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Clathrin-nanoparticles deliver BDNF to hippocampus and enhance neurogenesis, synaptogenesis and cognition in HIV/neuroAIDS mouse model. Commun Biol 2022; 5:236. [PMID: 35301411 PMCID: PMC8931075 DOI: 10.1038/s42003-022-03177-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 02/17/2022] [Indexed: 01/02/2023] Open
Abstract
Brain derived neurotrophic factor (BDNF) promotes the growth, differentiation, maintenance and survival of neurons. These attributes make BDNF a potentially powerful therapeutic agent. However, its charge, instability in blood, and poor blood brain barrier (BBB) penetrability have impeded its development. Here, we show that engineered clathrin triskelia (CT) conjugated to BDNF (BDNF-CT) and delivered intranasally increased hippocampal BDNF concentrations 400-fold above that achieved previously with intranasal BDNF alone. We also show that BDNF-CT targeted Tropomyosin receptor kinase B (TrkB) and increased TrkB expression and downstream signaling in iTat mouse brains. Mice were induced to conditionally express neurotoxic HIV Transactivator-of-Transcription (Tat) protein that decreases BDNF. Down-regulation of BDNF is correlated with increased severity of HIV/neuroAIDS. BDNF-CT enhanced neurorestorative effects in the hippocampus including newborn cell proliferation and survival, granule cell neurogenesis, synaptogenesis and increased dendritic integrity. BDNF-CT exerted cognitive-enhancing effects by reducing Tat-induced learning and memory deficits. These results show that CT bionanoparticles efficiently deliver BDNF to the brain, making them potentially powerful tools in regenerative medicine.
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Abdul-Salam VB, Russomanno G, Chien-Nien C, Mahomed AS, Yates LA, Wilkins MR, Zhao L, Gierula M, Dubois O, Schaeper U, Endruschat J, Wojciak-Stothard B. CLIC4/Arf6 Pathway. Circ Res 2019; 124:52-65. [PMID: 30582444 PMCID: PMC6325770 DOI: 10.1161/circresaha.118.313705] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
RATIONALE Increased expression of CLIC4 (chloride intracellular channel 4) is a feature of endothelial dysfunction in pulmonary arterial hypertension, but its role in disease pathology is not fully understood. OBJECTIVE To identify CLIC4 effectors and evaluate strategies targeting CLIC4 signaling in pulmonary hypertension. METHODS AND RESULTS Proteomic analysis of CLIC4-interacting proteins in human pulmonary artery endothelial cells identified regulators of endosomal trafficking, including Arf6 (ADP ribosylation factor 6) GTPase activating proteins and clathrin, while CLIC4 overexpression affected protein regulators of vesicular trafficking, lysosomal function, and inflammation. CLIC4 reduced BMPRII (bone morphogenetic protein receptor II) expression and signaling as a result of Arf6-mediated reduction in gyrating clathrin and increased lysosomal targeting of the receptor. BMPRII expression was restored by Arf6 siRNA, Arf inhibitor Sec7 inhibitor H3 (SecinH3), and inhibitors of clathrin-mediated endocytosis but was unaffected by chloride channel inhibitor, indanyloxyacetic acid 94 or Arf1 siRNA. The effects of CLIC4 on NF-κB (nuclear factor-kappa B), HIF (hypoxia-inducible factor), and angiogenic response were prevented by Arf6 siRNA and SecinH3. Sugen/hypoxia mice and monocrotaline rats showed elevated expression of CLIC4, activation of Arf6 and NF-κB, and reduced expression of BMPRII in the lung. These changes were established early during disease development. Lung endothelium-targeted delivery of CLIC4 siRNA or treatment with SecinH3 attenuated the disease, reduced CLIC4/Arf activation, and restored BMPRII expression in the lung. Endothelial colony-forming cells from idiopathic pulmonary hypertensive patients showed upregulation of CLIC4 expression and Arf6 activity, suggesting potential importance of this pathway in the human condition. CONCLUSIONS Arf6 is a novel effector of CLIC4 and a new therapeutic target in pulmonary hypertension.
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Affiliation(s)
- Vahitha B Abdul-Salam
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Giusy Russomanno
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Chen Chien-Nien
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Abdul S Mahomed
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Luke A Yates
- Section of Structural Biology (L.A.Y.), Department of Medicine, Imperial College London, United Kingdom
| | - Martin R Wilkins
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Lan Zhao
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Magdalena Gierula
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Oliver Dubois
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
| | - Ute Schaeper
- Silence Therapeutics GmbH, Berlin, Germany (U.S., J.E.)
| | | | - Beata Wojciak-Stothard
- From the Centre for Pharmacology and Therapeutics (V.B.A.-S., G.R., C.C.-N., A.S.M., M.R.W., L.Z., M.G., O.D., B.W.-S.), Department of Medicine, Imperial College London, United Kingdom
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Bricker BA, Peprah K, Kang HJ, Ablordeppey SY. Evaluation of SYA16263 as a new potential antipsychotic agent without catalepsy. Pharmacol Biochem Behav 2019; 179:55-62. [PMID: 30768942 DOI: 10.1016/j.pbb.2019.02.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 02/08/2019] [Accepted: 02/11/2019] [Indexed: 10/27/2022]
Abstract
SYA16263 exhibited moderate radioligand binding affinity at the D2 receptor and produced inhibition of apomorphine-induced climbing behavior in mice with an ED50 value of 3.88 mg/kg IP, predicting potential antipsychotic effects in humans. Analysis of plasma and brains from rats injected IP with SYA16263 over the course of 24 h revealed a log [brain]/[plasma] (log BB) at Cmax observed equal to 1.08, indicating that SYA16263 enters the brain and is predicted to cross the blood brain barrier (BBB) readily. When tested in animal behavior tests for catalepsy, SYA16263 did not produce catalepsy at doses up to 19 times the apomorphine ED50 value predicting little or no extra-pyramidal (EPS) side effects in humans. This is similar to aripiprazole, which is associated with a low incidence of EPS in humans, but unlike haloperidol which is known to cause severe EPS in humans. Functional activities for SYA16263 show that it acts as a D2 agonist at both the Gi and β-arrestin pathways, similar to, but better than aripiprazole, which could account for the absence of the catalepsy observed. Taken together, the receptor binding profile, the functional status, the animal behavioral tests and the log BB value, all provide evidence for further pre-clinical testing of SYA16263 as a potential antipsychotic agent with an interesting profile and a unique mechanism of action resulting in no EPS even up to 19 times the ED50 value.
