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Rysiewicz B, Błasiak E, Mystek P, Dziedzicka-Wasylewska M, Polit A. Beyond the G protein α subunit: investigating the functional impact of other components of the Gαi 3 heterotrimers. Cell Commun Signal 2023; 21:279. [PMID: 37817242 PMCID: PMC10566112 DOI: 10.1186/s12964-023-01307-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 09/05/2023] [Indexed: 10/12/2023] Open
Abstract
BACKGROUND Specific interactions between G protein-coupled receptors (GPCRs) and G proteins play a key role in mediating signaling events. While there is little doubt regarding receptor preference for Gα subunits, the preferences for specific Gβ and Gγ subunits and the effects of different Gβγ dimer compositions on GPCR signaling are poorly understood. In this study, we aimed to investigate the subcellular localization and functional response of Gαi3-based heterotrimers with different combinations of Gβ and Gγ subunits. METHODS Live-cell imaging microscopy and colocalization analysis were used to investigate the subcellular localization of Gαi3 in combination with Gβ1 or Gβ2 heterotrimers, along with representative Gγ subunits. Furthermore, fluorescence lifetime imaging microscopy (FLIM-FRET) was used to investigate the nanoscale distribution of Gαi3-based heterotrimers in the plasma membrane, specifically with the dopamine D2 receptor (D2R). In addition, the functional response of the system was assessed by monitoring intracellular cAMP levels and conducting bioinformatics analysis to further characterize the heterotrimer complexes. RESULTS Our results show that Gαi3 heterotrimers mainly localize to the plasma membrane, although the degree of colocalization is influenced by the accompanying Gβ and Gγ subunits. Heterotrimers containing Gβ2 showed slightly lower membrane localization compared to those containing Gβ1, but certain combinations, such as Gαi3β2γ8 and Gαi3β2γ10, deviated from this trend. Examination of the spatial arrangement of Gαi3 in relation to D2R and of changes in intracellular cAMP level showed that the strongest functional response is observed for those trimers for which the distance between the receptor and the Gα subunit is smallest, i.e. complexes containing Gβ1 and Gγ8 or Gγ10 subunit. Deprivation of Gαi3 lipid modifications resulted in a significant decrease in the amount of protein present in the cell membrane, but did not always affect intracellular cAMP levels. CONCLUSION Our studies show that the composition of G protein heterotrimers has a significant impact on the strength and specificity of GPCR-mediated signaling. Different heterotrimers may exhibit different conformations, which further affects the interactions of heterotrimers and GPCRs, as well as their interactions with membrane lipids. This study contributes to the understanding of the complex signaling mechanisms underlying GPCR-G-protein interactions and highlights the importance of the diversity of Gβ and Gγ subunits in G-protein signaling pathways. Video Abstract.
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Affiliation(s)
- Beata Rysiewicz
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Ewa Błasiak
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Paweł Mystek
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Marta Dziedzicka-Wasylewska
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Agnieszka Polit
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland.
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2
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Klenk C, Scrivens M, Niederer A, Shi S, Mueller L, Gersz E, Zauderer M, Smith ES, Strohner R, Plückthun A. A Vaccinia-based system for directed evolution of GPCRs in mammalian cells. Nat Commun 2023; 14:1770. [PMID: 36997531 PMCID: PMC10063554 DOI: 10.1038/s41467-023-37191-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 03/06/2023] [Indexed: 04/03/2023] Open
Abstract
Directed evolution in bacterial or yeast display systems has been successfully used to improve stability and expression of G protein-coupled receptors for structural and biophysical studies. Yet, several receptors cannot be tackled in microbial systems due to their complex molecular composition or unfavorable ligand properties. Here, we report an approach to evolve G protein-coupled receptors in mammalian cells. To achieve clonality and uniform expression, we develop a viral transduction system based on Vaccinia virus. By rational design of synthetic DNA libraries, we first evolve neurotensin receptor 1 for high stability and expression. Second, we demonstrate that receptors with complex molecular architectures and large ligands, such as the parathyroid hormone 1 receptor, can be readily evolved. Importantly, functional receptor properties can now be evolved in the presence of the mammalian signaling environment, resulting in receptor variants exhibiting increased allosteric coupling between the ligand binding site and the G protein interface. Our approach thus provides insights into the intricate molecular interplay required for GPCR activation.
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Affiliation(s)
- Christoph Klenk
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
| | - Maria Scrivens
- Vaccinex, Inc., 1895 Mt. Hope Avenue, Rochester, New York, 14620, NY, USA
| | - Anina Niederer
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Shuying Shi
- Vaccinex, Inc., 1895 Mt. Hope Avenue, Rochester, New York, 14620, NY, USA
| | - Loretta Mueller
- Vaccinex, Inc., 1895 Mt. Hope Avenue, Rochester, New York, 14620, NY, USA
| | - Elaine Gersz
- Vaccinex, Inc., 1895 Mt. Hope Avenue, Rochester, New York, 14620, NY, USA
| | - Maurice Zauderer
- Vaccinex, Inc., 1895 Mt. Hope Avenue, Rochester, New York, 14620, NY, USA
| | - Ernest S Smith
- Vaccinex, Inc., 1895 Mt. Hope Avenue, Rochester, New York, 14620, NY, USA
| | - Ralf Strohner
- MorphoSys AG, Semmelweisstr. 7, 82152, Planegg, Germany
| | - Andreas Plückthun
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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3
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Fonseca FV, Raffay TM, Xiao K, McLaughlin PJ, Qian Z, Grimmett ZW, Adachi N, Wang B, Hausladen A, Cobb BA, Zhang R, Hess DT, Gaston B, Lambert NA, Reynolds JD, Premont RT, Stamler JS. S-nitrosylation is required for β 2AR desensitization and experimental asthma. Mol Cell 2022; 82:3089-3102.e7. [PMID: 35931084 PMCID: PMC9391322 DOI: 10.1016/j.molcel.2022.06.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 04/18/2022] [Accepted: 06/28/2022] [Indexed: 12/22/2022]
Abstract
The β2-adrenergic receptor (β2AR), a prototypic G-protein-coupled receptor (GPCR), is a powerful driver of bronchorelaxation, but the effectiveness of β-agonist drugs in asthma is limited by desensitization and tachyphylaxis. We find that during activation, the β2AR is modified by S-nitrosylation, which is essential for both classic desensitization by PKA as well as desensitization of NO-based signaling that mediates bronchorelaxation. Strikingly, S-nitrosylation alone can drive β2AR internalization in the absence of traditional agonist. Mutant β2AR refractory to S-nitrosylation (Cys265Ser) exhibits reduced desensitization and internalization, thereby amplifying NO-based signaling, and mice with Cys265Ser mutation are resistant to bronchoconstriction, inflammation, and the development of asthma. S-nitrosylation is thus a central mechanism in β2AR signaling that may be operative widely among GPCRs and targeted for therapeutic gain.
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Affiliation(s)
- Fabio V Fonseca
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Thomas M Raffay
- Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Kunhong Xiao
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710, USA
| | - Precious J McLaughlin
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Zhaoxia Qian
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Zachary W Grimmett
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Naoko Adachi
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Benlian Wang
- Center for Proteomics and Bioinformatics, Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Alfred Hausladen
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Brian A Cobb
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Rongli Zhang
- Cardiovascular Research Institute, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Douglas T Hess
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Benjamin Gaston
- Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Nevin A Lambert
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - James D Reynolds
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH 44106, USA
| | - Richard T Premont
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH 44106, USA
| | - Jonathan S Stamler
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH 44106, USA.
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4
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Bondar A, Lazar J. Optical sensors of heterotrimeric G protein signaling. FEBS J 2020; 288:2570-2584. [DOI: 10.1111/febs.15655] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/26/2020] [Accepted: 12/03/2020] [Indexed: 01/14/2023]
Affiliation(s)
- Alexey Bondar
- Center for Nanobiology and Structural Biology Institute of Microbiology of the Czech Academy of Sciences Nove Hrady Czech Republic
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Prague Czech Republic
- Faculty of Science University of South Bohemia Ceske Budejovice Czech Republic
| | - Josef Lazar
- Center for Nanobiology and Structural Biology Institute of Microbiology of the Czech Academy of Sciences Nove Hrady Czech Republic
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Prague Czech Republic
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5
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Pritchard AB, Kanai SM, Krock B, Schindewolf E, Oliver-Krasinski J, Khalek N, Okashah N, Lambert NA, Tavares ALP, Zackai E, Clouthier DE. Loss-of-function of Endothelin receptor type A results in Oro-Oto-Cardiac syndrome. Am J Med Genet A 2020; 182:1104-1116. [PMID: 32133772 PMCID: PMC7202054 DOI: 10.1002/ajmg.a.61531] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 02/06/2020] [Accepted: 02/06/2020] [Indexed: 01/14/2023]
Abstract
Craniofacial morphogenesis is regulated in part by signaling from the Endothelin receptor type A (EDNRA). Pathogenic variants in EDNRA signaling pathway components EDNRA, GNAI3, PCLB4, and EDN1 cause Mandibulofacial Dysostosis with Alopecia (MFDA), Auriculocondylar syndrome (ARCND) 1, 2, and 3, respectively. However, cardiovascular development is normal in MFDA and ARCND individuals, unlike Ednra knockout mice. One explanation may be that partial EDNRA signaling remains in MFDA and ARCND, as mice with reduced, but not absent, EDNRA signaling also lack a cardiovascular phenotype. Here we report an individual with craniofacial and cardiovascular malformations mimicking the Ednra -/- mouse phenotype, including a distinctive micrognathia with microstomia and a hypoplastic aortic arch. Exome sequencing found a novel homozygous missense variant in EDNRA (c.1142A>C; p.Q381P). Bioluminescence resonance energy transfer assays revealed that this amino acid substitution in helix 8 of EDNRA prevents recruitment of G proteins to the receptor, abrogating subsequent receptor activation by its ligand, Endothelin-1. This homozygous variant is thus the first reported loss-of-function EDNRA allele, resulting in a syndrome we have named Oro-Oto-Cardiac Syndrome. Further, our results illustrate that EDNRA signaling is required for both normal human craniofacial and cardiovascular development, and that limited EDNRA signaling is likely retained in ARCND and MFDA individuals. This work illustrates a straightforward approach to identifying the functional consequence of novel genetic variants in signaling molecules associated with malformation syndromes.
