1
|
Yan R, Xia Y, Zhou K, Liu J, Sun Y, He C, Ge X, Yang M, Sun C, Yuan L, Li S, Yang B, Meng F, Cao L, Ruan C, Dai K. Essential role of glycoprotein Ibα in platelet activation. Blood Adv 2024; 8:3388-3401. [PMID: 38701351 PMCID: PMC11255362 DOI: 10.1182/bloodadvances.2023012308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/03/2024] [Accepted: 04/16/2024] [Indexed: 05/05/2024] Open
Abstract
ABSTRACT Glycoprotein Ibα (GPIbα), the ligand-binding subunit of platelet GPIb-IX complex, interacts with von Willebrand factor (VWF) exposed at the injured vessel wall, initiating platelet adhesion, activation, hemostasis, and thrombus formation. The cytoplasmic tail of GPIbα interacts with 14-3-3ζ, regulating the VWF-GPIbα-elicited signal transduction and VWF binding function of GPIbα. However, we unexpectedly found that the GPIbα-14-3-3ζ association, beyond VWF-dependent function, is essential for general platelet activation. We found that the myristoylated peptide of GPIbα C-terminus MPαC, a potential GPIbα inhibitor, by itself induced platelet aggregation, integrin αIIbβ3 activation, granule secretion, and phosphatidylserine (PS) exposure. Conversely, the deletion of the cytoplasmic tail of GPIbα in mouse platelets (10aa-/-) decreased platelet aggregation, integrin αIIbβ3 activation, granule secretion, and PS exposure induced by various physiological agonists. Phosphoproteome-based kinase activity profiling revealed significantly upregulated protein kinase C (PKC) activity in MPαC-treated platelets. MPαC-induced platelet activation was abolished by the pan-PKC inhibitor and PKCα deletion. Decreased PKC activity was observed in both resting and agonist-stimulated 10aa-/- platelets. GPIbα regulates PKCα activity by sequestering 14-3-3ζ from PKCα. In vivo, the deletion of the GPIbα cytoplasmic tail impaired mouse hemostasis and thrombus formation and protected against platelet-dependent pulmonary thromboembolism. Therefore, our findings demonstrate an essential role for the GPIbα cytoplasmic tail in regulating platelet general activation and thrombus formation beyond the VWF-GPIbα axis.
Collapse
Affiliation(s)
- Rong Yan
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Yue Xia
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Kangxi Zhou
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Jun Liu
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Yueyue Sun
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Chunyan He
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Xinxin Ge
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Mengnan Yang
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Chenglin Sun
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Liuxia Yuan
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Shujun Li
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Biao Yang
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Fanbi Meng
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Lijuan Cao
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Changgeng Ruan
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| | - Kesheng Dai
- Jiangsu Institute of Hematology, Cyrus Tang Medical Institute, The First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, National Clinical Research Center for Hematological Diseases, Suzhou, China
| |
Collapse
|
2
|
Song L, Luo J, Wang H, Huang D, Tan Y, Liu Y, Wang Y, Yu K, Zhang Y, Liu X, Li D, Luo ZQ. Legionella pneumophila regulates host cell motility by targeting Phldb2 with a 14-3-3ζ-dependent protease effector. eLife 2022; 11:73220. [PMID: 35175192 PMCID: PMC8871388 DOI: 10.7554/elife.73220] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 02/16/2022] [Indexed: 11/18/2022] Open
Abstract
The cytoskeleton network of eukaryotic cells is essential for diverse cellular processes, including vesicle trafficking, cell motility, and immunity, thus is a common target for bacterial virulence factors. A number of effectors from the bacterial pathogen Legionella pneumophila have been shown to modulate the function of host actin cytoskeleton to construct the Legionella-containing vacuole (LCV) permissive for its intracellular replication. In this study, we found that the Dot/Icm effector Lem8 (Lpg1290) is a protease whose activity is catalyzed by a Cys-His-Asp motif known to be associated with diverse biochemical activities. Intriguingly, we found that Lem8 interacts with the host regulatory protein 14-3-3ζ, which activates its protease activity. Furthermore, Lem8 undergoes self-cleavage in a process that requires 14-3-3ζ. We identified the Pleckstrin homology-like domain-containing protein Phldb2 involved in cytoskeleton organization as a target of Lem8 and demonstrated that Lem8 plays a role in the inhibition of host cell migration by attacking Phldb2.
Collapse
Affiliation(s)
- Lei Song
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Jingjing Luo
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Hongou Wang
- Department of Microbiology, Peking University Health Science Center, Peking, China
| | - Dan Huang
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Yunhao Tan
- Department of Biological Sciences, Purdue University, West Lafayette, United States
| | - Yao Liu
- Department of Biological Sciences, Purdue University, West Lafayette, United States
| | - Yingwu Wang
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Kaiwen Yu
- Department of Microbiology, Peking University Health Science Center, Peking, China
| | - Yong Zhang
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Xiaoyun Liu
- Department of Microbiology, Peking University Health Science Center, Peking, China
| | - Dan Li
- Department of Respiratory Medicine, Jilin University, Changchun, China
| | - Zhao-Qing Luo
- Department of Biological Science, Purdue University, West Lafayette, United States
| |
Collapse
|
3
|
14-3-3 proteins in platelet biology and glycoprotein Ib-IX signaling. Blood 2018; 131:2436-2448. [PMID: 29622550 DOI: 10.1182/blood-2017-09-742650] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 03/25/2018] [Indexed: 12/16/2022] Open
Abstract
Members of the 14-3-3 family of proteins function as adapters/modulators that recognize phosphoserine/phosphothreonine-based binding motifs in many intracellular proteins and play fundamental roles in signal transduction pathways of eukaryotic cells. In platelets, 14-3-3 plays a wide range of regulatory roles in phosphorylation-dependent signaling pathways, including G-protein signaling, cAMP signaling, agonist-induced phosphatidylserine exposure, and regulation of mitochondrial function. In particular, 14-3-3 interacts with several phosphoserine-dependent binding sites in the major platelet adhesion receptor, the glycoprotein Ib-IX complex (GPIb-IX), regulating its interaction with von Willebrand factor (VWF) and mediating VWF/GPIb-IX-dependent mechanosignal transduction, leading to platelet activation. The interaction of 14-3-3 with GPIb-IX also plays a critical role in enabling the platelet response to low concentrations of thrombin through cooperative signaling mediated by protease-activated receptors and GPIb-IX. The various functions of 14-3-3 in platelets suggest that it is a possible target for the treatment of thrombosis and inflammation.
Collapse
|
4
|
Sluchanko NN, Tugaeva KV, Greive SJ, Antson AA. Chimeric 14-3-3 proteins for unraveling interactions with intrinsically disordered partners. Sci Rep 2017; 7:12014. [PMID: 28931924 PMCID: PMC5607241 DOI: 10.1038/s41598-017-12214-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/05/2017] [Indexed: 01/01/2023] Open
Abstract
In eukaryotes, several “hub” proteins integrate signals from different interacting partners that bind through intrinsically disordered regions. The 14-3-3 protein hub, which plays wide-ranging roles in cellular processes, has been linked to numerous human disorders and is a promising target for therapeutic intervention. Partner proteins usually bind via insertion of a phosphopeptide into an amphipathic groove of 14-3-3. Structural plasticity in the groove generates promiscuity allowing accommodation of hundreds of different partners. So far, accurate structural information has been derived for only a few 14-3-3 complexes with phosphopeptide-containing proteins and a variety of complexes with short synthetic peptides. To further advance structural studies, here we propose a novel approach based on fusing 14-3-3 proteins with the target partner peptide sequences. Such chimeric proteins are easy to design, express, purify and crystallize. Peptide attachment to the C terminus of 14-3-3 via an optimal linker allows its phosphorylation by protein kinase A during bacterial co-expression and subsequent binding at the amphipathic groove. Crystal structures of 14-3-3 chimeras with three different peptides provide detailed structural information on peptide-14-3-3 interactions. This simple but powerful approach, employing chimeric proteins, can reinvigorate studies of 14-3-3/phosphoprotein assemblies, including those with challenging low-affinity partners, and may facilitate the design of novel biosensors.