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Affiliation(s)
- Barbara A Bricker
- Division of Basic Pharmaceutical Sciences, Florida A&M University, College of Pharmacy and Pharmaceutical Sciences, Tallahassee, FL 32307, USA
| | - Kwame Peprah
- Division of Basic Pharmaceutical Sciences, Florida A&M University, College of Pharmacy and Pharmaceutical Sciences, Tallahassee, FL 32307, USA
| | - Hye J Kang
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA; National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
| | - S Y Ablordeppey
- Division of Basic Pharmaceutical Sciences, Florida A&M University, College of Pharmacy and Pharmaceutical Sciences, Tallahassee, FL 32307, USA.
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Wee P, Wang Z. Regulation of EGFR Endocytosis by CBL During Mitosis. Cells 2018; 7:cells7120257. [PMID: 30544639 PMCID: PMC6315415 DOI: 10.3390/cells7120257] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/28/2018] [Accepted: 12/04/2018] [Indexed: 12/19/2022] Open
Abstract
The overactivation of epidermal growth factor (EGF) receptor (EGFR) is implicated in various cancers. Endocytosis plays an important role in EGFR-mediated cell signaling. We previously found that EGFR endocytosis during mitosis is mediated differently from interphase. While the regulation of EGFR endocytosis in interphase is well understood, little is known regarding the regulation of EGFR endocytosis during mitosis. Here, we found that contrary to interphase cells, mitotic EGFR endocytosis is more reliant on the activation of the E3 ligase CBL. By transfecting HeLa, MCF-7, and 293T cells with CBL siRNA or dominant-negative 70z-CBL, we found that at high EGF doses, CBL is required for EGFR endocytosis in mitotic cells, but not in interphase cells. In addition, the endocytosis of mutant EGFR Y1045F-YFP (mutation at the direct CBL binding site) is strongly delayed. The endocytosis of truncated EGFR Δ1044-YFP that does not bind to CBL is completely inhibited in mitosis. Moreover, EGF induces stronger ubiquitination of mitotic EGFR than interphase EGFR, and mitotic EGFR is trafficked to lysosomes for degradation. Furthermore, we showed that, different from interphase, low doses of EGF still stimulate EGFR endocytosis by non-clathrin mediated endocytosis (NCE) in mitosis. Contrary to interphase, CBL and the CBL-binding regions of EGFR are required for mitotic EGFR endocytosis at low doses. This is due to the mitotic ubiquitination of the EGFR even at low EGF doses. We conclude that mitotic EGFR endocytosis exclusively proceeds through CBL-mediated NCE.
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Affiliation(s)
- Ping Wee
- Department of Medical Genetics and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Zhixiang Wang
- Department of Medical Genetics and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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5
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Membrane targeting of inhibitory Smads through palmitoylation controls TGF-β/BMP signaling. Proc Natl Acad Sci U S A 2017; 114:13206-13211. [PMID: 29180412 PMCID: PMC5740658 DOI: 10.1073/pnas.1710540114] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
TGF-β/BMP (bone morphogenetic protein) signaling pathways play conserved roles in controlling embryonic development, tissue homeostasis, and stem cell regulation. Inhibitory Smads (I-Smads) have been shown to negatively regulate TGF-β/BMP signaling by primarily targeting the type I receptors for ubiquitination and turnover. However, little is known about how I-Smads access the membrane to execute their functions. Here we show that Dad, the Drosophila I-Smad, associates with the cellular membrane via palmitoylation, thereby targeting the BMP type I receptor for ubiquitination. By performing systematic biochemistry assays, we characterized the specific cysteine (Cys556) essential for Dad palmitoylation and membrane association. Moreover, we demonstrate that dHIP14, a Drosophila palmitoyl acyl-transferase, catalyzes Dad palmitoylation, thereby inhibiting efficient BMP signaling. Thus, our findings uncover a modification of the inhibitory Smads that controls TGF-β/BMP signaling activity.
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Pham CD, Smith CE, Hu Y, Hu JCC, Simmer JP, Chun YHP. Endocytosis and Enamel Formation. Front Physiol 2017; 8:529. [PMID: 28824442 PMCID: PMC5534449 DOI: 10.3389/fphys.2017.00529] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 07/10/2017] [Indexed: 12/12/2022] Open
Abstract
Enamel formation requires consecutive stages of development to achieve its characteristic extreme mineral hardness. Mineralization depends on the initial presence then removal of degraded enamel proteins from the matrix via endocytosis. The ameloblast membrane resides at the interface between matrix and cell. Enamel formation is controlled by ameloblasts that produce enamel in stages to build the enamel layer (secretory stage) and to reach final mineralization (maturation stage). Each stage has specific functional requirements for the ameloblasts. Ameloblasts adopt different cell morphologies during each stage. Protein trafficking including the secretion and endocytosis of enamel proteins is a fundamental task in ameloblasts. The sites of internalization of enamel proteins on the ameloblast membrane are specific for every stage. In this review, an overview of endocytosis and trafficking of vesicles in ameloblasts is presented. The pathways for internalization and routing of vesicles are described. Endocytosis is proposed as a mechanism to remove debris of degraded enamel protein and to obtain feedback from the matrix on the status of the maturing enamel.
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Affiliation(s)
- Cong-Dat Pham
- Department of Periodontics, School of Dentistry, University of Texas Health Science Center at San AntonioSan Antonio, TX, United States
| | - Charles E. Smith
- Department of Anatomy and Cell Biology, McGill UniversityMontreal, QC, Canada
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - Jan C-C. Hu
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - James P. Simmer
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - Yong-Hee P. Chun
- Department of Periodontics, School of Dentistry, University of Texas Health Science Center at San AntonioSan Antonio, TX, United States
- Department of Cell Systems & Anatomy, School of Medicine, University of Texas Health Science Center at San AntonioSan Antonio, TX, United States
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7
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Chen SY, Hsu YM, Lin YJ, Huang YC, Chen CJ, Lin WD, Liao WL, Chen YT, Lin WY, Liu YH, Yang JS, Sheu JC, Tsai FJ. Current concepts regarding developmental mechanisms in diabetic retinopathy in Taiwan. Biomedicine (Taipei) 2016; 6:7. [PMID: 27154195 PMCID: PMC4859317 DOI: 10.7603/s40681-016-0007-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 03/31/2016] [Indexed: 12/15/2022] Open
Abstract
Diabetic retinopathy (DR) is one of the most feared complications of diabetes and is a leading cause of acquired blindness in working adults. The prevalence of undiagnosed diabetes in Taiwan is about 4%, and the annual incidence of T2D (Type 2 Diabetes) in Taiwan is 1.8% following the 1985 WHO criteria. Multiple mechanisms have been shown in T2DR with some signaling pathways, including the polyol pathway, PKC pathway, AGEs pathway, and MAPK pathway. However, the cause of vision loss in diabetic retinopathy is complex and remains incompletely understood. Herein, we try to fully understand the new concepts regarding hyperglycemia-induced biochemical pathways contributing to DR pathophysiology. Our work may be able to provide new strategies for the prevention and treatment of diabetic vascular complications.