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Affiliation(s)
- Amanda Barone Pritchard
- Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Stanley M Kanai
- Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Bryan Krock
- Division of Genomic Diagnostics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Erica Schindewolf
- Center for Fetal Diagnosis and Treatment, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | | | - Nahla Khalek
- Center for Fetal Diagnosis and Treatment, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Najeah Okashah
- Department of Pharmacology and Toxicology, Medical College of Georgia-Augusta University, Augusta, Georgia, USA
| | - Nevin A Lambert
- Department of Pharmacology and Toxicology, Medical College of Georgia-Augusta University, Augusta, Georgia, USA
| | - Andre L P Tavares
- Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Elaine Zackai
- Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - David E Clouthier
- Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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6
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Dong M, Harikumar KG, Raval SR, Milburn JE, Clark C, Alcala-Torano R, Mobarec JC, Reynolds CA, Ghirlanda G, Christopoulos A, Wootten D, Sexton PM, Miller LJ. Rational development of a high-affinity secretin receptor antagonist. Biochem Pharmacol 2020; 177:113929. [PMID: 32217097 DOI: 10.1016/j.bcp.2020.113929] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 03/19/2020] [Indexed: 01/11/2023]
Abstract
The secretin receptor is a prototypic class B GPCR with substantial and broad pharmacologic importance. The aim of this project was to develop a high affinity selective antagonist as a new and important pharmacologic tool and to aid stabilization of this receptor in an inactive conformation for ultimate structural characterization. Amino-terminal truncation of the natural 27-residue ligand reduced biological activity, but also markedly reduced binding affinity. This was rationally and experimentally overcome with lactam stabilization of helical structure and with replacement of residues with natural and unnatural amino acids. A key new step in this effort was the replacement of peptide residue Leu22 with L-cyclohexylalanine (Cha) to enhance potential hydrophobic interactions with receptor residues Leu31, Val34, and Phe92 that were predicted from molecular modeling. Alanine-replacement mutagenesis of these residues markedly affected ligand binding and biological activity. The optimal antagonist ligand, (Y10,c[E16,K20],I17,Cha22,R25)sec(6-27), exhibited high binding affinity (4 nM), similar to natural secretin, and exhibited no demonstrable biological activity to stimulate cAMP accumulation, intracellular calcium mobilization, or β-arrestin-2 translocation. It acts as an orthosteric competitive antagonist, predicted to bind within the peptide-binding groove in the receptor extracellular domain. The analogous peptide that was one residue longer, retaining Thr5, exhibited partial agonist activity, while further truncation of even a single residue (Phe6) reduced binding affinity. This sec(6-27)-based peptide will be an important new tool for pharmacological and structural studies.
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Affiliation(s)
- Maoqing Dong
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, United States
| | - Kaleeckal G Harikumar
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, United States
| | - Sweta R Raval
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, United States
| | - Juliana E Milburn
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, United States
| | - Carolyn Clark
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, United States
| | - Rafael Alcala-Torano
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, United States
| | - Juan C Mobarec
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
| | - Christopher A Reynolds
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
| | - Giovanna Ghirlanda
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, United States
| | - Arthur Christopoulos
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, 3052 Victoria, Australia
| | - Denise Wootten
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, 3052 Victoria, Australia
| | - Patrick M Sexton
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, 3052 Victoria, Australia
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, United States.
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7
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Vaccinia Virus Glycoproteins A33, A34, and B5 Form a Complex for Efficient Endoplasmic Reticulum to trans-Golgi Network Transport. J Virol 2020; 94:JVI.02155-19. [PMID: 31941777 DOI: 10.1128/jvi.02155-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 12/23/2019] [Indexed: 01/10/2023] Open
Abstract
Orthopoxviruses produce two, antigenically distinct, infectious enveloped virions termed intracellular mature virions and extracellular virions. Extracellular virions are required for cell-to-cell spread and pathogenesis. Specific to the extracellular virion membrane, glycoproteins A33, A34, and B5 are highly conserved among orthopoxviruses and have roles during extracellular virion formation and subsequent infection. B5 is dependent on an interaction with either A33 or A34 for localization to the site of intracellular envelopment and incorporation into the envelope of released extracellular virions. In this report we show that an interaction between A33 and A34 can be detected in infected cells. Furthermore, we show that a three-protein complex between A33, A34, and B5 forms in the endoplasmic reticulum (ER) that disassociates post ER export. Finally, immunofluorescence reveals that coexpression of all three glycoproteins results in their localization to a juxtanuclear region that is presumably the site of intracellular envelopment. These results demonstrate the existence of two previously unidentified interactions: one between A33 and A34 and another simultaneous interaction between all three of the glycoproteins. Furthermore, these results indicate that interactions among A33, A34, and B5 are vital for proper intracellular trafficking and subcellular localization.IMPORTANCE The secondary intracellular envelopment of poxviruses at the trans-Golgi network to release infectious extracellular virus (EV) is essential for their spread and pathogenesis. Viral glycoproteins A33, A34, and B5 are critical for the efficient production of infectious EV and interactions among these proteins are important for their localization and incorporation into the outer extracellular virion membrane. We have uncovered a novel interaction between glycoproteins A33 and A34. Furthermore, we show that B5 can interact with the A33-A34 complex. Our analysis indicates that the three-protein complex has a role in ER exit and proper localization of the three glycoproteins to the intracellular site of wrapping. These results show that a complex set of interactions occur in the secretory pathway of infected cells to ensure proper glycoprotein trafficking and envelope content, which is important for the release of infectious poxvirus virions.
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Moosavi B, Mousavi B, Yang WC, Yang GF. Yeast-based assays for detecting protein-protein/drug interactions and their inhibitors. Eur J Cell Biol 2017. [PMID: 28645461 DOI: 10.1016/j.ejcb.2017.06.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Understanding cellular processes at molecular levels in health and disease requires the knowledge of protein-protein interactions (PPIs). In line with this, identification of PPIs at genome-wide scale is highly valuable to understand how different cellular pathways are interconnected, and it eventually facilitates designing effective drugs against certain PPIs. Furthermore, investigating PPIs at a small laboratory scale for deciphering certain biochemical pathways has been demanded for years. In this regard, yeast two hybrid system (Y2HS) has proven an extremely useful tool to discover novel PPIs, while Y2HS derivatives and novel yeast-based assays are contributing significantly to identification of protein-drug/inhibitor interaction at both large- and small-scale set-ups. These methods have been evolving over time to provide more accurate, reproducible and quantitative results. Here we briefly describe different yeast-based assays for identification of various protein-protein/drug/inhibitor interactions and their specific applications, advantages, shortcomings, and improvements. The broad range of yeast-based assays facilitates application of the most suitable method(s) for each specific need.
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Affiliation(s)
- Behrooz Moosavi
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PR China.
| | - Bibimaryam Mousavi
- Laboratory of Organometallics, Catalysis and Ordered Materials, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Wen-Chao Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PR China
| | - Guang-Fu Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PR China.
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10
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Jean-Alphonse FG, Wehbi VL, Chen J, Noda M, Taboas JM, Xiao K, Vilardaga JP. β 2-adrenergic receptor control of endosomal PTH receptor signaling via Gβγ. Nat Chem Biol 2016; 13:259-261. [PMID: 28024151 DOI: 10.1038/nchembio.2267] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 10/18/2016] [Indexed: 11/09/2022]
Abstract
Cells express several G-protein-coupled receptors (GPCRs) at their surfaces, transmitting simultaneous extracellular hormonal and chemical signals into cells. A comprehensive understanding of mechanisms underlying the integrated signaling response induced by distinct GPCRs is thus required. Here we found that the β2-adrenergic receptor, which induces a short cAMP response, prolongs nuclear cAMP and protein kinase A (PKA) activation by promoting endosomal cAMP production in parathyroid hormone (PTH) receptor signaling through the stimulatory action of G protein Gβγ subunits on adenylate cyclase type 2.
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Affiliation(s)
- Frédéric G Jean-Alphonse
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Vanessa L Wehbi
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Jingming Chen
- Department of Biomedical Engineering, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Masaki Noda
- Department of Molecular Pharmacology, Medical Research Institute Tokyo Medical and Dental University, Bunkyo-Ku, Tokyo, Japan
| | - Juan M Taboas
- Department of Biomedical Engineering, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.,McGowan Institute of Regenerative Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Kunhong Xiao
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Jean-Pierre Vilardaga
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Chen M, Liu S, Li W, Zhang Z, Zhang X, Zhang XE, Cui Z. Three-Fragment Fluorescence Complementation Coupled with Photoactivated Localization Microscopy for Nanoscale Imaging of Ternary Complexes. ACS NANO 2016; 10:8482-8490. [PMID: 27584616 DOI: 10.1021/acsnano.6b03543] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Many cellular processes are governed by molecular machineries that involve multiple protein interactions. However, visualizing and identifying multiprotein complexes such as ternary complexes inside cells is always challenging, particularly in the subdiffraction cellular space. Here, we developed a three-fragment fluorescence complementation system (TFFC) based on the splitting of a photoactivatable fluorescent protein, mIrisFP, for the imaging of ternary complexes inside living cells. Using a combination of TFFC and photoactivated localization microscopy (PALM), namely, the TFFC-PALM technique, we are able to identify the multi-interaction of a ternary complex with nanometer-level spatial resolution and single-molecule sensitivity. The TFFC-PALM system has been further applied to the analysis of the Gs ternary complex, which is composed of αs, β1, and γ2 subunits, providing further insights into the subcellular localization and function of G protein subunits at the single-molecule level. The TFFC-PALM represents a valuable method for the visualization and identification of ternary complexes inside cells at the nanometer scale.
