1
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Liu J, Zhang M, Dong H, Liu J, Mao A, Ning G, Cao Y, Zhang Y, Wang Q. Chemokine signaling synchronizes angioblast proliferation and differentiation during pharyngeal arch artery vasculogenesis. Development 2022; 149:285824. [PMID: 36468454 PMCID: PMC10114070 DOI: 10.1242/dev.200754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 11/14/2022] [Indexed: 12/09/2022]
Abstract
Developmentally, the great vessels of the heart originate from the pharyngeal arch arteries (PAAs). During PAA vasculogenesis, PAA precursors undergo sequential cell fate decisions that are accompanied by proliferative expansion. However, how these two processes are synchronized remains poorly understood. Here, we find that the zebrafish chemokine receptor Cxcr4a is expressed in PAA precursors, and genetic ablation of either cxcr4a or the ligand gene cxcl12b causes PAA stenosis. Cxcr4a is required for the activation of the downstream PI3K/AKT cascade, which promotes not only PAA angioblast proliferation, but also differentiation. AKT has a well-known role in accelerating cell-cycle progression through the activation of cyclin-dependent kinases. Despite this, we demonstrate that AKT phosphorylates Etv2 and Scl, the key regulators of angioblast commitment, on conserved serine residues, thereby protecting them from ubiquitin-mediated proteasomal degradation. Altogether, our study reveals a central role for chemokine signaling in PAA vasculogenesis through orchestrating angioblast proliferation and differentiation.
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Affiliation(s)
- Jie Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Mingming Zhang
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Haojian Dong
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, China.,Department of Cardiology, Guangdong Cardiovascular Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China
| | - Jingwen Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Aihua Mao
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Guozhu Ning
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Yu Cao
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Yiyue Zhang
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, China
| | - Qiang Wang
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, China
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2
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The CXCR4-CXCL12 axis promotes T cell reconstitution via efficient hematopoietic immigration. J Genet Genomics 2022; 49:1138-1150. [PMID: 35483564 DOI: 10.1016/j.jgg.2022.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 04/07/2022] [Accepted: 04/13/2022] [Indexed: 01/20/2023]
Abstract
T cells play a critical role in immunity to protect against pathogens and malignant cells. T cell immunodeficiency is detrimental, especially when T cell perturbation occurs during severe infection, irradiation, chemotherapy, and age-related thymic atrophy. Therefore, strategies that enhance T cell reconstitution provide considerable benefit and warrant intensive investigation. Here, we report the construction of a T cell ablation model in Tg(coro1a:DenNTR) zebrafish via metronidazole administration. The nascent T cells are mainly derived from the hematopoietic cells migrated from the kidney, the functional homolog of bone marrow and the complete recovery time is 6.5 days post-treatment. The cxcr4b gene is upregulated in the responsive hematopoietic cells. Functional interference of CXCR4 via both genetic and chemical manipulations does not greatly affect T lymphopoiesis, but delays T cell regeneration by disrupting hematopoietic migration. In contrast, cxcr4b accelerates the replenishment of hematopoietic cells in the thymus. Consistently, Cxcl12b, a ligand of Cxcr4, is increased in the thymic epithelial cells of the injured animals. Decreased or increased expression of Cxcl12b results in compromised or accelerated T cell recovery, respectively, similar to those observed with Cxcr4b. Taken together, our study reveals a role of CXCR4-CXCL12 signaling in promoting T cell recovery and provides a promising target for the treatment of immunodeficiency due to T cell injury.
