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Abstract
Non-communicable diseases, such as cardiovascular diseases, are the leading cause of mortality worldwide. For this reason, a tremendous effort is being made worldwide to effectively circumvent these afflictions, where insulin-like growth factor 1 (IGF1) is being proposed both as a marker and as a central cornerstone in these diseases, making it an interesting molecule to focus on. Firstly, at the initiation of metabolic deregulation by overfeeding, IGF1 is decreased/inhibited. Secondly, such deficiency seems to be intimately related to the onset of MetS and establishment of vascular derangements leading to atherosclerosis and finally playing a definitive part in cerebrovascular and myocardial accidents, where IGF1 deficiency seems to render these organs vulnerable to oxidative and apoptotic/necrotic damage. Several human cohort correlations together with basic/translational experimental data seem to confirm deep IGF1 implication, albeit with controversy, which might, in part, be given by experimental design leading to blurred result interpretation.
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Xu F, Takahashi H, Tanaka Y, Ichinose S, Niwa S, Wicklund MP, Hirokawa N. KIF1Bβ mutations detected in hereditary neuropathy impair IGF1R transport and axon growth. J Cell Biol 2018; 217:3480-3496. [PMID: 30126838 PMCID: PMC6168269 DOI: 10.1083/jcb.201801085] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Revised: 05/31/2018] [Accepted: 07/05/2018] [Indexed: 02/07/2023] Open
Abstract
Uncovering the mechanistic link between kinesin motors and neuropathy, Xu et al. identify functional KIF1Bβ mutations in human hereditary neuropathy to analyze them in mouse models. They propose that KIF1Bβ transports IGF1R and facilitates axonal outgrowth. Both of these effects are significantly affected by the clinical mutations. KIF1Bβ is a kinesin-3 family anterograde motor protein essential for neuronal development, viability, and function. KIF1Bβ mutations have previously been reported in a limited number of pedigrees of Charcot-Marie-Tooth disease type 2A (CMT2A) neuropathy. However, the gene responsible for CMT2A is still controversial, and the mechanism of pathogenesis remains elusive. In this study, we show that the receptor tyrosine kinase IGF1R is a new direct binding partner of KIF1Bβ, and its binding and transport is specifically impaired by the Y1087C mutation of KIF1Bβ, which we detected in hereditary neuropathic patients. The axonal outgrowth and IGF-I signaling of Kif1b−/− neurons were significantly impaired, consistent with decreased surface IGF1R expression. The complementary capacity of KIF1Bβ-Y1087C of these phenotypes was significantly impaired, but the binding capacity to synaptic vesicle precursors was not affected. These data have supported the relevance of KIF1Bβ in IGF1R transport, which may give new clue to the neuropathic pathogenesis.
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Affiliation(s)
- Fang Xu
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hironori Takahashi
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yosuke Tanaka
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Sotaro Ichinose
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Shinsuke Niwa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | | | - Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan .,Center of Excellence in Genome Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia
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Activation of insulin-like growth factor 1 receptor participates downstream of GPR30 in estradiol-17β-D-glucuronide-induced cholestasis in rats. Arch Toxicol 2017; 92:729-744. [PMID: 29090346 DOI: 10.1007/s00204-017-2098-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/17/2017] [Indexed: 01/01/2023]
Abstract
Estradiol-17β-D-glucuronide (E17G), through the activation of different signaling proteins, induces acute endocytic internalization of canalicular transporters in rat, including multidrug resistance-associated protein 2 (Abcc2) and bile salt export pump (Abcb11), generating cholestasis. Insulin-like growth factor 1 receptor (IGF-1R) is a membrane-bound tyrosine kinase receptor that can potentially interact with proteins activated by E17G. The aim of this study was to analyze the potential role of IGF-1R in the effects of E17G in isolated perfused rat liver (IPRL) and isolated rat hepatocyte couplets. In vitro, IGF-1R inhibition by tyrphostin AG1024 (TYR, 100 nM), or its knock-down with siRNA, strongly prevented E17G-induced impairment of Abcc2 and Abcb11 function and localization. The protection by TYR was not additive to that produced by wortmannin (PI3K inhibitor, 100 nM), and both protections share the same dependency on microtubule integrity, suggesting that IGF-1R shared the signaling pathway of PI3K/Akt. Further analysis of the activation of Akt and IGF-1R induced by E17G indicated a sequence of activation GPR30-IGF-1R-PI3K/Akt. In IPRL, an intraportal injection of E17G triggered endocytosis of Abcc2 and Abcb11, and this was accompanied by a sustained decrease in the bile flow and the biliary excretion of Abcc2 and Abcb11 substrates. TYR did not prevent the initial decay, but it greatly accelerated the recovery to normality of these parameters and the reinsertion of transporters into the canalicular membrane. In conclusion, the activation of IGF-1R is a key factor in the alteration of canalicular transporter function and localization induced by E17G, and its activation follows that of GPR30 and precedes that of PI3K/Akt.
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Partial IGF-1 deficiency is sufficient to reduce heart contractibility, angiotensin II sensibility, and alter gene expression of structural and functional cardiac proteins. PLoS One 2017; 12:e0181760. [PMID: 28806738 PMCID: PMC5555709 DOI: 10.1371/journal.pone.0181760] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 07/06/2017] [Indexed: 01/15/2023] Open
Abstract
Circulating levels of IGF-1 may decrease under several circumstances like ageing, metabolic syndrome, and advanced cirrhosis. This reduction is associated with insulin resistance, dyslipidemia, progression to type 2 diabetes, and increased risk for cardiovascular diseases. However, underlying mechanisms between IGF-1 deficiency and cardiovascular disease remain elusive. The specific aim of the present work was to study whether the partial IGF-1 deficiency influences heart and/or coronary circulation, comparing vasoactive factors before and after of ischemia-reperfusion (I/R). In addition, histology of the heart was performed together with cardiac gene expression for proteins involved in structure and function (extracellular matrix, contractile proteins, active peptides); carried out using microarrays, followed by RT-qPCR confirmation of the three experimental groups. IGF-1 partial deficiency is associated to a reduction in contractility and angiotensin II sensitivity, interstitial fibrosis as well as altered expression pattern of genes involved in extracellular matrix proteins, calcium dynamics, and cardiac structure and function. Although this work is descriptive, it provides a clear insight of the impact that partial IGF-1 deficiency on the heart and establishes this experimental model as suitable for studying cardiac disease mechanisms and exploring therapeutic options for patients under IGF-1 deficiency conditions.
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Hayashi H, Al Mamun A, Sakima M, Sato M. Activator of G-protein signaling 8 is involved in VEGF-mediated signal processing during angiogenesis. J Cell Sci 2016; 129:1210-22. [PMID: 26826188 DOI: 10.1242/jcs.181883] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/26/2016] [Indexed: 01/13/2023] Open
Abstract
Activator of G-protein signaling 8 (AGS8, also known as FNDC1) is a receptor-independent accessory protein for the Gβγ subunit, which was isolated from rat heart subjected to repetitive transient ischemia with the substantial development of collaterals. Here, we report the role of AGS8 in vessel formation by endothelial cells. Knockdown of AGS8 by small interfering RNA (siRNA) inhibited vascular endothelial growth factor (VEGF)-induced tube formation, as well as VEGF-stimulated cell growth and migration. VEGF stimulated the phosphorylation of the VEGF receptor-2 (VEGFR-2, also known as KDR), ERK1/2 and p38 MAPK; however, knockdown of AGS8 inhibited these signaling events. Signal alterations by AGS8 siRNA were associated with a decrease of cell surface VEGFR-2 and an increase of VEGFR-2 in the cytosol. Endocytosis blockers did not influence the decrease of VEGFR-2 by AGS8 siRNA, suggesting the involvement of AGS8 in VEGFR-2 trafficking to the plasma membrane. VEGFR-2 formed a complex with AGS8 in cells, and a peptide designed to disrupt AGS8-Gβγ interaction inhibited VEGF-induced tube formation. These data suggest a potential role for AGS8-Gβγ in VEGF signal processing. AGS8 might play a key role in tissue adaptation by regulating angiogenic events.
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Affiliation(s)
- Hisaki Hayashi
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Abdullah Al Mamun
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Miho Sakima
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Motohiko Sato
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
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Li C, Vu K, Hazelgrove K, Kuemmerle JF. Increased IGF-IEc expression and mechano-growth factor production in intestinal muscle of fibrostenotic Crohn's disease and smooth muscle hypertrophy. Am J Physiol Gastrointest Liver Physiol 2015; 309:G888-99. [PMID: 26428636 PMCID: PMC4669353 DOI: 10.1152/ajpgi.00414.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 09/27/2015] [Indexed: 01/31/2023]
Abstract
The igf1 gene is alternatively spliced as IGF-IEa and IGF-IEc variants in humans. In fibrostenotic Crohn's disease, the fibrogenic cytokine TGF-β1 induces IGF-IEa expression and IGF-I production in intestinal smooth muscle and results in muscle hyperplasia and collagen I production that contribute to stricture formation. Mechano-growth factor (MGF) derived from IGF-IEc induces skeletal and cardiac muscle hypertrophy following stress. We hypothesized that increased IGF-IEc expression and MGF production mediated smooth muscle hypertrophy also characteristic of fibrostenotic Crohn's disease. IGF-IEc transcripts and MGF protein were increased in muscle cells isolated from fibrostenotic intestine under regulation by endogenous TGF-β1. Erk5 and MEF2C were phosphorylated in vivo in fibrostenotic muscle; both were phosphorylated and colocalized to nucleus in response to synthetic MGF in vitro. Smooth muscle-specific protein expression of α-smooth muscle actin, γ-smooth muscle actin, and smoothelin was increased in affected intestine. Erk5 inhibition or MEF2C siRNA blocked smooth muscle-specific gene expression and hypertrophy induced by synthetic MGF. Conditioned media of cultured fibrostenotic muscle induced muscle hypertrophy that was inhibited by immunoneutralization of endogenous MGF or pro-IGF-IEc. The results indicate that TGF-β1-dependent IGF-IEc expression and MGF production in patients with fibrostenotic Crohn's disease regulates smooth muscle cell hypertrophy a critical factor that contributes to intestinal stricture formation.
