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Malik S, Kumar V, Liu CH, Shih KC, Krueger S, Nieh MP, Bahal R. Head on Comparison of Self- and Nano-assemblies of Gamma Peptide Nucleic Acid Amphiphiles. ADVANCED FUNCTIONAL MATERIALS 2022; 32:2109552. [PMID: 35210986 PMCID: PMC8863176 DOI: 10.1002/adfm.202109552] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Indexed: 05/14/2023]
Abstract
Peptide nucleic acids (PNAs) are nucleic acid analogs with superior hybridization properties and enzymatic stability than deoxyribonucleic acid (DNA). In addition to gene targeting applications, PNAs have garnered significant attention as bio-polymer due to the Watson-Crick -based molecular recognition and flexibility of synthesis. Here, we engineered PNA amphiphiles using chemically modified gamma PNA (8 mer in length) containing hydrophilic diethylene glycol units at the gamma position and covalently conjugated lauric acid (C12) as a hydrophobic moiety. Gamma PNA (γPNA) amphiphiles self-assemble into spherical vesicles. Further, we formulate nano-assemblies using the amphiphilic γPNA as a polymer via ethanol injection-based protocols. We perform comprehensive head-on comparison of the physicochemical and cellular uptake properties of PNA derived self- and nano-assemblies. Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) analysis reveal ellipsoidal morphology of γPNA nano-assemblies that results in superior cellular delivery compate to the spherical self-assembly. Next, we compare the functional activities of γPNA self-and nano-assemblies in lymphoma cells via multiple endpoints, including gene expression, cell viability, and apoptosis-based assays. Overall, we establish that γPNA amphiphile is a functionally active bio-polymer to formulate nano-assemblies for a wide range of biomedical applications.
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Affiliation(s)
- Shipra Malik
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, 06269, USA
| | - Vikas Kumar
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, 06269, USA
| | - Chung-Hao Liu
- Polymer Program, Institute of Material Sciences, University of Connecticut, 191 Auditorium Road, Storrs, CT, 06269, USA
| | - Kuo-Chih Shih
- Polymer Program, Institute of Material Sciences, University of Connecticut, 191 Auditorium Road, Storrs, CT, 06269, USA
| | - Susan Krueger
- National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, USA
| | - Mu-Ping Nieh
- Polymer Program, Institute of Material Sciences, University of Connecticut, 191 Auditorium Road, Storrs, CT, 06269, USA
| | - Raman Bahal
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, 06269, USA
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Yadegari-Dehkordi S, Firoozabadi SM, Forouzandeh Moghadam M, Shankayi Z. Role of Endocytosis Pathways in Electropermeablization of MCF7 Cells Using Low Voltage and High Frequency Electrochemotherapy. CELL JOURNAL 2021; 23:445-450. [PMID: 34455720 PMCID: PMC8405087 DOI: 10.22074/cellj.2021.7203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 03/16/2020] [Indexed: 11/22/2022]
Abstract
Objective The cell membrane is a major barrier for delivery of hydrophilic drugs and molecules into the cells. Although
low voltage and high frequency electric fields (LVHF) are proposed to overcome the cell membrane barrier, the
mechanism of membrane permeabilization is unclear. The aim of study is to investigate endocytosis pathways as a
possible mechanism for enhancing uptake of bleomycin by LVHF. Materials and Methods In this experimental study, MCF-7 cells were exposed to bleomycin or to electric fields with
various strengths (10-80 V/cm), frequency of 5 kHz, 4000 electric pulse and 100 µs duration in the presence and
absence of three endocytosis inhibitors-chlorpromazine (Cpz), amiloride (Amilo) and genistein (Geni). We determined
the efficiency of these chemotherapeutic agents in each group.
Results LVHF, depending on the intensity, induced different endocytosis pathways. Electric field strengths of 10 and
20 V/cm stimulated the macropinocytosis route. Clathrin-mediated endocytosis was observed at electric field intensities
of 10, 30, 60 and 70 V/cm, whereas induction of caveolae-mediated endocytosis was observed only at the lowest
electric field intensity (10 V/cm).
Conclusion The results of this study imply that LVHF can induce different endocytosis pathways in MCF-7 cells, which
leads to an increase in bleomycin uptake.
