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Cai T, Lenoir Capello R, Pi X, Wu H, Chou JJ. Structural basis of γ chain family receptor sharing at the membrane level. Science 2023; 381:569-576. [PMID: 37535730 DOI: 10.1126/science.add1219] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 06/23/2023] [Indexed: 08/05/2023]
Abstract
Common γ chain (γc) cytokine receptors, including interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21 receptors, are activated upon engagement with a common γc receptor (CD132) by concomitant binding of their ectodomains to an interleukin. In this work, we find that direct interactions between the transmembrane domains (TMDs) of both the γc and the interleukin receptors (ILRs) are also required for receptor activation. Moreover, the same γc TMD can specifically recognize multiple ILR TMDs of diverse sequences within the family. Heterodimer structures of γc TMD bound to IL-7 and IL-9 receptor TMDs-determined in a lipid bilayer-like environment by nuclear magnetic resonance spectroscopy-reveal a conserved knob-into-hole mechanism of recognition that mediates receptor sharing within the membrane. Thus, signaling in the γc receptor family requires specific heterotypic interactions of the TMDs.
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Affiliation(s)
- Tiantian Cai
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Rachel Lenoir Capello
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Xiong Pi
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Hao Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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2
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Molecular Cloning, Expression, Sequence Characterization and Structural Insight of Bubalus bubalis Growth Hormone-Receptor. Mol Biotechnol 2022:10.1007/s12033-022-00612-y. [DOI: 10.1007/s12033-022-00612-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 11/14/2022] [Indexed: 11/28/2022]
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3
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Sotolongo Bellón J, Birkholz O, Richter CP, Eull F, Kenneweg H, Wilmes S, Rothbauer U, You C, Walter MR, Kurre R, Piehler J. Four-color single-molecule imaging with engineered tags resolves the molecular architecture of signaling complexes in the plasma membrane. CELL REPORTS METHODS 2022; 2:100165. [PMID: 35474965 PMCID: PMC9017138 DOI: 10.1016/j.crmeth.2022.100165] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 11/19/2021] [Accepted: 01/13/2022] [Indexed: 12/22/2022]
Abstract
Localization and tracking of individual receptors by single-molecule imaging opens unique possibilities to unravel the assembly and dynamics of signaling complexes in the plasma membrane. We present a comprehensive workflow for imaging and analyzing receptor diffusion and interaction in live cells at single molecule level with up to four colors. Two engineered, monomeric GFP variants, which are orthogonally recognized by anti-GFP nanobodies, are employed for efficient and selective labeling of target proteins in the plasma membrane with photostable fluorescence dyes. This labeling technique enables us to quantitatively resolve the stoichiometry and dynamics of the interferon-γ (IFNγ) receptor signaling complex in the plasma membrane of living cells by multicolor single-molecule imaging. Based on versatile spatial and spatiotemporal correlation analyses, we identify ligand-induced receptor homo- and heterodimerization. Multicolor single-molecule co-tracking and quantitative single-molecule Förster resonance energy transfer moreover reveals transient assembly of IFNγ receptor heterotetramers and confirms its structural architecture.
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Affiliation(s)
- Junel Sotolongo Bellón
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Oliver Birkholz
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Christian P. Richter
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Florian Eull
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Hella Kenneweg
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Stephan Wilmes
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
- Division of Cell Signalling and Immunology, University of Dundee, School of Life Sciences, Dundee, UK
| | - Ulrich Rothbauer
- Pharmaceutical Biotechnology, Eberhard-Karls-University, Tübingen, Germany
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Changjiang You
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Mark R. Walter
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Rainer Kurre
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Jacob Piehler
- Department of Biology and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, Osnabrück, Germany
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Zhang Y, Gc S, Patel SB, Liu Y, Paterson AJ, Kappes JC, Jiang J, Frank SJ. Growth hormone (GH) receptor (GHR)-specific inhibition of GH-Induced signaling by soluble IGF-1 receptor (sol IGF-1R). Mol Cell Endocrinol 2019; 492:110445. [PMID: 31100495 PMCID: PMC6613819 DOI: 10.1016/j.mce.2019.05.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/06/2019] [Accepted: 05/07/2019] [Indexed: 12/31/2022]
Abstract
Human growth hormone (GH) binds and activates GH receptor (GHR) and prolactin (PRL) receptor (PRLR). LNCaP human prostate cancer cells express only GHR. A soluble fragment of IGF-1 receptor (IGF-1R) extracellular domain (sol IGF-1R) interacts with GHR and blocks GH signaling. We now explore sol IGF-1R's specificity for inhibiting GH signaling via GHR vs. PRLR and test GHR and PRLR extracellular domain inhibition determinants. Although T47D human breast cancer cells express GHR and PRLR, GH signaling is largely PRLR-mediated. In T47D, sol IGF-1R inhibited neither GH- nor PRL-induced STAT5 activation. However, sol IGF-1R inhibited GH-induced STAT5 activation in T47D-shPRLR cells, which harbor reduced PRLR. In MIN6 mouse β-cells, bovine GH (bGH) activates mouse GHR, not PRLR, while human GH activates mouse GHR and PRLR. In MIN6, sol IGF-1R inhibited bGH-induced STAT5 activation, but partially inhibited human GH-induced STAT5 activation. These findings suggest sol IGF-1R's inhibition is GHR-specific. Using a cellular reconstitution system, we compared effects of sol IGF-1R on signaling through GHR, PRLR, or chimeras in which extracellular subdomains 2 (S2) of the receptors were swapped. Sol IGF-1R inhibited GH-induced STAT5 activation in GHR-expressing, not PRLR-expressing cells, consistent with GHR specificity of sol IGF-1R. Interestingly, we found that GHR S2 (which harbors the GHR-GHR dimer interface) was required, but not sufficient for sol IGF-1R inhibition of GHR signaling. These results suggest sol IGF-1R specifically inhibits GH-induced GHR-mediated signaling, possibly through interaction with GHR S1 and S2 domains. Our findings have implications for GH antagonist development.
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Affiliation(s)
- Yue Zhang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sajina Gc
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sweta B Patel
- Department of Medicine, Division of Hematology and Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Ying Liu
- School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Andrew J Paterson
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - John C Kappes
- Department of Medicine, Division of Hematology and Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jing Jiang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Stuart J Frank
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, AL, 35233, USA.