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Affiliation(s)
- Chao Li
- 1Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia; and
| | - Kent Vu
- 1Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia; and
| | - Krystina Hazelgrove
- 1Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia; and
| | - John F. Kuemmerle
- 1Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia; and ,2Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Novel players in cardioprotection: Insulin like growth factor-1, angiotensin-(1–7) and angiotensin-(1–9). Pharmacol Res 2015; 101:41-55. [DOI: 10.1016/j.phrs.2015.06.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 06/27/2015] [Accepted: 06/28/2015] [Indexed: 12/14/2022]
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Li C, Iness A, Yoon J, Grider JR, Murthy KS, Kellum JM, Kuemmerle JF. Noncanonical STAT3 activation regulates excess TGF-β1 and collagen I expression in muscle of stricturing Crohn's disease. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2015; 194:3422-31. [PMID: 25740948 PMCID: PMC4369432 DOI: 10.4049/jimmunol.1401779] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Increased TGF-β1 and TGF-β1-dependent Collagen I production in intestinal mesenchymal cells result in fibrosis in patients with Montreal B2 fibrostenotic Crohn's disease. Numerous cytokines, including IL-6, are produced by activated mesenchymal cells themselves and activate STAT3. The aim of the current study was to determine the mechanisms by which STAT-3 activation might result in intestinal fibrosis. Cytokine levels were measured by ELISA. STAT3 and suppressor of cytokine signaling 3 protein levels were measured by immunoblot, STAT3-TGFB1 DNA-binding activity by chromatin immunoprecipitation, and TGFB1 transcriptional activity by luciferase reporter assay. TGF-β1 (TGFB1), Collagen1α1, and connective tissue growth factor (CTGF) gene expression was measured by quantitative RT-PCR. The role of STAT3 activation was determined using STAT3 inhibitor, Stattic, and by transfection of STAT3 mutants. Autocrine production of cytokines was increased in muscle cells of B2 phenotype patients from strictures and normal intestine in the same patient and compared with other Crohn's phenotypes, ulcerative colitis, and non-Crohn's patients. A unique pattern of STAT3 phosphorylation emerged: high STAT3(S727) and low STAT3(Y705) in strictures and the opposite in unaffected intestine. TGFB1 transcriptional activity was regulated by phospho-STAT3(S727) and was decreased by Stattic or dominant-negative STAT3(S727A). TGF-β1, COL1A1, and CTGF expression was inhibited by Stattic or dominant-negative STAT3(S727A). Treatment of normal muscle cells with IL-6 or expression of constitutively active STAT3(S727E) phenocopied muscle cells from strictured intestine. Neutralization of autocrine IL-6 reversed STAT3 phosphorylation and normalized expression of TGF-β1 in strictured intestinal muscle. The ability of Stattic to improve development of fibrosis was confirmed in mice with 2,4,6-trinitrobenzenesulfonic acid-induced colitis. We observed a unique phospho-STAT3(S727) response in patients with Montreal B2 Crohn's disease, particularly in response to IL-6 leading to increased TGF-β1, collagen, and CTGF production in ileal strictures.
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Affiliation(s)
- Chao Li
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298
| | - Audra Iness
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298
| | - Jennifer Yoon
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298
| | - John R Grider
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298; VCU Program in Enteric Neuromuscular Sciences, Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298; and
| | - Karnam S Murthy
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298; VCU Program in Enteric Neuromuscular Sciences, Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298; and
| | - John M Kellum
- Department of Surgery, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298
| | - John F Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298; VCU Program in Enteric Neuromuscular Sciences, Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298; and
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Lecat S, Belemnaba L, Galzi JL, Bucher B. Neuropeptide Y receptor mediates activation of ERK1/2 via transactivation of the IGF receptor. Cell Signal 2015; 27:1297-304. [PMID: 25817573 DOI: 10.1016/j.cellsig.2015.03.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 02/19/2015] [Accepted: 03/08/2015] [Indexed: 12/24/2022]
Abstract
Neuropeptide Y binds to G-protein coupled receptors whose action results in inhibition of adenylyl cyclase activity. Using HEK293 cells stably expressing the native neuropeptide Y Y1 receptors, we found that the NPY agonist elicits a transient phosphorylation of the extracellular signal-regulated kinases (ERK1/2). We first show that ERK1/2 activation following Y1 receptor stimulation is dependent on heterotrimeric Gi/o since it is completely inhibited by pre-treatment with pertussis toxin. In addition, ERK1/2 activation is internalization-independent since mutant Y1 receptors unable to recruit β-arrestins, can still activate ERK signaling to the same extent as wild-type receptors. We next show that this activation of the MAPK pathway is inhibited by the MEK inhibitor U0126, is not dependent on calcium signaling at the Y1 receptor (no effect upon inhibition of phospholipase C, protein kinase C or protein kinase D) but instead dependent on Gβ/γ and associated signaling pathways that activate PI3-kinase. Although inhibition of the epidermal-growth factor receptor tyrosine kinase did not influence NPY-induced ERK1/2 activation, we show that the inhibition of insulin growth factor receptor IGFR by AG1024 completely blocks activation of ERK1/2 by the Y1 receptor. This Gβ/γ-PI3K-AG1024-sensitive pathway does not involve activation of IGFR through the release of a soluble ligand by metalloproteinases since it is not affected by the metalloproteinase inhibitor marimastat. Finally, we found that a similar pathway, sensitive to wortmannin-AG1024 but insensitive to marimastat, is implicated in activation of ERK signaling in HEK293 cells by endogenously expressed GPCRs coupled to Gq-protein (muscarinic M3 receptors) or coupled to Gs-protein (endothelin ETB receptors). Our analysis is the first to show that β-arrestin recruitment to the NPY Y1 receptor is not necessary for MAPK activation by this receptor but that transactivation of the IGFR receptor is required.
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Affiliation(s)
- Sandra Lecat
- GPCRs, Pain and Inflammation Team, UMR7242, CNRS-University of Strasbourg, LabEx Medalis 300 Bvd Sébastien Brant, CS 10413, 67412 Illkirch, France.
| | - Lazare Belemnaba
- UMR 7213, CNRS-University of Strasbourg, Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, 74 route du Rhin, CS 60024, 67401 Illkirch, France
| | - Jean-Luc Galzi
- GPCRs, Pain and Inflammation Team, UMR7242, CNRS-University of Strasbourg, LabEx Medalis 300 Bvd Sébastien Brant, CS 10413, 67412 Illkirch, France
| | - Bernard Bucher
- UMR 7213, CNRS-University of Strasbourg, Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, 74 route du Rhin, CS 60024, 67401 Illkirch, France
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Troncoso R, Ibarra C, Vicencio JM, Jaimovich E, Lavandero S. New insights into IGF-1 signaling in the heart. Trends Endocrinol Metab 2014; 25:128-37. [PMID: 24380833 DOI: 10.1016/j.tem.2013.12.002] [Citation(s) in RCA: 165] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 11/16/2013] [Accepted: 12/02/2013] [Indexed: 01/15/2023]
Abstract
Insulin-like growth factor 1 (IGF-1) signaling regulates contractility, metabolism, hypertrophy, autophagy, senescence, and apoptosis in the heart. IGF-1 deficiency is associated with an increased risk of cardiovascular disease, whereas cardiac activation of IGF-1 receptor (IGF-1R) protects from the detrimental effects of a high-fat diet and myocardial infarction. IGF-1R activates multiple pathways through its intrinsic tyrosine kinase activity and through coupling to heterotrimeric G protein. These pathways involve classic second messengers, phosphorylation cascades, lipid signaling, Ca(2+) transients, and gene expression. In addition, IGF-1R triggers signaling in different subcellular locations including the plasma membrane, perinuclear T tubules, and also in internalized vesicles. In this review, we provide a fresh and updated view of the complex IGF-1 scenario in the heart, including a critical focus on therapeutic strategies.
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Affiliation(s)
- Rodrigo Troncoso
- Facultad de Ciencias Quimicas y Farmaceuticas & Facultad Medicina, Universidad de Chile, Santiago 838049, Chile; Centro de Estudios Moleculares de la Célula, Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago 838049, Chile
| | - Cristián Ibarra
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | | | - Enrique Jaimovich
- Centro de Estudios Moleculares de la Célula, Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago 838049, Chile
| | - Sergio Lavandero
- Facultad de Ciencias Quimicas y Farmaceuticas & Facultad Medicina, Universidad de Chile, Santiago 838049, Chile; Centro de Estudios Moleculares de la Célula, Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago 838049, Chile; Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Center, Dallas, TX, 75390-8573, USA.
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Wang Z, Dela Cruz R, Ji F, Guo S, Zhang J, Wang Y, Feng GS, Birnbaumer L, Jiang M, Chu WM. G(i)α proteins exhibit functional differences in the activation of ERK1/2, Akt and mTORC1 by growth factors in normal and breast cancer cells. Cell Commun Signal 2014; 12:10. [PMID: 24521094 PMCID: PMC3937014 DOI: 10.1186/1478-811x-12-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 02/01/2014] [Indexed: 12/29/2022] Open
Abstract
Background In a classic model, Giα proteins including Gi1α, Gi2α and Gi3α are important for transducing signals from Giα protein-coupled receptors (GiαPCRs) to their downstream cascades in response to hormones and neurotransmitters. Our previous study has suggested that Gi1α, Gi2α and Gi3α are also important for the activation of the PI3K/Akt/mTORC1 pathway by epidermal growth factor (EGF) and its family members. However, a genetic role of these Giα proteins in the activation of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) by EGF is largely unknown. Further, it is not clear whether these Giα proteins are also engaged in the activation of both the Akt/mTORC1 and ERK1/2 pathways by other growth factor family members. Additionally, a role of these Giα proteins in breast cancer remains to be elucidated. Results We found that Gi1/3 deficient MEFs with the low expression level of Gi2α showed defective ERK1/2 activation by EGFs, IGF-1 and insulin, and Akt and mTORC1 activation by EGFs and FGFs. Gi1/2/3 knockdown breast cancer cells exhibited a similar defect in the activations and a defect in in vitro growth and invasion. The Giα proteins associated with RTKs, Gab1, FRS2 and Shp2 in breast cancer cells and their ablation impaired Gab1’s interactions with Shp2 in response to EGF and IGF-1, or with FRS2 and Grb2 in response to bFGF. Conclusions Giα proteins differentially regulate the activation of Akt, mTORC1 and ERK1/2 by different families of growth factors. Giα proteins are important for breast cancer cell growth and invasion.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Meisheng Jiang
- Cancer Biology Program, University of Hawaii Cancer Center, 701 Ilalo Street, Honolulu, HI 96813, USA.