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Affiliation(s)
- Minghai Chen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Sanying Liu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Wei Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
| | - Zhiping Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
| | - Xiaowei Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
| | - Xian-En Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , Beijing 100101, China
| | - Zongqiang Cui
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
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Abstract
BACKGROUND The role of cAMP in regulating T cell activation and function has been controversial. cAMP is generally known as an immunosuppressant, but it is also required for generating optimal immune responses. As the effect of cAMP is likely to depend on its cellular context, the current study investigated whether the mechanism of activation of Gαs and adenylyl cyclase influences their effect on T cell receptor (TCR)-stimulated interleukin-2 (IL-2) mRNA levels. METHODS The effect of blocking Gs-coupled receptor (GsPCR)-mediated Gs activation on TCR-stimulated IL-2 mRNA levels in CD4(+) T cells was compared with that of knocking down Gαs expression or inhibiting adenylyl cyclase activity. The effect of knocking down Gαs expression on TCR-stimulated cAMP accumulation was compared with that of blocking GsPCR signaling. RESULTS ZM-241385, an antagonist to the Gs-coupled A2A adenosine receptor (A2AR), enhanced TCR-stimulated IL-2 mRNA levels in primary human CD4(+) T helper cells and in Jurkat T cells. A dominant negative Gαs construct, GαsDN3, also enhanced TCR-stimulated IL-2 mRNA levels. Similar to GsPCR antagonists, GαsDN3 blocked GsPCR-dependent activation of both Gαs and Gβγ. In contrast, Gαs siRNA and 2',5'-dideoxyadenosine (ddA), an adenylyl cyclase inhibitor, decreased TCR-stimulated IL-2 mRNA levels. Gαs siRNA, but not GαsDN3, decreased TCR-stimulated cAMP synthesis. Potentiation of IL-2 mRNA levels by ZM-241385 required at least two days of TCR stimulation, and addition of ddA after three days of TCR stimulation enhanced IL-2 mRNA levels. CONCLUSIONS GsPCRs play an inhibitory role in the regulation of TCR-stimulated IL-2 mRNA levels whereas Gαs and cAMP can play a stimulatory one. Additionally, TCR-dependent activation of Gαs does not appear to involve GsPCRs. These results suggest that the context of Gαs/cAMP activation and the stage of T cell activation and differentiation determine the effect on TCR-stimulated IL-2 mRNA levels.
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Comprehensive analysis of heterotrimeric G-protein complex diversity and their interactions with GPCRs in solution. Proc Natl Acad Sci U S A 2015; 112:E1181-90. [PMID: 25733868 DOI: 10.1073/pnas.1417573112] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Agonist binding to G-protein-coupled receptors (GPCRs) triggers signal transduction cascades involving heterotrimeric G proteins as key players. A major obstacle for drug design is the limited knowledge of conformational changes upon agonist binding, the details of interaction with the different G proteins, and the transmission to movements within the G protein. Although a variety of different GPCR/G protein complex structures would be needed, the transient nature of this complex and the intrinsic instability against dissociation make this endeavor very challenging. We have previously evolved GPCR mutants that display higher stability and retain their interaction with G proteins. We aimed at finding all G-protein combinations that preferentially interact with neurotensin receptor 1 (NTR1) and our stabilized mutants. We first systematically analyzed by coimmunoprecipitation the capability of 120 different G-protein combinations consisting of αi1 or αsL and all possible βγ-dimers to form a heterotrimeric complex. This analysis revealed a surprisingly unrestricted ability of the G-protein subunits to form heterotrimeric complexes, including βγ-dimers previously thought to be nonexistent, except for combinations containing β5. A second screen on coupling preference of all G-protein heterotrimers to NTR1 wild type and a stabilized mutant indicated a preference for those Gαi1βγ combinations containing γ1 and γ11. Heterotrimeric G proteins, including combinations believed to be nonexistent, were purified, and complexes with the GPCR were prepared. Our results shed new light on the combinatorial diversity of G proteins and their coupling to GPCRs and open new approaches to improve the stability of GPCR/G-protein complexes.
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14
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Masuho I, Martemyanov KA, Lambert NA. Monitoring G Protein Activation in Cells with BRET. Methods Mol Biol 2015; 1335:107-13. [PMID: 26260597 DOI: 10.1007/978-1-4939-2914-6_8] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Live-cell assays based on fluorescence and luminescence are now indispensable tools for the study of G protein signaling. Assays based on fluorescence and bioluminescence resonance energy transfer (FRET and BRET) have been particularly valuable for monitoring changes in second messengers, protein-protein interactions, and protein conformation. Here, we describe a BRET assay that monitors the release of free Gβγ dimers after activation of heterotrimers containing Gα subunits from all four G protein subfamilies. This assay provides useful kinetic and pharmacological information with reasonably high throughput using a standard laboratory equipment.
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Affiliation(s)
- Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL, 33458, USA
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15
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Chang MH, Chen AP, Romero MF. NBCe1A dimer assemble visualized by bimolecular fluorescence complementation. Am J Physiol Renal Physiol 2014; 306:F672-80. [PMID: 24477681 DOI: 10.1152/ajprenal.00284.2013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mutations in the electrogenic Na(+)/HCO3(-) cotransporter (NBCe1) that cause proximal renal tubular acidosis (pRTA), glaucoma, and cataracts in patients are recessive. Parents and siblings of these affected individuals seem asymptomatic although their tissues should make some mutant NBCe1 protein. Biochemical studies with AE1 and NBCe1 indicate that both, and probably all, Slc4 members form dimers. However, the physiologic implications of dimerization have not yet been fully explored. Here, human NBCe1A dimerization is demonstrated by biomolecular fluorescence complementation (BiFC). An enhanced yellow fluorescent protein (EYFP) fragment (1-158, EYFP(N)) or (159-238, EYFP(C)) was fused to the NH2 or COOH terminus of NBCe1A and mix-and-matched expressed in Xenopus oocyte. The EYFP fluorescent signal was observed only when both EYFP fragments are fused to the NH2 terminus of NBCe1A (EYFP(N)-N-NBCe1A w/ EYFP(C)-N-NBCe1A), and the electrophysiology data demonstrated this EYFP-NBCe1A coexpressed pair have wild-type transport function. These data suggest NBCe1A forms dimers and that NH2 termini from the two monomers are in close proximity, likely pair up, to form a functional unit. To explore the physiologic significance of NBCe1 dimerization, we chose two severe NBCe1 mutations (6.6 and 20% wild-type function individually): S427L (naturally occurring) and E91R (for NH2-terminal structure studies). When we coexpressed S427L and E91R, we measured 50% wild-type function, which can only occur if the S427L-E91R heterodimer is the functional unit. We hypothesize that the dominant negative effect of heterozygous NBCe1 carrier should be obvious if the mutated residues are structurally crucial to the dimer formation. The S427L-E91R heterodimer complex allows the monomers to structurally complement each other resulting in a dimer with wild-type like function.
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Affiliation(s)
- Min-Hwang Chang
- Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905.
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16
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Lv Y, Zhao X, Liu L, Du G, Zhou J, Chen J. A simple procedure for protein ubiquitination detection in Saccharomyces cerevisiae: Gap1p as an example. J Microbiol Methods 2013; 94:25-9. [PMID: 23611841 DOI: 10.1016/j.mimet.2013.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 04/14/2013] [Accepted: 04/14/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Yongkun Lv
- School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
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Hu Z, Hu J, Zhang Z, Shen WJ, Yun CC, Berlot CH, Kraemer FB, Azhar S. Regulation of expression and function of scavenger receptor class B, type I (SR-BI) by Na+/H+ exchanger regulatory factors (NHERFs). J Biol Chem 2013; 288:11416-35. [PMID: 23482569 DOI: 10.1074/jbc.m112.437368] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Scavenger receptor class B, type I (SR-BI) binds HDL and mediates selective delivery of cholesteryl esters (CEs) to the liver, adrenals, and gonads for product formation (bile acids and steroids). Because relatively little is known about SR-BI posttranslational regulation in steroidogenic cells, we examined the roles of Na(+)/H(+) exchanger regulatory factors (NHERFs) in regulating SR-BI expression, SR-BI-mediated selective CE uptake, and steroidogenesis. NHERF1 and NHERF2 mRNA and protein are expressed at varying levels in model steroidogenic cell lines and the adrenal, with only low expression of PDZK1 (NHERF3) and NHERF4. Dibutyryl cyclic AMP decreased NHERF1 and NHERF2 and increased SR-BI mRNA expression in primary rat granulosa cells and MLTC-1 cells, whereas ACTH had no effect on NHERF1 and NHERF2 mRNA levels but decreased their protein levels in rat adrenals. Co-immunoprecipitation, colocalization, bimolecular fluorescence complementation, and mutational analysis indicated that SR-BI associates with NHERF1 and NHERF2. NHERF1 and NHERF2 down-regulated SR-BI protein expression through inhibition of its de novo synthesis. NHERF1 and NHERF2 also inhibited SR-BI-mediated selective CE transport and steroidogenesis, which were markedly attenuated by partial deletions of the PDZ1 or PDZ2 domain of NHERF1, the PDZ2 domain of NHERF2, or the MERM domains of NHERF1/2 or by gene silencing of NHERF1/2. Moreover, an intact COOH-terminal PDZ recognition motif (EAKL) in SR-BI is needed. Transient transfection of hepatic cell lines with NHERF1 or NHERF2 caused a significant reduction in endogenous protein levels of SR-BI. Collectively, these data establish NHERF1 and NHERF2 as SR-BI protein binding partners that play a negative role in the regulation of SR-BI expression, selective CE transport, and steroidogenesis.
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Affiliation(s)
- Zhigang Hu
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, USA
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Ness JK, Snyder KM, Tapinos N. Lck tyrosine kinase mediates β1-integrin signalling to regulate Schwann cell migration and myelination. Nat Commun 2013; 4:1912. [PMID: 23715271 PMCID: PMC3674276 DOI: 10.1038/ncomms2928] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 04/24/2013] [Indexed: 12/12/2022] Open
Abstract
The interaction between laminin and β1-integrin on the surface of Schwann cells regulates Schwann cell proliferation, maturation and differentiation. However, the signalling mediators that fine-tune these outcomes are not fully elucidated. Here we show that lymphoid cell kinase is the crucial effector of β1-integrin signalling in Schwann cells. Lymphoid cell kinase is activated after laminin treatment of Schwann cells, while downregulation of β1-integrin with short interfering RNAs inhibits lymphoid cell kinase phosphorylation. Treatment of Schwann cells with a selective lymphoid cell kinase inhibitor reveals a pathway that involves paxillin and CrkII, which ultimately elevates Rac-GTP levels to induce radial lamellipodia formation. Inhibition of lymphoid cell kinase in Schwann cell-dorsal root ganglion cocultures and dorsal root ganglions from Lck(-/-) mice show a reduction of Schwann cell longitudinal migration, reduced myelin formation and internode length. Finally, Lck(-/-) mice exhibit delays in myelination, thinner myelin with abnormal g-ratios and aberrant myelin outfoldings. Our data implicate lymphoid cell kinase as a major regulator of cytoskeletal dynamics, migration and myelination in the peripheral nervous system.