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5
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Liu Y, Jiang J, Lepik B, Zhang Y, Zinn KR, Frank SJ. Subdomain 2, Not the Transmembrane Domain, Determines the Dimerization Partner of Growth Hormone Receptor and Prolactin Receptor. Endocrinology 2017; 158:3235-3248. [PMID: 28977606 PMCID: PMC5659695 DOI: 10.1210/en.2017-00469] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 07/27/2017] [Indexed: 01/09/2023]
Abstract
Growth hormone receptor (GHR) and prolactin (PRL) receptor (PRLR) are homologous transmembrane class I cytokine receptors. In humans, GH interacts with GHR homodimers or PRLR homodimers and PRL interacts with only PRLR homodimers to promote signaling. In human breast cancer cells endogenously expressing both receptors, GHR and PRLR specifically coimmunoprecipitate. We previously devised a split luciferase complementation assay to study GHR and PRLR assemblages. In this technique, firefly luciferase is split into two fragments (N- and C-terminal fragments of the luciferase), each without enzyme activity and tethered to the tails of two receptors. The fragments restore luciferase activity when brought close to each other by the receptors. Real-time ligand-induced complementation changes reflect the arrangement of receptors and indicate that GHR/PRLR is arranged as a heteromultimer comprised of GHR-GHR homodimers and PRLR-PRLR homodimers. We now dissect determinants for GHR and PRLR homodimerization versus heteroassociation. GHR and PRLR have extracellular domains comprised of the ligand-binding N-terminal subdomain 1 and a membrane-proximal subdomain 2 (S2), which fosters receptor-receptor contact. Based on previous studies of S2 versus the transmembrane domain (TMD) in GHR dimerization, we constructed GHR(PRLRS2), GHR(PRLRS2-TMD), and GHR(PRLRTMD), replacing GHR's S2 alone, S2 plus TMD, and TMD alone with PRLR's counterpart. We tested by complementation the ability of these chimeras and GHR or PRLR to homodimerize or heteroassociate. Comparing various combinations, we found GHR(PRLRS2) and GHR(PRLRS2-TMD) behaved as PRLR, whereas GHR(PRLRTMD) behaved as GHR regarding their dimerization partners. We conclude that S2 of GHR and PRLR, rather than their TMDs, determines their dimerization partner.
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Affiliation(s)
- Ying Liu
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Jing Jiang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Bradford Lepik
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Yue Zhang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Kurt R. Zinn
- Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Stuart J. Frank
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, Alabama 35294
- Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294
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6
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Ligand-induced type II interleukin-4 receptor dimers are sustained by rapid re-association within plasma membrane microcompartments. Nat Commun 2017; 8:15976. [PMID: 28706306 PMCID: PMC5519985 DOI: 10.1038/ncomms15976] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 05/16/2017] [Indexed: 12/14/2022] Open
Abstract
The spatiotemporal organization of cytokine receptors in the plasma membrane is still debated with models ranging from ligand-independent receptor pre-dimerization to ligand-induced receptor dimerization occurring only after receptor uptake into endosomes. Here, we explore the molecular and cellular determinants governing the assembly of the type II interleukin-4 receptor, taking advantage of various agonists binding the receptor subunits with different affinities and rate constants. Quantitative kinetic studies using artificial membranes confirm that receptor dimerization is governed by the two-dimensional ligand–receptor interactions and identify a critical role of the transmembrane domain in receptor dimerization. Single molecule localization microscopy at physiological cell surface expression levels, however, reveals efficient ligand-induced receptor dimerization by all ligands, largely independent of receptor binding affinities, in line with the similar STAT6 activation potencies observed for all IL-4 variants. Detailed spatiotemporal analyses suggest that kinetic trapping of receptor dimers in actin-dependent microcompartments sustains robust receptor dimerization and signalling. The contribution of ligands for cytokine receptor dimerization is still not fully understood. Here, the authors show the efficient ligand-induced dimerization of type II interleukin-4 receptor at the plasma membrane and the kinetic trapping of signalling complexes by actin-dependent membrane microdomains.
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Sakamoto A, Tsukamoto T, Furutani Y, Sudo Y, Shimada K, Tomita A, Kiyoi H, Kato T, Funatsu T. Live-cell single-molecule imaging of the cytokine receptor MPL for analysis of dynamic dimerization. J Mol Cell Biol 2016; 8:553-555. [DOI: 10.1093/jmcb/mjw027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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8
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Liu Y, Zhang Y, Jiang J, Lobie PE, Paulmurugan R, Langenheim JF, Chen WY, Zinn KR, Frank SJ. GHR/PRLR Heteromultimer Is Composed of GHR Homodimers and PRLR Homodimers. Mol Endocrinol 2016; 30:504-17. [PMID: 27003442 DOI: 10.1210/me.2015-1319] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
GH receptor (GHR) and prolactin (PRL) receptor (PRLR) are homologous transmembrane cytokine receptors. Each prehomodimerizes and ligand binding activates Janus Kinase 2 (JAK2)-signal transducer and activator of transcription (STAT) signaling pathways by inducing conformational changes within receptor homodimers. In humans, GHR is activated by GH, whereas PRLR is activated by both GH and PRL. We previously devised a split luciferase complementation assay, in which 1 receptor is fused to an N-terminal luciferase (Nluc) fragment, and the other receptor is fused to a C-terminal luciferase (Cluc) fragment. When receptors approximate, luciferase activity (complementation) results. Using this assay, we reported ligand-independent GHR-GHR complementation and GH-induced complementation changes characterized by acute augmentation above basal signal, consistent with induction of conformational changes that bring GHR cytoplasmic tails closer. We also demonstrated association between GHR and PRLR in T47D human breast cancer cells by coimmunoprecipitation, suggesting that, in addition to forming homodimers, these receptors form hetero-assemblages with functional consequences. We now extend these analyses to examine basal and ligand-induced complementation of coexpressed PRLR-Nluc and PRLR-Cluc chimeras and coexpressed GHR-Nluc and PRLR-Cluc chimeras. We find that PRLR-PRLR and GHR-PRLR form specifically interacting ligand-independent assemblages and that either GH or PRL augments PRLR-PRLR complementation, much like the GH-induced changes in GHR-GHR dimers. However, in contrast to the complementation patterns for GHR-GHR or PRLR-PRLR homomers, both GH and PRL caused decline in luciferase activity for GHR-PRLR heteromers. These and other data suggest that GHR and PRLR associate in complexes comprised of GHR-GHR/PRLR-PRLR heteromers consisting of GHR homodimers and PRLR homodimers, rather than GHR-PRLR heterodimers.
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Affiliation(s)
- Ying Liu
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Yue Zhang
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Jing Jiang
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Peter E Lobie
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Ramasamy Paulmurugan
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - John F Langenheim
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Wen Y Chen
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Kurt R Zinn
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Stuart J Frank
- Department of Medicine (Y.L., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism; Department of Radiology (K.R.Z.); and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
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9
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Wilmes S, Beutel O, Li Z, Francois-Newton V, Richter CP, Janning D, Kroll C, Hanhart P, Hötte K, You C, Uzé G, Pellegrini S, Piehler J. Receptor dimerization dynamics as a regulatory valve for plasticity of type I interferon signaling. ACTA ACUST UNITED AC 2015; 209:579-93. [PMID: 26008745 PMCID: PMC4442803 DOI: 10.1083/jcb.201412049] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Type I interferons (IFNs) activate differential cellular responses through a shared cell surface receptor composed of the two subunits, IFNAR1 and IFNAR2. We propose here a mechanistic model for how IFN receptor plasticity is regulated on the level of receptor dimerization. Quantitative single-molecule imaging of receptor assembly in the plasma membrane of living cells clearly identified IFN-induced dimerization of IFNAR1 and IFNAR2. The negative feedback regulator ubiquitin-specific protease 18 (USP18) potently interferes with the recruitment of IFNAR1 into the ternary complex, probably by impeding complex stabilization related to the associated Janus kinases. Thus, the responsiveness to IFNα2 is potently down-regulated after the first wave of gene induction, while IFNβ, due to its ∼100-fold higher binding affinity, is still able to efficiently recruit IFNAR1. Consistent with functional data, this novel regulatory mechanism at the level of receptor assembly explains how signaling by IFNβ is maintained over longer times compared with IFNα2 as a temporally encoded cause of functional receptor plasticity.