Collapse
Affiliation(s)
- Nikolai N Sluchanko
- A.N. Bach Institute of Biochemistry, Federal Research Center "Fundamentals of Biotechnology" of the Russian Academy of Sciences, 119071, Moscow, Russian Federation. .,Department of biophysics, School of Biology, Moscow State University, 119991, Moscow, Russian Federation.
| | - Kristina V Tugaeva
- A.N. Bach Institute of Biochemistry, Federal Research Center "Fundamentals of Biotechnology" of the Russian Academy of Sciences, 119071, Moscow, Russian Federation.,Department of biochemistry, School of Biology, Moscow State University, 119991, Moscow, Russian Federation
| | - Sandra J Greive
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, YO10 5DD, United Kingdom
| | - Alfred A Antson
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, YO10 5DD, United Kingdom
| |
Collapse
|
5
|
Sluchanko NN, Uversky VN. Hidden disorder propensity of the N-terminal segment of universal adapter protein 14-3-3 is manifested in its monomeric form: Novel insights into protein dimerization and multifunctionality. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:492-504. [PMID: 25747569 DOI: 10.1016/j.bbapap.2015.02.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 02/17/2015] [Accepted: 02/24/2015] [Indexed: 11/30/2022]
Abstract
The multiplicity of functions of 14-3-3 proteins, integrated into many cellular interactions and signaling networks, is primarily based upon their dimeric α-helical structure that is capable of binding phosphorylated protein partners as well as displaying a "moonlighting" chaperone-like activity. The structure and functions of 14-3-3 proteins are regulated in different ways, including Ser58 phosphorylation in the interface, which shifts equilibrium towards the formation of protein monomers whose role is poorly understood. While modification of Ser58 induced only partial dissociation, the engineered triple mutation of human 14-3-3ζ located in the first α-helix deeply monomerized the protein, allowing for a structural analysis of the monomeric form. Dimer-incapable 14-3-3 proteins retained binding capacity and specificity towards some phosphopartners, and also demonstrated increased chaperone-like activity on various substrates. Here, we found a substantial propensity of the N-terminal segment (~40 residues) of 14-3-3 proteins to intrinsic disorder, showing remarkable conservation across different isoforms and organisms. We hypothesized that this intrinsic disorder propensity, hidden in the α-helical 14-3-3 dimer, can be manifested upon its dissociation and interrogated novel monomeric 14-3-3ζ carrying both monomerizing and S58E mutations (14-3-3ζmS58E). CD spectroscopy showed that, at physiological temperatures, this protein has ~10-15% reduced helicity relative to the wild type protein, corresponding to roughly 40 residues. Along with the known flexibility of C-terminus, SAXS-based modeling of the 14-3-3ζmS58E structure strongly suggested pliability of its N-terminus. The unraveled disorder propensity of the N-terminal tails of 14-3-3 proteins provides new clues for better understanding of the molecular mechanisms of dimerization and multifunctionality of these universal adapter proteins.
Collapse
Affiliation(s)
- Nikolai N Sluchanko
- A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky prospect 33, Moscow 119071, Russian Federation.
| | - Vladimir N Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA; Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, Russian Federation; Biology Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia; Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russian Federation.
| |
Collapse
|
6
|
The yeast 14-3-3 proteins BMH1 and BMH2 differentially regulate rapamycin-mediated transcription. Biosci Rep 2014; 34:BSR20130096. [PMID: 27919033 PMCID: PMC3958127 DOI: 10.1042/bsr20130096] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 01/03/2014] [Accepted: 01/17/2014] [Indexed: 11/17/2022] Open
Abstract
14-3-3 proteins are highly conserved and have been found in all eukaryotic organisms investigated. They are involved in many varied cellular processes, and interact with hundreds of other proteins. Among many other roles in cells, yeast 14-3-3 proteins have been implicated in rapamycin-mediated cell signalling. We determined the transcription profiles of bmh1 and bmh2 yeast after treatment with rapamycin. We found that, under these conditions, BMH1 and BMH2 are required for rapamycin-induced regulation of distinct, but overlapping sets of genes. Both Bmh1 and Bmh2 associate with the promoters of at least some of these genes. BMH2, but not BMH1, attenuates the repression of genes involved in some functions required for ribosome biogenesis. BMH2 also attenuates the activation of genes sensitive to nitrogen catabolite repression.
Collapse
|
7
|
Dual phosphorylation of Btk by Akt/protein kinase b provides docking for 14-3-3ζ, regulates shuttling, and attenuates both tonic and induced signaling in B cells. Mol Cell Biol 2013; 33:3214-26. [PMID: 23754751 DOI: 10.1128/mcb.00247-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bruton's tyrosine kinase (Btk) is crucial for B-lymphocyte activation and development. Mutations in the Btk gene cause X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Using tandem mass spectrometry, 14-3-3ζ was identified as a new binding partner and negative regulator of Btk in both B-cell lines and primary B lymphocytes. The activated serine/threonine kinase Akt/protein kinase B (PKB) phosphorylated Btk on two sites prior to 14-3-3ζ binding. The interaction sites were mapped to phosphoserine pS51 in the pleckstrin homology domain and phosphothreonine pT495 in the kinase domain. The double-alanine, S51A/T495A, replacement mutant failed to bind 14-3-3ζ, while phosphomimetic aspartate substitutions, S51D/T495D, caused enhanced interaction. The phosphatidylinositol 3-kinase (PI3-kinase) inhibitor LY294002 abrogated S51/T495 phosphorylation and binding. A newly characterized 14-3-3 inhibitor, BV02, reduced binding, as did the Btk inhibitor PCI-32765 (ibrutinib). Interestingly, in the presence of BV02, phosphorylation of Btk, phospholipase Cγ2, and NF-κB increased strongly, suggesting that 14-3-3 also regulates B-cell receptor (BCR)-mediated tonic signaling. Furthermore, downregulation of 14-3-3ζ elevated nuclear translocation of Btk. The loss-of-function mutant S51A/T495A showed reduced tyrosine phosphorylation and ubiquitination. Conversely, the gain-of-function mutant S51D/T495D exhibited intense tyrosine phosphorylation, associated with Btk ubiquitination and degradation, likely contributing to the termination of BCR signaling. Collectively, this suggests that Btk could become an important new candidate for the general study of 14-3-3-mediated regulation.
Collapse
|
8
|
Sluchanko NN, Gusev NB. Oligomeric structure of 14-3-3 protein: What do we know about monomers? FEBS Lett 2012; 586:4249-56. [DOI: 10.1016/j.febslet.2012.10.048] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Revised: 10/20/2012] [Accepted: 10/26/2012] [Indexed: 10/27/2022]
|
9
|
Sluchanko NN, Artemova NV, Sudnitsyna MV, Safenkova IV, Antson AA, Levitsky DI, Gusev NB. Monomeric 14-3-3ζ has a chaperone-like activity and is stabilized by phosphorylated HspB6. Biochemistry 2012; 51:6127-38. [PMID: 22794279 PMCID: PMC3413243 DOI: 10.1021/bi300674e] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
![]()
Members of the 14-3-3 eukaryotic protein family predominantly
function
as dimers. The dimeric form can be converted into monomers upon phosphorylation
of Ser58 located at the subunit interface. Monomers are
less stable than dimers and have been considered to be either less
active or even inactive during binding and regulation of phosphorylated
client proteins. However, like dimers, monomers contain the phosphoserine-binding
site and therefore can retain some functions of the dimeric 14-3-3.
Furthermore, 14-3-3 monomers may possess additional functional roles
owing to their exposed intersubunit surfaces. Previously we have found
that the monomeric mutant of 14-3-3ζ (14-3-3ζm), like the wild type protein, is able to bind phosphorylated small
heat shock protein HspB6 (pHspB6), which is involved in the regulation
of smooth muscle contraction and cardioprotection. Here we report
characterization of the 14-3-3ζm/pHspB6 complex by
biophysical and biochemical techniques. We find that formation of
the complex retards proteolytic degradation and increases thermal
stability of the monomeric 14-3-3, indicating that interaction with
phosphorylated targets could be a general mechanism of 14-3-3 monomers
stabilization. Furthermore, by using myosin subfragment 1 (S1) as
a model substrate we find that the monomer has significantly higher
chaperone-like activity than either the dimeric 14-3-3ζ protein
or even HspB6 itself. These observations indicate that 14-3-3ζ
and possibly other 14-3-3 isoforms may have additional functional
roles conducted by the monomeric state.
Collapse
Affiliation(s)
- Nikolai N Sluchanko
- A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky Prospect 33, Moscow 119071, Russian Federation.
| | | | | | | | | | | | | |
Collapse
|
10
|
Identification of 14-3-3γ as a Mieap-interacting protein and its role in mitochondrial quality control. Sci Rep 2012; 2:379. [PMID: 22532927 PMCID: PMC3334856 DOI: 10.1038/srep00379] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 01/23/2012] [Indexed: 11/08/2022] Open
Abstract
Mieap, a p53-inducible protein, controls mitochondrial integrity by inducing the accumulation of lysosomal proteins within mitochondria. This phenomenon is designated MALM, for Mieap-induced accumulation of lysosome-like organelles within mitochondria. To identify this novel Mieap-interacting protein(s), we performed a two-dimensional image-converted analysis of liquid chromatography and mass spectrometry (2DICAL) on the proteins immunoprecipitated by an anti-Mieap antibody. We indentified 14-3-3γ as one of the proteins that was included in the Mieap-binding protein complex when MALM was induced. The interaction between Mieap and 14-3-3γ was confirmed on the exogenous and endogenous proteins. Interestingly, 14-3-3γ was localized within mitochondria when MALM occurred. A 14-3-3γ deficiency did not affect the accumulation of Mieap and lysosomal proteins within mitochondria, but dramatically inhibited the elimination of oxidized mitochondrial proteins. These results suggest that 14-3-3γ plays a critical role in eliminating oxidized mitochondrial proteins during the MALM process by interacting with Mieap within mitochondria.