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Affiliation(s)
- Shih-Yin Chen
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Yuan-Man Hsu
- Department of Biological Science and Technology, China Medical University, 404, Taichung, Taiwan
| | - Ying-Ju Lin
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Yu-Chuen Huang
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Chao-Jung Chen
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Wei-De Lin
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Wen-Lin Liao
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Yng-Tay Chen
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Wei-Yong Lin
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Yu-Huei Liu
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan
| | - Jai-Sing Yang
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan
| | - Jinn-Chyuan Sheu
- Institute of Biomedical Sciences, National Sun Yat-sen University, 804, Kaohsiung, Taiwan
| | - Fuu-Jen Tsai
- Genetics Center, Department of Medical Research, China Medical University Hospital, No. 2 Yuh Der Road, 404, Taichung, Taiwan.
- School of Chinese Medicine, China Medical University, 404, Taichung, Taiwan.
- Department of Medical Genetics, China Medical University Hospital, 404, Taichung, Taiwan.
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Kapus A, Janmey P. Plasma membrane--cortical cytoskeleton interactions: a cell biology approach with biophysical considerations. Compr Physiol 2013; 3:1231-81. [PMID: 23897686 DOI: 10.1002/cphy.c120015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
From a biophysical standpoint, the interface between the cell membrane and the cytoskeleton is an intriguing site where a "two-dimensional fluid" interacts with an exceedingly complex three-dimensional protein meshwork. The membrane is a key regulator of the cytoskeleton, which not only provides docking sites for cytoskeletal elements through transmembrane proteins, lipid binding-based, and electrostatic interactions, but also serves as the source of the signaling events and molecules that control cytoskeletal organization and remolding. Conversely, the cytoskeleton is a key determinant of the biophysical and biochemical properties of the membrane, including its shape, tension, movement, composition, as well as the mobility, partitioning, and recycling of its constituents. From a cell biological standpoint, the membrane-cytoskeleton interplay underlies--as a central executor and/or regulator--a multitude of complex processes including chemical and mechanical signal transduction, motility/migration, endo-/exo-/phagocytosis, and other forms of membrane traffic, cell-cell, and cell-matrix adhesion. The aim of this article is to provide an overview of the tight structural and functional coupling between the membrane and the cytoskeleton. As biophysical approaches, both theoretical and experimental, proved to be instrumental for our understanding of the membrane/cytoskeleton interplay, this review will "oscillate" between the cell biological phenomena and the corresponding biophysical principles and considerations. After describing the types of connections between the membrane and the cytoskeleton, we will focus on a few key physical parameters and processes (force generation, curvature, tension, and surface charge) and will discuss how these contribute to a variety of fundamental cell biological functions.
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Affiliation(s)
- András Kapus
- Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
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On eukaryotic intelligence: signaling system's guidance in the evolution of multicellular organization. Biosystems 2013; 114:8-24. [PMID: 23850535 DOI: 10.1016/j.biosystems.2013.06.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 06/28/2013] [Accepted: 06/30/2013] [Indexed: 12/11/2022]
Abstract
Communication with the environment is an essential characteristic of the living cell, even more when considering the origins and evolution of multicellularity. A number of changes and tinkering inventions were necessary in the evolutionary transition between prokaryotic and eukaryotic cells, which finally made possible the appearance of genuine multicellular organisms. In the study of this process, however, the transformations experimented by signaling systems themselves have been rarely object of analysis, obscured by other more conspicuous biological traits: incorporation of mitochondria, segregated nucleus, introns/exons, flagellum, membrane systems, etc. Herein a discussion of the main avenues of change from prokaryotic to eukaryotic signaling systems and a review of the signaling resources and strategies underlying multicellularity will be attempted. In the expansion of prokaryotic signaling systems, four main systemic resources were incorporated: molecular tools for detection of solutes, molecular tools for detection of solvent (Donnan effect), the apparatuses of cell-cycle control, and the combined system endocytosis/cytoskeleton. The multiple kinds of enlarged, mixed pathways that emerged made possible the eukaryotic revolution in morphological and physiological complexity. The massive incorporation of processing resources of electro-molecular nature, derived from the osmotic tools counteracting the Donnan effect, made also possible the organization of a computational tissue with huge information processing capabilities: the nervous system. In the central nervous systems of vertebrates, and particularly in humans, neurons have achieved both the highest level of molecular-signaling complexity and the highest degree of information-processing adaptability. Theoretically, it can be argued that there has been an accelerated pace of evolutionary change in eukaryotic signaling systems, beyond the other general novelties introduced by eukaryotic cells in their handling of DNA processes. Under signaling system's guidance, the whole processes of transcription, alternative splicing, mobile elements, and other elements of domain recombination have become closely intertwined and have propelled the differentiation capabilities of multicellular tissues and morphologies. An amazing variety of signaling and self-construction strategies have emerged out from the basic eukaryotic design of multicellular complexity, in millions and millions of new species evolved. This design can also be seen abstractly as a new kind of quasi-universal problem-solving 'engine' implemented at the biomolecular scale-providing the fundamentals of eukaryotic 'intelligence'. Analyzing in depth the problem-solving intelligence of eukaryotic cells would help to establish an integrative panorama of their information processing organization, and of their capability to handle the morphological and physiological complexity associated. Whether an informational updating of the venerable "cell theory" is feasible or not, becomes, at the time being - right in the middle of the massive data deluge/revolution from omic disciplines - a matter to careful consider.
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Paul S, Schaefer BC. A new look at T cell receptor signaling to nuclear factor-κB. Trends Immunol 2013; 34:269-81. [PMID: 23474202 DOI: 10.1016/j.it.2013.02.002] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Revised: 01/20/2013] [Accepted: 02/04/2013] [Indexed: 12/20/2022]
Abstract
Antigen stimulation of T cell receptor (TCR) signaling to nuclear factor (NF)-κB is required for T cell proliferation and differentiation of effector cells. The TCR-to-NF-κB pathway is generally viewed as a linear sequence of events in which TCR engagement triggers a cytoplasmic cascade of protein-protein interactions and post-translational modifications, ultimately culminating in the nuclear translocation of NF-κB. However, recent findings suggest a more complex picture in which distinct signalosomes, previously unrecognized proteins, and newly identified regulatory mechanisms play key roles in signal transmission. In this review, we evaluate recent data and suggest areas of future emphasis in the study of this important pathway.