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3
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Figiel DM, Elsayed R, Nelson AC. Investigating the molecular guts of endoderm formation using zebrafish. Brief Funct Genomics 2021:elab013. [PMID: 33754635 DOI: 10.1093/bfgp/elab013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 01/27/2021] [Accepted: 02/19/2021] [Indexed: 02/07/2023] Open
Abstract
The vertebrate endoderm makes major contributions to the respiratory and gastrointestinal tracts and all associated organs. Zebrafish and humans share a high degree of genetic homology and strikingly similar endodermal organ systems. Combined with a multitude of experimental advantages, zebrafish are an attractive model organism to study endoderm development and disease. Recent functional genomics studies have shed considerable light on the gene regulatory programs governing early zebrafish endoderm development, while advances in biological and technological approaches stand to further revolutionize our ability to investigate endoderm formation, function and disease. Here, we discuss the present understanding of endoderm specification in zebrafish compared to other vertebrates, how current and emerging methods will allow refined and enhanced analysis of endoderm formation, and how integration with human data will allow modeling of the link between non-coding sequence variants and human disease.
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Affiliation(s)
- Daniela M Figiel
- Medical Research Council Doctoral Training Partnership in Interdisciplinary Biomedical Research at Warwick Medical School
| | - Randa Elsayed
- Medical Research Council Doctoral Training Partnership in Interdisciplinary Biomedical Research at Warwick Medical School
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4
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Tschaikner PM, Regele D, Röck R, Salvenmoser W, Meyer D, Bouvier M, Geley S, Stefan E, Aanstad P. Feedback control of the Gpr161-G αs-PKA axis contributes to basal Hedgehog repression in zebrafish. Development 2021; 148:dev.192443. [PMID: 33531430 DOI: 10.1242/dev.192443] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 01/14/2021] [Indexed: 01/26/2023]
Abstract
Hedgehog (Hh) ligands act as morphogens to direct patterning and proliferation during embryonic development. Protein kinase A (PKA) is a central negative regulator of Hh signalling, and in the absence of Hh ligands, PKA activity prevents inappropriate expression of Hh target genes. The orphan G-protein-coupled receptor Gpr161 contributes to the basal Hh repression machinery by activating PKA. Gpr161 acts as an A-kinase-anchoring protein, and is itself phosphorylated by PKA, but the functional significance of PKA phosphorylation of Gpr161 in the context of Hh signalling remains unknown. Here, we show that loss of Gpr161 in zebrafish leads to constitutive activation of medium and low, but not maximal, levels of Hh target gene expression. Furthermore, we find that PKA phosphorylation-deficient forms of Gpr161, which we show directly couple to Gαs, display an increased sensitivity to Shh, resulting in excess high-level Hh signalling. Our results suggest that PKA feedback-mediated phosphorylation of Gpr161 may provide a mechanism for fine-tuning Gpr161 ciliary localisation and PKA activity.
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Affiliation(s)
- Philipp M Tschaikner
- Institute of Molecular Biology and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria.,Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria
| | - Dominik Regele
- Institute of Molecular Biology and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria
| | - Ruth Röck
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria
| | - Willi Salvenmoser
- Institute of Zoology and Center of Molecular Bioscience Innsbruck, University of Innsbruck, Innsbruck 6020, Austria
| | - Dirk Meyer
- Institute of Molecular Biology and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria
| | - Michel Bouvier
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montreal, QC H3T 1J4, Canada
| | - Stephan Geley
- Division of Molecular Pathophysiology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria
| | - Pia Aanstad
- Institute of Molecular Biology and Center for Molecular Biosciences, University of Innsbruck, Innsbruck 6020, Austria
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5
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Tschaikner P, Enzler F, Torres-Quesada O, Aanstad P, Stefan E. Hedgehog and Gpr161: Regulating cAMP Signaling in the Primary Cilium. Cells 2020; 9:cells9010118. [PMID: 31947770 PMCID: PMC7017137 DOI: 10.3390/cells9010118] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/20/2019] [Accepted: 12/29/2019] [Indexed: 12/14/2022] Open
Abstract
Compartmentalization of diverse types of signaling molecules contributes to the precise coordination of signal propagation. The primary cilium fulfills this function by acting as a spatiotemporally confined sensory signaling platform. For the integrity of ciliary signaling, it is mandatory that the ciliary signaling pathways are constantly attuned by alterations in both oscillating small molecules and the presence or absence of their sensor/effector proteins. In this context, ciliary G protein-coupled receptor (GPCR) pathways participate in coordinating the mobilization of the diffusible second messenger molecule 3',5'-cyclic adenosine monophosphate (cAMP). cAMP fluxes in the cilium are primarily sensed by protein kinase A (PKA) complexes, which are essential for the basal repression of Hedgehog (Hh) signaling. Here, we describe the dynamic properties of underlying signaling circuits, as well as strategies for second messenger compartmentalization. As an example, we summarize how receptor-guided cAMP-effector pathways control the off state of Hh signaling. We discuss the evidence that a macromolecular, ciliary-localized signaling complex, composed of the orphan GPCR Gpr161 and type I PKA holoenzymes, is involved in antagonizing Hh functions. Finally, we outline how ciliary cAMP-linked receptor pathways and cAMP-sensing signalosomes may become targets for more efficient combinatory therapy approaches to counteract dysregulation of Hh signaling.