Collapse
|
11
|
Sluchanko NN, Sudnitsyna MV, Seit-Nebi AS, Antson AA, Gusev NB. Properties of the monomeric form of human 14-3-3ζ protein and its interaction with tau and HspB6. Biochemistry 2011; 50:9797-808. [PMID: 21978388 DOI: 10.1021/bi201374s] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Dimers formed by seven isoforms of the human 14-3-3 protein participate in multiple cellular processes. The dimeric form has been extensively characterized; however, little is known about the structure and properties of the monomeric form of 14-3-3. The monomeric form is involved in the assembly of homo- and heterodimers, which could partially dissociate back into monomers in response to phosphorylation at Ser58. To obtain monomeric forms of human 14-3-3ζ, we produced four protein constructs with different combinations of mutated (M) or wild-type (W) segments E(5), (12)LAE(14), and (82)YREKIE(87). Under a wide range of expression conditions in Escherichia coli, the MMM and WMM mutants were insoluble, whereas WMW and MMW mutants were soluble, highly expressed, and purified to homogeneity. WMW and MMW mutants remained monomeric over a wide range of concentrations while retaining the α-helical structure characteristic of wild-type 14-3-3. However, WMW and MMW mutants were highly susceptible to proteolysis and had much lower thermal stabilities than the wild-type protein. Using WMW and MMW mutants, we show that the monomeric form interacts with the tau protein and with the HspB6 protein, in both cases forming complexes with a 1:1 stoichiometry, in contrast to the 2:1 and/or 2:2 complexes formed by wild-type 14-3-3. Significantly, this interaction requires phosphorylation of tau protein and HspB6. Because of minimal changes in structure, MMW and especially WMW mutant proteins are promising candidates for analyzing the effect of monomerization on the physiologically important properties of 14-3-3ζ.
Collapse
Affiliation(s)
- Nikolai N Sluchanko
- Department of Biochemistry, School of Biology, Moscow State University, Moscow 119991, Russian Federation
| | | | | | | | | |
Collapse
|
12
|
Sluchanko NN, Gusev NB. 14-3-3 proteins and regulation of cytoskeleton. BIOCHEMISTRY (MOSCOW) 2011; 75:1528-46. [PMID: 21417993 DOI: 10.1134/s0006297910130031] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The proteins of the 14-3-3 family are universal adapters participating in multiple processes running in the cell. We describe the structure, isoform composition, and distribution of 14-3-3 proteins in different tissues. Different elements of 14-3-3 structure important for dimer formation and recognition of protein targets are analyzed in detail. Special attention is paid to analysis of posttranslational modifications playing important roles in regulation of 14-3-3 function. The data of the literature concerning participation of 14-3-3 in regulation of intercellular contacts and different elements of cytoskeleton formed by microfilaments are analyzed. We also describe participation of 14-3-3 in regulation of small G-proteins and protein kinases important for proper functioning of cytoskeleton. The data on the interaction of 14-3-3 with different components of microtubules are presented, and the probable role of 14-3-3 in developing of certain neurodegenerative diseases is discussed. The data of the literature concerning the role of 14-3-3 in formation and normal functioning of intermediate filaments are also reviewed. It is concluded that due to its adapter properties 14-3-3 plays an important role in cytoskeleton regulation. The cytoskeletal proteins that are abundant in the cell might compete with the other protein targets of 14-3-3 and therefore can indirectly regulate many intracellular processes that are dependent on 14-3-3.
Collapse
Affiliation(s)
- N N Sluchanko
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Russia
| | | |
Collapse
|
13
|
Han D, Ye G, Liu T, Chen C, Yang X, Wan B, Pan Y, Yu L. Functional identification of a novel 14-3-3 epsilon splicing variant suggests dimerization is not necessary for 14-3-3 epsilon to inhibit UV-induced apoptosis. Biochem Biophys Res Commun 2010; 396:401-6. [DOI: 10.1016/j.bbrc.2010.04.104] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 04/17/2010] [Indexed: 10/19/2022]
|
14
|
Agassandian M, Chen BB, Schuster CC, Houtman JCD, Mallampalli RK. 14-3-3zeta escorts CCTalpha for calcium-activated nuclear import in lung epithelia. FASEB J 2009; 24:1271-83. [PMID: 20007511 DOI: 10.1096/fj.09-136044] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Integrity of animal biomembranes is critical to preserve normal cellular functions and viability. Phosphatidylcholine, an indispensible membrane component, requires the enzyme CCTalpha for its biosynthesis. Nuclear expression of CCTalpha is needed for expansion of the nuclear membrane network, but mechanisms for CCTalpha nuclear import are unknown. Herein, we show that in epithelia, extracellular Ca(2+) triggers CCTalpha cytoplasmic-nuclear translocation. CCTalpha nuclear import was associated with binding to 14-3-3zeta, a key regulator of protein trafficking. 14-3-3zeta was both sufficient and required for CCTalpha nuclear import. Helix G within the 14-3-3zeta binding groove interacts with a putative molecular signature within the CCTalpha carboxyl-terminal phosphoserine motif (residues 328-343). 14-3-3zeta was critically involved in preserving phosphatidylcholine synthesis and cell viability in a model of Pseudomonas aeruginosa infection where Ca(2+) concentrations increase within epithelia. Thus, 14-3-3zeta controls CCTalpha nuclear import in response to calcium signals, thereby regulating mammalian phospholipid synthesis. Agassandian, M., Chen, B. B., Schuster, C. C., Houtman, J. C. D., Mallampalli, R. K. 14-3-3zeta escorts CCTalpha for calcium-activated nuclear import in lung epithelia.
Collapse
Affiliation(s)
- Marianna Agassandian
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa, USA
| | | | | | | | | |
Collapse
|
15
|
Messaritou G, Grammenoudi S, Skoulakis EMC. Dimerization is essential for 14-3-3zeta stability and function in vivo. J Biol Chem 2009; 285:1692-700. [PMID: 19920133 DOI: 10.1074/jbc.m109.045989] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Members of the conserved 14-3-3 protein family spontaneously self-assemble as homo- and heterodimers via conserved sequences in the first four (alphaA-alphaD) of the nine helices that comprise them. Dimeric 14-3-3s bind conserved motifs in diverse protein targets involved in multiple essential cellular processes including signaling, intracellular trafficking, cell cycle regulation, and modulation of enzymatic activities. However, recent mostly in vitro evidence has emerged, suggesting functional and regulatory roles for monomeric 14-3-3s. We capitalized on the simplicity of the 14-3-3 family in Drosophila to investigate in vivo 14-3-3zeta monomer properties and functionality. We report that dimerization is essential for the stability and function of 14-3-3zeta in neurons. Moreover, we reveal the contribution of conserved amino acids in helices A and D to homo- and heterodimerization and their functional consequences on the viability of animals devoid of endogenous 14-3-3zeta. Finally, we present evidence suggesting endogenous homeostatic adjustment of the levels of the second family member in Drosophila, D14-3-3epsilon, to transgenic monomeric and dimerization-competent 14-3-3zeta.