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Affiliation(s)
- Sajedeh Yadegari-Dehkordi
- Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | | | - Mehdi Forouzandeh Moghadam
- Department of Medical Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Zeinab Shankayi
- Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
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Yadegari Dehkordi S, Firoozabadi SM, Forouzandeh Moghadam M, Shankayi Z. Endocytosis induction by high-pulsed magnetic fields to overcome cell membrane barrier and improve chemotherapy efficiency. Electromagn Biol Med 2021; 40:438-445. [PMID: 33977836 DOI: 10.1080/15368378.2021.1923026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cell membrane acts as a barrier to the entry of impermeable drugs into cells. Recent studies have suggested that using magnetic fields can enable molecules to overcome the cell membrane barrier. However, the mechanism of membrane permeabilization remains unclear. Therefore, we evaluated the increases in bleomycin (CT) uptake, a non-permanent chemotherapy agent, using high-pulsed magnetic fields and investigated whether endocytosis was involved in the process. This study exposed MCF-7 cells to magnetic fields (2.2 T strength, different number of 28 and 56 pulses, and frequency of 1 and 10 Hz) in order to investigate whether this approach could promote the cell-killing efficiency of bleomycin. The involvement of endocytosis as a possible mechanism was tested by exposing cells to three endocytosis inhibitors, namely chlorpromazine, genistein, and amiloride. Our results illustrated that magnetic fields, depending on their conditions, could induce different endocytosis pathways. In such conditions as 10 Hz-28 pulses, 10 Hz-56 pulses, and 1 Hz-56 pulse, clathrin-mediated endocytosis was observed. Moreover, macropinocytosis was induced by the 10 Hz magnetic field and caveolae-mediated endocytosis occurred in all the magnetic field conditions. The findings imply that high-pulsed magnetic fields generate different endocytosis pathways in the MCF-7 cells, thus increasing the efficiency of chemotherapy agents.
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Affiliation(s)
- Sajedeh Yadegari Dehkordi
- Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | | | - Mehdi Forouzandeh Moghadam
- Department of Medical Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Zeinab Shankayi
- Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
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Endocytic Internalization of Herpes Simplex Virus 1 in Human Keratinocytes at Low Temperature. J Virol 2021; 95:JVI.02195-20. [PMID: 33239453 PMCID: PMC7851553 DOI: 10.1128/jvi.02195-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Herpes simplex virus 1 (HSV-1) can adopt a variety of pathways to accomplish cellular internalization. In human keratinocytes representing the natural target cell of HSV-1, both direct plasma membrane fusion and endocytic uptake have been found. The impact of either pathway in successful infection, however, remains to be fully understood. To address the role of each internalization mode, we performed infection studies at low temperature as a tool to interfere with endocytic pathways. Interestingly, successful HSV-1 entry in primary human keratinocytes and HaCaT cells was observed even at 7°C, although delayed compared to infection at 37°C. Moreover, ex vivo infection of murine epidermis demonstrated that virus entry at 7°C is not only accomplished in cultured cells but also in tissue. Control experiments with cholera toxin B confirmed a block of endocytic uptake at 7°C. In addition, uptake of dextran by macropinosomes and phagocytic uptake of latex beads was also inhibited at 7°C. Infection of nectin-1-deficient murine keratinocytes affirmed that the entry at 7°C was receptor-dependent. Strikingly, the lysosomotropic agent, ammonium chloride, strongly inhibited HSV-1 entry suggesting a role for endosomal acidification. Ultrastructural analyses in turn revealed free capsids in the cytoplasm as well as virus particles in vesicles after infection at 7°C supporting both plasma membrane fusion and endocytic internalization as already observed at 37°C. Overall, entry of HSV-1 at 7°C suggests that the virus can efficiently adopt nectin-1-dependent unconventional vesicle uptake mechanisms in keratinocytes strengthening the role of endocytic internalization for successful infection.IMPORTANCE The human pathogen herpes simplex virus 1 (HSV-1) relies on multiple internalization pathways to initiate infection. Our focus is on the entry in human keratinocytes, the major in vivo target during primary and recurrent infection. While antivirals reduce the severity of clinical cases, there is no cure or vaccine against HSV. To develop strategies that interfere with virus penetration, we need to understand the various parameters and conditions that determine virus entry. Here, we addressed the impact of virus internalization via vesicles by blocking endocytic processes at low temperature. Intriguingly, we detected entry of HSV-1 even at 7°C which led to infection of primary keratinocytes and epidermal tissue. Moreover, electron microscopy of human keratinocytes at 7°C support that internalization is based on fusion of the viral envelope with the plasma membrane as well as vesicle membranes. These results provide novel insights into conditions that still allow endocytic internalization of HSV-1.