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Affiliation(s)
- Philipp Tschaikner
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria; (P.T.); (F.E.); (O.T.-Q.)
- Institute of Molecular Biology, University of Innsbruck, 6020 Innsbruck, Austria;
| | - Florian Enzler
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria; (P.T.); (F.E.); (O.T.-Q.)
| | - Omar Torres-Quesada
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria; (P.T.); (F.E.); (O.T.-Q.)
| | - Pia Aanstad
- Institute of Molecular Biology, University of Innsbruck, 6020 Innsbruck, Austria;
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria; (P.T.); (F.E.); (O.T.-Q.)
- Correspondence: ; Tel.: +43-512-507-57531; Fax: +43-512-507-57599
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6
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Nelson AC, Cutty SJ, Gasiunas SN, Deplae I, Stemple DL, Wardle FC. In Vivo Regulation of the Zebrafish Endoderm Progenitor Niche by T-Box Transcription Factors. Cell Rep 2018; 19:2782-2795. [PMID: 28658625 PMCID: PMC5494305 DOI: 10.1016/j.celrep.2017.06.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 04/28/2017] [Accepted: 05/31/2017] [Indexed: 01/15/2023] Open
Abstract
T-box transcription factors T/Brachyury homolog A (Ta) and Tbx16 are essential for correct mesoderm development in zebrafish. The downstream transcriptional networks guiding their functional activities are poorly understood. Additionally, important contributions elsewhere are likely masked due to redundancy. Here, we exploit functional genomic strategies to identify Ta and Tbx16 targets in early embryogenesis. Surprisingly, we discovered they not only activate mesodermal gene expression but also redundantly regulate key endodermal determinants, leading to substantial loss of endoderm in double mutants. To further explore the gene regulatory networks (GRNs) governing endoderm formation, we identified targets of Ta/Tbx16-regulated homeodomain transcription factor Mixl1, which is absolutely required in zebrafish for endoderm formation. Interestingly, we find many endodermal determinants coordinately regulated through common genomic occupancy by Mixl1, Eomesa, Smad2, Nanog, Mxtx2, and Pou5f3. Collectively, these findings augment the endoderm GRN and reveal a panel of target genes underlying the Ta, Tbx16, and Mixl1 mutant phenotypes.
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Affiliation(s)
- Andrew C Nelson
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK; School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
| | - Stephen J Cutty
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Saule N Gasiunas
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Isabella Deplae
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Derek L Stemple
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, UK
| | - Fiona C Wardle
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK.