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Affiliation(s)
- Stephan Wilmes
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Oliver Beutel
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Zhi Li
- Institut Pasteur, Cytokine Signaling Unit, Centre National de la Recherche Scientifique URA1961, 75724 Paris, France
| | - Véronique Francois-Newton
- Institut Pasteur, Cytokine Signaling Unit, Centre National de la Recherche Scientifique URA1961, 75724 Paris, France
| | - Christian P Richter
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Dennis Janning
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Cindy Kroll
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Patrizia Hanhart
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Katharina Hötte
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Changjiang You
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
| | - Gilles Uzé
- Centre National de la Recherche Scientifique Montpellier, 34095 Montpellier, France
| | - Sandra Pellegrini
- Institut Pasteur, Cytokine Signaling Unit, Centre National de la Recherche Scientifique URA1961, 75724 Paris, France
| | - Jacob Piehler
- Department of Biology, Division of Biophysics, University of Osnabrück, 49074 Osnabrück, Germany
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10
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Waters M, Brooks A. JAK2 activation by growth hormone and other cytokines. Biochem J 2015; 466:1-11. [PMID: 25656053 PMCID: PMC4325515 DOI: 10.1042/bj20141293] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 11/17/2014] [Accepted: 11/24/2014] [Indexed: 12/30/2022]
Abstract
Growth hormone (GH) and structurally related cytokines regulate a great number of physiological and pathological processes. They do this by coupling their single transmembrane domain (TMD) receptors to cytoplasmic tyrosine kinases, either as homodimers or heterodimers. Recent studies have revealed that many of these receptors exist as constitutive dimers rather than being dimerized as a consequence of ligand binding, which has necessitated a new paradigm for describing their activation process. In the present study, we describe a model for activation of the tyrosine kinase Janus kinase 2 (JAK2) by the GH receptor homodimer based on biochemical data and molecular dynamics simulations. Binding of the bivalent ligand reorientates and rotates the receptor subunits, resulting in a transition from a form with parallel TMDs to one where the TMDs separate at the point of entry into the cytoplasm. This movement slides the pseudokinase inhibitory domain of one JAK kinase away from the kinase domain of the other JAK within the receptor dimer-JAK complex, allowing the two kinase domains to interact and trans-activate. This results in phosphorylation and activation of STATs and other signalling pathways linked to this receptor which then regulate postnatal growth, metabolism and stem cell activation. We believe that this model will apply to most if not all members of the class I cytokine receptor family, and will be useful in the design of small antagonists and agonists of therapeutic value.
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Key Words
- class i cytokine receptors
- cytokine receptor signalling
- growth hormone
- growth hormone receptor
- janus kinase 2 (jak2)
- srk family kinases
- cntf, ciliary neurotropic factor
- crh, cytokine receptor homology
- ct-1, cardiotropin-1
- ecd, extracellular domain
- epo, erythropoietin
- fniii, fibronectin iii-like
- gh, growth hormone
- gm-csf, granulocyte-macrophage colony-stimulating factor
- jak, janus kinase
- jm, juxtamembrane
- mab, monoclonal antibody
- osm, oncostatin-m
- pk, pseudokinase
- tmd, transmembrane domain
- tpo, thrombopoietin
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Affiliation(s)
- Michael J. Waters
- *Institute for Molecular Bioscience, The University of Queensland Institute, QLD 4072, Australia
| | - Andrew J. Brooks
- *Institute for Molecular Bioscience, The University of Queensland Institute, QLD 4072, Australia
- †The University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, QLD 4072, Australia
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Davies KT, Tsagkogeorga G, Bennett NC, Dávalos LM, Faulkes CG, Rossiter SJ. Molecular evolution of growth hormone and insulin-like growth factor 1 receptors in long-lived, small-bodied mammals. Gene 2014; 549:228-36. [DOI: 10.1016/j.gene.2014.07.061] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 07/16/2014] [Accepted: 07/23/2014] [Indexed: 10/25/2022]
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12
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Gan Y, Buckels A, Liu Y, Zhang Y, Paterson AJ, Jiang J, Zinn KR, Frank SJ. Human GH receptor-IGF-1 receptor interaction: implications for GH signaling. Mol Endocrinol 2014; 28:1841-54. [PMID: 25211187 DOI: 10.1210/me.2014-1174] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
GH signaling yields multiple anabolic and metabolic effects. GH binds the transmembrane GH receptor (GHR) to activate the intracellular GHR-associated tyrosine kinase, Janus kinase 2 (JAK2), and downstream signals, including signal transducer and activator of transcription 5 (STAT5) activation and IGF-1 gene expression. Some GH effects are partly mediated by GH-induced IGF-1 via IGF-1 receptor (IGF-1R), a tyrosine kinase receptor. We previously demonstrated in non-human cells that GH causes formation of a GHR-JAK2-IGF-1R complex and that presence of IGF-1R (even without IGF-1 binding) augments proximal GH signaling. In this study, we use human LNCaP prostate cancer cells as a model system to further study the IGF-1R's role in GH signaling. GH promoted JAK2 and GHR tyrosine phosphorylation and STAT5 activation in LNCaP cells. By coimmunoprecipitation and a new split luciferase complementation assay, we find that GH augments GHR/IGF-1R complex formation, which is inhibited by a Fab of an antagonistic anti-GHR monoclonal antibody. Short hairpin RNA-mediated IGF-1R silencing in LNCaP cells reduced GH-induced GHR, JAK2, and STAT5 phosphorylation. Similarly, a soluble IGF-1R extracellular domain fragment (sol IGF-1R) interacts with GHR in response to GH and blunts GH signaling. Sol IGF-1R also markedly inhibits GH-induced IGF-1 gene expression in both LNCaP cells and mouse primary osteoblast cells. On the basis of these and other findings, we propose a model in which IGF-1R augments GH signaling by allowing a putative IGF-1R-associated molecule that regulates GH signaling to access the activated GHR/JAK2 complex and envision sol IGF-1R as a dominant-negative inhibitor of this IGF-1R-mediated augmentation. Physiological implications of this new model are discussed.