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Zhang X, Ren J, Wang J, Li S, Zou Q, Gao N. Receptor-mediated endocytosis generates nanomechanical force reflective of ligand identity and cellular property. J Cell Physiol 2018; 233:5908-5919. [PMID: 29243828 DOI: 10.1002/jcp.26400] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 12/12/2017] [Indexed: 01/07/2023]
Abstract
Whether environmental (thermal, chemical, and nutrient) signals generate quantifiable, nanoscale, mechanophysical changes in the cellular plasma membrane has not been well elucidated. Assessment of such mechanophysical properties of plasma membrane may shed lights on fundamental cellular process. Atomic force microscopic (AFM) measurement of the mechanical properties of live cells was hampered by the difficulty in accounting for the effects of the cantilever motion and the associated hydrodynamic force on the mechanical measurement. These challenges have been addressed in our recently developed control-based AFM nanomechanical measurement protocol, which enables a fast, noninvasive, broadband measurement of the real-time changes in plasma membrane elasticity in live cells. Here we show using this newly developed AFM platform that the plasma membrane of live mammalian cells exhibits a constant and quantifiable nanomechanical property, the membrane elasticity. This mechanical property sensitively changes in response to environmental factors, such as the thermal, chemical, and growth factor stimuli. We demonstrate that different chemical inhibitors of endocytosis elicit distinct changes in plasma membrane elastic modulus reflecting their specific molecular actions on the lipid configuration or the endocytic machinery. Interestingly, two different growth factors, EGF and Wnt3a, elicited distinct elastic force profiles revealed by AFM at the plasma membrane during receptor-mediated endocytosis. By applying this platform to genetically modified cells, we uncovered a previously unknown contribution of Cdc42, a key component of the cellular trafficking network, to EGF-stimulated endocytosis at plasma membrane. Together, this nanomechanical AFM study establishes an important foundation that is expandable and adaptable for investigation of cellular membrane evolution in response to various key extracellular signals.
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Affiliation(s)
- Xiao Zhang
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Juan Ren
- Department of Mechanical Engineering, Iowa State University, Ames, Iowa
| | - Jingren Wang
- Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, New Jersey
| | - Shixie Li
- Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, New Jersey
| | - Qingze Zou
- Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, New Jersey
| | - Nan Gao
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
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Ahire JH, Behray M, Webster CA, Wang Q, Sherwood V, Saengkrit N, Ruktanonchai U, Woramongkolchai N, Chao Y. Synthesis of Carbohydrate Capped Silicon Nanoparticles and their Reduced Cytotoxicity, In Vivo Toxicity, and Cellular Uptake. Adv Healthc Mater 2015; 4:1877-86. [PMID: 26121084 DOI: 10.1002/adhm.201500298] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/03/2015] [Indexed: 12/12/2022]
Abstract
The development of smart targeted nanoparticles (NPs) that can identify and deliver drugs at a sustained rate directly to cancer cells may provide better efficacy and lower toxicity for treating primary and advanced metastatic tumors. Obtaining knowledge of the diseases at the molecular level can facilitate the identification of biological targets. In particular, carbohydrate-mediated molecular recognitions using nano-vehicles are likely to increasingly affect cancer treatment methods, opening a new area in biomedical applications. Here, silicon NPs (SiNPs) capped with carbohydrates including galactose, glucose, mannose, and lactose are successfully synthesized from amine terminated SiNPs. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] analysis shows an extensive reduction in toxicity of SiNPs by functionalizing with carbohydrate moiety both in vitro and in vivo. Cellular uptake is investigated with flow cytometry and confocal fluorescence microscope. The results show the carbohydrate capped SiNPs can be internalized in the cells within 24 h of incubation, and can be taken up more readily by cancer cells than noncancerous cells. Moreover, these results reinforce the use of carbohydrates for the internalization of a variety of similar compounds into cancer cells.