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Affiliation(s)
- Jennifer K. Ness
- Molecular Neuroscience Laboratory, Weis Center for Research, Geisinger Clinic, 100 North Academy Avenue, Danville, Pennsylvania 17822, USA
| | - Kristin M. Snyder
- Molecular Neuroscience Laboratory, Weis Center for Research, Geisinger Clinic, 100 North Academy Avenue, Danville, Pennsylvania 17822, USA
| | - Nikos Tapinos
- Molecular Neuroscience Laboratory, Weis Center for Research, Geisinger Clinic, 100 North Academy Avenue, Danville, Pennsylvania 17822, USA
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Kalló I, Mohácsik P, Vida B, Zeöld A, Bardóczi Z, Zavacki AM, Farkas E, Kádár A, Hrabovszky E, Arrojo e Drigo R, Dong L, Barna L, Palkovits M, Borsay BA, Herczeg L, Lechan RM, Bianco AC, Liposits Z, Fekete C, Gereben B. A novel pathway regulates thyroid hormone availability in rat and human hypothalamic neurosecretory neurons. PLoS One 2012; 7:e37860. [PMID: 22719854 PMCID: PMC3377717 DOI: 10.1371/journal.pone.0037860] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 04/25/2012] [Indexed: 11/29/2022] Open
Abstract
Hypothalamic neurosecretory systems are fundamental regulatory circuits influenced by thyroid hormone. Monocarboxylate-transporter-8 (MCT8)-mediated uptake of thyroid hormone followed by type 3 deiodinase (D3)-catalyzed inactivation represent limiting regulatory factors of neuronal T3 availability. In the present study we addressed the localization and subcellular distribution of D3 and MCT8 in neurosecretory neurons and addressed D3 function in their axons. Intense D3-immunoreactivity was observed in axon varicosities in the external zone of the rat median eminence and the neurohaemal zone of the human infundibulum containing axon terminals of hypophysiotropic parvocellular neurons. Immuno-electronmicroscopy localized D3 to dense-core vesicles in hypophysiotropic axon varicosities. N-STORM-superresolution-microscopy detected the active center containing C-terminus of D3 at the outer surface of these organelles. Double-labeling immunofluorescent confocal microscopy revealed that D3 is present in the majority of GnRH, CRH and GHRH axons but only in a minority of TRH axons, while absent from somatostatin-containing neurons. Bimolecular-Fluorescence-Complementation identified D3 homodimers, a prerequisite for D3 activity, in processes of GT1-7 cells. Furthermore, T3-inducible D3 catalytic activity was detected in the rat median eminence. Triple-labeling immunofluorescence and immuno-electronmicroscopy revealed the presence of MCT8 on the surface of the vast majority of all types of hypophysiotropic terminals. The presence of MCT8 was also demonstrated on the axon terminals in the neurohaemal zone of the human infundibulum. The unexpected role of hypophysiotropic axons in fine-tuned regulation of T3 availability in these cells via MCT8-mediated transport and D3-catalyzed inactivation may represent a novel regulatory core mechanism for metabolism, growth, stress and reproduction in rodents and humans.
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Affiliation(s)
- Imre Kalló
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Neuroscience, Faculty of Information Technology, Pázmány Péter Catholic University, Budapest, Hungary
| | - Petra Mohácsik
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Barbara Vida
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Anikó Zeöld
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zsuzsanna Bardóczi
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Ann Marie Zavacki
- Thyroid Section, Division of Endocrinology, Diabetes and Hypertension, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Erzsébet Farkas
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Andrea Kádár
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Erik Hrabovszky
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Rafael Arrojo e Drigo
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine Miami, Florida, United States of America
| | - Liping Dong
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine Miami, Florida, United States of America
| | - László Barna
- Nikon Microscopy Center, Institute of Experimental Medicine, Budapest, Hungary
| | - Miklós Palkovits
- Human Brain Tissue Bank, Semmelweis University, Budapest, Hungary
| | - Beáta A. Borsay
- Department of Forensic Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Herczeg
- Department of Forensic Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Ronald M. Lechan
- Tupper Research Institute and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, Boston, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Antonio C. Bianco
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine Miami, Florida, United States of America
| | - Zsolt Liposits
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Neuroscience, Faculty of Information Technology, Pázmány Péter Catholic University, Budapest, Hungary
| | - Csaba Fekete
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
- Tupper Research Institute and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, Boston, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Balázs Gereben
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine Miami, Florida, United States of America
- * E-mail:
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20
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Duda T, Pertzev A, Sharma RK. Differential Ca(2+) sensor guanylate cyclase activating protein modes of photoreceptor rod outer segment membrane guanylate cyclase signaling. Biochemistry 2012; 51:4650-7. [PMID: 22642846 DOI: 10.1021/bi300572w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photoreceptor ROS-GC1 (rod outer segment membrane guanylate cyclase) is a vital component of phototransduction. It is a bimodal Ca(2+) signal transduction switch, operating between 20 and ∼1000 nM. Modulated by Ca(2+) sensors guanylate cyclase activating proteins 1 and 2 (GCAP1 and GCAP2, respectively), decreasing [Ca(2+)](i) from 200 to 20 nM progressively turns it "on", as does the modulation by the Ca(2+) sensor S100B, increasing [Ca(2+)](i) from 100 to 1000 nM. The GCAP mode plays a vital role in phototransduction in both rods and cones and the S100B mode in the transmission of neural signals to cone ON-bipolar cells. Through a programmed domain deletion, expression, in vivo fluorescence spectroscopy, and in vitro reconstitution experiments, this study demonstrates that the biochemical mechanisms modulated by two GCAPs in Ca(2+) signaling of ROS-GC1 activity are totally different. (1) They involve different structural domains of ROS-GC1. (2) Their signal migratory pathways are opposite: GCAP1 downstream and GCAP2 upstream. (3) Importantly, the isolated catalytic domain, translating the GCAP-modulated Ca(2+) signal into the generation of cyclic GMP, in vivo, exists as a homodimer, the two subunits existing in an antiparallel conformation. Furthermore, the findings demonstrate that the N-terminally placed signaling helix domain is not required for the catalytic domain's dimeric state. The upstream GCAP2-modulated pathway is the first of its kind to be observed for any member of the membrane guanylate cyclase family. It defines a new model of Ca(2+) signal transduction.
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Affiliation(s)
- Teresa Duda
- The Unit of Regulatory and Molecular Biology, Salus University, Elkins Park, PA 19027, USA.
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21
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Schumacher J. Tools for Botrytis cinerea: New expression vectors make the gray mold fungus more accessible to cell biology approaches. Fungal Genet Biol 2012; 49:483-97. [PMID: 22503771 DOI: 10.1016/j.fgb.2012.03.005] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/16/2012] [Accepted: 03/17/2012] [Indexed: 01/01/2023]
Abstract
Targeted gene inactivation is extensively used in the plant pathogenic fungus Botrytis cinerea for gene function analysis while strategies involving the expression of reporter genes have been rarely used due to the lack of appropriate expression vectors. Hence, an approach was initiated to establish an expression system for B.cinerea possessing the following features: (i) the targeted integration of constructs at defined gene loci which are dispensable under standard growth conditions, (ii) the use of promoter and terminator sequences allowing optimal gene expression, (iii) the use of codon-optimized reporter genes (Leroch et al., 2011), (iv) the use of multiple selection markers, and (v) the incorporation of a highly efficient cloning system. A set of basic vectors was generated by yeast recombinational cloning permitting a variety of protein fusions. The successful application of the expression system for labeling F-actin, the cytosol, the nuclei, the membrane, the ER and the peroxisomes was demonstrated. In addition, cloning vectors for bimolecular fluorescence complementation (BiFC) analyses for studying protein-protein interactions in situ were generated by splitting the codon-optimized gfp. The functionality of the constructed BiFC vectors was validated by demonstrating the interaction of the two white collar-like transcription factors BcWCL1 and BcWCL2 in the nuclei of growing B. cinerea hyphae.
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Affiliation(s)
- Julia Schumacher
- Institut für Biologie und Biotechnologie der Pflanzen, Westf. Wilhelms-Universität Münster, Hindenburgplatz 55, 48143 Münster, Germany.
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Live-cell visualization of transmembrane protein oligomerization and membrane fusion using two-fragment haptoEGFP methodology. Biosci Rep 2012; 32:333-43. [DOI: 10.1042/bsr20110100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Protein interactions play key roles throughout all subcellular compartments. In the present paper, we report the visualization of protein interactions throughout living mammalian cells using two oligomerizing MV (measles virus) transmembrane glycoproteins, the H (haemagglutinin) and the F (fusion) glycoproteins, which mediate MV entry into permissive cells. BiFC (bimolecular fluorescence complementation) has been used to examine the dimerization of these viral glycoproteins. The H glycoprotein is a type II membrane-receptor-binding homodimeric glycoprotein and the F glycoprotein is a type I disulfide-linked membrane glycoprotein which homotrimerizes. Together they co-operate to allow the enveloped virus to enter a cell by fusing the viral and cellular membranes. We generated a pair of chimaeric H glycoproteins linked to complementary fragments of EGFP (enhanced green fluorescent protein) – haptoEGFPs – which, on association, generate fluorescence. Homodimerization of H glycoproteins specifically drives this association, leading to the generation of a fluorescent signal in the ER (endoplasmic reticulum), the Golgi and at the plasma membrane. Similarly, the generation of a pair of corresponding F glycoprotein–haptoEGFP chimaeras also produced a comparable fluorescent signal. Co-expression of H and F glycoprotein chimaeras linked to complementary haptoEGFPs led to the formation of fluorescent fusion complexes at the cell surface which retained their biological activity as evidenced by cell-to-cell fusion.