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Carrasco L, Cea P, Rocco P, Peña-Oyarzún D, Rivera-Mejias P, Sotomayor-Flores C, Quiroga C, Criollo A, Ibarra C, Chiong M, Lavandero S. Role of Heterotrimeric G Protein and Calcium in Cardiomyocyte Hypertrophy Induced by IGF-1. J Cell Biochem 2014; 115:712-20. [DOI: 10.1002/jcb.24712] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 11/05/2013] [Indexed: 01/09/2023]
Affiliation(s)
- Loreto Carrasco
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Paola Cea
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Paola Rocco
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Daniel Peña-Oyarzún
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Pablo Rivera-Mejias
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Cristian Sotomayor-Flores
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Clara Quiroga
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Alfredo Criollo
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Departamento Ciencias Básicas y Comunitarias; Facultad Odontología; Universidad de Chile; Santiago Chile
| | - Cristian Ibarra
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Department of Medical Biochemistry and Biophysics; Karolinska Institutet; Stockholm Sweden
| | - Mario Chiong
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
| | - Sergio Lavandero
- Advanced Center for Chronic Diseases; Universidad de Chile; Santiago Chile
- Centro Estudios Moleculares de la Celula; Facultad de Ciencias y Farmacéuticas; Universidad de Chile; Santiago Chile
- Instituto de Ciencias Biomédicas; Facultad Medicina; Universidad de Chile; Santiago Chile
- Cardiology Division; Department of Internal Medicine; University of Texas Southwestern Medical Center; Dallas Texas
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Increased activation of latent TGF-β1 by αVβ3 in human Crohn's disease and fibrosis in TNBS colitis can be prevented by cilengitide. Inflamm Bowel Dis 2013; 19:2829-39. [PMID: 24051933 PMCID: PMC3889641 DOI: 10.1097/mib.0b013e3182a8452e] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Strictures develop in >30% of patients affected with Crohn's disease. No available medication prevents stricture development in susceptible patients. In Crohn's strictures, but not adjacent normal intestine, TGF-β1 increases in muscularis smooth muscle, increasing collagen I production and strictures. Muscle cells express αVβ3 integrin containing an Arg-Gly-Asp (RGD) binding domain. The aim was to determine whether increased TGF-β1 levels in strictures were the result of latent TGF-β1, which contains an RGD sequence, binding to and activation by αVβ3; and whether cilengitide, which is an RGD-containing αVβ3 integrin inhibitor, decreases TGF-β1 activation and development of fibrosis in chronic 2,4,6 trinitrobenzene sulfonic acid (TNBS)-induced colitis. DESIGN Muscle cells isolated from Crohn's disease strictures and normal resection margin and from the colon of rats after 42 days of chronic TNBS-induced colitis were used to prepare RNA and protein lysates and to initiate primary cultures. The mechanisms leading to increased TGF-β1 activation, collagen I production, and fibrosis were examined in human muscle and in rats. Human cultured cells in vitro and rats in vivo were treated with cilengitide to determines it efficacy to decrease TGF-β1-activation, collagen production, and decrease the development of fibrosis. RESULTS Latent TGF-β1 is activated by the αVβ3 RGD domain in human and rat intestinal smooth muscles. Increased activation of TGF-β1 in Crohn's disease and in TNBS-induced colitis causes increased collagen production, and fibrosis that could be inhibited by cilengitide. CONCLUSIONS Cilengitide, an αVβ3 integrin RGD inhibitor, could be a novel treatment to diminish excess TGF-β1 activation, collagen I production, and development of fibrosis in Crohn's disease.
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Identification of novel signalling roles and targets for G(α) and G(βγ) downstream of the insulin-like growth factor 1 receptor in vascular smooth muscle cells. Biochem J 2013. [PMID: 23186281 DOI: 10.1042/bj20112158] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Vascular dysfunction is the underlying cause of nearly 80% of heart disease cases, and its initiation and progression can be exacerbated by circulating factors, such as IGF-1 (insulin-like growth factor 1). IGF-1, which is highly homologous with insulin, elicits a response via a classical tyrosine kinase receptor, the IGF-1R (IGF-1 receptor). However, it has been suggested that the IGF-1R may also be coupled to a heterotrimeric G-protein and can thus modulate cellular processes via this alternate pathway. The objective of the present study was to investigate the structural aspects of IGF-1R coupling to a heterotrimeric G-protein in VSMCs [vascular SMCs (smooth muscle cells)], as well as examine the contribution of this pathway to cellular responses that are related to vascular disease. We found that the intracellular subunit of the IGF-1R precipitates with two G-protein subunits. The G(βγ)-mediated pathway contributes to both proliferation and migration. We also show that IGF-1 specifically activates G(αi) and can directly interact with both G(αi1) and G(αi2). A phospho-screen using a novel specific G(αi)-peptide inhibitor reveals a number of potential downstream effectors of this pathway, although our results show that it is not essential for SMC proliferation or migration.
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15
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O’Kusky J, Ye P. Neurodevelopmental effects of insulin-like growth factor signaling. Front Neuroendocrinol 2012; 33:230-51. [PMID: 22710100 PMCID: PMC3677055 DOI: 10.1016/j.yfrne.2012.06.002] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 05/09/2012] [Accepted: 06/07/2012] [Indexed: 11/28/2022]
Abstract
Insulin-like growth factor (IGF) signaling greatly impacts the development and growth of the central nervous system (CNS). IGF-I and IGF-II, two ligands of the IGF system, exert a wide variety of actions both during development and in adulthood, promoting the survival and proliferation of neural cells. The IGFs also influence the growth and maturation of neural cells, augmenting dendritic growth and spine formation, axon outgrowth, synaptogenesis, and myelination. Specific IGF actions, however, likely depend on cell type, developmental stage, and local microenvironmental milieu within the brain. Emerging research also indicates that alterations in IGF signaling likely contribute to the pathogenesis of some neurological disorders. This review summarizes experimental studies and shed light on the critical roles of IGF signaling, as well as its mechanisms, during CNS development.
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Affiliation(s)
- John O’Kusky
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada V5Z 1M9
| | - Ping Ye
- Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
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16
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Kuemmerle JF. Insulin-like growth factors in the gastrointestinal tract and liver. Endocrinol Metab Clin North Am 2012; 41:409-23, vii. [PMID: 22682638 PMCID: PMC3372868 DOI: 10.1016/j.ecl.2012.04.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The liver is a major source of insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) that are present in the circulation and have important endocrine activities relating to energy metabolism, body size, carcinogenesis, and various organ-specific functions. Although IGFs have only minor effects on the normal liver itself, production of IGFs and IGFBPs in a tissue-specific manner in the gastrointestinal tract exert important regulatory effects on cellular proliferation, survival, and apoptosis. IGFs and IGFBPs play important regulatory roles in the response of both the liver and the gastrointestinal tract to inflammation and in the development of neoplasia.
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Affiliation(s)
- John F Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341, USA.
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Siddiqui S, Fang M, Ni B, Lu D, Martin B, Maudsley S. Central role of the EGF receptor in neurometabolic aging. Int J Endocrinol 2012; 2012:739428. [PMID: 22754566 PMCID: PMC3382947 DOI: 10.1155/2012/739428] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 05/01/2012] [Indexed: 12/20/2022] Open
Abstract
A strong connection between neuronal and metabolic health has been revealed in recent years. It appears that both normal and pathophysiological aging, as well as neurodegenerative disorders, are all profoundly influenced by this "neurometabolic" interface, that is, communication between the brain and metabolic organs. An important aspect of this "neurometabolic" axis that needs to be investigated involves an elucidation of molecular factors that knit these two functional signaling domains, neuronal and metabolic, together. This paper attempts to identify and discuss a potential keystone signaling factor in this "neurometabolic" axis, that is, the epidermal growth factor receptor (EGFR). The EGFR has been previously demonstrated to act as a signaling nexus for many ligand signaling modalities and cellular stressors, for example, radiation and oxidative radicals, linked to aging and degeneration. The EGFR is expressed in a wide variety of cells/tissues that pertain to the coordinated regulation of neurometabolic activity. EGFR signaling has been highlighted directly or indirectly in a spectrum of neurometabolic conditions, for example, metabolic syndrome, diabetes, Alzheimer's disease, cancer, and cardiorespiratory function. Understanding the positioning of the EGFR within the neurometabolic domain will enhance our appreciation of the ability of this receptor system to underpin highly complex physiological paradigms such as aging and neurodegeneration.