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Affiliation(s)
- Yujun Gan
- Department of Medicine (Y.G., A.B., Y.L., Y.Z., A.J.P., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Departments of Radiology (K.R.Z.) and Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
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13
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Liu Y, Berry PA, Zhang Y, Jiang J, Lobie PE, Paulmurugan R, Langenheim JF, Chen WY, Zinn KR, Frank SJ. Dynamic analysis of GH receptor conformational changes by split luciferase complementation. Mol Endocrinol 2014; 28:1807-19. [PMID: 25188449 DOI: 10.1210/me.2014-1153] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The transmembrane GH receptor (GHR) exists at least in part as a preformed homodimer on the cell surface. Structural and biochemical studies suggest that GH binds GHR in a 1:2 stoichiometry to effect acute GHR conformational changes that trigger the activation of the receptor-associated tyrosine kinase, Janus kinase 2 (JAK2), and downstream signaling. Despite information about GHR-GHR association derived from elegant fluorescence resonance energy transfer/bioluminescence resonance energy transfer studies, an assessment of the dynamics of GH-induced GHR conformational changes has been lacking. To this end, we used a split luciferase complementation assay that allowed detection in living cells of specific ligand-independent GHR-GHR interaction. Furthermore, GH treatment acutely augmented complementation of enzyme activity between GHRs fused, respectively, to N- and C-terminal fragments of firefly luciferase. Analysis of the temporal pattern of GH-induced complementation changes, pharmacological manipulation, genetic alteration of JAK2 levels, and truncation of the GHR intracellular domain (ICD) tail suggested that GH acutely enhances proximity of the GHR homodimer partners independent of the presence of JAK2, phosphorylation of GHR-luciferase chimeras, or an intact ICD. However, subsequent reduction of complementation requires JAK2 kinase activity and the ICD tail. This conclusion is in contrast to existing models of the GHR activation process.
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Affiliation(s)
- Ying Liu
- Department of Medicine (Y.L., P.A.B., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Departments of Radiology (K.R.Z.), and Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; Cancer Science Institute of Singapore and Department of Pharmacology (P.E.L.), National University of Singapore, Singapore 119077; Department of Radiology (R.P.), Stanford University School of Medicine, Palo Alto, California 94304; Department of Biological Sciences (J.F.L., W.Y.C.), Clemson University, Clemson, South Carolina 29634; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
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14
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Xu J, Sun D, Jiang J, Deng L, Zhang Y, Yu H, Bahl D, Langenheim JF, Chen WY, Fuchs SY, Frank SJ. The role of prolactin receptor in GH signaling in breast cancer cells. Mol Endocrinol 2012. [PMID: 23192981 DOI: 10.1210/me.2012-1297] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH and prolactin (PRL) are structurally related hormones that exert important effects in disparate target tissues. Their receptors (GHR and PRLR) reside in the cytokine receptor superfamily and share signaling pathways. In humans, GH binds both GHR and PRLR, whereas PRL binds only PRLR. Both hormones and their receptors may be relevant in certain human and rodent cancers, including breast cancer. GH and PRL promote signaling in human T47D breast cancer cells that express both GHR and PRLR. Furthermore, GHR and PRLR associate in a fashion augmented acutely by GH, even though GH primarily activates PRLR, rather than GHR, in these cells. To better understand PRLR's impact, we examined the effects of PRLR knockdown on GHR availability and GH sensitivity in T47D cells. T47D-ShPRLR cells, in which PRLR expression was reduced by stable short hairpin RNA (shRNA) expression, were compared with T47D-SCR control cells. PRLR knockdown decreased the rate of GHR proteolytic turnover, yielding GHR protein increase and ensuing sensitization of these cells to GHR signaling events including phosphorylation of GHR, Janus kinase 2, and signal transducer and activator of transcription 5 (STAT5). Unlike in T47D-SCR cells, acute GH signaling in T47D-ShPRLR cells was not blocked by the PRLR antagonist G129R but was inhibited by the GHR-specific antagonist, anti-GHR(ext-mAb). Thus, GH's use of GHR rather than PRLR was manifested when PRLR was reduced. In contrast to acute effects, GH incubation for 2 h or longer yielded diminished STAT5 phosphorylation in T47D-ShPRLR cells compared with T47D-SCR, a finding perhaps explained by markedly greater GH-induced GHR down-regulation in cells with diminished PRLR. However, when stimulated with repeated 1-h pulses of GH separated by 3-h washout periods to more faithfully mimic physiological GH pulsatility, T47D-ShPRLR cells exhibited greater transactivation of a STAT5-responsive luciferase reporter than did T47D-SCR cells. Our data suggest that PRLR's presence meaningfully affects GHR use in breast cancer cells.
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Affiliation(s)
- Jie Xu
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Abstract
Prolactin and the prolactin receptors are members of a family of hormone/receptor pairs which include GH, erythropoietin, and other ligand/receptor pairs. The mechanisms of these ligand/receptor pairs have broad similarities, including general structures, ligand/receptor stoichiometries, and activation of several common signaling pathways. But significant variations in the structural and mechanistic details are present among these hormones and their type 1 receptors. The prolactin receptor is particularly interesting because it can be activated by three sequence-diverse human hormones: prolactin, GH, and placental lactogen. This system offers a unique opportunity to compare the detailed molecular mechanisms of these related hormone/receptor pairs. This review critically evaluates selected literature that informs these mechanisms, compares the mechanisms of the three lactogenic hormones, compares the mechanism with those of other class 1 ligand/receptor pairs, and identifies information that will be required to resolve mechanistic ambiguities. The literature describes distinct mechanistic differences between the three lactogenic hormones and their interaction with the prolactin receptor and describes more significant differences between the mechanisms by which other related ligands interact with and activate their receptors.
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Affiliation(s)
- Charles L Brooks
- Departments of Veterinary Biosciences and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
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Pang X, Zhou HX. A common model for cytokine receptor activation: combined scissor-like rotation and self-rotation of receptor dimer induced by class I cytokine. PLoS Comput Biol 2012; 8:e1002427. [PMID: 22412367 PMCID: PMC3297564 DOI: 10.1371/journal.pcbi.1002427] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 01/27/2012] [Indexed: 11/19/2022] Open
Abstract
The precise mechanism by which the binding of a class I cytokine to the extracellular domain of its corresponding receptor transmits a signal through the cell membrane remains unclear. Receptor activation involves a cytokine-receptor complex with a 1∶2 stoichiometry. Previously we used our transient-complex theory to calculate the rate constant of the initial cytokine-receptor binding to form a 1∶1 complex. Here we computed the binding pathway leading to the 1∶2 activation complex. Three cytokine systems (growth hormone, erythropoietin, and prolactin) were studied, and the focus was on the binding of the extracellular domain of the second receptor molecule after forming the 1∶1 complex. According to the transient-complex theory, translational and rotation diffusion of the binding entities bring them together to form a transient complex, which has near-native relative separation and orientation but not the short-range specific native interactions. Subsequently conformational rearrangement leads to the formation of the native complex. We found that the changes in relative orientations between the two receptor molecules from the transient complex to the 1∶2 native complex are similar for the three cytokine-receptor systems. We thus propose a common model for receptor activation by class I cytokines, involving combined scissor-like rotation and self-rotation of the two receptor molecules. Both types of rotations seem essential: the scissor-like rotation separates the intracellular domains of the two receptor molecules to make room for the associated Janus kinase molecules, while the self-rotation allows them to orient properly for transphosphorylation. This activation model explains a host of experimental observations. The transient-complex based approach presented here may provide a strategy for designing antagonists and prove useful for elucidating activation mechanisms of other receptors.