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Affiliation(s)
- Suman Paul
- Department of Microbiology and Immunology, Uniformed Services University, Bethesda, MD 20814, USA
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11
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Abstract
A long-standing paradigm in cell biology is the shutdown of endocytosis during mitosis. There is consensus that transferrin uptake is inhibited after entry into prophase and that it resumes in telophase. A recent study proposed that endocytosis is continuous throughout the cell cycle and that the observed inhibition of transferrin uptake is due to a decrease in available transferrin receptor at the cell surface, and not to a shutdown of endocytosis. This challenge to the established view is gradually becoming accepted. Because of this controversy, we revisited the question of endocytic activity during mitosis. Using an antibody uptake assay and controlling for potential changes in surface receptor density, we demonstrate the strong inhibition of endocytosis in mitosis of CD8 chimeras containing any of the three major internalization motifs for clathrin-mediated endocytosis (YXXΦ, [DE]XXXL[LI], or FXNPXY) or a CD8 protein with the cytoplasmic tail of the cation-independent mannose 6-phosphate receptor. The shutdown is not gradual: We describe a binary switch from endocytosis being "on" in interphase to "off" in mitosis as cells traverse the G(2)/M checkpoint. In addition, we show that the inhibition of transferrin uptake in mitosis occurs despite abundant transferrin receptor at the surface of HeLa cells. Our study finds no support for the recent idea that endocytosis continues during mitosis, and we conclude that endocytosis is temporarily shutdown during early mitosis.
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12
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Nuclear translocation and functions of growth factor receptors. Semin Cell Dev Biol 2012; 23:165-71. [DOI: 10.1016/j.semcdb.2011.09.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Accepted: 09/08/2011] [Indexed: 01/24/2023]
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13
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Protein-protein interactions in clathrin vesicular assembly: radial distribution of evolutionary constraints in interfaces. PLoS One 2012; 7:e31445. [PMID: 22384024 PMCID: PMC3285160 DOI: 10.1371/journal.pone.0031445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 01/10/2012] [Indexed: 11/19/2022] Open
Abstract
In eukaryotic organisms clathrin-coated vesicles are instrumental in the processes of endocytosis as well as intracellular protein trafficking. Hence, it is important to understand how these vesicles have evolved across eukaryotes, to carry cargo molecules of varied shapes and sizes. The intricate nature and functional diversity of the vesicles are maintained by numerous interacting protein partners of the vesicle system. However, to delineate functionally important residues participating in protein-protein interactions of the assembly is a daunting task as there are no high-resolution structures of the intact assembly available. The two cryoEM structures closely representing intact assembly were determined at very low resolution and provide positions of Cα atoms alone. In the present study, using the method developed by us earlier, we predict the protein-protein interface residues in clathrin assembly, taking guidance from the available low-resolution structures. The conservation status of these interfaces when investigated across eukaryotes, revealed a radial distribution of evolutionary constraints, i.e., if the members of the clathrin vesicular assembly can be imagined to be arranged in spherical manner, the cargo being at the center and clathrins being at the periphery, the detailed phylogenetic analysis of these members of the assembly indicated high-residue variation in the members of the assembly closer to the cargo while high conservation was noted in clathrins and in other proteins at the periphery of the vesicle. This points to the strategy adopted by the nature to package diverse proteins but transport them through a highly conserved mechanism.
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de la Vega M, Burrows JF, Johnston JA. Ubiquitination: Added complexity in Ras and Rho family GTPase function. Small GTPases 2011; 2:192-201. [PMID: 22145091 DOI: 10.4161/sgtp.2.4.16707] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 07/08/2011] [Accepted: 07/08/2011] [Indexed: 12/17/2022] Open
Abstract
The regulation of the small GTPases leading to their membrane localization has long been attributed to processing of their C-terminal CAAX box. As deregulation of many of these GTPases have been implicated in cancer and other disorders, prenylation and methylation of this CAAX box has been studied in depth as a possibility for drug targeting, but unfortunately, to date no drug has proved clinically beneficial. However, these GTPases also undergo other modifications that may be important for their regulation. Ubiquitination has long been demonstrated to regulate the fate of numerous cellular proteins and recently it has become apparent that many GTPases, along with their GAPs, GeFs and GDis, undergo ubiquitination leading to a variety of fates such as re-localization or degradation. in this review we focus on the recent literature demonstrating that the regulation of small GTPases by ubiquitination, either directly or indirectly, plays a considerable role in controlling their function and that targeting these modifications could be important for disease treatment.
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Affiliation(s)
- Michelle de la Vega
- Centre for Infection and Immunity; School of Medicine, Dentistry and Biomedical Sciences; Queen's University; Belfast, UK
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15
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Fu W, Jiang Q, Zhang C. Novel functions of endocytic player clathrin in mitosis. Cell Res 2011; 21:1655-61. [PMID: 21709692 DOI: 10.1038/cr.2011.106] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Clathrin has been widely recognized as a pivotal player in endocytosis, in which several adaptors and accessory proteins are involved. Recent studies suggested that clathrin is also essential for cell division. Here this review mainly focuses on the clathrin-dependent mechanisms involved in spindle assembly and chromosome alignment. In mitosis, clathrin forms a complex with phosphorylated TACC3 to ensure spindle stability and proper chromosome alignment. The clathrin-regulated mechanism in mitosis requires the crosstalk among clathrin, spindle assembly factors (SAFs), Ran-GTP and mitotic kinases. Meanwhile, a coordinated mechanism is required for role transitions of clathrin during endocytosis and mitosis. Taken together, the findings of the multiple functions of clathrin besides endocytosis have expanded our understanding of the basic cellular activities.
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Affiliation(s)
- Wenxiang Fu
- The MOE Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
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Zhu XD, Zhuang Y, Ben JJ, Qian LL, Huang HP, Bai H, Sha JH, He ZG, Chen Q. Caveolae-dependent endocytosis is required for class A macrophage scavenger receptor-mediated apoptosis in macrophages. J Biol Chem 2011; 286:8231-8239. [PMID: 21205827 DOI: 10.1074/jbc.m110.145888] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SR-A (class A macrophage scavenger receptor) is a transmembrane receptor that can bind many different ligands, including modified lipoproteins that are relevant to the development of vascular diseases. However, the precise endocytic pathways of SR-A/mediated ligands internalization are not fully characterized. In this study, we show that the SR-A/ligand complex can be endocytosed by both clathrin- and caveolae-dependent pathways. Internalizations of SR-A-lipoprotein (such as acLDL) complexes primarily go through clathrin-dependent endocytosis. In contrast, macrophage apoptosis triggered by SR-A-fucoidan internalization requires caveolae-dependent endocytosis. The caveolae-dependent process activates p38 kinase and JNK signaling, whereas the clathrin-mediated endocytosis elicits ERK signaling. Our results suggest that different SR-A endocytic pathways have distinct functional consequences due to the activation of different signaling cascades in macrophages.