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Dingus J, Hildebrandt JD. Synthesis and assembly of G protein βγ dimers: comparison of in vitro and in vivo studies. Subcell Biochem 2012; 63:155-80. [PMID: 23161138 DOI: 10.1007/978-94-007-4765-4_9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The heterotrimeric GTP-binding proteins (G proteins) are the canonical cellular machinery used with the approximately 700 G protein-coupled receptors (GPCRs) in the human genome to transduce extracellular signals across the plasma membrane. The synthesis of the constituent G protein subunits, and their assembly into Gβγ dimers and G protein heterotrimers, determines the signaling repertoire for G-protein/GPCR signaling in cells. These synthesis/assembly -processes are intimately related to two other overlapping events in the intricate pathway leading to formation of G protein signaling complexes, posttranslational modification and intracellular trafficking of G proteins. The assembly of the Gβγ dimer is a complex process involving multiple accessory proteins and organelles. The mechanisms involved are becoming increasingly appreciated, but are still incompletely understood. In vitro and in vivo (cellular) studies provide different perspectives of these processes, and a comparison of them can provide insight into both our current level of understanding and directions to be taken in future investigations.
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Affiliation(s)
- Jane Dingus
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, SC, 29425, USA
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Sheridan DC, Moua O, Lorenzon NM, Beam KG. Bimolecular fluorescence complementation and targeted biotinylation provide insight into the topology of the skeletal muscle Ca ( 2+) channel β1a subunit. Channels (Austin) 2012; 6:26-40. [PMID: 22522946 DOI: 10.4161/chan.18916] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In skeletal muscle, L-type calcium channels (DHPRs), localized to plasma membrane sarcoplasmic reticulum junctions, are tightly packed into groups of four termed tetrads. Here, we have used bimolecular fluorescence complementation (BiFC) and targeted biotinylation to probe the structure and organization of β1a subunits associated with native CaV 1.1 in DHPRs of myotubes. The construct YN-β1a-YC, in which the non-fluorescent fragments of YFP ("YN" corresponding to YFP residues 1-158, and "YC" corresponding to YFP residues 159-238) were fused, respectively, to the N- and C-termini of β1a, was fully functional and displayed yellow fluorescence within DHPR tetrads after expression in β1-knockout (β1KO) myotubes; this yellow fluorescence demonstrated the occurrence of BiFC of YN and YC on the β1a N- and C-termini. In these experiments, we avoided overexpression because control experiments in non-muscle cells indicated that this could result in non-specific BiFC. BiFC of YN-β1a-YC in DHPR tetrads appeared to be intramolecular between N- and C-termini of individual β1a subunits rather than between adjacent DHPRs because BiFC (1) was observed for YN-β1a-YC co-expressed with CaV 1.2 (which does not form tetrads) and (2) was not observed after co-expression of YN-β1a-YN plus YC-β1a-YC in β1KO myotubes. Thus, β1a function is compatible with N- and C-termini being close enough together to allow BiFC. However, both termini appeared to have positional freedom and not to be closely opposed by other junctional proteins since both were accessible to gold-streptavidin conjugates. Based on these results, a model is proposed for the arrangement of β1a subunits in DHPR tetrads.
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Affiliation(s)
- David C Sheridan
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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Gabay M, Pinter ME, Wright FA, Chan P, Murphy AJ, Valenzuela DM, Yancopoulos GD, Tall GG. Ric-8 proteins are molecular chaperones that direct nascent G protein α subunit membrane association. Sci Signal 2011; 4:ra79. [PMID: 22114146 DOI: 10.1126/scisignal.2002223] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ric-8A (resistance to inhibitors of cholinesterase 8A) and Ric-8B are guanine nucleotide exchange factors that enhance different heterotrimeric guanine nucleotide-binding protein (G protein) signaling pathways by unknown mechanisms. Because transgenic disruption of Ric-8A or Ric-8B in mice caused early embryonic lethality, we derived viable Ric-8A- or Ric-8B-deleted embryonic stem (ES) cell lines from blastocysts of these mice. We observed pleiotropic G protein signaling defects in Ric-8A(-/-) ES cells, which resulted from reduced steady-state amounts of Gα(i), Gα(q), and Gα(13) proteins to <5% of those of wild-type cells. The amounts of Gα(s) and total Gβ protein were partially reduced in Ric-8A(-/-) cells compared to those in wild-type cells, and only the amount of Gα(s) was reduced substantially in Ric-8B(-/-) cells. The abundances of mRNAs encoding the G protein α subunits were largely unchanged by loss of Ric-8A or Ric-8B. The plasma membrane residence of G proteins persisted in the absence of Ric-8 but was markedly reduced compared to that in wild-type cells. Endogenous Gα(i) and Gα(q) were efficiently translated in Ric-8A(-/-) cells but integrated into endomembranes poorly; however, the reduced amounts of G protein α subunits that reached the membrane still bound to nascent Gβγ. Finally, Gα(i), Gα(q), and Gβ(1) proteins exhibited accelerated rates of degradation in Ric-8A(-/-) cells compared to those in wild-type cells. Together, these data suggest that Ric-8 proteins are molecular chaperones required for the initial association of nascent Gα subunits with cellular membranes.
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Affiliation(s)
- Meital Gabay
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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26
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Piotrowska U, Adler G, Kozicki I. Diverse β subunits of heterotrimeric G proteins are present in thyroid plasma membranes. Biochem Biophys Res Commun 2011; 414:350-4. [PMID: 21964289 DOI: 10.1016/j.bbrc.2011.09.075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 09/14/2011] [Indexed: 10/17/2022]
Abstract
The functioning of heterotrimeric G protein α subunits in the transduction of hormonal signals to appropriate intracellular responses is well recognized. Much less is known about the distribution of isoforms and functions of G protein β subunits. Here, using specific antibodies, we documented that in plasma membranes of the thyroid cell line Nthy-ori 3-1 all Gβ isoforms-Gβ(1), Gβ(2), Gβ(3), Gβ(4) and Gβ(5) are present, while the Gβ(3) occurs in minute amount. In plasma membrane fraction isolated from pooled postoperative thyroids of patients with nodular goiter and Graves' disease, the Gβ(1), Gβ(2), Gβ(4) and Gβ(5) subunits were found, whereas Gβ(3) could not be detected. Competition studies revealed that the Gβ(2) is the principal Gβ subunit in membranes from cultured thyroid cells, originated from normal thyroid, as well as in membranes from patients' thyroids. This suggests that Gβ(2) subunit cooperates with Gα(s) subunit, the most active of the Gα variants, during stimulation of adenylate cyclase which constitutes the main route of physiological thyroid stimulation.
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Affiliation(s)
- Urszula Piotrowska
- Medical Centre of Postgraduate Education, Department of Biochemistry, 01 813 Warsaw, Poland
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27
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Thompson JL, Shuttleworth TJ. Orai channel-dependent activation of phospholipase C-δ: a novel mechanism for the effects of calcium entry on calcium oscillations. J Physiol 2011; 589:5057-69. [PMID: 21878525 DOI: 10.1113/jphysiol.2011.214437] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The frequency of oscillatory Ca(2+) signals is a major determinant in the selective activation of discrete downstream responses in non-excitable cells. An important modulator of this oscillation frequency is known to be the rate of agonist-activated Ca(2+) entry. However precisely how this is achieved and the respective roles of store-operated versus store-independent Ca(2+) entry pathways in achieving this are unclear. Here, we examine the possibility that a direct stimulation of a phospholipase C (PLC) by the entering Ca(2+) can induce a modulation of Ca(2+) oscillation frequency, and examine the roles of the endogenous store-operated and store-independent Orai channels (CRAC and ARC channels, respectively) in such a mechanism. Using the decline in the magnitude of currents through expressed PIP(2)-dependent Kir2.1 channels as a sensitive assay for PLC activity, we show that simple global increases in Ca(2+) concentrations over the physiological range do not significantly affect PLC activity. Similarly, maximal activation of endogenous CRAC channels also fails to affect PLC activity. In contrast, equivalent activation of endogenous ARC channels resulted in a 10-fold increase in the measured rate of PIP(2) depletion. Further experiments show that this effect is strictly dependent on the Ca(2+) entering via these channels, rather than the gating of the channels or the arachidonic acid used to activate them, and that it reflects the activation of a PLCδ by local Ca(2+) concentrations immediately adjacent to the active channels. Finally, based on the effects of expression of either a dominant-negative mutant Orai3 that is an essential component of the ARC channel, or a catalytically compromised mutant PLCδ, it was shown that this specific action of the store-independent ARC channel-mediated Ca(2+) entry on PLCδ has a significant impact on the oscillation frequency of the Ca(2+) signals activated by low concentrations of agonist.
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Affiliation(s)
- Jill L Thompson
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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28
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Qin K, Dong C, Wu G, Lambert NA. Inactive-state preassembly of G(q)-coupled receptors and G(q) heterotrimers. Nat Chem Biol 2011; 7:740-7. [PMID: 21873996 PMCID: PMC3177959 DOI: 10.1038/nchembio.642] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 06/29/2011] [Indexed: 12/29/2022]
Abstract
G protein-coupled receptors (GPCRs) transmit signals by forming active-state complexes with heterotrimeric G proteins. It has been suggested that some GPCRs also assemble with G proteins before ligand-induced activation and that inactive-state preassembly facilitates rapid and specific G protein activation. However, no mechanism of preassembly has been described, and no functional consequences of preassembly have been demonstrated. Here we show that M(3) muscarinic acetylcholine receptors (M3R) form inactive-state complexes with G(q) heterotrimers in intact cells. The M3R C terminus is sufficient, and a six-amino-acid polybasic sequence distal to helix 8 ((565)KKKRRK(570)) is necessary for preassembly with G(q). Replacing this sequence with six alanine residues prevents preassembly, slows the rate of G(q) activation and decreases steady-state agonist sensitivity. That other G(q)-coupled receptors possess similar polybasic regions and also preassemble with G(q) suggests that these GPCRs may use a common preassembly mechanism to facilitate activation of G(q) heterotrimers.