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Affiliation(s)
- Xiaodong Pang
- Department of Physics, Florida State University, Tallahassee, Florida, United States of America
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
| | - Huan-Xiang Zhou
- Department of Physics, Florida State University, Tallahassee, Florida, United States of America
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
- * E-mail:
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Jiang J, Wan Y, Wang X, Xu J, Harris JM, Lobie PE, Zhang Y, Zinn KR, Waters MJ, Frank SJ. Inhibitory GH receptor extracellular domain monoclonal antibodies: three-dimensional epitope mapping. Endocrinology 2011; 152:4777-88. [PMID: 21990310 PMCID: PMC3230063 DOI: 10.1210/en.2011-1336] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GH receptor (GHR) mediates the anabolic and metabolic effects of GH. We previously characterized a monoclonal antibody (anti-GHR(ext-mAb)) that reacts with subdomain 2 of the rabbit GHR extracellular domain (ECD) and is a conformation-specific inhibitor of GH signaling in cells bearing rabbit or human GHR. Notably, this antibody has little effect on GH binding and also inhibits inducible metalloproteolysis of the GHR that occurs in the perimembranous ECD stem region. In the current study, we demonstrate that anti-GHR(ext-mAb) inhibits GH-dependent cellular proliferation and also inhibits hepatic GH signaling in vivo in mice that adenovirally express rabbit GHR, as assessed with our noninvasive bioluminescence hepatic signaling assay. A separate monoclonal antibody (anti-GHR(mAb 18.24)) is a sister clone of anti-GHR(ext-mAb). Here, we demonstrate that anti-GHR(mAb 18.24) also inhibits rabbit and human GHR signaling and inducible receptor proteolysis. Further, we use a random PCR-generated mutagenic expression system to map the three-dimensional epitopes in the rabbit GHR ECD for both anti-GHR(ext-mAb) and anti-GHR(mAb 18.24). We find that each of the two antibodies has similar, but nonidentical, discontinuous epitopes that include regions of subdomain 2 encompassing the dimerization interface. These results have fundamental implications for understanding the role of the dimerization interface and subdomain 2 in GHR activation and regulated GHR metalloproteolysis and may inform development of therapeutics that target GHR.
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Affiliation(s)
- Jing Jiang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0012, USA
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18
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Bernier AJ, Zhang J, Lillehoj E, Shaw ARE, Gunasekara N, Hugh JC. Non-cysteine linked MUC1 cytoplasmic dimers are required for Src recruitment and ICAM-1 binding induced cell invasion. Mol Cancer 2011; 10:93. [PMID: 21798038 PMCID: PMC3161956 DOI: 10.1186/1476-4598-10-93] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 07/28/2011] [Indexed: 12/26/2022] Open
Abstract
Background The mucin MUC1, a type I transmembrane glycoprotein, is overexpressed in breast cancer and has been correlated with increased metastasis. We were the first to report binding between MUC1 and Intercellular adhesion molecule-1 (ICAM-1), which is expressed on stromal and endothelial cells throughout the migratory tract of a metastasizing breast cancer cell. Subsequently, we found that MUC1/ICAM-1 binding results in pro-migratory calcium oscillations, cytoskeletal reorganization, and simulated transendothelial migration. These events were found to involve Src kinase, a non-receptor tyrosine kinase also implicated in breast cancer initiation and progression. Here, we further investigated the mechanism of MUC1/ICAM-1 signalling, focusing on the role of MUC1 dimerization in Src recruitment and pro-metastatic signalling. Methods To assay MUC1 dimerization, we used a chemical crosslinker which allowed for the detection of dimers on SDS-PAGE. We then generated MUC1 constructs containing an engineered domain which allowed for manipulation of dimerization status through the addition of ligands to the engineered domain. Following manipulation of dimerization, we immunoprecipitated MUC1 to investigate recruitment of Src, or assayed for our previously observed ICAM-1 binding induced events. To investigate the nature of MUC1 dimers, we used both non-reducing SDS-PAGE and generated a mutant construct lacking cysteine residues. Results We first demonstrate that the previously observed MUC1/ICAM-1signalling events are dependent on the activity of Src kinase. We then report that MUC1 forms constitutive cytoplasmic domain dimers which are necessary for Src recruitment, ICAM-1 induced calcium oscillations and simulated transendothelial migration. The dimers are not covalently linked constitutively or following ICAM-1 binding. In contrast to previously published reports, we found that membrane proximal cysteine residues were not involved in dimerization or ICAM-1 induced signalling. Conclusions Our data implicates non-cysteine linked MUC1 dimerization in cell signalling pathways required for cancer cell migration.
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Affiliation(s)
- Ashlyn J Bernier
- Department of Laboratory Medicine and Pathology, 3-70 Heritage Medical Research Centre, University of Alberta, Edmonton, AB, T6G 2S2, Canada
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Xu J, Zhang Y, Berry PA, Jiang J, Lobie PE, Langenheim JF, Chen WY, Frank SJ. Growth hormone signaling in human T47D breast cancer cells: potential role for a growth hormone receptor-prolactin receptor complex. Mol Endocrinol 2011; 25:597-610. [PMID: 21310852 DOI: 10.1210/me.2010-0255] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH receptor (GHR) and prolactin (PRL) receptor (PRLR) are structurally similar cytokine receptor superfamily members that are highly conserved among species. GH has growth-promoting and metabolic effects in various tissues in vertebrates, including humans. PRL is essential for regulation of lactation in mammals. Recent studies indicate that breast tissue bears GHR and PRLR and that both GH and PRL may impact development or behavior of breast cancer cells. An important facet of human GH (hGH) and human PRL (hPRL) biology is that although hPRL interacts only with hPRLR, hGH binds well to both hGHR and hPRLR. Presently, we investigated potential signaling effects of both hormones in the estrogen receptor- and progesterone receptor-positive human T47D breast cancer cell line. We found that this cell type expresses ample GHR and PRLR and responds well to both hGH and hPRL, as evidenced by activation of the Janus kinase 2/signal transducer and activator of transcription 5 pathway. Immunoprecipitation studies revealed specific GHR-PRLR association in these cells that was acutely enhanced by GH treatment. Although GH caused formation of disulfide-linked and chemically cross-linked GHR dimers in T47D cells, GH preferentially induced tyrosine phosphorylation of PRLR rather than GHR. Notably, both a GHR-specific ligand antagonist (B2036) and a GHR-specific antagonist monoclonal antibody (anti-GHR(ext-mAb)) failed to inhibit GH-induced signal transducer and activator of transcription 5 activation. In contrast, although the non-GHR-specific GH antagonist (G120R) and the PRL antagonist (G129R) individually only partially inhibited GH-induced activation, combined treatment with these two antagonists conferred greater inhibition than either alone. These data indicate that endogenous GHR and PRLR associate (possibly as a GHR-PRLR heterodimer) in human breast cancer cells and that GH signaling in these cells is largely mediated by the PRLR in the context of both PRLR-PRLR homodimers and GHR-PRLR heterodimers, broadening our understanding of how these related hormones and their related receptors may function in physiology and pathophysiology.