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7
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Pillay LM, Mackowetzky KJ, Widen SA, Waskiewicz AJ. Somite-Derived Retinoic Acid Regulates Zebrafish Hematopoietic Stem Cell Formation. PLoS One 2016; 11:e0166040. [PMID: 27861498 PMCID: PMC5115706 DOI: 10.1371/journal.pone.0166040] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 10/11/2016] [Indexed: 01/14/2023] Open
Abstract
Hematopoietic stem cells (HSCs) are multipotent progenitors that generate all vertebrate adult blood lineages. Recent analyses have highlighted the importance of somite-derived signaling factors in regulating HSC specification and emergence from dorsal aorta hemogenic endothelium. However, these factors remain largely uncharacterized. We provide evidence that the vitamin A derivative retinoic acid (RA) functions as an essential regulator of zebrafish HSC formation. Temporal analyses indicate that RA is required for HSC gene expression prior to dorsal aorta formation, at a time when the predominant RA synthesis enzyme, aldh1a2, is strongly expressed within the paraxial mesoderm and somites. Previous research implicated the Cxcl12 chemokine and Notch signaling pathways in HSC formation. Consequently, to understand how RA regulates HSC gene expression, we surveyed the expression of components of these pathways in RA-depleted zebrafish embryos. During somitogenesis, RA-depleted embryos exhibit altered expression of jam1a and jam2a, which potentiate Notch signaling within nascent endothelial cells. RA-depleted embryos also exhibit a severe reduction in the expression of cxcr4a, the predominant Cxcl12b receptor. Furthermore, pharmacological inhibitors of RA synthesis and Cxcr4 signaling act in concert to reduce HSC formation. Our analyses demonstrate that somite-derived RA functions to regulate components of the Notch and Cxcl12 chemokine signaling pathways during HSC formation.
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Affiliation(s)
- Laura M Pillay
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
| | - Kacey J Mackowetzky
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
| | - Sonya A Widen
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
| | - Andrew Jan Waskiewicz
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.,Women & Children's Health Research Institute, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
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8
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Ogaki S, Omori H, Morooka M, Shiraki N, Ishida S, Kume S. Late stage definitive endodermal differentiation can be defined by Daf1 expression. BMC DEVELOPMENTAL BIOLOGY 2016; 16:19. [PMID: 27245320 PMCID: PMC4888667 DOI: 10.1186/s12861-016-0120-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 05/23/2016] [Indexed: 02/06/2023]
Abstract
Background Definitive endoderm (DE) gives rise to the respiratory apparatus and digestive tract. Sox17 and Cxcr4 are useful markers of the DE. Previously, we identified a novel DE marker, Decay accelerating factor 1(Daf1/CD55), by identifying DE specific genes from the expression profile of DE derived from mouse embryonic stem cells (ESCs) by microarray analysis, and in situ hybridization of early embryos. Daf1 is expressed in a subpopulation of E-cadherin + Cxcr4+ DE cells. The characteristics of the Daf1-expressing cells during DE differentiation has not been examined. Results In this report, we utilized the ESC differentiation system to examine the characteristics of Daf1-expressing DE cells. We found that Daf1 expression could discriminate late DE from early DE. Early DE cells are Daf1-negative (DE-) and late DE cells are Daf1-positive (DE+). We also found that Daf1+ late DE cells show low proliferative and low cell matrix adhesive characteristics. Furthermore, the purified SOX17low early DE cells gave rise to Daf1+ Sox17high late DE cells. Conclusion Daf1-expressing late definitive endoderm proliferates slowly and show low adhesive capacity. Electronic supplementary material The online version of this article (doi:10.1186/s12861-016-0120-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Soichiro Ogaki
- School of Life Science and Technology, Tokyo Institute of Technology, 4259-B-25 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8501, Japan.,Stem Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Honjo 2-2-1, Kumamoto, 860-0811, Japan.,Division of Pharmacology, National Institute of Health Science, 1-18-1 Kamiyoga Setagaya-ku, Tokyo, 158-8501, Japan
| | - Hisayoshi Omori
- Stem Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Honjo 2-2-1, Kumamoto, 860-0811, Japan
| | - Mayu Morooka
- Stem Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Honjo 2-2-1, Kumamoto, 860-0811, Japan
| | - Nobuaki Shiraki
- School of Life Science and Technology, Tokyo Institute of Technology, 4259-B-25 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8501, Japan
| | - Seiichi Ishida
- Division of Pharmacology, National Institute of Health Science, 1-18-1 Kamiyoga Setagaya-ku, Tokyo, 158-8501, Japan
| | - Shoen Kume
- School of Life Science and Technology, Tokyo Institute of Technology, 4259-B-25 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8501, Japan. .,Stem Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Honjo 2-2-1, Kumamoto, 860-0811, Japan.