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Affiliation(s)
- Kou Qin
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, USA
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29
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Cai H, Devreotes PN. Moving in the right direction: how eukaryotic cells migrate along chemical gradients. Semin Cell Dev Biol 2011; 22:834-41. [PMID: 21821139 DOI: 10.1016/j.semcdb.2011.07.020] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 07/19/2011] [Accepted: 07/23/2011] [Indexed: 02/07/2023]
Abstract
Many cells have the ability to grow or migrate towards chemical cues. Oriented growth and movement require detection of the external chemical gradient, transduction of signals, and reorganization of the cytoskeleton. Recent studies in Dictyostelium discoideum and mammalian neutrophils have revealed a complex signaling network that enables cells to migrate in chemical gradients.
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Affiliation(s)
- Huaqing Cai
- The Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
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30
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CODA-RET reveals functional selectivity as a result of GPCR heteromerization. Nat Chem Biol 2011; 7:624-30. [PMID: 21785426 PMCID: PMC3158273 DOI: 10.1038/nchembio.623] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 05/16/2011] [Indexed: 01/09/2023]
Abstract
Here we present a novel method that combines protein complementation with resonance energy transfer to study conformational changes in response to activation of a defined G protein-coupled receptor heteromer, and we apply the approach to the putative dopamine D1-D2 receptor heteromer. Remarkably, the potency of the D2 receptor (D2R) agonist R(–)-Propylnorapomorphine (NPA) to change the Gαi conformation via the D2R protomer in the D1-D2 heteromer was enhanced 10-fold relative to that observed in the D2R homomer. In contrast, the potencies of the D2R agonists dopamine and quinpirole were the same in the homomer and heteromer. Thus, we have uncovered a molecular mechanism for functional selectivity, in which a drug acts differently at a GPCR protomer depending on the identity of the second protomer that participates in forming the signaling unit, opening the door to enhanced pharmacological specificity through targeting differences between homomeric and heteromeric signaling.
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31
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Huang P, Galloway CA, Yoon Y. Control of mitochondrial morphology through differential interactions of mitochondrial fusion and fission proteins. PLoS One 2011; 6:e20655. [PMID: 21647385 PMCID: PMC3103587 DOI: 10.1371/journal.pone.0020655] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 05/09/2011] [Indexed: 12/25/2022] Open
Abstract
Mitochondria in mammals are organized into tubular networks that undergo frequent shape change. Mitochondrial fission and fusion are the main components mediating the mitochondrial shape change. Perturbation of the fission/fusion balance is associated with many disease conditions. However, underlying mechanisms of the fission/fusion balance are not well understood. Mitochondrial fission in mammals requires the dynamin-like protein DLP1/Drp1 that is recruited to the mitochondrial surface, possibly through the membrane-anchored protein Fis1 or Mff. Additional dynamin-related GTPases, mitofusin (Mfn) and OPA1, are associated with the outer and inner mitochondrial membranes, respectively, and mediate fusion of the respective membranes. In this study, we found that two heptad-repeat regions (HR1 and HR2) of Mfn2 interact with each other, and that Mfn2 also interacts with the fission protein DLP1. The association of the two heptad-repeats of Mfn2 is fusion inhibitory whereas a positive role of the Mfn2/DLP1 interaction in mitochondrial fusion is suggested. Our results imply that the differential binding of Mfn2-HR1 to HR2 and DLP1 regulates mitochondrial fusion and that DLP1 may act as a regulatory factor for efficient execution of both fusion and fission of mitochondria.
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Affiliation(s)
- Pinwei Huang
- Mitochondrial Research and Innovation Group, Department of Anesthesiology, Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Chad A. Galloway
- Mitochondrial Research and Innovation Group, Department of Anesthesiology, Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Yisang Yoon
- Mitochondrial Research and Innovation Group, Department of Anesthesiology, Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
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32
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Lee JS, Baldridge A, Feng S, SiQiang Y, Kim YK, Tolbert LM, Chang YT. Fluorescence response profiling for small molecule sensors utilizing the green fluorescent protein chromophore and its derivatives. ACS COMBINATORIAL SCIENCE 2011; 13:32-8. [PMID: 21247122 DOI: 10.1021/co100012k] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using a fluorescence response profile, a systematic examination was performed for synthetic chromophores of the green fluorescent protein (GFP) to discover new small molecule sensors. A group of 41 benzylideneimidazolinone compounds (BDI) was prepared and screened toward 94 biologically relevant analytes to generate fluorescence response profiles. From the response pattern, compounds containing aminobenzyl and heteroaromatic cyclic substructures revealed a pH dependent emission decrease effect, and unlike other fluorescence scaffolds, most BDIs showed fluorescence quenching when mixed with proteins. On the basis of the primary response profile, we obtained three selective fluorescence turn-on sensors for pH, human serum albumin (HSA), and total ribonucleic acid (RNA). Following analysis, a fluorescence response profile testing four nucleic acids revealed the alkyloxy (Ph-OR) functional group in the para position of benzyl analogues contributes to RNA selectivity. Among the primary hit compounds, BDI 2 showed outstanding selectivity toward total RNA with 5-fold emission enhancement. Finally, BDI 24 showed selective fluorescence increase to HSA (K(d) = 3.57 μM) with a blue-shifted emission max wavelength (Δλ(em) = 15 nm). These examples of fluorescence sensor discovery by large-scale fluorescence response profiling demonstrate the general applicability of this approach and the usefulness of the response profiles.
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Affiliation(s)
- Jun-Seok Lee
- Life/Health Division, Integrated Omics Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, South Korea
| | - Anthony Baldridge
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | | | - Yang SiQiang
- Laboratory of Bioimaging Probe Development, Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Biopolis 138667, Singapore
| | - Yun Kyung Kim
- Life/Health Division, Integrated Omics Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, South Korea
| | - Laren M. Tolbert
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Young-Tae Chang
- Laboratory of Bioimaging Probe Development, Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Biopolis 138667, Singapore
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33
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Pétrin D, Hébert TE. Imaging-based approaches to understanding g protein-coupled receptor signalling complexes. Methods Mol Biol 2011; 756:37-60. [PMID: 21870219 DOI: 10.1007/978-1-61779-160-4_2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In the last 10 years, imaging assays based on resonance energy transfer (RET) and protein fragment complementation have made it possible to study interactions between components of G protein-coupled receptor (GPCR) signalling complexes in living cells under physiological conditions. Here, we consider the history of such approaches, the current tools available and how they have changed our understanding of GPCR signalling. We also discuss some theoretical and methodological issues important when combining the different types of assay.
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Affiliation(s)
- Darlaine Pétrin
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC, Canada
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34
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Hynes TR, Yost EA, Yost SM, Berlot CH. Multicolor BiFC analysis of G protein βγ complex formation and localization. Methods Mol Biol 2011; 756:229-43. [PMID: 21870229 DOI: 10.1007/978-1-61779-160-4_12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cells co-express multiple G protein β and γ subunit isoforms, but the extent to which individual subunits associate to form particular βγ complexes is not known. This issue is important because in vivo knockout experiments suggest that specific βγ complexes may have unique functions despite the fact that most complexes exhibit similar properties when assayed in reconstituted systems. This chapter describes how multicolor bimolecular fluorescence complementation (BiFC) can be used in living cells to study the association preferences of β and γ subunits. Multicolor BiFC determines the association preferences of these subunits by quantifying the two fluorescent complexes formed when β or γ subunits fused to amino terminal fragments of yellow fluorescent protein (YFP-N) and cyan fluorescent protein (CFP-N) compete for interaction with limiting amounts of a common γ or β subunit, respectively, fused to a carboxyl terminal fragment of CFP (CFP-C). One means by which βγ complexes may differ from each other and thereby mediate unique functions in vivo is in the kinetics and patterns of their internalization responses to stimulation of G protein-coupled receptors (GPCRs). Methods are described for imaging and quantifying the internalization of pairs of βγ complexes in response to GPCR stimulation in living cells.
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Affiliation(s)
- Thomas R Hynes
- Weis Center for Research, Geisinger Clinic, Danville, PA, USA
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35
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Sung MK, Huh WK. In vivo quantification of protein-protein interactions in Saccharomyces cerevisiae using bimolecular fluorescence complementation assay. J Microbiol Methods 2010; 83:194-201. [PMID: 20828586 DOI: 10.1016/j.mimet.2010.08.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 08/24/2010] [Accepted: 08/31/2010] [Indexed: 01/14/2023]
Abstract
Most of the biological processes are carried out and regulated by dynamic networks of protein-protein interactions. In this study, we demonstrate the feasibility of the bimolecular fluorescence complementation (BiFC) assay for in vivo quantitative analysis of protein-protein interactions in Saccharomyces cerevisiae. We show that the BiFC assay can be used to quantify not only the amount but also the cell-to-cell variation of protein-protein interactions in S. cerevisiae. In addition, we show that protein sumoylation and condition-specific protein-protein interactions can be quantitatively analyzed by using the BiFC assay. Taken together, our results validate that the BiFC assay is a very effective method for quantitative analysis of protein-protein interactions in living yeast cells and has a great potential as a versatile tool for the study of protein function.
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Affiliation(s)
- Min-Kyung Sung
- School of Biological Sciences and Research Center for Functional Cellulomics, Institute of Microbiology, Seoul National University, Seoul 151-747, Republic of Korea
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36
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Gβγ is a negative regulator of AP-1 mediated transcription. Cell Signal 2010; 22:1254-66. [DOI: 10.1016/j.cellsig.2010.04.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Accepted: 04/12/2010] [Indexed: 11/18/2022]
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37
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Swaney KF, Huang CH, Devreotes PN. Eukaryotic chemotaxis: a network of signaling pathways controls motility, directional sensing, and polarity. Annu Rev Biophys 2010; 39:265-89. [PMID: 20192768 DOI: 10.1146/annurev.biophys.093008.131228] [Citation(s) in RCA: 362] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Chemotaxis, the directed migration of cells in chemical gradients, is a vital process in normal physiology and in the pathogenesis of many diseases. Chemotactic cells display motility, directional sensing, and polarity. Motility refers to the random extension of pseudopodia, which may be driven by spontaneous actin waves that propagate through the cytoskeleton. Directional sensing is mediated by a system that detects temporal and spatial stimuli and biases motility toward the gradient. Polarity gives cells morphologically and functionally distinct leading and lagging edges by relocating proteins or their activities selectively to the poles. By exploiting the genetic advantages of Dictyostelium, investigators are working out the complex network of interactions between the proteins that have been implicated in the chemotactic processes of motility, directional sensing, and polarity.