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Affiliation(s)
- Xu-Dong Zhu
- From the Institute of Reproductive Medicine and; Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and
| | - Yan Zhuang
- Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and
| | - Jing-Jing Ben
- Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and
| | - Ling-Ling Qian
- Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and
| | - Han-Peng Huang
- Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and
| | - Hui Bai
- Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and
| | - Jia-Hao Sha
- From the Institute of Reproductive Medicine and
| | - Zhi-Gang He
- the Division of Neuroscience, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Qi Chen
- From the Institute of Reproductive Medicine and; Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, Nanjing Medical University, Nanjing 210029, China and.
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Liu L, Shi H, Chen X, Wang Z. Regulation of EGF-Stimulated EGF Receptor Endocytosis During M Phase. Traffic 2010; 12:201-17. [DOI: 10.1111/j.1600-0854.2010.01141.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Gorbea C, Pratt G, Ustrell V, Bell R, Sahasrabudhe S, Hughes RE, Rechsteiner M. A protein interaction network for Ecm29 links the 26 S proteasome to molecular motors and endosomal components. J Biol Chem 2010; 285:31616-33. [PMID: 20682791 DOI: 10.1074/jbc.m110.154120] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ecm29 is a 200-kDa HEAT repeat protein that binds the 26 S proteasome. Genome-wide two-hybrid screens and mass spectrometry have identified molecular motors, endosomal components, and ubiquitin-proteasome factors as Ecm29-interacting proteins. The C-terminal half of human Ecm29 binds myosins and kinesins; its N-terminal region binds the endocytic proteins, Vps11, Rab11-FIP4, and rabaptin. Whereas full-length FLAG-Ecm29, its C-terminal half, and a small central fragment of Ecm29 remain bound to glycerol-gradient-separated 26 S proteasomes, the N-terminal half of Ecm29 does not. Confocal microscopy showed that Ecm-26 S proteasomes are present on flotillin-positive endosomes, but they are virtually absent from caveolin- and clathrin-decorated endosomes. Expression of the small central fragment of Ecm29 markedly reduces proteasome association with flotillin-positive endosomes. Identification of regions within Ecm29 capable of binding molecular motors, endosomal proteins, and the 26 S proteasome supports the hypothesis that Ecm29 serves as an adaptor for coupling 26 S proteasomes to specific cellular compartments.
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Affiliation(s)
- Carlos Gorbea
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA
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IL-7 induces rapid clathrin-mediated internalization and JAK3-dependent degradation of IL-7Ralpha in T cells. Blood 2010; 115:3269-77. [PMID: 20190194 DOI: 10.1182/blood-2009-10-246876] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Interleukin-7 (IL-7) is an essential cytokine for T-cell development and homeostasis. It is well established that IL-7 promotes the transcriptional down-regulation of IL7RA, leading to decreased IL-7Ralpha surface expression. However, it is currently unknown whether IL-7 regulates the intracellular trafficking and early turnover of its receptor on ligand binding. Here, we show that, in steady-state T cells, IL-7Ralpha is slowly internalized and degraded while a significant fraction recycles back to the surface. On IL-7 stimulation, there is rapid IL-7Ralpha endocytosis via clathrin-coated pits, decreased receptor recycling, and accelerated lysosome and proteasome-dependent degradation. In accordance, the half-life of IL-7Ralpha decreases from 24 hours to approximately 3 hours after IL-7 treatment. Interestingly, we further demonstrate that clathrin-dependent endocytosis is necessary for efficient IL-7 signal transduction. In turn, pretreatment of T cells with JAK3 or pan-JAK inhibitors suggests that IL-7Ralpha degradation depends on the activation of the IL-7 signaling effector JAK3. Overall, our findings indicate that IL-7 triggers rapid IL-7Ralpha endocytosis, which is required for IL-7-mediated signaling and subsequent receptor degradation.
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Abstract
Endocytosis has long been thought of as simply a way for cells to internalize nutrients and membrane-associated molecules. But an explosive growth in knowledge has given a new dimension to our understanding of this process. It now seems that endocytosis is a master organizer of signalling circuits, with one of its main roles being the resolution of signals in space and time. Many of the functions of endocytosis that are emerging from recent research cannot yet be reconciled with the canonical view of intracellular trafficking but, instead, point to endocytosis being integrated at a deeper level in the cellular 'master plan' (the cellular network of signalling circuits that lie at the base of the cell's make-up). Deconvolution of this level, which we call the 'endocytic matrix', might uncover a fundamental aspect of how a cell is built.
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21
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Gerondopoulos A, Jackson T, Monaghan P, Doyle N, Roberts LO. Murine norovirus-1 cell entry is mediated through a non-clathrin-, non-caveolae-, dynamin- and cholesterol-dependent pathway. J Gen Virol 2010; 91:1428-38. [PMID: 20147520 DOI: 10.1099/vir.0.016717-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For many viruses, endocytosis and exposure to the low pH within acidic endosomes is essential for infection. It has previously been reported that feline calicivirus uses clathrin-mediated endocytosis for entry into mammalian cells. Here, we report that infection of RAW264.7 macrophages by the closely related murine norovirus-1 (MNV-1) does not require the clathrin pathway, as infection was not inhibited by expression of dominant-negative Eps15 or by knockdown of the adaptin-2 complex. Further, infection was not inhibited by reagents that raise endosomal pH. RAW264.7 macrophages were shown not to express caveolin, and flotillin depletion did not inhibit infection, suggesting that caveolae and the flotillin pathway are not required for cell entry. However, MNV-1 infection was inhibited by methyl-beta-cyclodextrin and the dynamin inhibitor, dynasore. Addition of these drugs to the cells after a period of virus internalization did not inhibit infection, suggesting the involvement of cholesterol-sensitive lipid rafts and dynamin in the entry mechanism. Macropinocytosis (MPC) was shown to be active in RAW264.7 macrophages (as indicated by uptake of dextran) and could be blocked by 5-(N-ethyl-N-isopropyl) amiloride (EIPA), which is reported to inhibit this pathway. However, infection was enhanced in the presence of EIPA. Similarly, actin disruption, which also inhibits MPC, resulted in enhanced infection. These results suggest that MPC could contribute to virus degradation or that inhibition of MPC could lead to the upregulation of other endocytic pathways of virus uptake.