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Affiliation(s)
- Sana Siddiqui
- Receptor Pharmacology Unit, National Institute on Aging, Baltimore, MD 21224, USA
| | - Meng Fang
- Receptor Pharmacology Unit, National Institute on Aging, Baltimore, MD 21224, USA
| | - Bin Ni
- Receptor Pharmacology Unit, National Institute on Aging, Baltimore, MD 21224, USA
| | - Daoyuan Lu
- Receptor Pharmacology Unit, National Institute on Aging, Baltimore, MD 21224, USA
| | - Bronwen Martin
- Metabolism Unit, National Institute on Aging, Baltimore, MD 21224, USA
| | - Stuart Maudsley
- Receptor Pharmacology Unit, National Institute on Aging, Baltimore, MD 21224, USA
- *Stuart Maudsley:
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Rebois RV, Hébert TE. Protein Complexes Involved in Heptahelical Receptor-Mediated Signal Transduction. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308243] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Perrault R, Wright B, Storie B, Hatherell A, Zahradka P. Tyrosine kinase-independent activation of extracellular-regulated kinase (ERK) 1/2 by the insulin-like growth factor-1 receptor. Cell Signal 2011; 23:739-46. [DOI: 10.1016/j.cellsig.2010.12.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 12/22/2010] [Indexed: 10/18/2022]
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20
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Mahavadi S, Flynn RS, Grider JR, Qiao L, Murthy KS, Hazelgrove KB, Kuemmerle JF. Amelioration of excess collagen IαI, fibrosis, and smooth muscle growth in TNBS-induced colitis in IGF-I(+/-) mice. Inflamm Bowel Dis 2011; 17:711-9. [PMID: 20722057 PMCID: PMC2990779 DOI: 10.1002/ibd.21437] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 06/22/2010] [Indexed: 12/24/2022]
Abstract
BACKGROUND Strictures occur in ≈ 30% of patients with Crohn's disease (CD) and are characterized by intestinal smooth muscle hyperplasia, hypertrophy, and fibrosis due to excess extracellular matrix production including collagen. Insulin-like growth factor-I (IGF-I) expression is increased in smooth muscle cells of the muscularis propria in CD and in animal models of CD, including trinitrobenzene sulfonic acid (TNBS)-induced colitis. While upregulated IGF-I is conjectured to cause smooth muscle cell growth and collagen production in the inflamed intestine, its role in the development of fibrosis has not been directly demonstrated. METHODS Colitis was induced in IGF-I(+/-) or wildtype C57BL/6J mice by rectal administration of TNBS or ethanol vehicle. After 7 days, colonic smooth muscle cells were isolated and used to prepare RNA or protein lysates. Transcript levels of IGF-IEa, IGF binding protein (IGFBP)-3, IGFBP-5, TGF-β1, and collagen IαI were measured by quantitative reverse-transcription polymerase chain reaction (RT-PCR). Corresponding protein levels were measured by Western blot or enzyme-linked immunosorbent assay (ELISA). Fibrosis was measured using digital image analysis of Masson's trichrome-stained histologic sections. RESULTS In IGF-I(+/-) mice, which express significantly lower levels of IGF-I than wildtype, the response to TNBS-induced colitis: upregulation of IGF-I, IGFBP-3, IGFBP-5 muscle growth, and collagen IαI expression, the resulting collagen deposition, and fibrosis are all significantly diminished compared to C57BL/6J wildtype controls. TGF-β1 expression and its increase following TNBS administration are not altered in IGF-I(+/-) mice compared to wildtype. CONCLUSIONS The findings indicate that IGF-I is a key regulator in intestinal smooth muscle hyperplasia and excess collagen production that leads to fibrosis and long term to stricture formation.
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Affiliation(s)
- Sunila Mahavadi
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
| | - Robert S. Flynn
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
| | - John R. Grider
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341,Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
| | - Liya Qiao
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
| | - Karnam S. Murthy
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341,Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
| | - Krystina B. Hazelgrove
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
| | - John F. Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341,Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0341
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Zhao D, Bakirtzi K, Zhan Y, Zeng H, Koon HW, Pothoulakis C. Insulin-like growth factor-1 receptor transactivation modulates the inflammatory and proliferative responses of neurotensin in human colonic epithelial cells. J Biol Chem 2011; 286:6092-9. [PMID: 21212273 DOI: 10.1074/jbc.m110.192534] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Neurotensin (NT) is a gastrointestinal neuropeptide that modulates intestinal inflammation and healing by binding to its high-affinity receptor NTR1. The dual role of NT in inflammation and healing is demonstrated in models of colitis induced by Clostridium difficile toxin A and dextran sulfate sodium, respectively, and involves NF-κB-dependent IL-8 expression and EGF receptor-mediated MAPK activation in human colonocytes. However, the detailed signaling pathways involved in these responses remain to be elucidated. We report here that NT/NTR1 coupling in human colonic epithelial NCM460 cells activates tyrosine phosphorylation of the insulin-like growth factor-1 receptor (IGF-1R) in a time- and dose-dependent manner. NT also rapidly induces Src tyrosine phosphorylation, whereas pretreatment of cells with the Src inhibitor PP2 before NT exposure decreases NT-induced IGF-1R phosphorylation. In addition, inhibition of IGF-1R activation by either its specific antagonist AG1024 or siRNA against IGF-1 significantly reduces NT-induced IL-8 expression and NF-κB-dependent reporter gene expression. Pretreatment with AG1024 also inhibits Akt activation and apoptosis induced by NT. Silencing of Akt expression by siRNA also substantially attenuates NT-induced IL-8 promoter activity and NF-κB-dependent reporter gene expression. This is the first report to indicate that NT transactivates IGF-1R and that this response is linked to Akt phosphorylation and NF-κB activation, contributing to both pro-inflammatory and tissue repair signaling pathways in response to NT in colonic epithelial cells. We propose that IGF-1R activation represents a previously unrecognized key pathway involved in the mechanisms by which NT and NTR1 modulate colonic inflammation and inflammatory bowel disease.
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Affiliation(s)
- Dezheng Zhao
- Division of Gastroenterology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 022115, USA.
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Flynn RS, Mahavadi S, Murthy KS, Grider JR, Kellum JM, Akbari H, Kuemmerle JF. Endogenous IGFBP-3 regulates excess collagen expression in intestinal smooth muscle cells of Crohn's disease strictures. Inflamm Bowel Dis 2011; 17:193-201. [PMID: 20848532 PMCID: PMC4863983 DOI: 10.1002/ibd.21351] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND Stricture formation occurs in ≈30% of patients with Crohn's disease (CD) and is a significant cause of morbidity. Strictures are characterized by intestinal smooth muscle cell hyperplasia, smooth muscle cell hypertrophy, and fibrosis due to excess net extracellular matrix production, including collagen. Transforming growth factor-β1 (TGF-β1) has profibrotic effects in many tissues due to its ability to regulate collagen expression and extracellular matrix dynamics. We previously showed that both insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) and TGF-β1 are expressed by normal human intestinal smooth muscle cells, bind to, and activate TGF-βRII/I receptors in these cells. METHODS Smooth muscle cells isolated from the muscularis propria of patients were used to prepare RNA, protein lysates, or placed into primary culture. IGFBP-3, TGF-β1, and collagen IαI expression was measured with quantitative reverse-transcription polymerase chain reaction (RT-PCR) and protein levels by enzyme-linked immunosorbent assay (ELISA) or immunoblot. RESULTS Expression and production of IGFBP-3, TGF-β1, and collagen IαI were significantly increased specifically in smooth muscle cells isolated from regions of strictured intestine in CD compared to nonstrictured histologically normal resection margin. IGFBP-3 and TGF-β1 regulated collagen IαI expression and production via a TGF-βRII/I-dependent and Smad2/3-dependent mechanism. Upregulated (excess) collagen IαI expression and production in smooth muscle cells of strictures and basal collagen IαI in smooth muscle cells of normal margin were inhibited by immunoneutralization of IGFBP-3 or TGF-β1. CONCLUSIONS The findings indicate that upregulated endogenous IGFBP-3 and TGF-β1 expression regulates excess collagen IαI production and contributes to fibrosis and stricture formation in CD.
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Affiliation(s)
- Robert S. Flynn
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Sunila Mahavadi
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Karnam S. Murthy
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia,Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - John R. Grider
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia,Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - John M. Kellum
- Department of Surgery, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Homayoon Akbari
- Department of Surgery, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - John F. Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia,Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Flynn RS, Murthy KS, Grider JR, Kellum JM, Kuemmerle JF. Endogenous IGF-I and alphaVbeta3 integrin ligands regulate increased smooth muscle hyperplasia in stricturing Crohn's disease. Gastroenterology 2010; 138:285-93. [PMID: 19751734 PMCID: PMC2813387 DOI: 10.1053/j.gastro.2009.09.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 08/07/2009] [Accepted: 09/03/2009] [Indexed: 12/24/2022]
Abstract
BACKGROUND & AIMS Insulin-like growth factor-I (IGF-I) regulates human intestinal smooth muscle growth by stimulating proliferation and inhibiting apoptosis. IGF-I-stimulated growth is augmented when alphaVbeta3 integrin is occupied by its ligands, fibronectin and vitronectin. Increased IGF-I expression and muscle cell hyperplasia are features of stricturing Crohn's disease (CD); however, the role of IGF-I in stricture formation is unknown. The aim was to identify the functional role of endogenous IGF-I and alphaVbeta3 integrin ligands in regulating muscle cell hyperplasia in stricturing CD. METHODS Smooth muscle cells were isolated from muscularis propria of stricturing CD or normal margins. Quantitative polymerase chain reaction, immunoblot analysis, and enzyme-linked immunosorbent assay were used to measure fibronectin, vitronectin, alphaVbeta3 integrin, and IGF-I levels. Activation of the IGF-I receptor, Erk1/2, p70S6 kinase, and GSK-3beta was measured by immunoblot. Proliferation was quantified by Ki67 immunostaining and [(3)H]thymidine incorporation. Apoptosis was measured from caspase-3 cleavage and nucleosome accumulation. RESULTS IGF-I, vitronectin, and fibronectin RNA and protein levels were increased 1.8- to 3.4-fold in muscle cells from strictures over normal margins. Basal IGF-I receptor phosphorylation was increased 320% in strictured over normal muscle, and basal Erk1/2, p70S6 kinase, and GSK-3beta phosphorylation were increased 205%-292% in strictures. In muscle cells from strictures, Ki67 immunoreactivity and [(3)H]thymidine incorporation were increased and apoptosis was decreased compared with normal margins. Antagonists of the IGF-I receptor or alphaVbeta3 integrin reversed these changes. CONCLUSIONS Smooth muscle cell hyperplasia in stricturing CD is regulated by increased endogenous IGF-I and alphaVbeta3 integrin ligands that regulate augmented proliferation and diminished apoptosis.