Collapse
Affiliation(s)
- Georgia Messaritou
- Institute of Molecular Biology and Genetics, Biomedical Sciences Research Centre, Alexander Fleming, Vari 16672, Greece
| | | | | |
Collapse
|
16
|
Mangin PH, Receveur N, Wurtz V, David T, Gachet C, Lanza F. Identification of five novel 14-3-3 isoforms interacting with the GPIb-IX complex in platelets. J Thromb Haemost 2009; 7:1550-5. [PMID: 19558434 DOI: 10.1111/j.1538-7836.2009.03530.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Binding of von Willebrand factor to the platelet glycoprotein (GP)Ib-IX complex initiates a signaling cascade leading to integrin alpha(IIb)beta(3) activation, a key process in hemostasis and thrombosis. Interaction of 14-3-3zeta with the intracytoplasmic domain of GPIb appears to be a major effector of this activation pathway. OBJECTIVE The aim of our study was to determine whether other members of the 14-3-3 family bind to GPIb-IX. RESULTS In this study, western blot analyses showed that platelets also contain the 14-3-3beta, 14-3-3gamma, 14-3-3epsilon, 14-3-3eta and 14-3-3theta isoforms, but lack 14-3-3sigma. Coimmunoprecipitation studies in platelets and CHO transfectants demonstrated that all six 14-3-3 isoforms expressed in platelets, including, as previously reported, 14-3-3zeta, bind to GPIb-IX. In addition, their interaction was found to critically require the same GPIbalpha domains (580-590 and 605-610) already identified as essential for 14-3-3zeta binding, in agreement with the conservation of the sequence of the I-helix among these different isoforms. Pull-down experiments indicated that all six 14-3-3 isoforms present in platelets bind to GPIbbeta. In contrast, deletion or mutation of the GPIbbeta intracytoplasmic tail did not affect the interaction of GPIb-IX with the 14-3-3 isoforms, questioning the importance of this domain. CONCLUSIONS Our study suggests that, to inhibit GPIb-induced integrin alpha(IIb)beta(3) activation, a more appropriate strategy than inhibiting individual 14-3-3 isoforms would be to target the 14-3-3-binding motif on GPIb or, alternatively, the conserved 14-3-3 I-helix.
Collapse
Affiliation(s)
- P H Mangin
- INSERM UMR_S 949, EFS-Alsace, Université de Strasbourg, Strasbourg, France.
| | | | | | | | | | | |
Collapse
|
17
|
Sluchanko NN, Chernik IS, Seit-Nebi AS, Pivovarova AV, Levitsky DI, Gusev NB. Effect of mutations mimicking phosphorylation on the structure and properties of human 14-3-3ζ. Arch Biochem Biophys 2008; 477:305-12. [DOI: 10.1016/j.abb.2008.05.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/27/2008] [Accepted: 05/30/2008] [Indexed: 10/22/2022]
|
18
|
Moreira JMA, Shen T, Ohlsson G, Gromov P, Gromova I, Celis JE. A combined proteome and ultrastructural localization analysis of 14-3-3 proteins in transformed human amnion (AMA) cells: definition of a framework to study isoform-specific differences. Mol Cell Proteomics 2008; 7:1225-1240. [PMID: 18378962 DOI: 10.1074/mcp.m700439-mcp200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/26/2024] Open
Abstract
The 14-3-3 proteins constitute a family of highly conserved and broadly expressed multifunctional polypeptides that are involved in a variety of important cellular processes that include cell cycle progression, growth, differentiation, and apoptosis. Although the exact cellular function(s) of 14-3-3 proteins is not fully elucidated, as a rule these proteins act by binding to protein ligands, thus regulating their activity; so far more than 300 cellular proteins have been reported to interact with 14-3-3 proteins. Binding to cognate interacting partners is isoform-specific, but redundancy also exists as several binding peptides can be recognized by all isoforms, and some functions can be carried out by any isoform indistinctly. Moreover by interacting with different ligands in a spatially and temporally regulated fashion the same isoform can play multiple possibly even opposing roles where the resultant cellular outcome will be determined by the integration of the various effects. Although there is a large body of literature on specific aspects of 14-3-3 biology, not much is known on the coordinated aspects of 14-3-3 isoform expression, post-translational modifications, and subcellular localization. To address the question of isoform-specific differences, we carried out a comparative analysis of the patterns of expression, phosphorylation, and subcellular localization of the 14-3-3 beta, epsilon, sigma, tau, and zeta protein isoforms in transformed human amnion (AMA) cells. To validate as well as broaden our observations we analyzed the occurrence of the various isoforms in a large number of established cell lines and mammary and urothelial tissue specimens. Given the systematic approach we undertook and our application of isoform-discriminating technologies to the analysis of various cellular systems, we expect the data presented in this study to serve as an enabling resource for researchers working with 14-3-3 proteins.
Collapse
Affiliation(s)
- José M A Moreira
- Department of Proteomics in Cancer, Institute of Cancer Biology and Danish Centre for Translational Breast Cancer Research (DCTB), Danish Cancer Society, DK-2100 Copenhagen, Denmark
| | | | | | | | | | | |
Collapse
|
19
|
Luo SZ, Mo X, Afshar-Kharghan V, Srinivasan S, López JA, Li R. Glycoprotein Ibalpha forms disulfide bonds with 2 glycoprotein Ibbeta subunits in the resting platelet. Blood 2006; 109:603-9. [PMID: 17008541 PMCID: PMC1785083 DOI: 10.1182/blood-2006-05-024091] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is widely accepted that glycoprotein (GP) Ib contains one Ibalpha and one Ibbeta subunit that are connected by a disulfide bond. It is unclear which Cys residue in Ibalpha, C484 or C485, forms the disulfide bond with Ibbeta. Using mutagenesis studies in transfected Chinese hamster ovary (CHO) cells, we found that both C484 and C485 formed a disulfide bond with C122 in Ibbeta. In the context of isolated peptides containing the Ibalpha or Ibbeta transmembrane domain and nearby Cys residue, C484 and C485 in the Ibalpha peptide were both capable of forming a disulfide bond with the Ibbeta peptide. Furthermore, coimmunoprecipitation of epitope-tagged subunits showed that at least 2 Ibbeta subunits but only 1 Ibalpha and 1 IX subunit were present in the GP Ib-IX complex. Finally, the size difference between GP Ib from transfected CHO cells and human platelets was attributed to a combination of sequence polymorphism and glycosylation difference in Ibalpha, not the number of Ibbeta subunits therein. Overall, these results demonstrate that Ibalpha is covalently connected to 2 Ibbeta subunits in the resting platelet, necessitating revision of the subunit stoichiometry of the GP Ib-IX-V complex. The alphabeta2 composition in GP Ib may provide the basis for possible disulfide rearrangement in the receptor complex.
Collapse
Affiliation(s)
- Shi-Zhong Luo
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston
| | - Xi Mo
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston
| | - Vahid Afshar-Kharghan
- Thrombosis Research Section, Department of Medicine, Baylor College of Medicine, Houston, TX
| | - Sankaranarayanan Srinivasan
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston
| | - José A. López
- Puget Sound Blood Center, Division of Hematology, Department of Medicine, University of Washington, Seattle
| | - Renhao Li
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston
- Correspondence: Renhao Li,
Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, MSB 6.130, 6431 Fannin St, Houston, TX 77030; e-mail:
| |
Collapse
|
20
|
Bustos DM, Iglesias AA. Intrinsic disorder is a key characteristic in partners that bind 14-3-3 proteins. Proteins 2006; 63:35-42. [PMID: 16444738 DOI: 10.1002/prot.20888] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Proteins named 14-3-3 can bind more than 200 different proteins, mostly (but not exclusively) when they are at a phosphorylated state. These partner proteins are involved in different cellular processes, such as cell signaling, transcription factors, cellular morphology, and metabolism; this suggests pleiotropic functionality for 14-3-3 proteins. Recent efforts to establish a rational classification of 14-3-3 binding partners showed neither structural nor functional relatedness in this group of proteins. Using three natural predictors of disorder in proteins, and the structural available information, we show that >90% of 14-3-3 protein partners contain disordered regions. This percentage is significantly high when compared with recent studies on cell signaling and cancer-related proteins or RNA chaperons. More important, almost all 14-3-3-binding sites are inside disordered regions, this reinforcing the importance of structural disorder in this class of proteins. We also propose that a disorder-to-order transition occurs in the binding of 14-3-3 proteins with their partners. We discuss the consequences of the latter for consensus binding sequences, specificity, affinity, and thermodynamic control.
Collapse
Affiliation(s)
- Diego M Bustos
- Instituto Tecnológico de Chascomús-IIB-INTECH, Camino Circunvalación, Chascomús, Argentina.
| | | |
Collapse
|
21
|
Dai K, Bodnar R, Berndt MC, Du X. A critical role for 14-3-3zeta protein in regulating the VWF binding function of platelet glycoprotein Ib-IX and its therapeutic implications. Blood 2005; 106:1975-81. [PMID: 15941906 PMCID: PMC1373670 DOI: 10.1182/blood-2005-01-0440] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The platelet receptor for von Willebrand factor (VWF), glycoprotein (GP) Ib-IX, mediates platelet adhesion and activation. The cytoplasmic domains of the GPIb alpha and beta subunits contain binding sites for the phosphorylation-dependent signaling molecule, 14-3-3zeta. Here we show that a novel membrane-permeable inhibitor of 14-3-3zeta-GPIbalpha interaction, MPalphaC, potently inhibited VWF binding to platelets and VWF-mediated platelet adhesion under flow conditions. MPalphaC also inhibited VWF-dependent platelet agglutination induced by ristocetin. Furthermore, activation of the VWF binding function of GPIb-IX induced by GPIbbeta dephosphorylation is diminished by mutagenic disruption of the 14-3-3zeta binding site in the C-terminal domain of GPIbalpha, mimicking MPalphaC-induced inhibition, indicating that the inhibitory effect of MPalphaC is likely to be caused by disruption of 14-3-3zeta binding to GPIbalpha. These data suggest a novel 14-3-3zeta-dependent regulatory mechanism that controls the VWF binding function of GPIb-IX, and also suggest a new type of antiplatelet agent that may be potentially useful in preventing or treating thrombosis.