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Affiliation(s)
- Andreas Gerondopoulos
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK
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22
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Marín MP, Esteban-Pretel G, Ponsoda X, Romero AM, Ballestín R, López C, Megías L, Timoneda J, Molowny A, Canales JJ, Renau-Piqueras J. Endocytosis in Cultured Neurons Is Altered by Chronic Alcohol Exposure. Toxicol Sci 2010; 115:202-13. [DOI: 10.1093/toxsci/kfq040] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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23
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Han JY, Im J, Choi JN, Lee CH, Park HJ, Park DK, Yun CH, Han SH. Induction of IL-8 expression by Cordyceps militaris grown on germinated soybeans through lipid rafts formation and signaling pathways via ERK and JNK in A549 cells. JOURNAL OF ETHNOPHARMACOLOGY 2010; 127:55-61. [PMID: 19799982 DOI: 10.1016/j.jep.2009.09.051] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 09/21/2009] [Accepted: 09/22/2009] [Indexed: 05/28/2023]
Abstract
AIM OF THE STUDY In order to elucidate immunoregulatory mechanisms of Cordyceps militaris, a methanol extract of Cordyceps militaris grown on germinated soybeans was prepared and its immunoregulatory effect in the human lung epithelial cells was investigated by examining its ability to induce IL-8 expression. MATERIALS AND METHODS Cordyceps militaris grown on germinated soybeans was extracted with 80% methanol (GSC4M) and used for stimulation of a human lung epithelial cell-line, A549. An enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction were performed to examine the production of IL-8 protein and its mRNA, respectively. For the analysis of transcription factors regulating IL-8 transcriptional activation, the nuclear fraction was extracted from GSC4M-treated A549 cells and subjected to electrophoretic mobility shift assay. RESULTS GSC4M induced IL-8 protein secretion and its mRNA expression from A549 cells in a dose- and time-dependent manner. GSC4M-induced IL-8 expression was inhibited by an inhibitor for lipid rafts formation but not by that for clathrin-coated pits. In addition, signaling pathways for GSC4M-induced IL-8 expression were mediated through ERK and JNK but hardly through p38 kinase. Furthermore, GSC4M augmented the DNA-binding activity of the transcription factors AP-1, NF-IL6, and NF-kappaB, all of which are involved in the transcriptional activation of the IL-8 gene. CONCLUSION Cordyceps militaris grown on germinated soybeans stimulates lung epithelial cells to produce IL-8 through lipid rafts formation and signaling pathways via ERK and JNK.
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Affiliation(s)
- Ji Young Han
- Department of Oral Microbiology & Immunology, Dental Research Institute, and BK21 Program, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea
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24
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Soutar AK. Regulation of the LDL receptor in familial hypercholesterolemia. ACTA ACUST UNITED AC 2009. [DOI: 10.2217/clp.09.60] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Although the critical role of T-cell receptor (TCR) microclusters in T-cell activation is now widely accepted, the mechanisms of regulation of these TCR-rich structures, which also contain enzymes, adapters, and effectors, remain poorly defined. Soon after microcluster formation, several signaling proteins rapidly dissociate from the TCR. Recent studies from our laboratory demonstrated that the movement of the adapters linker for activation of T cells (LAT) and Src homology 2 domain-containing leukocyte protein of 76 kDa (SLP-76) away from initial microcluster formation sites represents endocytic events. Ubiquitylation, Cbl proteins, and multiple endocytic pathways are involved in the internalization events that disassemble signaling microclusters. Several recent studies have indicated that microcluster movement and centralization plays an important role in signal termination. We suggest that microcluster movement is directly linked to endocytic events, thus implicating endocytosis of microclusters as a means to regulate signaling output of the T cell.
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Affiliation(s)
- Lakshmi Balagopalan
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Valarie A. Barr
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Lawrence E. Samelson
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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26
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Di Fiore PP. Endocytosis, signaling and cancer, much more than meets the eye. Preface. Mol Oncol 2009; 3:273-9. [PMID: 19628439 DOI: 10.1016/j.molonc.2009.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Accepted: 06/12/2009] [Indexed: 11/24/2022] Open
Affiliation(s)
- Pier Paolo Di Fiore
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare at IFOM-IEO Campus, 20139 Milan, Italy.
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Bogdanovic E, Coombs N, Dumont DJ. Oligomerized Tie2 localizes to clathrin-coated pits in response to angiopoietin-1. Histochem Cell Biol 2009; 132:225-37. [PMID: 19424712 DOI: 10.1007/s00418-009-0603-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2009] [Indexed: 12/27/2022]
Abstract
The tyrosine kinase receptor Tie2 is expressed on endothelial cells, and together with its ligand angiopoietin-1 (Ang1), is important for angiogenesis and vascular stability. Upon activation by Ang1, Tie2 is rapidly internalized and degraded, a mechanism most likely necessary to attenuate receptor activity. Using immunogold electron microscopy, we show that on the surface of endothelial cells, Tie2 is arranged in variably sized clusters containing dimers and higher order oligomers. Clusters of Tie2 were expressed on the apical and basolateral plasma membranes, and on the tips of microvilli. Upon activation by Ang1, Tie2 co-localized with the clathrin heavy chain at the apical and basolateral plasma membranes and within endothelial cells indicating that Tie2 internalizes through clathrin-coated pits. Inhibiting cellular endocytosis by depleting cellular potassium or by acidifying the cytosol blocked the internalization of Tie2 in response to Ang1. Our results suggest that one pathway mediating the internalization of Tie2 in response to Ang1 is through clathrin-coated pits.
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Affiliation(s)
- Elena Bogdanovic
- Molecular and Cellular Biology Research, Sunnybrook Research Institute, 2075 Bayview Avenue, Research Building, S-218, Toronto, ON, M4N 3M5, Canada
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28
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Abstract
Alzheimer's disease is characterized by the progressive deposition of beta-amyloid (Abeta) within the brain parenchyma and its subsequent accumulation into senile plaques. Pathogenesis of the disease is associated with perturbations in Abeta homeostasis and the inefficient clearance of these soluble and insoluble peptides from the brain. Microglia have been reported to mediate the clearance of fibrillar Abeta (fAbeta) through receptor-mediated phagocytosis; however, their participation in clearance of soluble Abeta peptides (sAbeta) is largely unknown. We report that microglia internalize sAbeta from the extracellular milieu through a nonsaturable, fluid phase macropinocytic mechanism that is distinct from phagocytosis and receptor-mediated endocytosis both in vitro and in vivo. The uptake of sAbeta is dependent on both actin and tubulin dynamics and does not involve clathrin assembly, coated vesicles or membrane cholesterol. Upon internalization, fluorescently labeled sAbeta colocalizes to pinocytic vesicles. Microglia rapidly traffic these soluble peptides into late endolysosomal compartments where they are subject to degradation. Additionally, we demonstrate that the uptake of sAbeta and fAbeta occurs largely through distinct mechanisms and upon internalization are segregated into separate subcellular vesicular compartments. Significantly, we found that upon proteolytic degradation of fluorescently labeled sAbeta, the fluorescent chromophore is retained by the microglial cell. These studies identify an important mechanism through which microglial cells participate in the maintenance of Abeta homeostasis, through their capacity to constitutively clear sAbeta peptides from the brain.