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Affiliation(s)
- Robert S. Flynn
- Department of Medicine, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA
| | - Karnam S. Murthy
- Department of Medicine, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA,Department of Physiology, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA
| | - John R. Grider
- Department of Medicine, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA,Department of Physiology, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA
| | - John M. Kellum
- Department of Surgery, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA
| | - John F. Kuemmerle
- Department of Medicine, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA,Department of Physiology, Medical College of Virginia Campus Virginia Commonwealth University, Richmond, VA
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Flynn RS, Mahavadi S, Murthy KS, Kellum JM, Kuemmerle JF. Insulin-like growth factor-binding protein-5 stimulates growth of human intestinal muscle cells by activation of G{alpha}i3. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1232-8. [PMID: 19808657 PMCID: PMC2850095 DOI: 10.1152/ajpgi.00323.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In human intestinal smooth muscle cells, endogenous insulin-like growth factor-I (IGF-I) regulates growth and IGF-binding protein-5 (IGFBP-5) expression. The effects of IGF-I are facilitated by IGFBP-5. We previously showed that IGFBP-5 acts independently of IGF-I in human intestinal muscle to stimulate proliferation and upregulate IGF-I production by activation of Erk1/2 and p38 MAPK. Thus a positive feedback loop exists between IGF-I and IGFBP-5, whereby both stimulate muscle growth and production of the other factor. In Crohn's disease, IGF-I and IGFBP-5 expression are increased and contribute to stricture formation through this effect on muscle growth. To determine the signaling pathways coupling IGFBP-5 to MAPK activation and growth, smooth muscle cells were isolated from muscularis propria of human intestine and placed into primary culture. Erk1/2 and p38 MAPK activation and type I collagen production were measured by immunoblot. Proliferation was measured by [(3)H]thymidine incorporation. Activation of specific G proteins was measured by ELISA. AG1024, an IGF-I receptor tyrosine kinase inhibitor, was used to isolate the IGF-I-independent effects of IGFBP-5. IGFBP-5-induced phosphorylation of Erk1/2 and p38 MAPK and proliferation were abolished by pertussis toxin, implying the participation of Gi. IGFBP-5 specifically activated Gi3 but not other G proteins. Transfection of an inhibitory Galphai minigene specifically inhibited MAPK activation, proliferation, and both collagen-I and IGF-I production. Our results indicate that endogenous IGFBP-5 activates Gi3 and regulates smooth muscle growth, IGF-I production, and collagen production via the alpha-subunit of Gi3, independently of IGF-I, in normal human intestinal muscle cells.
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Affiliation(s)
| | | | | | - John M. Kellum
- 3Surgery, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Singh J, Mehendiratta V, Del Galdo F, Jimenez SA, Cohen S, DiMarino AJ, Rattan S. Immunoglobulins from scleroderma patients inhibit the muscarinic receptor activation in internal anal sphincter smooth muscle cells. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1206-13. [PMID: 19779020 PMCID: PMC2850093 DOI: 10.1152/ajpgi.00286.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Systemic sclerosis (SSc) IgGs affecting the M(3)-muscarinic receptor (M(3)-R) have been proposed to be responsible for the gastrointestinal (GI) dysmotility in this disease. However, the effect of SSc IgGs on smooth muscle cell (SMC) function has not been studied. We determined the effect of SSc IgGs on the muscarinic receptor activation by bethanechol (BeCh; methyl derivate of carbachol) in SMC and smooth muscle strips from rat internal anal sphincter. IgGs were purified from GI-symptomatic SSc patients and normal volunteers, with protein G-Sepharose columns. SMC lengths were determined via computerized digital micrometry. The presence of M(3)-R and IgG-M(3)-R complex was determined by Western blot. IgGs from SSc patients but not from normal volunteers caused significant and concentration-dependent inhibition of BeCh response (P < 0.05). The maximal shortening of 22.2 +/- 1.2% caused by 10(-4) M BeCh was significantly attenuated to 8.3 +/- 1.2% by 1 mg/ml of SSc IgGs (P < 0.05). Experiments performed in smooth muscle strips revealed a similar effect of SSc IgG that was fully reversible. In contrast to the effect on BeCh, the SSc IgGs caused no significant effect (P > 0.05) on K(+) depolarization and alpha(1)-adrenoceptor activation by phenylephrine. Western blot studies revealed the specific presence of SSc IgG-M(3)-R complex. SSc IgGs attenuated M(3)-R activation, which was reversible with antibody removal. These data suggest that SSc GI dysmotility may be caused by autoantibodies that inhibit the muscarinic neurotransmission. Future treatment of SSc patients may be directed at the removal or neutralization of these antibodies.
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Affiliation(s)
- Jagmohan Singh
- 1Department of Medicine, Division of Gastroenterology and Hepatology, and
| | | | - Francesco Del Galdo
- 2Scleroderma Center and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Sergio A. Jimenez
- 2Scleroderma Center and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania
| | | | | | - Satish Rattan
- 1Department of Medicine, Division of Gastroenterology and Hepatology, and
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Hazelgrove KB, Flynn RS, Qiao LY, Grider JR, Kuemmerle JF. Endogenous IGF-I and alpha v beta3 integrin ligands regulate increased smooth muscle growth in TNBS-induced colitis. Am J Physiol Gastrointest Liver Physiol 2009; 296:G1230-7. [PMID: 19359426 PMCID: PMC2697946 DOI: 10.1152/ajpgi.90508.2008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Endogenous insulin-like growth factor-I (IGF-I) regulates intestinal smooth muscle growth by concomitantly stimulating proliferation and inhibiting apoptosis. IGF-I-stimulated growth is augmented by the alpha(v)beta(3) integrin ligands vitronectin and fibronectin. IGF-I expression in smooth muscle is increased in both TNBS-induced colitis and Crohn's disease. We hypothesized that intestinal inflammation increased vitronectin and fibronectin expression by smooth muscle and, along with IGF-I upregulation, increased intestinal muscle growth. Intestinal smooth muscle cells were examined 7 days following the induction of TNBS-induced colitis. Although alpha(v)beta(3) integrin expression was not altered by TNBS-induced colitis, vitronectin and fibronectin levels were increased by 80 +/- 10% and 90 +/- 15%, above control levels, respectively. Basal IGF-I receptor phosphorylation in inflamed muscle from TNBS-treated rats was increased by 86 +/- 8% over vehicle-treated controls. Basal ERK1/2, p70S6 kinase, and GSK-3beta phosphorylation in muscle cells of TNBS-treated rats were also increased by 140-180%. TNBS treatment increased basal muscle cell proliferation by 130 +/- 15% and decreased apoptosis by 20 +/- 2% compared with that in vehicle-treated controls. The changes in proliferation and apoptosis were reversed by an IGF-I receptor tyrosine kinase inhibitor or an alpha(v)beta(3) integrin antagonist. The results suggest that smooth muscle hyperplasia in TNBS-induced colitis partly results from the upregulation of endogenous IGF-I and ligands of alpha(v)beta(3) integrin that mediate increased smooth muscle cell proliferation and decreased apoptosis. This paper has identified one mechanism regulating smooth muscle hyperplasia, a feature of stricture formation that occurs in the chronically inflamed intestine of TNBS-induced colitis and potentially Crohn's disease.
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Affiliation(s)
- Krystina B. Hazelgrove
- Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Robert S. Flynn
- Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Li-Ya Qiao
- Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - John R. Grider
- Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - John F. Kuemmerle
- Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Drozdowski L, Thomson ABR. Intestinal hormones and growth factors: effects on the small intestine. World J Gastroenterol 2009; 15:385-406. [PMID: 19152442 PMCID: PMC2653359 DOI: 10.3748/wjg.15.385] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.
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Plesneva SA, Kuznetsova LA, Shpakov AO, Sharova TS, Pertseva MN. Study of structural-functional arrangement of the adenylyl cyclase signaling mechanism of action of insulin-like growth factor 1 revealed in muscle tissue of representatives of vertebrates and invertebrates. J EVOL BIOCHEM PHYS+ 2008. [DOI: 10.1134/s0022093008050022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Hayabuchi Y, Willars G, Standen N, Davies N. Insulin-like growth factor-I inhibits rat arterial KATP channels through pI 3-kinase. Biochem Biophys Res Commun 2008; 374:742-6. [DOI: 10.1016/j.bbrc.2008.07.100] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Accepted: 07/18/2008] [Indexed: 11/28/2022]
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Humpert PM, Djuric Z, Zeuge U, Oikonomou D, Seregin Y, Laine K, Eckstein V, Nawroth PP, Bierhaus A. Insulin stimulates the clonogenic potential of angiogenic endothelial progenitor cells by IGF-1 receptor-dependent signaling. Mol Med 2008; 14:301-8. [PMID: 18309377 DOI: 10.2119/2007-00052.humpert] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Accepted: 02/19/2008] [Indexed: 11/06/2022] Open
Abstract
Endothelial progenitor cells (EPCs) have been shown to be involved in vascular regeneration and angiogenesis in experimental diabetes. Because insulin therapy mobilizes circulating progenitor cells, we studied the effects of insulin on outgrowth of EPCs from peripheral blood mononuclear cells of healthy volunteers and patients with type 2 diabetes. Insulin increased the formation of EPC colony-forming units in a dose-dependent manner, half-maximal at 1.5 nM and peaking at 15 nM. Inhibiting the insulin receptor with neutralizing antibodies or antisense oligonucleotides had no effect on EPC outgrowth.(1) In contrast, targeting the human insulin-like growth factor 1 (IGF-1) receptor with neutralizing antibodies significantly suppressed insulin-induced outgrowth of EPCs from both healthy controls and patients with type 2 diabetes. This IGF-1 receptor-mediated insulin effect on EPC growth was at least in part dependent on MAP kinases(2) and was abrogated when extracellular signal-regulated kinase 1/2 (Erk1/2) and protein kinase 38 (p38) activity was inhibited. To study the functional relevance of the observed insulin effects, we studied EPC-induced tube formation of bovine endothelial cells in vitro. Insulin-stimulated EPCs incorporated into the endothelial tubes and markedly enhanced tube formation. In conclusion, this is the first study showing an insulin-mediated activation of the IGF-1 receptor leading to an increased clonogenic and angiogenic potential of EPCs in vitro.
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Affiliation(s)
- Per M Humpert
- Department of Medicine I and Clinical Chemistry, University Clinics Heidelberg, Germany.