Collapse
Affiliation(s)
- Kesheng Dai
- Department of Pharmacology, College of Medicine, University of Illinois at Chicago, 835 South Wolcott Ave, Chicago, IL 60612, USA
| | | | | | | |
Collapse
|
22
|
Mangin P, David T, Lavaud V, Cranmer SL, Pikovski I, Jackson SP, Berndt MC, Cazenave JP, Gachet C, Lanza F. Identification of a novel 14-3-3ζ binding site within the cytoplasmic tail of platelet glycoprotein Ibα. Blood 2004; 104:420-7. [PMID: 15054037 DOI: 10.1182/blood-2003-08-2881] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe glycoprotein Ib-V-IX (GPIb-V-IX) complex interacts with subendothelial von Willebrand factor (VWF) to ensure recruitment of platelets at sites of vascular injury, a process that culminates in integrin αIIbβ3-dependent stable adhesion and spreading. Interaction of the 14-3-3ζ adaptor protein with the C-terminal 606-610 phosphoserine motif of the GPIbα subunit has been implicated in the control of αIIbβ3 activation and cell spreading. In this study, we have examined potentially novel 14-3-3ζ binding sites by expressing mutant forms of GPIbα in Chinese-hamster-ovary (CHO) cells. Analysis of a series of neighboring 11-12 residue deletions identified a critical role for the 580-LVAGRRPSALS-590 sequence in promoting GPIbα-14-3-3ζ interaction. Development of a phosphospecific antibody demonstrated high levels of phosphorylation of the Ser587 and Ser590 residues in resting platelets (which became dephosphorylated during platelet spreading on VWF), and peptides containing these phosphorylated residues effectively displaced 14-3-3ζ from GPIbα. Analysis of single and double alanine substitutions of Ser587 and Ser590 demonstrated a major role for these residues in promoting GPIbα-14-3-3ζ binding. Moreover, these cell lines exhibited a defect in cell spreading on immobilized VWF. These studies demonstrate the existence of a second major 14-3-3ζ binding site within the cytoplasmic tail of GPIbα that has an important functional role in regulating integrin-dependent cell spreading. (Blood. 2004;104:420-427)
Collapse
Affiliation(s)
- Pierre Mangin
- INSERM U.311, Etablissement Français du Sang-Alsace, 10 rue Spielmann, BP 36, 67065 Strasbourg Cedex, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Shen YH, Godlewski J, Bronisz A, Zhu J, Comb MJ, Avruch J, Tzivion G. Significance of 14-3-3 self-dimerization for phosphorylation-dependent target binding. Mol Biol Cell 2003; 14:4721-33. [PMID: 14551260 PMCID: PMC266786 DOI: 10.1091/mbc.e02-12-0821] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
14-3-3 proteins via binding serine/threonine-phosphorylated proteins regulate diverse intracellular processes in all eukaryotic organisms. Here, we examine the role of 14-3-3 self-dimerization in target binding, and in the susceptibility of 14-3-3 to undergo phosphorylation. Using a phospho-specific antibody developed against a degenerated mode-1 14-3-3 binding motif (RSxpSxP), we demonstrate that most of the 14-3-3-associated proteins in COS-7 cells are phosphorylated on sites that react with this antibody. The binding of these phosphoproteins depends on 14-3-3 dimerization, inasmuch as proteins associated in vivo with a monomeric 14-3-3 form are not recognized by the phospho-specific antibody. The role of 14-3-3 dimerization in the phosphorylation-dependent target binding is further exemplified with two well-defined 14-3-3 targets, Raf and DAF-16. Raf and DAF-16 can bind both monomeric and dimeric 14-3-3; however, whereas phosphorylation of specific Raf and DAF-16 sites is required for binding to dimeric 14-3-3, binding to monomeric 14-3-3 forms is entirely independent of Raf and DAF-16 phosphorylation. We also find that dimerization diminishes 14-3-3 susceptibility to phosphorylation. These findings establish a significant role of 14-3-3 dimerization in its ability to bind targets in a phosphorylation-dependent manner and point to a mechanism in which 14-3-3 phosphorylation and dimerization counterregulate each other.
Collapse
Affiliation(s)
- Ying H Shen
- Cardiovascular Research Institute, Division of Molecular Cardiology, The Texas A&M University System Health Science Center, College of Medicine, Temple, Texas 76504, USA
| | | | | | | | | | | | | |
Collapse
|
24
|
Zhou Y, Reddy S, Murrey H, Fei H, Levitan IB. Monomeric 14-3-3 protein is sufficient to modulate the activity of the Drosophila slowpoke calcium-dependent potassium channel. J Biol Chem 2003; 278:10073-80. [PMID: 12529354 DOI: 10.1074/jbc.m211907200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Drosophila 14-3-3zeta (D14-3-3zeta) modulates the activity of the Slowpoke calcium-dependent potassium channel (dSlo) by interacting with the dSlo binding protein, Slob. We show here that D14-3-3zeta forms dimers in vitro. Site-directed mutations in its putative dimerization interface result in a dimerization-deficient form of D14-3-3zeta. Both the wild-type and dimerization-deficient forms of D14-3-3zeta bind to Slob with similar affinity and form complexes with dSlo. When dSlo and Slob are expressed in mammalian cells, the dSlo channel activity is similarly modulated by co-expression of either the wild-type or the dimerization-deficient form of D14-3-3zeta. In addition, dSlo is still modulated by wild-type D14-3-3zeta in the presence of a 14-3-3 mutant, which does not itself bind to Slob but forms heterodimers with the wild-type 14-3-3. These data, taken together, suggest that monomeric D14-3-3zeta is capable of modulating dSlo channel activity in this regulatory complex.
Collapse
Affiliation(s)
- Yi Zhou
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
| | | | | | | | | |
Collapse
|
25
|
Dai JG, Murakami K. Constitutively and autonomously active protein kinase C associated with 14-3-3 zeta in the rodent brain. J Neurochem 2003; 84:23-34. [PMID: 12485398 DOI: 10.1046/j.1471-4159.2003.01254.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Persistent activation of protein kinase C (PKC) is required for the expression of synaptic plasticity in the brain. There are several mechanisms proposed that can lead to the prolonged activation of PKC. These include long lasting production of lipid activators (diacylglycerol and fatty acid) through mitogen-activated protein (MAP) kinase pathway, and a modification of PKC by reactive oxygen species. In nerve growth factor (NGF)-differentiated PC12 cells, we found that constitutive and autonomous Ca2+-independent PKC activity is associated with 14-3-3 zeta. Because PKC and 14-3-3 zeta are both involved in synaptic plasticity and learning and memory, we examined whether PKC interacts with 14-3-3 zeta in the brain and whether the PKC/14-3-3 zeta complex has autonomous activity. Here we show that three subclasses of PKC, Ca2+-dependent classical PKC, Ca2+-independent novel PKC, and Ca2+-independent and diacylglycerol-insensitive atypical PKC, all interact with 14-3-3 zeta in the rodent brain. The pool size of 14-3-3 zeta bound form of PKC is small (1-4% of each PKC isoform), but they show constitutive and autonomous activity. Our study indicates that the binding of PKC with 14-3-3 zeta is at least in part independent of phosphorylation of PKC and that the C1 domain of PKC is involved in the binding. As both molecules are enriched in synaptic locus, the constitutive PKC activity and its interaction with 14-3-3 zeta could be a mechanism for the persistent PKC activation in the brain.