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Abstract
Endocytic mechanisms control the lipid and protein composition of the plasma membrane, thereby regulating how cells interact with their environments. Here, we review what is known about mammalian endocytic mechanisms, with focus on the cellular proteins that control these events. We discuss the well-studied clathrin-mediated endocytic mechanisms and dissect endocytic pathways that proceed independently of clathrin. These clathrin-independent pathways include the CLIC/GEEC endocytic pathway, arf6-dependent endocytosis, flotillin-dependent endocytosis, macropinocytosis, circular doral ruffles, phagocytosis, and trans-endocytosis. We also critically review the role of caveolae and caveolin1 in endocytosis. We highlight the roles of lipids, membrane curvature-modulating proteins, small G proteins, actin, and dynamin in endocytic pathways. We discuss the functional relevance of distinct endocytic pathways and emphasize the importance of studying these pathways to understand human disease processes.
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Affiliation(s)
- Gary J Doherty
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
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30
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Abstract
Cell–cell signaling mediated by the Notch receptor is iteratively involved in numerous developmental contexts, and its dysregulation has been associated with inherited genetic disorders and cancers. The core components of the signaling pathway have been identified for some time, but the study of the modulation of the pathway in different cellular contexts has revealed many layers of regulation. These include complex sugar modifications in the extracellular domain as well as transit of Notch through defined cellular compartments, including specific endosomes.
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Affiliation(s)
- An-Chi Tien
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
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31
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Phosphorylation events and the modulation of aquaporin 2 cell surface expression. Curr Opin Nephrol Hypertens 2009; 17:491-8. [PMID: 18695390 DOI: 10.1097/mnh.0b013e3283094eb1] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW This review highlights the role of phosphorylation in the trafficking and targeting of aquaporin 2. Current knowledge will be put into the context of modulating the cell surface expression of aquaporin 2 by vasopressin in renal epithelial cells, which is critical for regulation of urinary concentration and control of fluid and electrolyte homeostasis. RECENT FINDINGS In addition to previously identified phosphorylation sites on aquaporin 2, new data have revealed three other serine residues in the C-terminus whose phosphorylation is altered by vasopressin. Several steps in aquaporin 2 recycling, including exocytosis and endocytosis, are coordinated by phosphorylation and dephosphorylation to regulate cell surface accumulation. Aquaporin 2 phosphorylation on serine 256 regulates aquaporin 2 association with proteins that are involved in trafficking, including hsc/hsp70 and myelin and lymphocyte-associated protein. SUMMARY Aquaporin 2 trafficking is regulated by phosphorylation of serine 256 and other amino acid residues in its cytoplasmic domain. These events increase or decrease interaction of aquaporin 2 with key regulatory proteins to determine the cellular distribution and fate of aquaporin 2, both after vasopressin addition and under baseline conditions. Better understanding of these mechanisms may provide new therapeutic avenues for patients with X-linked nephrogenic diabetes insipidus, as well as providing basic cell biological information relevant to membrane trafficking processes in general.
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Croning MDR, Marshall MC, McLaren P, Armstrong JD, Grant SGN. G2Cdb: the Genes to Cognition database. Nucleic Acids Res 2008; 37:D846-51. [PMID: 18984621 PMCID: PMC2686544 DOI: 10.1093/nar/gkn700] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Neuroscience databases linking genes, proteins, (patho)physiology, anatomy and behaviour across species will be valuable in a broad range of studies of the nervous system. G2Cdb is such a neuroscience database aiming to present a global view of the role of synapse proteins in physiology and disease. G2Cdb warehouses sets of genes and proteins experimentally elucidated by proteomic mass spectroscopy of signalling complexes and proteins biochemically isolated from mammalian synapse preparations, giving an experimentally validated definition of the constituents of the mammalian synapse. Using automated text-mining and expert (human) curation we have systematically extracted information from published neurobiological studies in the fields of synaptic signalling electrophysiology and behaviour in knockout and other transgenic mice. We have also surveyed the human genetics literature for associations to disease caused by mutations in synaptic genes. The synapse proteome datasets that G2Cdb provides offer a basis for future work in synapse biology and provide useful information on brain diseases. They have been integrated in a such way that investigators can rapidly query whether a gene or protein is found in brain-signalling complex(es), has a phenotype in rodent models or whether mutations are associated with a human disease. G2Cdb can be freely accessed at http://www.genes2cognition.org.
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Affiliation(s)
- Mike D R Croning
- Genes to Cognition Programme, Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, UK
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Dittmann K, Mayer C, Kehlbach R, Rodemann HP. Radiation-induced caveolin-1 associated EGFR internalization is linked with nuclear EGFR transport and activation of DNA-PK. Mol Cancer 2008; 7:69. [PMID: 18789131 PMCID: PMC2546440 DOI: 10.1186/1476-4598-7-69] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Accepted: 09/12/2008] [Indexed: 11/22/2022] Open
Abstract
Background To elucidate the role of src kinase in caveolin-1 driven internalization and nuclear transport of EGFR linked to regulation of DNA-repair in irradiated cells. Results Ionizing radiation resulted in src kinase stabilization, activation and subsequent src mediated caveolin-1 Y14- and EGFR Y845-phosphorylations. Both phosphorylations were radiation specific and could not be observed after treatment with EGF. Inhibition of EGFR by the antibody Erbitux resulted in a strong accumulation of caveolin/EGFR complexes within the cytoplasm, which could not be further increased by irradiation. Radiation-induced caveolin-1- and EGFR-phosphorylations were associated with nuclear EGFR transport and activation of DNA-PK, as detected by phosphorylation at T2609. Blockage of src activity by the specific inhibitor PP2, decreased nuclear transport of EGFR and inhibited caveolin-1- and DNA-PK-phosphorylation. Knockdown of src by specific siRNA blocked EGFR phosphorylation at Y845, phosphorylation of caveolin-1 at Y14 and abolished EGFR transport into the nucleus and phosphorylation of DNA-PK. Consequently, both knockdown of src by specific siRNA and also inhibition of src activity by PP2 resulted in an enhanced residual DNA-damage as quantified 24 h after irradiation and increased radiosensitivity. Conclusion Src kinase activation following irradiation triggered caveolin-1 dependent EGFR internalization into caveolae. Subsequently EGFR shuttled into the nucleus. As a consequence, inhibition of internalization and nuclear transport of EGFR blocked radiation-induced phosphorylation of DNA-PK and hampered repair of radiation-induced double strand breaks.