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Hawkes C, Amritraj A, Macdonald RG, Jhamandas JH, Kar S. Heterotrimeric G proteins and the single-transmembrane domain IGF-II/M6P receptor: functional interaction and relevance to cell signaling. Mol Neurobiol 2008; 35:329-45. [PMID: 17917122 DOI: 10.1007/s12035-007-0021-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 11/30/1999] [Accepted: 04/02/2007] [Indexed: 12/11/2022]
Abstract
The G protein-coupled receptor (GPCR) family represents the largest and most versatile group of cell surface receptors. Classical GPCR signaling constitutes ligand binding to a seven-transmembrane domain receptor, receptor interaction with a heterotrimeric G protein, and the subsequent activation or inhibition of downstream intracellular effectors to mediate a cellular response. However, recent reports on direct, receptor-independent G protein activation, G protein-independent signaling by GPCRs, and signaling of nonheptahelical receptors via trimeric G proteins have highlighted the intrinsic complexities of G protein signaling mechanisms. The insulin-like growth factor-II/mannose-6 phosphate (IGF-II/M6P) receptor is a single-transmembrane glycoprotein whose principal function is the intracellular transport of lysosomal enzymes. In addition, the receptor also mediates some biological effects in response to IGF-II binding in both neuronal and nonneuronal systems. Multidisciplinary efforts to elucidate the intracellular signaling pathways that underlie these effects have generated data to suggest that the IGF-II/M6P receptor might mediate transmembrane signaling via a G protein-coupled mechanism. The purpose of this review is to outline the characteristics of traditional and nontraditional GPCRs, to relate the IGF-II/M6P receptor's structure with its role in G protein-coupled signaling and to summarize evidence gathered over the years regarding the putative signaling of the IGF-II/M6P receptor mediated by a G protein.
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Affiliation(s)
- C Hawkes
- Department of Psychiatry, Centre for Alzheimer and Neurodegenerative Research, University of Alberta, Edmonton, AB, T6G 2B7, Canada
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Lok KC, Fu AKY, Ip FCF, Wong YH, Ip NY. Expression of G protein β subunits in rat skeletal muscle after nerve injury: Implication in the regulation of neuregulin signaling. Neuroscience 2007; 146:594-603. [PMID: 17368953 DOI: 10.1016/j.neuroscience.2007.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 02/02/2007] [Accepted: 02/03/2007] [Indexed: 11/21/2022]
Abstract
Tight regulation of gene transcription is critical in muscle development as well as during the formation and maintenance of the neuromuscular junction (NMJ). We previously demonstrated that the transcription of G protein beta1 (Gbeta1) is enhanced by treatment of cultured myotubes with neuregulin (NRG), a trophic factor that plays an important role in neural development. In the current study, we report that the transcript levels of Gbeta1 and Gbeta2 subunits in skeletal muscle are up-regulated following sciatic nerve injury or blockade of nerve activity. These observations prompted us to explore the possibility that G protein subunits regulate NRG-mediated signaling and gene transcription. We showed that overexpression of Gbeta1 or Gbeta2 in COS7 cells attenuates NRG-induced extracellular signal-regulated kinase (ERK) 1/2 activation, whereas suppression of Gbeta2 expression in C2C12 myotubes enhances NRG-mediated ERK1/2 activation and c-fos transcription. These results suggest that expression of Gbeta protein negatively regulates NRG-stimulated gene transcription in cultured myotubes. Taken together, our observations provide evidence that specific heterotrimeric G proteins regulate NRG-mediated signaling and gene transcription during rat muscle development.
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Affiliation(s)
- K-C Lok
- Department of Biochemistry, Biotechnology Research Institute and Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay Road, Hong Kong, China
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de Godoy MAF, Patel CA, Waldman SA, Katsuki M, Regan RF, Rattan S. H-ras inhibits RhoA/ROCK leading to a decrease in the basal tone in the internal anal sphincter. Gastroenterology 2007; 132:1401-9. [PMID: 17408635 DOI: 10.1053/j.gastro.2007.01.043] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Accepted: 01/04/2007] [Indexed: 01/13/2023]
Abstract
BACKGROUND & AIMS The present studies evaluated the role of H-ras and its implications in the RhoA/Rho kinase (ROCK) pathway in regulating basal tone in the internal anal sphincter (IAS). METHODS Studies were performed in the IAS from the wild-type (H-ras(+/+)) and knock-out (H-ras(-/-)) mice. The basal tone of smooth muscle strips was measured by isometric force transducers. Length of smooth muscle cells (SMC) isolated from the IAS in the basal state was determined by phase contrast microscopy. Experiments were repeated in the presence of Y 27632, a ROCK inhibitor. Involvement of the RhoA/ROCK machinery was analyzed by reverse-transcription polymerase chain reaction, Western blot, and immunocytochemistry. Reversal of H-ras knock-out effect was evaluated by transfection of SMCs with the constitutively activated (G12V) mutant. RESULTS Basal tone of the H-ras(-/-) IAS was significantly higher and resistant to relaxation by Y 27632, compared with the H-ras(+/+) IAS. Similarly, the length of SMCs from H-ras(-/-) IAS was significantly shorter. Y 27632 eliminated this difference. RhoA immunoreactivity shifted from cytoplasm to plasma membrane in H-ras(-/-) SMCs, a change typically associated with contraction. Further, SMCs from H-ras(-/-) mice exhibited higher levels of the contractile proteins ROCK II, phosphorylated-MYPT(1) and phosphorylated-MLC(20). Transfection with the G12V mutant increased the length of H-ras(-/-) cells. Conversely, the dominant negative H-ras (S17N) mutant decreased the length of H-ras(+/+) cells. CONCLUSIONS H-ras negatively regulates basal tone in the IAS by inhibiting RhoA/Rho-kinase machinery. Studies may have significant relevance in the pathophysiology and therapy of certain anorectal motility disorders associated with the IAS dysfunction.
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Affiliation(s)
- Márcio A F de Godoy
- Departments of Medicine, Division of Gastroenterology & Hepatology, Pharmacology and Experimental Therapeutics, and Emergency Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennyslvania 19107, USA
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Caraiscos VB, Bonin RP, Newell JG, Czerwinska E, Macdonald JF, Orser BA. Insulin increases the potency of glycine at ionotropic glycine receptors. Mol Pharmacol 2007; 71:1277-87. [PMID: 17308032 DOI: 10.1124/mol.106.033563] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanisms by which insulin modulates neuronal plasticity and pain processes remain poorly understood. Here we report that insulin rapidly increases the function of glycine receptors in murine spinal neurons and recombinant human glycine receptors expressed in human embryonic kidney cells. Whole-cell patch-clamp recordings showed that insulin reversibly enhanced current evoked by exogenous glycine and increased the amplitude of spontaneous glycinergic miniature inhibitory postsynaptic currents recorded in cultured spinal neurons. Insulin (1 microM) also shifted the glycine concentration-response plot to the left and reduced the glycine EC(50) value from 52 to 31 microM. Currents evoked by a submaximal concentration of glycine were increased to approximately 140% of control. The glycine receptor alpha subunit was sufficient for the enhancement by insulin because currents from recombinant homomeric alpha(1) receptors and heteromeric alpha(1)beta receptors were both increased. Insulin acted at the insulin receptor via pathways dependent on tyrosine kinase and phosphatidylinositol 3 kinase because the insulin effect was eliminated by the insulin receptor antagonist, hydroxy-2-naphthalenylmethylphosphonic acid trisacetoxymethyl ester, the tyrosine kinase inhibitor lavendustin A, and the phosphatidylinositol 3 kinase antagonist wortmannin. Together, these results show that insulin has a novel regulatory action on the potency of glycine for ionotropic glycine receptors.
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Affiliation(s)
- Valerie B Caraiscos
- Institute of Medical Science, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
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35
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El-Shewy HM, Johnson KR, Lee MH, Jaffa AA, Obeid LM, Luttrell LM. Insulin-like Growth Factors Mediate Heterotrimeric G Protein-dependent ERK1/2 Activation by Transactivating Sphingosine 1-Phosphate Receptors. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84052-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Abstract
Receptor tyrosine kinases (RTKs) are a unique family of cell surface receptors, each containing a common intracellular domain that has tyrosine kinase activity. However, RTKs share many signaling molecules with another unique family of cell surface receptors, the seven-transmembrane receptors (7TMRs), and these receptor families can activate similar signaling cascades. In this review of RTK signaling, we describe the role of cross talk between RTKs and 7TMRs, focusing specifically on the role played in this process by beta-arrestins and by G proteins.
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Affiliation(s)
- Christopher J Hupfeld
- Department of Medicine, Division of Endocrinology and Metabolism, University of California San Diego, La Jolla, California 92093, USA.
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37
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El-Shewy HM, Johnson KR, Lee MH, Jaffa AA, Obeid LM, Luttrell LM. Insulin-like growth factors mediate heterotrimeric G protein-dependent ERK1/2 activation by transactivating sphingosine 1-phosphate receptors. J Biol Chem 2006; 281:31399-407. [PMID: 16926156 DOI: 10.1074/jbc.m605339200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Although several studies have shown that a subset of insulin-like growth factor (IGF) signals require the activation of heterotrimeric G proteins, the molecular mechanisms underlying IGF-stimulated G protein signaling remain poorly understood. Here, we have studied the mechanism by which endogenous IGF receptors activate the ERK1/2 mitogen-activated protein kinase cascade in HEK293 cells. In these cells, treatment with pertussis toxin and expression of a Galpha(q/11)-(305-359) peptide that inhibits G(q/11) signaling additively inhibited IGF-stimulated ERK1/2 activation, indicating that the signal was almost completely G protein-dependent. Treatment with IGF-1 or IGF-2 promoted translocation of green fluorescent protein (GFP)-tagged sphingosine kinase (SK) 1 from the cytosol to the plasma membrane, increased endogenous SK activity within 30 s of stimulation, and caused a statistically significant increase in intracellular and extracellular sphingosine 1-phosphate (S1P) concentration. Using a GFP-tagged S1P1 receptor as a biological sensor for the generation of physiologically relevant S1P levels, we found that IGF-1 and IGF-2 induced GFP-S1P receptor internalization and that the effect was blocked by pretreatment with the SK inhibitor, dimethylsphingosine. Treating cells with dimethylsphingosine, silencing SK1 expression by RNA interference, and blocking endogenous S1P receptors with the competitive antagonist VPC23019 all significantly inhibited IGF-stimulated ERK1/2 activation, suggesting that IGFs elicit G protein-dependent ERK1/2 activation by stimulating SK1-dependent transactivation of S1P receptors. Given the ubiquity of SK and S1P receptor expression, S1P receptor transactivation may represent a general mechanism for G protein-dependent signaling by non-G protein-coupled receptors.
