVerse ScienceDirect
Growth Hormone & IGF Research journal homepage: www.elsevier.com/locate/ghir
Oral Presentations
Wednesday, 17 October 2012 OL Posttranscriptional regulation of the insulin and IGF system M. Gorospe1 . 1 Laboratory of Molecular Biology and Immunology, Baltimore, MD, United States Insulin and IGFs regulate glucose homeostasis. Acute and long-term alterations in glucose levels trigger changes in the concentration of insulin and IGF and modulate insulin and IGF signaling pathways. These processes are tightly regulated by posttranscriptional mechanisms that alter the stability and translation of mRNAs encoding insulin, IGF, and their receptors. The half-life and translation of mRNAs are governed by RNA-binding proteins and noncoding RNAs that interact with target mRNAs. RNA-binding proteins and microRNAs associate with mRNAs encoding insulin, IGFs, and their receptors in order to elicit timely, versatile, and tissue-specific changes in insulin and IGF function. To illustrate these regulatory events, I will discuss the recent discovery of HuD as an RNA-binding protein expressed in pancreatic b cells under control by the insulin receptor signaling pathway [1]. In mouse b cells, HuD associated with the 5 -untranslated region of preproinsulin (Ins2) mRNA and modulated HuD abundance without altering Ins2 mRNA levels. Specifically, HuD was found to repress Ins2 mRNA translation and insulin production. Following treatment with glucose, HuD rapidly dissociated from Ins2 mRNA and enabled insulin biosynthesis. Importantly, HuD knockout mice displayed higher insulin levels in pancreatic islets, while HuD-overexpressing mice exhibited lower levels of insulin in islets and in plasma. The identification of HuD as a key regulator of insulin translation in pancreatic b cells underscores the role of mRNA-binding factors in the control of glucose metabolism. Reference(s) [1] Lee, E.K., Kim, W., Tominaga, K., Martindale, J.L., Yang, X., Subaran, S.S., Carlson, O.D., Kulkarni, R. Akamatsu, W., Okano, H., PerroneBizzozero, N.I., de Cabo, R., Egan, J.M., and Gorospe, M.: RNA-binding protein HuD controls insulin translation. Molecular Cell 45(6): 826–35 (2012).
Thursday, 18 October 2012 PL01 Two years in GH K. Ho No abstract available. PL02 IGF receptor signalling and regulation in cancer R. O’Connor. Department of Biochemistry, University College Cork, Cork, Ireland The C terminal tail of the IGF-1R is only 48% similar to the Insulin Receptor and may mediate key differences in regulation and function between these two highly conserved Receptor Tyrosine 1096-6374/$ - see front matter © 2012 Elsevier Ltd. All rights reserved.
Kinases. This domain is essential for cooperation of IGF-1 signalling with adhesion and GPCR signalling in cancer cells and also participates in regulating receptor kinase activity, trafficking and degradation. In particular, mutation of the 1248-SFYYS-1252 motif has a profound impact on receptor tyrosine kinase activity, signalling, and trafficking. Crystallographic structures of the IGF-1R kinase domain demonstrate that the 1248-SFYYS-1252 motif is tightly packed against the kinase C-lobe, and this interaction would be modified by phosphorylation of either serine or tyrosine residues. However the phosphorylation status and mechanisms of action of this motif are poorly understood. To address this we have begun to investigate the phosphorylation, cellular kinases, interacting proteins and effects on IGF-1R kinase activity and signalling associated with the serine and tyrosine residues within the 1248-SFYYS-1252 motif.
OR01: GH secretion and excess OR01-1 Early postnatal nutrition programs the somatotropic axis through epigenetic mechanism L. Kappeler1,2 , E.C. Cottrell3 , A. Dahan1 , I. Hellstrom2 , C. Caldji2 , T. Zhang2 , J. Diorio2 , J.R. Seckl3 , Y. Le Bouc1 , M.J. Meaney2,4 . 1 Inserm, Centre De Recherche St Antoine, Paris, France; 2 Sackler Program for Epigenetics & Psychobiology of McGill University, Douglas Mental health Institute, Montr´eal, Canada; 3 Endocrinology Unit, the Queen’s Medical Research Institute, Edinburgh, United Kingdom; 4 Singapore Institute for Clinical Sciences, Singapore, Singapore Our previous findings suggest that differential activation of the IGF-1R programs the activity of GH secretion in adulthood. Such studies have used a transgenic mouse model carrying a brain specific igf-1r knockout, or a physiological one experiencing a decrease of circulating IGF-I by a transient decrease of nutrition during the early postnatal period. We studied GHRH and somatostatin (SRIH) neurons that demonstrate a persistent alteration in our models to determine molecular mechanisms involved in the programming of the GH axis activity. Effects occurring at the transcriptional level strongly suggest epigenetic influences in programming neuronal expression with changes of histones marks and DNA methylation. Accordingly, ChIP against histone H3 acetylated on the lysine 9 (H3K9ac) or histone H4 monomethylated on the lysine 20 (H4K20me1) highlight increased enrichment of the srih promoter in adult mice previously restricted during early postnatal period as compared with control. These changes are associated with a decreased frequency of cytosine methylation in the CpG island present in the srih promoter and correlate well with the persistent increased transcription. In contrast, no modifications were observed in the promoter of GHRH. We infused epigenetic modifiers intracerebroventrically (icv) for 14 days in order to understand implication of epigenetic mechanisms in the control of SRIH and GHRH expression. Icv infusion of deacetylase inhibitor Trichostatin A (TSA) in adult control mice was performed to mimic the restricted phenotype regarding epigenetic status. In agreement with our hypothesis, control mice infused with TSA show increased association of H3K9ac and H4K20me1 with the srih promoter. In contrast, restricted mice icv-infused with the