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Affiliation(s)
- Jie Xu
- Department of Medicine, University of Alabama at Birmingham, Alabama 35294-0012, USA
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Abstract
Growth hormone is widely used clinically to promote growth and anabolism and for other purposes. Its actions are mediated via the growth hormone receptor, both directly by tyrosine kinase activation and indirectly by induction of insulin-like growth factor 1 (IGF-1). Insensitivity to growth hormone (Laron syndrome) can result from mutations in the growth hormone receptor and can be treated with IGF-1. This treatment is, however, not fully effective owing to the loss of the direct actions of growth hormone and altered availability of exogenous IGF-1. Excessive activation of the growth hormone receptor by circulating growth hormone results in gigantism and acromegaly, whereas cell transformation and cancer can occur in response to autocrine activation of the receptor. Advances in understanding the mechanism of receptor activation have led to a model in which the growth hormone receptor exists as a constitutive dimer. Binding of the hormone realigns the subunits by rotation and closer apposition, resulting in juxtaposition of the catalytic domains of the associated tyrosine-protein kinase JAK2 below the cell membrane. This change results in activation of JAK2 by transphosphorylation, then phosphorylation of receptor tyrosines in the cytoplasmic domain, which enables binding of adaptor proteins, as well as direct phosphorylation of target proteins. This model is discussed in the light of salient information from closely related class 1 cytokine receptors, such as the erythropoietin, prolactin and thrombopoietin receptors.
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Affiliation(s)
- Andrew J Brooks
- The University of Queensland, Institute for Molecular Bioscience, St Lucia, Qld 4072, Australia.
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Vijayakumar A, Novosyadlyy R, Wu Y, Yakar S, LeRoith D. Biological effects of growth hormone on carbohydrate and lipid metabolism. Growth Horm IGF Res 2010; 20:1-7. [PMID: 19800274 PMCID: PMC2815161 DOI: 10.1016/j.ghir.2009.09.002] [Citation(s) in RCA: 186] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 09/01/2009] [Accepted: 09/04/2009] [Indexed: 01/05/2023]
Abstract
This review will summarize the metabolic effects of growth hormone (GH) on the adipose tissue, liver, and skeletal muscle with focus on lipid and carbohydrate metabolism. The metabolic effects of GH predominantly involve the stimulation of lipolysis in the adipose tissue resulting in an increased flux of free fatty acids (FFAs) into the circulation. In the muscle and liver, GH stimulates triglyceride (TG) uptake, by enhancing lipoprotein lipase (LPL) expression, and its subsequent storage. The effects of GH on carbohydrate metabolism are more complicated and may be mediated indirectly via the antagonism of insulin action. Furthermore, GH has a net anabolic effect on protein metabolism although the molecular mechanisms of its actions are not completely understood. The major questions that still remain to be answered are (i) What are the molecular mechanisms by which GH regulates substrate metabolism? (ii) Does GH affect substrate metabolism directly or indirectly via IGF-1 or antagonism of insulin action?
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Affiliation(s)
- Archana Vijayakumar
- Division of Endocrinology, Diabetes and Bone Diseases, The Samuel Bronfman Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA
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Cannata D, Vijayakumar A, Fierz Y, LeRoith D. The GH/IGF-1 axis in growth and development: new insights derived from animal models. Adv Pediatr 2010; 57:331-51. [PMID: 21056746 DOI: 10.1016/j.yapd.2010.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Dara Cannata
- Division of Endocrinology, Diabetes and Bone Diseases, The Samuel Bronfman Department of Medicine, Mount Sinai School of Medicine, One Gustave L. Levy Place, Atran 4th Floor-36, PO Box 1055, New York, NY 10029-6574, USA
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Growth hormone receptor targeting to lipid rafts requires extracellular subdomain 2. Biochem Biophys Res Commun 2010; 391:414-8. [DOI: 10.1016/j.bbrc.2009.11.072] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Accepted: 11/10/2009] [Indexed: 11/21/2022]
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Poger D, Mark AE. Turning the growth hormone receptor on: Evidence that hormone binding induces subunit rotation. Proteins 2009; 78:1163-74. [DOI: 10.1002/prot.22636] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Clevenger CV, Gadd SL, Zheng J. New mechanisms for PRLr action in breast cancer. Trends Endocrinol Metab 2009; 20:223-9. [PMID: 19535262 DOI: 10.1016/j.tem.2009.03.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 03/05/2009] [Accepted: 03/06/2009] [Indexed: 12/23/2022]
Abstract
Prolactin (PRL) is a pleiotrophic hormone that contributes to the growth of normal and malignant breast tissues. PRL signals through its receptor (PRLr), a transmembrane receptor that belongs to the cytokine receptor family. The mechanism of how the PRL:PRLr interaction triggers activation of signaling networks remains enigmatic. This review examines the effect of ligand binding on PRLr and the processes that initiate receptor-associated signaling. Evidence for PRLr predimerization in the absence of ligand and the actions of the prolyl isomerase cyclophilin A in ligand-induced activation of PRLr-associated Jak2 kinase are discussed. These studies reveal that ligand-induced conformational change of the PRLr complex is necessary for its function and open avenues for therapies to inhibit PRLr action in breast cancer.
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Affiliation(s)
- Charles V Clevenger
- Department of Pathology and Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL 60611, USA.
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Li CJ, Elsasser TH, Kahl S. AKT/eNOS signaling module functions as a potential feedback loop in the growth hormone signaling pathway. J Mol Signal 2009; 4:1. [PMID: 19320971 PMCID: PMC2666727 DOI: 10.1186/1750-2187-4-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 03/25/2009] [Indexed: 02/02/2023] Open
Abstract
Background While evidence suggested that the activity states of Protein kinase B (AKT/PKB) and endothelial nitric oxide synthase (eNOS) play an important role in the progression of the Growth Hormone (GH) signal cascade, the implication of the activation of AKT/PKB and eNOS in terms of their function in the signaling pathway was not clear. Results Using a specific AKT/PKB inhibitor and a functional proteomic approach, we were able to detect the activities of multiple signal transduction pathway elements, the downstream targets of the AKT/PKB pathway and the modification of those responses by treatment with GH. Inhibiting the AKT/PKB activity reduced or eliminated the activation (phosphorylation) of eNOS. We demonstrated that the progression of the GH signal cascade is influenced by the activity status of AKT and eNOS, wherein the suppression of AKT activity appears to augment the activity of extracellular signal-regulated kinases 1 and 2 (Erk1/2) and to antagonize the deactivation (phosphorylation) of cyclin-dependent kinase 2 (CDC2/Cdk1) induced by GH. Phosphorylation of GSK3a/b (glycogen synthase kinase 3), the downstream target of AKT/PKB, was inhibited by the AKT/PKB inhibitor. GH did not increase phosphorylation of ribosomal S6 kinase 1 (RSK1) in normal cells but increases phosphorylation of RSK1 in cells pre-treated with the AKT and eNOS inhibitors. Conclusion The MAP kinase and CDC2 kinase-dependent intracellular mechanisms are involved in or are the targets of the GH's action processes, and these activities are probably directly or indirectly modulated by AKT/PKB pathways. We propose that the AKT/PKB-eNOS module likely functions as a negative feedback mediator of GH actions.