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Affiliation(s)
- Hesham M El-Shewy
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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38
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Kuemmerle JF. Occupation of alphavbeta3-integrin by endogenous ligands modulates IGF-I receptor activation and proliferation of human intestinal smooth muscle. Am J Physiol Gastrointest Liver Physiol 2006; 290:G1194-202. [PMID: 16195423 DOI: 10.1152/ajpgi.00345.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have previously shown that endogenous IGF-I regulates growth of human intestinal smooth muscle cells by stimulating proliferation and inhibiting apoptosis. In active Crohn's disease, expression of IGF-I and the alpha(v)beta(3)-integrin receptor ligands fibronectin and vitronectin is increased. The aim of the present study was to determine whether occupation of the alpha(v)beta(3)-receptor influences IGF-I receptor tyrosine kinase activation and function in human intestinal smooth muscle cells. In untreated cells, IGF-I elicited time-dependent tyrosine phosphorylation of its cognate receptor that was maximal within 2 min and sustained for 30 min. In the presence of the alpha(v)beta(3)-ligand fibronectin, IGF-I-stimulated IGF-I receptor activation was augmented. Conversely, in the presence of the alpha(v)beta(3)-specific disintegrin echistatin, IGF-I-stimulated IGF-I receptor tyrosine kinase phosphorylation was inhibited. IGF-I-stimulated IGF-I receptor activation was accompanied by recruitment of the adapter protein IRS-1, activation of Erk1/2, p70S6 kinase, and proliferation. These effects were augmented by fibronectin and attenuated by echistatin. IGF-I also elicited time-dependent recruitment of protein tyrosine phosphatase SHP-2 that coincided with dephosphorylation of the tyrosine phosphorylated IGF-I receptor tyrosine kinase. The alpha(v)beta(3)-disintegrin echistatin accelerated the rate of SHP-2 recruitment and deactivation of the IGF-I receptor tyrosine kinase. The results show that occupancy of the alpha(v)beta(3)-integrin receptor modulates IGF-I-induced IGF-I receptor activation and function in human intestinal muscle cells. We hypothesize that the concomitant increases in the expression of alpha(v)beta(3)-ligands and of IGF-I in active Crohn's disease may contribute to muscle hyperplasia and stricture formation by acting in concert to augment IGF-I-stimulated IGF-I receptor tyrosine kinase activity and IGF-I-mediated muscle cell growth.
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Affiliation(s)
- John F Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, 23298-0341, USA.
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39
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Ye P, D'Ercole AJ. Insulin-like growth factor actions during development of neural stem cells and progenitors in the central nervous system. J Neurosci Res 2006; 83:1-6. [PMID: 16294334 DOI: 10.1002/jnr.20688] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Insulin-like growth factor-I (IGF-I) plays a key role in normal development. Recent studies show that IGF-I exerts a wide variety actions in the central nervous system during development as well as in adulthood. This report reviews recent developments on IGF-I actions and its mechanisms in the central nervous system, with a focus on its actions during the development of neural stem cells and progenitors. Available data strongly indicate that IGF-I shortens the length of the cell cycle in neuron progenitors during embryonic life and has an influence on the growth of all neural cell types. The phosphatidylinositol-3 kinase/Akt and mitogen-activated protein kinase pathways seem to be the predominant mediators of IGF-I-stimulated neural cell proliferation and survival. IGF-I actions, however, likely depend on cell type, developmental stage, and microenvironmental milieu.
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Affiliation(s)
- Ping Ye
- Department of Pediatrics, The University of North Carolina at Chapel Hill, 27599-7220, USA.
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Leung T, Chen H, Stauffer AM, Giger KE, Sinha S, Horstick EJ, Humbert JE, Hansen CA, Robishaw JD. Zebrafish G protein gamma2 is required for VEGF signaling during angiogenesis. Blood 2006; 108:160-6. [PMID: 16537812 PMCID: PMC1895829 DOI: 10.1182/blood-2005-09-3706] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Vascular endothelial growth factor (VEGF) is a major mediator of pathologic angiogenesis, a process necessary for the formation of new blood vessels to support tumor growth. Historically, VEGF has been thought to signal via receptor tyrosine kinases, which are not typically considered to be G protein dependent. Here, we show that targeted knockdown of the G protein gng2 gene (Ggamma2) blocks the normal angiogenic process in developing zebrafish embryos. Moreover, loss of gng2 function inhibits the ability of VEGF to promote the angiogenic sprouting of blood vessels by attenuating VEGF induced phosphorylation of phospholipase C-gamma1 (PLCgamma1) and serine/threonine kinase (AKT). Collectively, these results demonstrate a novel interaction between Ggamma2- and VEGF-dependent pathways to regulate the angiogenic process in a whole-animal model. Blocking VEGF function using a humanized anti-VEGF antibody has emerged as a promising treatment for colorectal, non-small lung cell, and breast cancers. However, this treatment may cause considerable side effects. Our findings provide a new opportunity for cotargeting G protein- and VEGF-dependent pathways to synergistically block pathologic angiogenesis, which may lead to a safer and more efficacious therapeutic regimen to fight cancer.
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Affiliation(s)
- Tinchung Leung
- Weis Center for Research, Geisinger Health System, Danville, PA 17822, USA
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41
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Kovach SJ, Price JA, Shaw CM, Theodorakis NG, McKillop IH. Role of cyclic-AMP responsive element binding (CREB) proteins in cell proliferation in a rat model of hepatocellular carcinoma. J Cell Physiol 2006; 206:411-9. [PMID: 16110470 DOI: 10.1002/jcp.20474] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The role of cyclic adenosine monophosphate (cAMP) is poorly understood in the regulation of normal and abnormal hepatic cell growth. In this study, we examined the regulation of intracellular cAMP levels and its effect on nuclear cAMP responsive elements (CREs) in a rat model of hepatocellular carcinoma (HCC). Tumorigenic liver cells were cultured from an in vivo model of HCC and the role of cAMP in cell mitogenesis determined. These data demonstrated agents that elevate intracellular cAMP ([cAMP]i) levels caused significant dose-dependent inhibition of serum-stimulated mitogenesis in HCC cells. Cells were next analyzed for transcription factor expression and activity following increased [cAMP]i. These data demonstrated time- and dose-dependent increases in CRE binding protein (pCREB) activity, a maximal response occurring after 10-20 min before returning to basal levels within 60 min. In contrast, increased [cAMP]i levels led to sustained inducible cAMP early repressor (ICER) II/IIgamma mRNA and protein induction. To understand these data in relation to the in vivo setting, HCC tumors were analyzed and compared to pair-matched normal liver (NL) samples. These studies demonstrated significantly elevated Gsalpha-protein expression in HCC versus NL in the absence of significant changes in basal cAMP levels. Analysis of total and active CREB demonstrated significantly increased total CREB/pCREB in HCC versus NL. Further analysis of CRE expression demonstrated significantly increased expression of ICER mRNA and protein in HCC versus sham operated (Sh). These data demonstrate cAMP, while capable of stimulating promitogenic CREB activation inhibits cell mitogenesis in HCC possibly via ICER induction.
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Affiliation(s)
- Stephen J Kovach
- Department of Surgery, University of Rochester Medical Center, Rochester, New York, USA
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Popken GJ, Dechert-Zeger M, Ye P, D'Ercole AJ. Brain Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2005; 567:187-220. [PMID: 16372399 DOI: 10.1007/0-387-26274-1_8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- Gregory J Popken
- Division Pediatric Endocrinology, Department of Pediatrics, University of North Carolina at Chapel Hill, NC 27599-7039, USA
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43
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El Yafi F, Winkler R, Delvenne P, Boussif N, Belaiche J, Louis E. Altered expression of type I insulin-like growth factor receptor in Crohn's disease. Clin Exp Immunol 2005; 139:526-33. [PMID: 15730399 PMCID: PMC1809313 DOI: 10.1111/j.1365-2249.2004.02724.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The fibrotic and antiapoptotic effects of insulin-like growth factors (IGF) are mediated by type I IGF receptor (IGF-1R). IGFs could play a role in intestinal stricturing and in the maintenance of inflammation in Crohn's disease (CD). We aimed to describe IGF-1R expression in CD intestinal lesions, to compare it to other intestinal inflammatory diseases and to correlate it with fibrosis and apoptosis. IGF-1R expression and apoptosis (active caspase-3) were studied by immunohistochemistry. Surgical intestinal specimens [17 CD, nine controls, six diverticulitis and four ulcerative colitis (UC)] were used. IGF-1R was expressed transmurally mainly by inflammatory cells (IC) and smooth muscle cells, both in diseased intestine and controls. IGF-1R positive IC were increased in the mucosa and the submucosa of CD (P < 0.007), and in involved areas compared to uninvolved areas (P = 0.03). In UC, the number of IGF-1R positive IC was only increased in the mucosa, and was not different from controls in the submucosa. In diverticulitis, the number of IGF-1R positive IC did not differ from controls. In CD submucosa, IGF-1R expression in IC was inversely correlated with apoptosis in uninvolved areas (P = 0.01). Expression of IGF-1R in submucosal fibroblast-like cells, subserosal adipocytes and hypertrophic nervous plexi was specific for CD. We have shown a transmural altered expression of IGF-1R in CD. This may suggest a role for IGF-1R in the maintenance of chronic inflammation and stricture formation in CD.
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Affiliation(s)
- F El Yafi
- Department of Gastroenterology, CHU of Liège, Liège, Belgium
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Kristiansen K. Molecular mechanisms of ligand binding, signaling, and regulation within the superfamily of G-protein-coupled receptors: molecular modeling and mutagenesis approaches to receptor structure and function. Pharmacol Ther 2004; 103:21-80. [PMID: 15251227 DOI: 10.1016/j.pharmthera.2004.05.002] [Citation(s) in RCA: 392] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The superfamily of G-protein-coupled receptors (GPCRs) could be subclassified into 7 families (A, B, large N-terminal family B-7 transmembrane helix, C, Frizzled/Smoothened, taste 2, and vomeronasal 1 receptors) among mammalian species. Cloning and functional studies of GPCRs have revealed that the superfamily of GPCRs comprises receptors for chemically diverse native ligands including (1) endogenous compounds like amines, peptides, and Wnt proteins (i.e., secreted proteins activating Frizzled receptors); (2) endogenous cell surface adhesion molecules; and (3) photons and exogenous compounds like odorants. The combined use of site-directed mutagenesis and molecular modeling approaches have provided detailed insight into molecular mechanisms of ligand binding, receptor folding, receptor activation, G-protein coupling, and regulation of GPCRs. The vast majority of family A, B, C, vomeronasal 1, and taste 2 receptors are able to transduce signals into cells through G-protein coupling. However, G-protein-independent signaling mechanisms have also been reported for many GPCRs. Specific interaction motifs in the intracellular parts of these receptors allow them to interact with scaffold proteins. Protein engineering techniques have provided information on molecular mechanisms of GPCR-accessory protein, GPCR-GPCR, and GPCR-scaffold protein interactions. Site-directed mutagenesis and molecular dynamics simulations have revealed that the inactive state conformations are stabilized by specific interhelical and intrahelical salt bridge interactions and hydrophobic-type interactions. Constitutively activating mutations or agonist binding disrupts such constraining interactions leading to receptor conformations that associates with and activate G-proteins.