Collapse
Affiliation(s)
- Jian-Guo Dai
- Department of Biology, University of Vermont, Burlington, Vermont 05405, USA
| | | |
Collapse
|
26
|
Henriksson ML, Francis MS, Peden A, Aili M, Stefansson K, Palmer R, Aitken A, Hallberg B. A nonphosphorylated 14-3-3 binding motif on exoenzyme S that is functional in vivo. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:4921-9. [PMID: 12383250 DOI: 10.1046/j.1432-1033.2002.03191.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
14-3-3 proteins play an important role in a multitude of signalling pathways. The interactions between 14-3-3 and other signalling proteins, such as Raf and KSR (kinase suppressor of Ras), occur in a phospho-specific manner. Recently, a phosphorylation-independent interaction has been reported to occur between 14-3-3 and several proteins, for example 5-phosphatase, p75NTR-associated cell death executor (NADE) and the bacterial toxin Exoenzyme S (ExoS), an ADP-ribosyltransferase from Pseudomonas aeruginosa. In this study we have identified the amino acid residues on ExoS, which are responsible for its specific interaction with 14-3-3. Furthermore, we show that a peptide derived from ExoS, containing the 14-3-3 interaction site, effectively competes out the interaction between ExoS and 14-3-3. In addition, competition with this peptide blocks ExoS modification of Ras in our Ras modification assay. We show that the ExoS protein interacts with all isoforms of the 14-3-3 family tested. Moreover, in vivo an ExoS protein lacking the 14-3-3 binding site has a reduced capacity to ADP ribosylate cytoplasmic proteins, e.g. Ras, and shows a reduced capacity to change the morphology of infected cells.
Collapse
|
27
|
Niu J, Scheschonka A, Druey KM, Davis A, Reed E, Kolenko V, Bodnar R, Voyno-Yasenetskaya T, Du X, Kehrl J, Dulin NO. RGS3 interacts with 14-3-3 via the N-terminal region distinct from the RGS (regulator of G-protein signalling) domain. Biochem J 2002; 365:677-84. [PMID: 11985497 PMCID: PMC1222729 DOI: 10.1042/bj20020390] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2002] [Revised: 04/17/2002] [Accepted: 05/01/2002] [Indexed: 11/17/2022]
Abstract
RGS3 belongs to a family of the regulators of G-protein signalling (RGS), which bind and inhibit the G alpha subunits of heterotrimeric G-proteins via a homologous RGS domain. Increasing evidence suggests that RGS proteins can also interact with targets other than G-proteins. Employing yeast two-hybrid screening of a cDNA library, we identified an interaction between RGS3 and the phosphoserine-binding protein 14-3-3. This interaction was confirmed by in vitro binding and co-immunoprecipitation experiments. RGS3-deletion analysis revealed the presence of a single 14-3-3-binding site located outside of the RGS domain. Ser(264) was then identified as the 14-3-3-binding site of RGS3. The S(264)A mutation resulted in the loss of RGS3 binding to 14-3-3, without affecting its ability to bind G alpha(q). Signalling studies showed that the S(264)A mutant was more potent than the wild-type RGS3 in inhibition of G-protein-mediated signalling. Binding experiments revealed that RGS3 exists in two separate pools, either 14-3-3-bound or G-protein-bound, and that the 14-3-3-bound RGS3 is unable to interact with G-proteins. These data are consistent with the model wherein 14-3-3 serves as a scavenger of RGS3, regulating the amounts of RGS3 available for binding G-proteins. This study describes a new level in the regulation of G-protein signalling, in which the inhibitors of G-proteins, RGS proteins, can themselves be regulated by phosphorylation and binding 14-3-3.
Collapse
Affiliation(s)
- Jiaxin Niu
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, U.S.A
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Kasirer-Friede A, Ware J, Leng L, Marchese P, Ruggeri ZM, Shattil SJ. Lateral clustering of platelet GP Ib-IX complexes leads to up-regulation of the adhesive function of integrin alpha IIbbeta 3. J Biol Chem 2002; 277:11949-56. [PMID: 11812775 DOI: 10.1074/jbc.m108727200] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Binding of von Willebrand factor (VWF) to GP Ib-IX mediates initial platelet adhesion and increases the subsequent adhesive function of alpha(IIb)beta(3). Because these responses are promoted most effectively by large VWF multimers, we hypothesized that receptor clustering modulates GP Ib-IX function. To test this, GP IX was fused at its cytoplasmic tail to tandem repeats of FKBP, and GP Ib-IX(FKBP)(2) and alpha(IIb)beta(3) were expressed in Chinese hamster ovary cells. Under flow conditions at wall shear rates of up to 2000 s(-1), GP Ib-IX(FKBP)(2) mediated cell tethering to immobilized VWF, just as in platelets. Conditional oligomerization of GP Ib-IX(FKBP)(2) by AP20187, a cell-permeable FKBP dimerizer, caused a decrease in cell translocation velocities on VWF (p < 0.001). Moreover, clustering of GP Ib-IX(FKBP)(2) by AP20187 led to an increase in alpha(IIb)beta(3) function, manifested under static conditions by increased cell adhesion to fibrinogen (p < 0.01) and under flow by increased stable cell adhesion to VWF (p < 0.04). Clustering of GP Ib-IX(FKBP)(2) also stimulated rapid tyrosine phosphorylation of ectopically expressed Syk, a putative downstream effector of GP Ib-IX in platelets. These studies establish that GP Ib-IX oligomerization, per se, affects the interaction of this receptor with VWF and its ability to influence the adhesive function of alpha(IIb)beta(3). By extrapolation, GP Ib-IX clustering in platelets may promote thrombus formation.
Collapse
Affiliation(s)
- Ana Kasirer-Friede
- Departments of Cell Biology and Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
| | | | | | | | | | | |
Collapse
|
29
|
Dent J, Kato K, Peng XR, Martinez C, Cattaneo M, Poujol C, Nurden P, Nurden A, Trimble WS, Ware J. A prototypic platelet septin and its participation in secretion. Proc Natl Acad Sci U S A 2002; 99:3064-9. [PMID: 11880646 PMCID: PMC122473 DOI: 10.1073/pnas.052715199] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Studies are presented characterizing platelet CDCrel-1, a protein expressed to high levels by megakaryocytes and belonging to a family of conserved proteins, termed septin. Septin filaments originally were identified in yeast as essential for budding but have become increasingly associated with processes in higher eukaryotic cells involving active membrane movement such as cytokinesis and vesicle trafficking. Direct proof of an in vivo function for septins in higher eukaryotes is limited to the characterization of the Drosophila septin, termed PNUT. We present studies identifying platelet CDCrel-1 as a protein kinase substrate in the presence of known platelet agonists. The immunopurification of CDCrel-1 revealed it to be part of a macromolecular complex containing a protein involved in platelet secretion, syntaxin 4. Moreover, CDCrel-1 was localized in situ to areas surrounding platelet-storage granules. The relevance of CDCrel-1 to normal platelet function was established with the characterization of platelets from a CDCrel-1(Null) mouse. As compared with platelets from wild-type littermates, CDCrel-1(Null) platelets aggregate and release stored [14C]serotonin in the presence of subthreshold levels of collagen. These results provide new insights into the mechanisms regulating platelet secretion and identify platelet septins as a protein family contributing to membrane trafficking within the megakaryocyte and platelet.
Collapse
Affiliation(s)
- Judith Dent
- Division of Experimental Hemostasis and Thrombosis, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Chung JJ, Shikano S, Hanyu Y, Li M. Functional diversity of protein C-termini: more than zipcoding? Trends Cell Biol 2002; 12:146-50. [PMID: 11859027 DOI: 10.1016/s0962-8924(01)02241-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The carboxylated (C)-terminus of proteins, which includes the single terminal alpha-carboxyl group and preceding residues, is uniquely positioned to serve as a recognition signature for a variety of cell-biological processes, including protein targeting, subcellular anchoring and the static and dynamic formation of macromolecular complexes. The terminal sequence motifs can be processed by posttranslational modifications, thereby providing a means to increase sequence diversity and to regulate interactions. Several classes of protein domains have been identified that are either designed for or are capable of interacting with protein C-termini - these include PDZ and TPR domains. The interactions between these protein domains and various terminal epitopes play an important role in specifying cell-biological functions. The combination of diversity and the plasticity of the chemistry of C-termini provides mechanisms for spatial and temporal specificity that are exploited by a variety of biological processes, ranging from specifying prokaryotic protein degradation to nucleating mammalian neuronal signaling complexes. Understanding the diverse functions of protein C-termini might also provide an important indexing criterion for functional proteomics.