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Affiliation(s)
- Kristen F Swaney
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA
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38
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Wang B, Ardura JA, Romero G, Yang Y, Hall RA, Friedman PA. Na/H exchanger regulatory factors control parathyroid hormone receptor signaling by facilitating differential activation of G(alpha) protein subunits. J Biol Chem 2010; 285:26976-26986. [PMID: 20562104 DOI: 10.1074/jbc.m110.147785] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Na/H exchanger regulatory factors, NHERF1 and NHERF2, are adapter proteins involved in targeting and assembly of protein complexes. The parathyroid hormone receptor (PTHR) interacts with both NHERF1 and NHERF2. The NHERF proteins toggle PTHR signaling from predominantly activation of adenylyl cyclase in the absence of NHERF to principally stimulation of phospholipase C when the NHERF proteins are expressed. We hypothesized that this signaling switch occurs at the level of the G protein. We measured G protein activation by [(35)S]GTPgammaS binding and G(alpha) subtype-specific immunoprecipitation using three different cellular models of PTHR signaling. These studies revealed that PTHR interactions with NHERF1 enhance receptor-mediated stimulation of G(alpha)(q) but have no effect on stimulation of G(alpha)(i) or G(alpha)(s). In contrast, PTHR associations with NHERF2 enhance receptor-mediated stimulation of both G(alpha)(q) and G(alpha)(i) but decrease stimulation of G(alpha)(s). Consistent with these functional data, NHERF2 formed cellular complexes with both G(alpha)(q) and G(alpha)(i), whereas NHERF1 was found to interact only with G(alpha)(q). These findings demonstrate that NHERF interactions regulate PTHR signaling at the level of G proteins and that NHERF1 and NHERF2 exhibit isotype-specific effects on G protein activation.
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Affiliation(s)
- Bin Wang
- Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Juan A Ardura
- Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Guillermo Romero
- Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Yanmei Yang
- Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Randy A Hall
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Peter A Friedman
- Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261.
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39
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Ciruela F, Vilardaga JP, Fernández-Dueñas V. Lighting up multiprotein complexes: lessons from GPCR oligomerization. Trends Biotechnol 2010; 28:407-15. [PMID: 20542584 DOI: 10.1016/j.tibtech.2010.05.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2010] [Revised: 04/27/2010] [Accepted: 05/05/2010] [Indexed: 11/18/2022]
Abstract
Spatiotemporal characterization of protein-protein interactions (PPIs) is essential in determining the molecular mechanisms of intracellular signaling processes. In this review, we discuss how new methodological strategies derived from non-invasive fluorescence- and luminescence-based approaches (FRET, BRET, BiFC and BiLC), when applied to the study of G protein-coupled receptor (GPCR) oligomerization, can be used to detect specific PPIs in live cells. These technologies alone or in concert with complementary methods (SRET, BRET or BiFC, and SNAP-tag or TR-FRET) can be extremely powerful approaches for PPI visualization, even between more than two proteins. Here we provide a comprehensive update on all the biotechnological aspects, including the strengths and weaknesses, of new fluorescence- and luminescence-based methodologies, with a specific focus on their application for studying PPIs.
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Affiliation(s)
- Francisco Ciruela
- Unitat de Farmacologia, Departament de Patologia i Terapèutica Experimental, Facultat de Medicina, IDIBELL-Universitat de Barcelona, 08907 Barcelona, Spain.
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40
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Rose RH, Briddon SJ, Holliday ND. Bimolecular fluorescence complementation: lighting up seven transmembrane domain receptor signalling networks. Br J Pharmacol 2009; 159:738-50. [PMID: 20015298 DOI: 10.1111/j.1476-5381.2009.00480.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
There is increasing complexity in the organization of seven transmembrane domain (7TM) receptor signalling pathways, and in the ability of their ligands to modulate and direct this signalling. Underlying these events is a network of protein interactions between the 7TM receptors themselves and associated effectors, such as G proteins and beta-arrestins. Bimolecular fluorescence complementation, or BiFC, is a technique capable of detecting these protein-protein events essential for 7TM receptor function. Fluorescent proteins, such as those from Aequorea victoria, are split into two non-fluorescent halves, which then tag the proteins under study. On association, these fragments refold and regenerate a mature fluorescent protein, producing a BiFC signal indicative of complex formation. Here, we review the experimental criteria for successful application of BiFC, considered in the context of 7TM receptor signalling events such as receptor dimerization, G protein and beta-arrestin signalling. The advantages and limitations of BiFC imaging are compared with alternative resonance energy transfer techniques. We show that the essential simplicity of the fluorescent BiFC measurement allows high-content and advanced imaging applications, and that it can probe more complex multi-protein interactions alone or in combination with resonance energy transfer. These capabilities suggest that BiFC techniques will become ever more useful in the analysis of ligand and 7TM receptor pharmacology at the molecular level of protein-protein interactions.
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Affiliation(s)
- Rachel H Rose
- Institute of Cell Signalling, School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, UK
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41
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Hou YX, Li CZ, Palaniyandi K, Magtibay PM, Homolya L, Sarkadi B, Chang XB. Effects of putative catalytic base mutation E211Q on ABCG2-mediated methotrexate transport. Biochemistry 2009; 48:9122-31. [PMID: 19691360 DOI: 10.1021/bi900675v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
ABCG2 is a half-ATP binding cassette (ABC) drug transporter that consists of a nucleotide binding domain (NBD) followed by a transmembrane domain. This half-ABC transporter is thought to form a homodimer in the plasma membrane where it transports anticancer drugs across the biological membranes in an ATP-dependent manner. Substitution of the putative catalytic residue E211 with a nonacidic amino acid glutamine (E211Q) completely abolished its ATPase activity and ATP-dependent methotrexate transport, suggesting that ATP hydrolysis is required for the ATP-dependent solute transport. However, whether one ATP hydrolysis or two ATP hydrolyses in the homodimer of ABCG2 with the NBD.ATP.ATP.NBD sandwich structure is/are required for the ATP-dependent solute transport is not known yet. To address this question, we have made an YFP/ABCG2 fusion protein and expressed this 99 kDa fusion protein alone or along with the 70 kDa E211Q-mutated ABCG2 in BHK cells. Although membrane vesicles prepared from BHK cells expressing YFP/ABCG2 exert higher ATPase activity than that of wt ABCG2, the dATP-dependent methotrexate transport activities of these two proteins are the same. Interestingly, membrane vesicles prepared from BHK cells expressing both YFP/ABCG2 and E211Q-mutated ABCG2 (with a ratio of 1:1) form homodimers and heterodimer and exert 55% of wt ABCG2 ATPase activity that can be further enhanced by anticancer drugs, suggesting that the wt NBD in the heterodimer of YFP/ABCG2 and E211Q may be able to hydrolyze ATP. Furthermore, the membrane vesicles containing both YFP/ABCG2 and E211Q exert approximately 79% of wt ABCG2-mediated methotrexate transport activity, implying that the heterodimer harboring YFP/ABCG2 and E211Q may be able to transport the anticancer drug methotrexate across the biological membranes.
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Affiliation(s)
- Yue-xian Hou
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 13400 East Shea Boulevard, Scottsdale, Arizona 85259, USA
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Poe JA, Smithgall TE. HIV-1 Nef dimerization is required for Nef-mediated receptor downregulation and viral replication. J Mol Biol 2009; 394:329-42. [PMID: 19781555 DOI: 10.1016/j.jmb.2009.09.047] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/15/2009] [Accepted: 09/17/2009] [Indexed: 10/20/2022]
Abstract
Nef, a human immunodeficiency virus type 1 (HIV-1) accessory factor capable of interaction with a diverse array of host cell signaling molecules, is essential for high-titer HIV replication and AIDS progression. Previous biochemical and structural studies have suggested that Nef may form homodimers and higher-order oligomers in HIV-infected cells, which may be required for both immune and viral receptor downregulation as well as viral replication. Using bimolecular fluorescence complementation, we provide the first direct evidence for Nef dimers within HIV host cells and identify the structural requirements for dimerization in vivo. Bimolecular fluorescence complementation analysis shows that the multiple hydrophobic and electrostatic interactions found within the dimerization interface of the Nef X-ray crystal structure are essential for dimerization in cells. Nef dimers localized to the plasma membrane as well as the trans-Golgi network, two subcellular localizations essential for Nef function. Mutations in the Nef dimerization interface dramatically reduced both Nef-induced CD4 downregulation and HIV replication. Viruses expressing dimerization-defective Nef mutants were disabled to the same extent as HIV that fails to express Nef in terms of replication. These results identify the Nef dimerization region as a potential molecular target for antiretroviral drug discovery.
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Affiliation(s)
- Jerrod A Poe
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, E1240 Biomedical Science Tower, Pittsburgh, PA 15261, USA
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Sebag JA, Hinkle PM. Opposite effects of the melanocortin-2 (MC2) receptor accessory protein MRAP on MC2 and MC5 receptor dimerization and trafficking. J Biol Chem 2009; 284:22641-8. [PMID: 19535343 DOI: 10.1074/jbc.m109.022400] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
MC2 (ACTH) receptors require MC2 receptor accessory protein (MRAP) to reach the cell surface. In this study, we show that MRAP has the opposite effect on the closely related MC5 receptor. In enzyme-linked immunosorbent assay and microscopy experiments, MC2 receptor was retained in the endoplasmic reticulum in the absence of MRAP and targeted to the plasma membrane with MRAP. MC5 receptor was at the plasma membrane in the absence of MRAP, but trapped intracellularly when expressed with MRAP. Using bimolecular fluorescence complementation, where one fragment of yellow fluorescent protein (YFP) was fused to receptors and another to MRAP, we showed that MC2 receptor-MRAP dimers were present at the plasma membrane, whereas MC5 receptor-MRAP dimers were intracellular. Both MC2 and MC5 receptors co-precipitated with MRAP. MRAP did not alter expression of beta2-adrenergic receptors or co-precipitate with them. To determine if MRAP affects formation of receptor oligomers, we co-expressed MC2 receptors fused to YFP fragments in the presence or absence of MRAP. YFP fluorescence, reporting MC2 receptor homodimers, was readily detectable with or without MRAP. In contrast, MC5 receptor homodimers were visible in the absence of MRAP, but little fluorescence was observed by microscopic analysis when MRAP was co-expressed. Co-precipitation of differentially tagged receptors confirmed that MRAP blocks MC5 receptor dimerization. The regions of MRAP required for its effects on MC2 and MC5 receptors differed. These results establish that MRAP forms stable complexes with two different melanocortin receptors, facilitating surface expression of MC2 receptor but disrupting dimerization and surface localization of MC5 receptor.