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9
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Röck R, Bachmann V, Bhang HEC, Malleshaiah M, Raffeiner P, Mayrhofer JE, Tschaikner PM, Bister K, Aanstad P, Pomper MG, Michnick SW, Stefan E. In-vivo detection of binary PKA network interactions upon activation of endogenous GPCRs. Sci Rep 2015; 5:11133. [PMID: 26099953 PMCID: PMC4477410 DOI: 10.1038/srep11133] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 05/14/2015] [Indexed: 12/21/2022] Open
Abstract
Membrane receptor-sensed input signals affect and modulate intracellular protein-protein interactions (PPIs). Consequent changes occur to the compositions of protein complexes, protein localization and intermolecular binding affinities. Alterations of compartmentalized PPIs emanating from certain deregulated kinases are implicated in the manifestation of diseases such as cancer. Here we describe the application of a genetically encoded Protein-fragment Complementation Assay (PCA) based on the Renilla Luciferase (Rluc) enzyme to compare binary PPIs of the spatially and temporally controlled protein kinase A (PKA) network in diverse eukaryotic model systems. The simplicity and sensitivity of this cell-based reporter allows for real-time recordings of mutually exclusive PPIs of PKA upon activation of selected endogenous G protein-coupled receptors (GPCRs) in cancer cells, xenografts of mice, budding yeast, and zebrafish embryos. This extends the application spectrum of Rluc PCA for the quantification of PPI-based receptor-effector relationships in physiological and pathological model systems.
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Affiliation(s)
- Ruth Röck
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Verena Bachmann
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Hyo-Eun C Bhang
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical School, Baltimore, MD 21287, USA
| | - Mohan Malleshaiah
- Département de Biochimie, Université de Montréal, H3C 3J7 Montréal, Québec, Canada
| | - Philipp Raffeiner
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Johanna E Mayrhofer
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Philipp M Tschaikner
- Institute of Molecular Biology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Klaus Bister
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Pia Aanstad
- Institute of Molecular Biology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Martin G Pomper
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical School, Baltimore, MD 21287, USA
| | - Stephen W Michnick
- Département de Biochimie, Université de Montréal, H3C 3J7 Montréal, Québec, Canada
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
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10
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Abstract
Hedgehog (Hh) signaling plays pivotal roles in embryonic development and adult tissue homeostasis, and its deregulation leads to numerous human disorders including cancer. Binding of Hh to Patched (Ptc), a twelve-transmembrane protein, alleviates its inhibition of Smoothened (Smo), a seven-transmembrane protein related to G-protein-coupled receptors (GPCRs), leading to Smo phosphorylation and activation. Smo acts through intracellular signaling complexes to convert the latent transcription factor Cubitus interruptus (Ci)/Gli from a truncated repressor to a full-length activator, leading to derepression/activation of Hh target genes. Increasing evidence suggests that phosphorylation participates in almost every step in the signal relay from Smo to Ci/Gli, and that differential phosphorylation of several key pathway components may be crucial for translating the Hh morphogen gradient into graded pathway activities. In this review, we focus on the multifaceted roles that phosphorylation plays in Hh signal transduction, and discuss the conservation and difference between Drosophila and mammalian Hh signaling mechanisms.
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