Collapse
Affiliation(s)
- Jean Ju Chung
- Dept of Physiology, Johns Hopkins University School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205, USA
| | | | | | | |
Collapse
|
31
|
Tzivion G, Avruch J. 14-3-3 proteins: active cofactors in cellular regulation by serine/threonine phosphorylation. J Biol Chem 2002; 277:3061-4. [PMID: 11709560 DOI: 10.1074/jbc.r100059200] [Citation(s) in RCA: 383] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Guri Tzivion
- Cardiovascular Research Institute, Division of Molecular Cardiology, Texas A&M University System Health Science Center, College of Medicine, Temple, Texas 76504, USA
| | | |
Collapse
|
32
|
|
33
|
Abstract
The 14-3-3 proteins are a part of an emerging family of proteins and protein domains that bind to serine/threonine-phosphorylated residues in a context specific manner, analogous to the Src homology 2 (SH2) and phospho-tyrosine binding (PTB) domains. 14-3-3 proteins bind and regulate key proteins involved in various physiological processes such as intracellular signaling (e.g. Raf, MLK, MEKK, PI-3 kinase, IRS-1), cell cycling (e.g. Cdc25, Wee1, CDK2, centrosome), apoptosis (e.g. BAD, ASK-1) and transcription regulation (e.g. FKHRL1, DAF-16, p53, TAZ, TLX-2, histone deacetylase). In contrast to SH2 and PTB domains, which serve mainly to mediate protein-protein interactions, 14-3-3 proteins in many cases alter the function of the target protein, thus allowing them to serve as direct regulators of their targets. This review focuses on the various mechanisms employed by the 14-3-3 proteins in the regulation of their diverse targets, the structural basis for 14-3-3-target protein interaction with emphasis on the role of 14-3-3 dimerization in target protein binding and regulation and provides an insight on 14-3-3 regulation itself.
Collapse
Affiliation(s)
- G Tzivion
- Division of Molecular Cardiology, Cardiovascular Research Institute, The Texas A&M University System Health Science Center, College of Medicine, Temple, Texas, TX 76504, USA.
| | | | | |
Collapse
|
34
|
Englund GD, Bodnar RJ, Li Z, Ruggeri ZM, Du X. Regulation of von Willebrand factor binding to the platelet glycoprotein Ib-IX by a membrane skeleton-dependent inside-out signal. J Biol Chem 2001; 276:16952-9. [PMID: 11278380 DOI: 10.1074/jbc.m008048200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The platelet receptor for von Willebrand factor (vWF), glycoprotein Ib-IX (GPIb-IX), mediates initial platelet adhesion and activation. We show here that the receptor function of GPIb-IX is regulated intracellularly via its link to the filamin-associated membrane skeleton. Deletion of the filamin binding site in GPIb(alpha) markedly enhances ristocetin- (or botrocetin)-induced vWF binding and allows GPIb-IX-expressing cells to adhere to immobilized vWF under both static and flow conditions. Cytochalasin D (CD) that depolymerizes actin also enhances vWF binding to wild type GPIb-IX. Thus, vWF binding to GPIb-IX is negatively regulated by the filamin-associated membrane skeleton. In contrast to native vWF, binding of the isolated recombinant vWF A1 domain to wild type and filamin binding-deficient mutants of GPIb-IX is comparable, suggesting that the membrane skeleton-associated GPIb-IX is in a state that prevents access to the A1 domain in macromolecular vWF. In platelets, there is a balance of membrane skeleton-associated and free forms of GPIb-IX. Treatment of platelets with CD increases the free form and enhances vWF binding. CD also reverses the inhibitory effects of prostaglandin E1 on vWF binding to GPIb-IX. Thus, GPIb-IX-dependent platelet adhesion is doubly controlled by vWF conformation and a membrane skeleton-dependent inside-out signal.
Collapse
Affiliation(s)
- G D Englund
- Department of Pharmacology, University of Illinois, College of Medicine, Chicago, Illinois 60612, USA
| | | | | | | | | |
Collapse
|
35
|
Abstract
The 14-3-3 proteins are a family of conserved regulatory molecules expressed in all eukaryotic cells. A striking feature of the 14-3-3 proteins is their ability to bind a multitude of functionally diverse signaling proteins, including kinases, phosphatases, and transmembrane receptors. This plethora of interacting proteins allows 14-3-3 to play important roles in a wide range of vital regulatory processes, such as mitogenic signal transduction, apoptotic cell death, and cell cycle control. In this review, we examine the structural basis for 14-3-3-ligand interactions, proposed functions of 14-3-3 in various signaling pathways, and emerging views of mechanisms that regulate 14-3-3 actions.
Collapse
Affiliation(s)
- H Fu
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
| | | | | |
Collapse
|
36
|
Hashiguchi M, Sobue K, Paudel HK. 14-3-3zeta is an effector of tau protein phosphorylation. J Biol Chem 2000; 275:25247-54. [PMID: 10840038 DOI: 10.1074/jbc.m003738200] [Citation(s) in RCA: 171] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurofibrillary tangles associated with Alzheimer's disease are composed mainly of paired helical filaments that are formed by the aggregation of abnormally phosphorylated microtubule-associated protein tau. 14-3-3, a highly conserved protein family that exists as seven isoforms and regulates diverse cellular processes is present in neurofibrillary tangles (Layfield, R., Fergusson, J., Aitken, A., Lowe, J., Landon, M., Mayer, R. J. (1996) Neurosci. Lett. 209, 57-60). The role of 14-3-3 in Alzheimer's disease pathogenesis is not known. In this study, we found that the 14-3-3zeta isoform is associated with tau in brain extract and profoundly stimulates cAMP-dependent protein kinase catalyzed in vitro phosphorylation on Ser(262)/Ser(356) located within the microtubule-binding region of tau. 14-3-3zeta binds to both phosphorylated and nonphosphorylated tau, and the binding site is located within the microtubule-binding region of tau. From brain extract, 14-3-3zeta co-purifies with microtubules, and tubulin blocks 14-3-3zeta-tau binding. Among four 14-3-3 isoforms tested, beta and zeta but not gamma and epsilon associate with tau. Our data suggest that 14-3-3zeta is a tau protein effector and may be involved in the abnormal tau phosphorylation occurring during Alzheimer's disease ontogeny.
Collapse
Affiliation(s)
- M Hashiguchi
- Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
| | | | | |
Collapse
|
37
|
Abstract
The 14-3-3 proteins constitute a family that is highly conserved in a wide range of organisms, including higher eukaryotes, invertebrates and plants. Variants of 14-3-3 proteins assembled in homo- and heterodimers were found to interact with diverse cellular proteins. Until recently, the biological role of 14-3-3 members was still poorly understood. However, the results of an increasing number of studies on their structure and function are converging to define 14-3-3 proteins as a novel type of adaptor that modulates interactions between components involved in signal transduction pathway and in cell cycle control.
Collapse
Affiliation(s)
- V Baldin
- Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération Université Paul Sabatier-CNRS, Toulouse, France
| |
Collapse
|
38
|
Seimiya H, Sawada H, Muramatsu Y, Shimizu M, Ohko K, Yamane K, Tsuruo T. Involvement of 14-3-3 proteins in nuclear localization of telomerase. EMBO J 2000; 19:2652-61. [PMID: 10835362 PMCID: PMC212742 DOI: 10.1093/emboj/19.11.2652] [Citation(s) in RCA: 241] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2000] [Revised: 03/29/2000] [Accepted: 03/29/2000] [Indexed: 11/14/2022] Open
Abstract
Maintenance of telomeres is implicated in chromosome stabilization and cell immortalization. Telomerase, which catalyzes de novo synthesis of telomeres, is activated in germ cells and most cancers. Telomerase activity is regulated by gene expression for its catalytic subunit, TERT, whereas several lines of evidence have suggested a post-translational regulation of telomerase activity. Here we identify the 14-3-3 signaling proteins as human TERT (hTERT)-binding partners. A dominant-negative 14-3-3 redistributed hTERT, which was normally predominant in the nucleus, into the cytoplasm. Consistent with this observation, hTERT-3A, a mutant that could not bind 14-3-3, was localized into the cytoplasm. Leptomycin B, an inhibitor of CRM1/exportin 1-mediated nuclear export, or disruption of a nuclear export signal (NES)-like motif located just upstream of the 14-3-3 binding site in hTERT impaired the cytoplasmic localization of hTERT. Compared with wild-type hTERT, hTERT-3A increased its association with CRM1. 14-3-3 binding was not required for telomerase activity either in vitro or in cell extracts. These observations suggest that 14-3-3 enhances nuclear localization of TERT by inhibiting the CRM1 binding to the TERT NES-like motif.
Collapse
Affiliation(s)
- H Seimiya
- Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo 170-8455, Japan.
| | | | | | | | | | | | | |
Collapse
|
39
|
MacNicol MC, Muslin AJ, MacNicol AM. Disruption of the 14-3-3 binding site within the B-Raf kinase domain uncouples catalytic activity from PC12 cell differentiation. J Biol Chem 2000; 275:3803-9. [PMID: 10660530 DOI: 10.1074/jbc.275.6.3803] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A number of Raf-associated proteins have recently been identified, including members of the 14-3-3 family of phosphoserine-binding proteins. Although both positive and negative regulatory functions have been ascribed for 14-3-3 interactions with Raf-1, the mechanisms by which 14-3-3 binding modulates Raf activity have not been fully established. We report that mutational disruption of 14-3-3 binding to the B-Raf catalytic domain inhibits B-Raf biological activity. Expression of the isolated B-Raf catalytic domain (B-Rafcat) induces PC12 cell differentiation in the absence of nerve growth factor. By contrast, the B-Rafcat 14-3-3 binding mutant, B-Rafcat S728A, was severely compromised for the induction of PC12 cell differentiation. Interestingly, the B-Rafcat 14-3-3 binding mutant retained significant in vitro catalytic activity. In Xenopus oocytes, the analogous full-length B-Raf 14-3-3 binding mutant blocked progesterone-stimulated maturation and the activation of endogenous mitogen-activated protein kinase kinase and mitogen-activated protein kinase. Similarly, the full-length B-Raf 14-3-3 binding mutant inhibited nerve growth factor-stimulated PC12 cell differentiation. We conclude that 14-3-3 interaction with the catalytic domain is not required for kinase activity per se but is essential to couple B-Raf catalytic activity to downstream effector activation.