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Affiliation(s)
- Kurt Kristiansen
- Department of Pharmacology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
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Kuemmerle JF, Murthy KS, Bowers JG. IGFBP-3 activates TGF-beta receptors and directly inhibits growth in human intestinal smooth muscle cells. Am J Physiol Gastrointest Liver Physiol 2004; 287:G795-802. [PMID: 15178549 DOI: 10.1152/ajpgi.00009.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have shown that human intestinal smooth muscle cells produce IGF-I and IGF binding protein-3 (IGFBP-3). Endogenous IGF-I acts in autocrine fashion to stimulate growth of these cells. IGFBP-3 inhibits the binding of IGF-I to its receptor and thereby inhibits IGF-I-stimulated growth. In several carcinoma cell lines and some normal cells, IGFBP-3 regulates growth independently of IGF-I. Two mechanisms for this effect have been identified: IGFBP-3 can directly activate transforming growth factor-beta (TGF-beta) receptors or it can undergo direct nuclear translocation. The aim of the present study was to determine whether IGFBP-3 acts independently of IGF-I and to characterize the mechanisms mediating this effect in human intestinal smooth muscle cells. The direct effects of IGFBP-3 were determined in the presence of an IGF-I receptor antagonist to eliminate its IGF-I-dependent effects. Affinity labeling of TGF-beta receptors (TGF-betaRI, TGF-betaRII, and TGF-betaRV) with 125I-labeled TGF-beta1 showed that IGFBP-3 displaced binding to TGF-betaRII and TGF-betaRV in a concentration-dependent fashion. IGFBP-3 stimulated TGF-betaRII-dependent serine phosphorylation (activation) of both TGF-betaRI and of its primary substrate, Smad2(Ser465/467). IGFBP-3 also caused IGF-I-independent inhibition of basal [3H]thymidine incorporation. The effects of IGFBP-3 on Smad2 phosphorylation and on smooth muscle cell proliferation were independent of TGF-beta1 and were abolished by transfection of Smad2 siRNA. Immunoneutralization of IGFBP-3 increased basal [3H]thymidine incorporation, implying that endogenous IGFBP-3 inhibits proliferation. We conclude that endogenous IGFBP-3 directly inhibits proliferation of human intestinal smooth muscle cells by activation of TGF-betaRI and Smad2, an effect that is independent of its effect on IGF-I-stimulated growth.
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Affiliation(s)
- John F Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298-0711, USA.
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Patel TB. Single Transmembrane Spanning Heterotrimeric G Protein-Coupled Receptors and Their Signaling Cascades. Pharmacol Rev 2004; 56:371-85. [PMID: 15317909 DOI: 10.1124/pr.56.3.4] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Heptahelical of serpentine receptors such as the adrenergic receptors are well known to mediate their actions via heterotrimeric GTP-binding proteins. Likewise, receptors that traverse the cell membrane once have been shown to mediate their biological actions by activating several different mechanisms including stimulation of their intrinsic tyrosine kinase activities or the kinase activities of other proteins. Some of these single transmembrane receptors have an intrinsic guanylyl cyclase activity and can stimulate the cyclic GMP second messenger system; however, over the last few years, several studies have shown the involvement of heterotrimeric GTP-binding proteins in mediating signals that eventually culminate in the biological actions of single transmembrane spanning receptors and proteins. These receptors include the receptor tyrosine kinases that mediate the actions of growth factors such as epidermal growth factor, insulin, insulin-like growth factor as well as receptors for atrial natiuretic hormone or the zona pellucida protein (ZP3) and integrins. In this review, the significance of the coupling of the single transmembrane spanning receptors to G proteins has been highlighted by providing several examples of the concept that signaling via these receptors may involve the activation of multiple signaling cascades.
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Affiliation(s)
- Tarun B Patel
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60513, USA.
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Verma-Kurvari S, Parada LF. Identification of tyrosine kinases expressed in the male mouse gubernaculum during development. Dev Dyn 2004; 230:660-5. [PMID: 15254900 DOI: 10.1002/dvdy.20090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The gubernaculum is a mesenchymal tissue that connects the gonads to the inguinal abdominal wall in the mammalian embryo. During gestation in the male, differential development of the gubernaculum and regression of the cranial suspensory ligament coordinate the first phase of testicular descent. As many as 1-3% newborn boys show impaired testicular descent, in part due to problems in gubernacular development. Little is known about the signaling molecules and cascades that are required for the development and differentiation of the gubernaculum. Protein tyrosine kinases comprise a large class of proteins that play important roles in proliferation, differentiation, and many aspects of cell-cell signaling in tissues. To date, no information on the existence of members of tyrosine kinase family in gubernaculum is available. We used a reverse transcription-polymerase chain reaction approach to identify 25 individual members of cytoplasmic and receptor tyrosine kinase classes in the developing male gubernaculum. The analysis of cellular distribution suggests that each tyrosine kinase examined may play a unique role in gubernacular development and differentiation.
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Affiliation(s)
- Sunita Verma-Kurvari
- Center for Developmental Biology, University of Texas Southwestern Medical Center, Dallas, 73590, USA
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Waters C, Pyne S, Pyne NJ. The role of G-protein coupled receptors and associated proteins in receptor tyrosine kinase signal transduction. Semin Cell Dev Biol 2004; 15:309-23. [PMID: 15125894 DOI: 10.1016/j.semcdb.2003.12.020] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It is well established that stimulation of G-protein coupled receptors (GPCRs) can activate signalling from receptor tyrosine kinases by a process termed transactivation. Indeed, in recent years, it has become apparent that transactivation is a general phenomenon that has been demonstrated for many unrelated GPCRs and receptor tyrosine kinases. In this case the GPCR/G-protein participation is up-stream of the receptor tyrosine kinase. Substantial research has addressed these findings but meanwhile another mechanism of cross talk has been slowly emerging. For over a decade, a growing body of evidence has demonstrated that numerous growth factors use G-proteins and attendant signalling molecules such as beta-arrestins that participate down-stream of the receptor tyrosine kinase to signal to effectors, such as p42/p44 MAPK. This review highlights this novel mechanism of cross talk between receptor tyrosine kinases and GPCRs, which is distinct from growth factor receptor transactivation by GPCRs.
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Affiliation(s)
- Catherine Waters
- Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 ONR, Scotland, UK
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Kuemmerle JF, Zhou H, Bowers JG. IGF-I stimulates human intestinal smooth muscle cell growth by regulation of G1 phase cell cycle proteins. Am J Physiol Gastrointest Liver Physiol 2004; 286:G412-9. [PMID: 14592948 DOI: 10.1152/ajpgi.00403.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Autocrine production of insulin-like growth factor-I (IGF-I) regulates growth of human intestinal muscle cells by activation of distinct phosphatidylinositol 3-kinase (PI3-kinase)-dependent and ERK1/2-dependent pathways. The aim of the present study was to determine the mechanisms by which IGF-I regulates the G(1) phase of the cell cycle and muscle cell proliferation. Incubation of quiescent cells with IGF-I stimulated time-dependent cell cycle progression measured by using fluorescence-activated cell sorting analysis and by incorporation of [(3)H]thymidine. Studies using a microarray-based approach were used initially to identify genes expressed in human intestinal muscle encoding proteins known to participate in the G(1) phase of the cell cycle that were regulated by IGF-I. Incubation of muscle cells for 24 h with IGF-I elicited greater than fivefold increase in the expression of cyclin D1 and greater than twofold increase in retinoblastoma protein (Rb1). IGF-I elicited a time-dependent increase in cyclin D1 protein levels mediated jointly by ERK1/2-dependent and PI3-kinase-dependent mechanisms. Increase in cyclin D1 levels was accompanied by a time-dependent increase in cyclin D1-dependent cyclin-dependent kinase-4 (CDK4) activity. IGF-I also elicited a rapid time-dependent increase in Rb-(Ser807/811) phosphorylation, the specific target of the cyclin D(1)-dependent CDK4 kinase, and a slower increase in total Rb protein levels. We conclude that IGF-I stimulates G(1) phase progression, DNA synthesis, and cell proliferation of human intestinal smooth muscle cells. Effects of IGF-I on proliferation are mediated jointly by ERK1/2-dependent and PI3-kinase-dependent pathways that regulate cyclin D1 levels, CDK4 activity, and Rb activity.
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Affiliation(s)
- John F Kuemmerle
- Department of Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, PO Box 980711, Richmond, VA 23298-0711, USA.
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Abstract
Signal transduction research investigating mechanisms of androgen-independent prostate cancer cell proliferation has historically focused on the role of androgen and peptide growth factor receptors. More recent work has raised the idea that intracellular signaling mechanisms triggered by extracellular hormonal factors acting through heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) can also mediate and sustain this pathologic process. Prostate cancer patients with advanced disease express elevated levels of GPCRs and GPCR ligands, suggesting that the GPCR system is activated in the cancerous gland and may contribute to tumor growth. Importantly, inhibition of G protein signaling attenuates prostate cancer cell growth in animal models. The nature of intracellular signaling pathways mediating mitogenic effects of GPCRs in prostate cancer is poorly defined, although the G protein-dependent activation of the Ras-to-mitogen-activated protein kinase pathway has emerged as a critical regulatory event. Activated GPCRs may also exert their mitogenic effects in the prostate by activating the androgen receptor.
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Affiliation(s)
- Yehia Daaka
- Department of Surgery and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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