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Affiliation(s)
- Cong-Jun Li
- Bovine Functional Genomics laboratory, Animal and Natural Resources Institute, Agricultural Research Service, US Department of Agriculture, 10300 Baltimore Ave,, BARC EAST, Building 200, Room 209, Beltsville, MD 20705, USA.
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Wang X, Yang N, Deng L, Li X, Jiang J, Gan Y, Frank SJ. Interruption of growth hormone signaling via SHC and ERK in 3T3-F442A preadipocytes upon knockdown of insulin receptor substrate-1. Mol Endocrinol 2009; 23:486-96. [PMID: 19164446 DOI: 10.1210/me.2008-0407] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Insulin receptor substrate-1 (IRS-1) is a docking protein tyrosine phosphorylated in response to insulin, IGF-1, GH, and other cytokines. IRS-1 has an N-terminal plekstrin homology domain (which facilitates membrane localization), a phosphotyrosine-binding domain [which associates with tyrosine-phosphorylated insulin receptor or IGF-1 receptor (IGF-1R)], and tyrosine residues that, when phosphorylated, bind signaling molecules. The role of IRS-1 in GH signaling is uncertain. We previously reported that IRS-1 and Janus kinase 2 associate independently of tyrosine phosphorylation via IRS-1's N terminus and that IRS-1 reconstitution greatly enhances GH-induced ERK, but not STAT5, activation. We now use GH-responsive 3T3-F442A preadipocytes to study the influence of IRS-1 on GH action. We stably transfected cells with vector only (Control) or a vector encoding IRS-1 short hairpin RNA [knockdown (KD)] and compared representative clones. Immunoblotting confirmed more than 80% knockdown of IRS-1 in KD cells. GH caused characteristic Janus kinase 2 and STAT5 activation in both Control and KD cells, but ERK activation was dramatically reduced in KD cells in GH time course and dose-response experiments. Notably, GH-induced Src homology collagen (SHC) activation and SHC-Grb2 association in KD cells were also markedly diminished compared with Control cells. Subcellular fractionation revealed that IRS-1 in Control cells was largely cytosolic, but the component isolated with plasma membranes was highly enriched in lipid raft membranes (LR). In KD cells, GH-induced ERK activation in the LR fraction was particularly diminished compared with Control cells. These data suggest that LR-enriched IRS-1 contributes substantially to GH-induced ERK activation in LR in 3T3-F442A fibroblasts. Furthermore, our results are consistent with IRS-1 residing upstream of SHC in the GH-induced ERK-signaling pathway.
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Affiliation(s)
- Xiangdong Wang
- University of Alabama at Birmingham, Birmingham, Alabama 35294-0012, USA
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McDoom I, Ma X, Kirabo A, Lee KY, Ostrov DA, Sayeski PP. Identification of tyrosine 972 as a novel site of Jak2 tyrosine kinase phosphorylation and its role in Jak2 activation. Biochemistry 2008; 47:8326-34. [PMID: 18636744 DOI: 10.1021/bi800867d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Jak2 is a 130 kDa tyrosine kinase that is important in a number of cellular signaling pathways. Its function is intrinsically regulated by the phosphorylation of a handful of its 49 tyrosines. Here, we report that tyrosine 972 (Y972) is a novel site of Jak2 phosphorylation and, hence, autoregulation. Specifically, we found that Y972 is phosphorylated and confirmed that this residue resides on the surface of the protein. Using expression plasmids that expressed either wild-type Jak2 or a full-length Jak2 cDNA containing a single Y972F substitution mutation, we investigated the consequences of losing Y972 phosphorylation on Jak2 function. We determined that the loss of Y972 phosphorylation significantly reduced the levels of both Jak2 total tyrosine phosphorylation and phosphorylation of Y1007/Y1008. Additionally, Y972 phosphorylation was shown to be important for maximal kinase function. Interestingly, in response to classical cytokine activation, the Jak2 Y972F mutant exhibited a moderately impaired level of activation when compared to the wild-type protein. However, when Jak2 was activated via a GPCR ligand, the ability of the Y972F mutant to be activated was completely lost, therefore suggesting a differential role of Y972 in Jak2 activation. Finally, we found that phosphorylation of Y972 enhances Jak2 kinase function via a mechanism that appears to stabilize the active conformation of the protein. Collectively, our results suggest that Y972 is a novel site of Jak2 phosphorylation and plays an important differential role in ligand-dependent Jak2 activation via a mechanism that involves stabilization of the Jak2 active conformation.
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Affiliation(s)
- Issam McDoom
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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Wang X, Jiang J, Warram J, Baumann G, Gan Y, Menon RK, Denson LA, Zinn KR, Frank SJ. Endotoxin-induced proteolytic reduction in hepatic growth hormone (GH) receptor: a novel mechanism for GH insensitivity. Mol Endocrinol 2008; 22:1427-37. [PMID: 18323468 DOI: 10.1210/me.2007-0561] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
GH is an important anabolic hormone. We previously demonstrated in cell culture that the cell surface GH receptor (GHR) is susceptible to inducible metalloproteolytic cleavage that yields the shed receptor extracellular domain (called GH binding protein) and renders the cells desensitized to subsequent GH stimulation. Sepsis and inflammatory states are associated with hepatic desensitization to GH, although disparate mechanisms have been postulated in various animal models. Using C3H/HeJ mice, we now demonstrate that administration of lipopolysaccharide (LPS) causes marked hepatic desensitization to GH, assessed by monitoring signal transducer and activator of transcription 5 tyrosine phosphorylation and nuclear accumulation and with a novel noninvasive bioluminescence imaging system to track in vivo hepatic GH signaling serially in individual mice. This endotoxin-induced desensitization was accompanied by marked loss of hepatic GHR, which was not explained by changes in GHR mRNA abundance. Furthermore, we observe that LPS causes GH-binding protein shedding of a hepatically expressed wild-type GHR but not a GHR with a mutation in the metalloprotease cleavage site. These data suggest that in this model system, LPS-induced desensitization to GH is associated with proteolytic GHR cleavage. These data are the first to demonstrate inducible in vivo GHR proteolysis and suggest this is a mechanism to regulate GH sensitivity and its anabolic effects during sepsis or inflammation.