Collapse
Affiliation(s)
- M C MacNicol
- Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA
| | | | | |
Collapse
|
40
|
Abstract
Shear stress causes the platelet glycoprotein (Gp) Ib/IX/V to bind to von Willebrand factor, resulting in platelet adhesion. GpIb/IX/V also functions to stimulate transmembranous signaling, leading to platelet activation and the expression of a ligand-receptive GpIIb-IIIa complex. The highly conserved cytoplasmic domain of GpIb binds directly to a dimeric 14-3-3 adapter protein ζ isoform. To explore structural determinants of GpIb/IX/V binding to 14-3-3ζ, the authors examined 14-3-3ζ interactions with GpIb and GpIbβ in heterologous cells and platelets. Truncations of GpIb at amino acid 542 or 594, or deletions of residues 542 through 590, inhibited binding of 14-3-3ζ. Deletion of GpIb from Trp570 to Ser590 eliminated 14-3-3ζ binding, and deletion of the sequence from Arg542-Trp570 enhanced binding of 14-3-3ζ to GpIb. All GpIb mutations that eliminated GpIb binding to the GST-14-3-3ζ fusion protein also eliminated GpIbβ binding to the fusion protein. Forskolin treatment of Chinese hamster ovary cells expressing wild-type GpIb/β/IX resulted in the phosphorylation of GpIbβ associated with enhanced binding of GpIbβ to GST-14-3-3ζ fusion protein and increased 14-3-3ζ coimmunoprecipitated with GpIb. When intact human platelets aggregated in response to 90 dynes/cm2 shear stress, 14-3-3ζ disassociated from GpIb. Prostacyclin treatment of platelets inhibited shear stress-induced aggregation and the release of 14-3-3ζ from GpIb. These data demonstrate that amino acid residues in the cytoskeletal interaction domains of GpIb regulate 14-3-3ζ binding to GpIb/β/IX, and suggest that protein kinase A-dependent phosphorylation of GpIbβ enhances 14-3-3ζ binding to the GpIb/IX/V complex in human platelets.
Collapse
|
41
|
Fuglsang AT, Visconti S, Drumm K, Jahn T, Stensballe A, Mattei B, Jensen ON, Aducci P, Palmgren MG. Binding of 14-3-3 protein to the plasma membrane H(+)-ATPase AHA2 involves the three C-terminal residues Tyr(946)-Thr-Val and requires phosphorylation of Thr(947). J Biol Chem 1999; 274:36774-80. [PMID: 10593986 DOI: 10.1074/jbc.274.51.36774] [Citation(s) in RCA: 229] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
14-3-3 proteins play a regulatory role in a diverse array of cellular functions such as apoptosis, regulation of the cell cycle, and regulation of gene transcription. The phytotoxin fusicoccin specifically induces association of virtually any 14-3-3 protein to plant plasma membrane H(+)-ATPase. The 14-3-3 binding site in the Arabidopsis plasma membrane H(+)-ATPase AHA2 was localized to the three C-terminal residues of the enzyme (Tyr(946)-Thr-Val). Binding of 14-3-3 protein to this target was induced by phosphorylation of Thr(947) (K(D) = 88 nM) and was in practice irreversible in the presence of fusicoccin (K(D) = 7 nM). Mass spectrometry analysis demonstrated that AHA2 expressed in yeast was phosphorylated at Thr(947). We conclude that the extreme end of AHA2 contains an unusual high-affinity binding site for 14-3-3 protein.
Collapse
Affiliation(s)
- A T Fuglsang
- Department of Plant Biology, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg, Copenhagen, Denmark
| | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Gu M, Xi X, Englund GD, Berndt MC, Du X. Analysis of the roles of 14-3-3 in the platelet glycoprotein Ib-IX-mediated activation of integrin alpha(IIb)beta(3) using a reconstituted mammalian cell expression model. J Cell Biol 1999; 147:1085-96. [PMID: 10579727 PMCID: PMC2169335 DOI: 10.1083/jcb.147.5.1085] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/1999] [Accepted: 10/18/1999] [Indexed: 11/22/2022] Open
Abstract
We have reconstituted the platelet glycoprotein (GP) Ib-IX-mediated activation of the integrin alpha(IIb)beta(3) in a recombinant DNA expression model, and show that 14-3-3 is important in GPIb-IX signaling. CHO cells expressing alpha(IIb)beta(3) adhere poorly to vWF. Cells expressing GPIb-IX adhere to vWF in the presence of botrocetin but spread poorly. Cells coexpressing integrin alpha(IIb)beta(3) and GPIb-IX adhere and spread on vWF, which is inhibited by RGDS peptides and antibodies against alpha(IIb)beta(3). vWF binding to GPIb-IX also activates soluble fibrinogen binding to alpha(IIb)beta(3) indicating that GPIb-IX mediates a cellular signal leading to alpha(IIb)beta(3) activation. Deletion of the 14-3-3-binding site in GPIbalpha inhibited GPIb-IX-mediated fibrinogen binding to alpha(IIb)beta(3) and cell spreading on vWF. Thus, 14-3-3 binding to GPIb-IX is important in GPIb-IX signaling. Expression of a dominant negative 14-3-3 mutant inhibited cell spreading on vWF, suggesting an important role for 14-3-3. Deleting both the 14-3-3 and filamin-binding sites of GPIbalpha induced an endogenous integrin-dependent cell spreading on vWF without requiring alpha(IIb)beta(3), but inhibited vWF-induced fibrinogen binding to alpha(IIb)beta(3). Thus, while different activation mechanisms may be responsible for vWF interaction with different integrins, GPIb-IX-mediated activation of alpha(IIb)beta(3) requires 14-3-3 interaction with GPIbalpha.
Collapse
Affiliation(s)
- Minyi Gu
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Ilinois 60612
| | - Xiaodong Xi
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Ilinois 60612
| | - Graham D. Englund
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Ilinois 60612
| | | | - Xiaoping Du
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Ilinois 60612
| |
Collapse
|
43
|
Bodnar RJ, Gu M, Li Z, Englund GD, Du X. The cytoplasmic domain of the platelet glycoprotein Ibalpha is phosphorylated at serine 609. J Biol Chem 1999; 274:33474-9. [PMID: 10559231 DOI: 10.1074/jbc.274.47.33474] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alpha chain of the platelet von Willebrand factor receptor, glycoprotein (GP) Ib, is not known to be phosphorylated. Here, we report that the cytoplasmic domain of GPIbalpha is phosphorylated at Ser(609); this was detected by immunoblotting with an anti-phosphopeptide antibody, anti-pS609, that specifically recognizes the GPIbalpha C-terminal sequence S(606)GHSL(610) only when Ser(609) is phosphorylated. Immunoabsorption with anti-pS609 removed almost all of the GPIbalpha from platelet lysates, indicating a high proportion of GPIbalpha phosphorylation. Anti-pS609 inhibited GPIb-IX binding to the intracellular signaling molecule, 14-3-3zeta. Dephosphorylation of GPIb-IX with potato acid phosphatase inhibited anti-pS609 binding and also 14-3-3zeta binding. A synthetic phosphopeptide corresponding to the GPIbalpha C-terminal sequence (SIRYSGHpSL), but not a nonphosphorylated identical peptide, abolished GPIb-IX binding to 14-3-3zeta. Thus, phosphorylation at Ser(609) of GPIbalpha is important for 14-3-3zeta binding to GPIb-IX. In certain regions of spreading platelets, particularly at the periphery, there was a reduction in GPIbalpha staining by anti-pS609 as observed under a confocal microscope, indicating that a subpopulation of GPIbalpha molecules in these regions is dephosphorylated. These data suggest that phosphorylation and dephosphorylation at Ser(609) of GPIbalpha regulates GPIb-IX interaction with 14-3-3 and may play important roles in the process of platelet adhesion and spreading.
Collapse
Affiliation(s)
- R J Bodnar
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
| | | | | | | | | |
Collapse
|