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Affiliation(s)
- Klaus Dittmann
- Division of Radiobiology and Environmental Research, Department of Radiation Oncology University of Tübingen, Röntgenweg 11, 72076 Tübingen, Germany.
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Sigismund S, Argenzio E, Tosoni D, Cavallaro E, Polo S, Di Fiore PP. Clathrin-mediated internalization is essential for sustained EGFR signaling but dispensable for degradation. Dev Cell 2008; 15:209-19. [PMID: 18694561 DOI: 10.1016/j.devcel.2008.06.012] [Citation(s) in RCA: 489] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Revised: 06/11/2008] [Accepted: 06/20/2008] [Indexed: 12/31/2022]
Abstract
Clathrin-mediated endocytosis (CME) is the major pathway of epidermal growth factor receptor (EGFR) internalization. It is commonly believed that CME mediates long-term attenuation of EGFR signaling by targeting the receptor for degradation. However, the EGFR can also be internalized through (a) clathrin-independent pathway(s), and it remains unclear why distinct mechanisms of internalization have evolved. Here, we report that EGFRs internalized via CME are not targeted for degradation, but instead are recycled to the cell surface. By contrast, clathrin-independent internalization preferentially commits the receptor to degradation. This finding has profound implications for signaling, as by skewing EGFR fate toward recycling rather than degradation, CME prolongs the duration of signaling. Our data show that CME determines the longevity of some EGFR-activated signaling pathways and that EGF-dependent biological responses, such as DNA synthesis, absolutely require CME. Thus, CME of the EGFR unexpectedly has a greater impact on receptor signaling than on receptor degradation.
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Affiliation(s)
- Sara Sigismund
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy
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35
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Abstract
From the signaling point of view, endocytosis has long been regarded as a major mechanism of attenuation, through the degradation of signaling receptors and, in some cases, of their ligands. This outlook has changed, over the past decade, as it has become clear that signaling persists in the endocytic route, and that intracellular endocytic stations (the 'signaling endosomes') actually contribute to the sorting of signals in space and time. Endocytosis-mediated recycling of receptors and of signaling molecules to specific regions of the plasma membrane is also coming into focus as a major mechanism in the execution of spatially restricted functions, such as cell motility. In addition, emerging evidence connects endocytosis as a whole, or individual endocytic proteins, to complex cellular programs, such as the control of the cell cycle, mitosis, apoptosis and cell fate determination. Thus, endocytosis seems to be deeply ingrained into the cell regulation blueprint and its subversion is predicted to play an important role in human diseases: first and foremost, cancer.
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Affiliation(s)
- Letizia Lanzetti
- Dipartimento di Scienze Oncologiche, Università degli Studi di Torino, Istituto per la Ricerca e la Cura del Cancro, Candiolo, Turin, Italy
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36
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Sacher R, Stergiou L, Pelkmans L. Lessons from genetics: interpreting complex phenotypes in RNAi screens. Curr Opin Cell Biol 2008; 20:483-9. [PMID: 18602470 DOI: 10.1016/j.ceb.2008.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 06/10/2008] [Accepted: 06/10/2008] [Indexed: 11/16/2022]
Abstract
Mammalian cell biology is witnessing a new era in which cellular processes are explained through dynamic networks of interacting cellular components. In this fast-pacing field, where image-based RNAi screening is taking a central role, there is a strong need to improve ways to capture such interactions in space and time. Cell biologists traditionally depict these events by confining themselves to the level of a single cell, or to many population-averaged cells. Similarly, classical geneticists observe and interpret phenotypes in a single organism to delineate signaling processes, but have also described genetic phenomena in populations of organisms. The analogy in the two approaches inspired us to draw parallels with, and take lessons from concepts in classical genetics.
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Affiliation(s)
- Raphael Sacher
- Institute of Molecular Systems Biology, ETH Zürich, Wolfgang-Pauli Street 16, 8093 Zürich, Switzerland.
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Pandey MS, Harris EN, Weigel JA, Weigel PH. The cytoplasmic domain of the hyaluronan receptor for endocytosis (HARE) contains multiple endocytic motifs targeting coated pit-mediated internalization. J Biol Chem 2008; 283:21453-61. [PMID: 18539600 DOI: 10.1074/jbc.m800886200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hyaluronic acid (HA) receptor for endocytosis (HARE) is the primary scavenger receptor for HA and chondroitin sulfates in mammals. The two human isoforms of HARE (full-length 315-kDa and a 190-kDa proteolytic cleavage product), which are type I single-pass membrane proteins, are highly expressed in sinusoidal endothelial cells of lymph nodes, liver, and spleen. Their identical HARE cytoplasmic domains contain four candidate AP-2/clathrin-mediated endocytic signaling motifs as follows: YSYFRI(2485), FQHF(2495), NPLY(2519), and DPF(2534) (315-HARE numbering). Stably transfected cells expressing 190-HARE(DeltaYSYFRI), 190-HARE(DeltaFQHF), or 190-HARE(DeltaNPLY) (lacking Motifs 1, 2, or 3) had decreased (125)I-HA endocytosis rates of approximately 49, approximately 39, and approximately 56%, respectively (relative to wild type). In contrast, 190-HARE(DeltaDPF) cells (lacking Motif 4) showed no change in HA endocytic rate. Deletions of motifs 1 and 2 or of 1, 2, and 4 decreased the rate of HA endocytosis by only approximately 41%. Endocytosis was approximately 95% decreased in mutants lacking all four motifs. Cells expressing a 190-HARE(Y2519A) mutant of the NPLY motif retained 85-90% of wild type endocytosis, whereas this mutation in the triple motif deletant decreased endocytosis to approximately 7% of wild type. Tyr in NPLY(2519) is thus important for endocytosis. All HARE mutants showed similar HA binding and degradation of the internalized HA, indicating that altering endocytic motifs did not affect ectodomain binding of HA or targeting of internalized HA to lysosomes. We conclude that, although NPLY may be the most important motif, it functions together with two other endocytic motifs; thus three signal sequences (YSYFRI, FQHF, and NPLY) provide redundancy to mediate coated pit targeting and endocytosis of HARE.
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Affiliation(s)
- Madhu S Pandey
- Department of Biochemistry and Molecular Biology, and Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190, USA
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