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Affiliation(s)
- Julien A Sebag
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA
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Fluorescence complementation via EF-hand interactions. J Biotechnol 2009; 142:205-13. [PMID: 19500621 DOI: 10.1016/j.jbiotec.2009.05.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 05/06/2009] [Accepted: 05/12/2009] [Indexed: 11/20/2022]
Abstract
Fluorescence complementation technology with fluorescent proteins is a powerful approach to investigate molecular recognition by monitoring fluorescence enhancement when non-fluorescent fragments of fluorescent proteins are fused with target proteins, resulting in a new fluorescent complex. Extension of the technology to calcium-dependent protein-protein interactions has, however, rarely been reported. Here, a linker containing trypsin cleavage sites was grafted onto enhanced green fluorescent protein (EGFP). Under physiological conditions, a modified fluorescent protein, EGFP-T1, was cleaved into two major fragments which continue to interact with each other, exhibiting strong optical and fluorescence signals. The larger fragment, comprised of amino acids 1-172, including the chromophore, retains only weak fluorescence. Strong green fluorescence was observed when plasmid DNA encoding complementary EGFP fragments fused to the EF-hand motifs of calbindin D9k (EF1 and EF2) were co-transfected into HeLa cells, suggesting that chromophore maturation and fluorescence complementation from EGFP fragments can be accomplished intracellularly by reassembly of EF-hand motifs, which have a strong tendency for dimerization. Moreover, an intracellular calcium increase upon addition of a calcium ionophore, ionomycin in living cells, results in an increase of fluorescence signal. This novel application of calcium-dependent fluorescence complementation has the potential to monitor protein-protein interactions triggered by calcium signalling pathways in living cells.
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Hollins B, Kuravi S, Digby GJ, Lambert NA. The c-terminus of GRK3 indicates rapid dissociation of G protein heterotrimers. Cell Signal 2009; 21:1015-21. [PMID: 19258039 DOI: 10.1016/j.cellsig.2009.02.017] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Accepted: 02/20/2009] [Indexed: 10/21/2022]
Abstract
Signals mediated by heterotrimeric G proteins often develop over the course of tens of milliseconds, and could require either conformational rearrangement or complete physical dissociation of Galphabetagamma heterotrimers. Although it is known that some active heterotrimers are dissociated (into Galpha and Gbetagamma) at steady-state, it is not clear that dissociation occurs quickly enough to participate in rapid signaling. Here we show that fusion proteins containing the c-terminus of GPCR kinase 3 (GRK3ct) and either the fluorescent protein cerulean or Renilla luciferase bind to venus-labeled Gbetagamma dimers (Gbetagamma-V), resulting in Förster or bioluminescence resonance energy transfer (FRET or BRET). GRK3ct fusion proteins are freely-diffusible, and do not form preassembled complexes with G proteins. GRK3ct fusion proteins bind to free Gbetagamma-V dimers but not to rearranged heterotrimers, and thus can report G protein dissociation with high temporal resolution. We find that heterotrimer dissociation can occur in living cells in less than 100 ms. Under the conditions of these experiments diffusion and collision of masGRK3ct fusion proteins and Gbetagamma-V were not rate-limiting. These results indicate that G protein heterotrimers can dissociate quickly enough to participate in rapid signaling.
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Affiliation(s)
- Bettye Hollins
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912, USA
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Dave RH, Saengsawang W, Yu JZ, Donati R, Rasenick MM. Heterotrimeric G-proteins interact directly with cytoskeletal components to modify microtubule-dependent cellular processes. Neurosignals 2009; 17:100-8. [PMID: 19212143 DOI: 10.1159/000186693] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Accepted: 11/05/2008] [Indexed: 01/07/2023] Open
Abstract
A large percentage of current drugs target G-protein-coupled receptors, which couple to well-known signaling pathways involving cAMP or calcium. G-proteins themselves may subserve a second messenger function. Here, we review the role of tubulin and microtubules in directly mediating effects of heterotrimeric G-proteins on neuronal outgrowth, shape and differentiation. G-protein-tubulin interactions appear to be regulated by neurotransmitter activity, and, in turn, regulate the location of Galpha in membrane microdomains (such as lipid rafts) or the cytosol. Tubulin binds with nanomolar affinity to Gsalpha, Gialpha1 and Gqalpha (but not other Galpha subunits) as well as Gbeta(1)gamma(2) subunits. Galpha subunits destabilize microtubules by stimulating tubulin's GTPase, while Gbetagamma subunits promote microtubule stability. The same region on Gsalpha that binds adenylyl cyclase and Gbetagamma also interacts with tubulin, suggesting that cytoskeletal proteins are novel Galpha effectors. Additionally, intracellular Gialpha-GDP, in concert with other GTPase proteins and Gbetagamma, regulates the position of the mitotic spindle in mitosis. Thus, G-protein activation modulates cell growth and differentiation by directly altering microtubule stability. Further studies are needed to fully establish a structural mechanism of this interaction and its role in synaptic plasticity.
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Affiliation(s)
- Rahul H Dave
- Department of Physiology and Biophysics, University of Illinois Chicago, Chicago, Il 60612-7342, USA
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McIntire WE. Structural determinants involved in the formation and activation of G protein betagamma dimers. Neurosignals 2009; 17:82-99. [PMID: 19212142 DOI: 10.1159/000186692] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 05/13/2008] [Indexed: 01/08/2023] Open
Abstract
Heterotrimeric G proteins, composed of an alpha, beta and gamma subunit, represent one of the most important and dynamic families of signaling proteins. As a testament to the significance of G protein signaling, the hundreds of seven-transmembrane-spanning receptors that interact with G proteins are estimated to occupy 1-2% of the human genome. This broad diversity of receptors is echoed in the number of potential heterotrimer combinations that can arise from the 23 alpha subunit, 7 beta subunit and 12 gamma subunit isoforms that have been identified. The potential for such vast complexity implies that the receptor G protein interface is the site of much regulation. The historical model for the activation of a G protein holds that activated receptor catalyzes the exchange of GDP for GTP on the alpha subunit, inducing a conformational change that substantially lowers the affinity of alpha for betagamma. This decreased affinity enables dissociation of betagamma from alpha and receptor. The free form of betagamma is thought to activate effectors, until the hydrolysis of GTP by G alpha (aided by RGS proteins) allows the subunits to re-associate, effectively deactivating the G protein until another interaction with activated receptor.
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Affiliation(s)
- William E McIntire
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA 22908, USA.
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Dittman J. Chapter 2 Worm Watching: Imaging Nervous System Structure and Function in Caenorhabditis elegans. ADVANCES IN GENETICS 2009; 65:39-78. [DOI: 10.1016/s0065-2660(09)65002-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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Robitaille M, Héroux I, Baragli A, Hébert TE. Novel tools for use in bioluminescence resonance energy transfer (BRET) assays. Methods Mol Biol 2009; 574:215-34. [PMID: 19685312 DOI: 10.1007/978-1-60327-321-3_18] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Recent advances in imaging assays based on bioluminescence resonance energy transfer (BRET) have made it possible to study protein/protein interactions in living cells under physiological conditions. Here we describe protocols for these assays including relevant positive and negative controls, and we also show how they can be combined with protein complementation assays such as bimolecular fluorescence complementation (BiFC) to study three- and four-partner interactions. We also describe a BRET assay that uses SNAP-tagged proteins as a fluorescence acceptor molecule for the bioluminescent donor.
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Sebag JA, Hinkle PM. Regions of melanocortin 2 (MC2) receptor accessory protein necessary for dual topology and MC2 receptor trafficking and signaling. J Biol Chem 2008; 284:610-618. [PMID: 18981183 DOI: 10.1074/jbc.m804413200] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
MRAP, melanocortin 2 (MC2) receptor accessory protein, is required for trafficking by the MC2 (ACTH) receptor. MRAP is a single transmembrane protein that forms highly unusual antiparallel homodimers. We used molecular complementation to ask where MRAP achieves dual topology. Fragments of yellow fluorescent protein (YFP) were fused to the NH2 or COOH terminus of MRAP such that YFP fluorescence could occur only in antiparallel homodimers; fluorescence was present in the endoplasmic reticulum. MRAP retained dual topology after deletion of most of the amino terminus. In contrast, deletion of residues 31-37, just NH2-terminal to the transmembrane domain, forced MRAP into a single Nexo/Ccyt orientation and blocked its ability to promote MC2 receptor trafficking and homodimerize. When the transmembrane domain of MRAP was replaced with the corresponding region from RAMP3, dual topology was retained but MRAP was inactive. Insertion of MRAP residues 29-37 conferred dual topology to RAMP3, normally in an Nexo/Ccyt orientation. When expressed with MRAPDelta1-30, MRAPDelta10-20, or MRAPDelta21-30, MC2 receptor was localized on the plasma membrane but unable to respond to ACTH. Residues 18-21 of MRAP were critical; MC2 receptor expressed with MRAP(18-21A) localized to the plasma membrane but did not bind 125I-ACTH or increase cAMP in response to ACTH. A newly identified MRAP homolog, MRAP2, lacks amino acids 18LDYI21 of MRAP and, like MRAP(18-21A), allows MC2 receptor trafficking but not signaling. MRAP2 with an LDYI insertion functions like MRAP. These results demonstrate that MRAP not only facilitates MC2 receptor trafficking but also allows properly localized receptor to bind ACTH and consequently signal.
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Affiliation(s)
- Julien A Sebag
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642
| | - Patricia M Hinkle
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642.
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