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Affiliation(s)
- Xiangdong Wang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0012, USA
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Fang P, Girgis R, Little BM, Pratt KL, Guevara-Aguirre J, Hwa V, Rosenfeld RG. Growth hormone (GH) insensitivity and insulin-like growth factor-I deficiency in Inuit subjects and an Ecuadorian cohort: functional studies of two codon 180 GH receptor gene mutations. J Clin Endocrinol Metab 2008; 93:1030-7. [PMID: 18073295 DOI: 10.1210/jc.2007-2022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
CONTEXT Among more than 250 cases of GH insensitivity syndrome (GHIS) reported to date, the largest cohort was identified in southern Ecuador. In the Ecuadorian GHIS cohort, a sense mutation (GAA>GAG) at codon E180 of GH receptor [GHR (E180sp)] results in deletion of codons 181-188. No functional studies of this mutation have been performed, nor have different mutations at codon 180 been reported. OBJECTIVE We now report identification of a novel GHR mutation, also within codon E180, in two distantly related GHIS subjects of Inuit origin and provide mechanistic insights into the defects caused by the Inuit and Ecuadorian GHR mutations. PATIENTS The two Inuit subjects, with heights of -5 sd score and -7 sd score, respectively, had elevated circulating levels of GH but low levels of GH-binding protein, IGF-I, and IGF-binding protein-3. RESULTS Both Inuit subjects carry the same novel nonsense homozygous GHR mutation at codon E180 (GAA->TAA, E180X). In vitro reconstitution experiments demonstrated that GHR (E180sp), but not GHR (E180X), could be stably expressed. GHR (E180sp), however, could not bind GH and could neither activate signal transducer and activator of transcription-5b nor induce -5b-dependent gene expression on GH treatment. Furthermore, the GHR (E180sp), which has a deletion of eight amino acid residues within the GHR dimerization domain, although retaining the ability to homodimerize, was defective in trafficking to the cell surface. CONCLUSIONS The E180X mutation identified in two Inuit patients resulted in a truncated, unstably expressed GHR variant, whereas the E180 splicing mutation previously identified in the Ecuadorian cohort, affected both GH binding and GHR trafficking and rendered the abnormal GHR nonfunctional.
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Affiliation(s)
- Peng Fang
- Department of Pediatrics, NRC5, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239-3098, USA
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Strunk JJ, Gregor I, Becker Y, Li Z, Gavutis M, Jaks E, Lamken P, Walz T, Enderlein J, Piehler J. Ligand binding induces a conformational change in ifnar1 that is propagated to its membrane-proximal domain. J Mol Biol 2008; 377:725-39. [PMID: 18294654 DOI: 10.1016/j.jmb.2008.01.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 12/20/2007] [Accepted: 01/07/2008] [Indexed: 10/22/2022]
Abstract
The type I interferon (IFN) receptor plays a key role in innate immunity against viral and bacterial infections. Here, we show by intramolecular Förster resonance energy transfer spectroscopy that ligand binding induces substantial conformational changes in the ectodomain of ifnar1 (ifnar1-EC). Binding of IFN alpha 2 and IFN beta induce very similar conformations of ifnar1, which were confirmed by single-particle electron microscopy analysis of the ternary complexes formed by IFN alpha 2 or IFN beta with the two receptor subunits ifnar1-EC and ifnar2-EC. Photo-induced electron-transfer-based fluorescence quenching and single-molecule fluorescence lifetime measurements revealed that the ligand-induced conformational change in the membrane-distal domains of ifnar1-EC is propagated to its membrane-proximal domain, which is not involved in ligand recognition but is essential for signal activation. Temperature-dependent ligand binding studies as well as stopped-flow fluorescence experiments corroborated a multistep conformational change in ifnar1 upon ligand binding. Our results thus suggest that the relatively intricate architecture of the type I IFN receptor complex is designed to propagate the ligand binding event to and possibly even across the membrane by conformational changes.
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Affiliation(s)
- Jennifer Julia Strunk
- Institute of Biochemistry, Johann Wolfgang Goethe-University, Biocenter N210, Max-von-Laue-Strasse 9, 60438 Frankfurt am Main, Germany
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Yang N, Langenheim JF, Wang X, Jiang J, Chen WY, Frank SJ. Activation of growth hormone receptors by growth hormone and growth hormone antagonist dimers: insights into receptor triggering. Mol Endocrinol 2007; 22:978-88. [PMID: 18096690 DOI: 10.1210/me.2007-0424] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH binds dimerized GH receptors (GHRs) to form a trimolecular complex and induces downstream signaling events. The mechanism by which GH binding converts the inactive predimerized GHR to its active signaling conformation is uncertain. GH has no axis of symmetry. Its interaction with GHR is mediated by two asymmetric binding sites on GH, each with distinct affinity. Site 1 is of high affinity and is thought to mediate the first binding step. Mutation of binding site 2 (as in the human GH mutant, G120R) disrupts the second binding but leaves site 1 binding intact. G120R is a GH antagonist; it binds only one GHR and thus fails to signal, and it prevents productive GHR binding by normal GH. We previously demonstrated that prolactin receptor signaling was achieved by a dimeric version of a prolactin antagonist. We now employ assays of cellular signaling and receptor conformational changes to examine whether GH molecules harboring two site 1 regions can trigger GHR activation. We used recombinantly produced GH-GH and G120R-G120R dimers in which monomers in tandem are connected by a short linker peptide. Rabbit GHR-expressing human fibrosarcoma cells (C14) were treated with GH, G120R, GH-GH, or G120R-G120R. As expected, GH and GH-GH, but not G120R, induced GHR disulfide linkage, as assessed by anti-GHR blotting of cell extracts resolved by SDS-PAGE under nonreducing conditions. Disulfide linkage of GHRs reflects attainment of the active signaling conformation. Likewise, GH and GH-GH, but not G120R, caused Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5) activation. Notably, G120R-G120R, despite its lack of an intact site 2 in either dimer partner, also promoted GHR disulfide linkage and JAK2 and STAT5 activation, albeit less potently than either GH or GH-GH. Time-course responses of the three agonists were similar in terms of JAK2 and STAT5 activation. Pretreatment of cells with our conformation-sensitive inhibitory monoclonal antibody, anti-GHR ext-mAb, prevented ligand-induced receptor activation for all three agonists. GHR was also rendered less immunoprecipitable by anti-GHR ext-mAb after treatment with these agonists. These results are important in that they indicate that a ligand with two intact binding sites 1 causes GHR to adopt similar conformational changes as does GH and thus triggers activation of JAK2 and downstream signaling. Furthermore, we infer that there is substantial flexibility in the GHR extracellular domain, such that it productively accommodates GH dimers that are much larger than GH.
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Affiliation(s)
- Ning Yang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0012, USA
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Li Z, Strunk JJ, Lamken P, Piehler J, Walz T. The EM structure of a type I interferon-receptor complex reveals a novel mechanism for cytokine signaling. J Mol Biol 2007; 377:715-24. [PMID: 18252254 DOI: 10.1016/j.jmb.2007.12.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 11/30/2007] [Accepted: 12/04/2007] [Indexed: 11/28/2022]
Abstract
Type I interferons (IFNs) have pleiotropic effects, including antiviral, antiproliferative, and immunomodulatory responses. All type I IFNs bind to a shared receptor consisting of the two transmembrane proteins ifnar1 and ifnar2. We used negative stain electron microscopy to calculate a three-dimensional reconstruction of the ternary complex formed by a triple mutant IFN alpha2 with the ectodomains of ifnar1 and ifnar2. We present a model of the complex obtained by placing atomic models of subunits into the density map of the complex. The complex of IFN alpha2 with its receptor (a class II cytokine receptor) shows structural similarities to the complexes formed by growth hormone and erythropoietin with their receptors (members of the class I cytokine receptor family). Despite different assembly mechanisms, class I and class II cytokine receptors thus appear to initiate signaling through similar arrangements of the receptors induced by the binding of their respective ligands.
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Affiliation(s)
- Zongli Li
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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