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Affiliation(s)
| | - Mehrnaz Behray
- School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| | - Carl A. Webster
- School of Pharmacy; University of East Anglia; Norwich NR4 7TJ UK
| | - Qi Wang
- School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| | | | - Nattika Saengkrit
- National Nanotechnology Center (NANOTEC); National Science and Technology Development Agency (NSTDA); Pathumthani 12120 Thailand
| | - Uracha Ruktanonchai
- National Nanotechnology Center (NANOTEC); National Science and Technology Development Agency (NSTDA); Pathumthani 12120 Thailand
| | - Noppawan Woramongkolchai
- National Nanotechnology Center (NANOTEC); National Science and Technology Development Agency (NSTDA); Pathumthani 12120 Thailand
| | - Yimin Chao
- School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
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Abstract
The ubiquitous pannexin 1 (Panx1) ion- and metabolite-permeable channel mediates the release of ATP, a potent signalling molecule. In the present study, we provide striking evidence that ATP, in turn, stimulates internalization of Panx1 to intracellular membranes. These findings hold important implications for understanding the regulation of Panx1 when extracellular ATP is elevated. In the nervous system, this includes phenomena such as synaptic plasticity, pain, precursor cell development and stroke; outside of the nervous system, this includes things like skeletal and smooth muscle activity and inflammation. Within 15 min, ATP led to significant Panx1-EGFP internalization. In a series of experiments, we determined that hydrolysable ATP is the most potent stimulator of Panx1 internalization. We identified two possible mechanisms for Panx1 internalization, including activation of ionotropic purinergic (P2X) receptors and involvement of a putative ATP-sensitive residue in the first extracellular loop of Panx1 (Trp(74)). Internalization was cholesterol-dependent, but clathrin, caveolin and dynamin independent. Detailed analysis of Panx1 at specific endosome sub-compartments confirmed that Panx1 is expressed in endosome membranes of the classical degradation pathway under basal conditions and that elevation of ATP levels diverts a sub-population to recycling endosomes. This is the first report detailing endosome localization of Panx1 under basal conditions and the potential for ATP regulation of its surface expression. Given the ubiquitous expression profile of Panx1 and the importance of ATP signalling, these findings are of critical importance for understanding the role of Panx1 in health and disease.
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Chaiyadet S, Smout M, Johnson M, Whitchurch C, Turnbull L, Kaewkes S, Sotillo J, Loukas A, Sripa B. Excretory/secretory products of the carcinogenic liver fluke are endocytosed by human cholangiocytes and drive cell proliferation and IL6 production. Int J Parasitol 2015; 45:773-81. [PMID: 26187786 DOI: 10.1016/j.ijpara.2015.06.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 05/18/2015] [Accepted: 06/06/2015] [Indexed: 01/22/2023]
Abstract
Liver fluke infection caused by Opisthorchis viverrini remains a major public health problem in many parts of Asia including Thailand, Lao PDR, Vietnam and Cambodia, where there is a strikingly high incidence of cholangiocarcinoma (CCA - hepatic cancer of the bile duct epithelium). Among other factors, uptake of O. viverrini excretory/secretory products (OvES) by biliary epithelial cells has been postulated to be responsible for chronic inflammation and proliferation of cholangiocytes, but the mechanisms by which cells internalise O. viverrini excretory/secretory products are still unknown. Herein we incubated normal human cholangiocytes (H69), human cholangiocarcinoma cells (KKU-100, KKU-M156) and human colon cancer (Caco-2) cells with O. viverrini excretory/secretory products and analysed the effects of different endocytic inhibitors to address the mechanism of cellular uptake of ES proteins. Opisthorchis viverrini excretory/secretory products was internalised preferentially by liver cell lines, and most efficiently/rapidly by H69 cells. There was no evidence for trafficking of ES proteins to cholangiocyte organelles, and most of the fluorescence was detected in the cytoplasm. Pretreatment with clathrin inhibitors significantly reduced the uptake of O. viverrini excretory/secretory products, particularly by H69 cells. Opisthorchis viverrini excretory/secretory products induced proliferation of liver cells (H69 and CCA lines) but not intestinal (Caco-2) cells, and proliferation was blocked using inhibitors of the classical endocytic pathways (clathrin and caveolae). Opisthorchis viverrini excretory/secretory products drove IL6 secretion by H69 cells but not Caco-2 cells, and cytokine secretion was significantly reduced by endocytosis inhibitors. This the first known study to address the endocytosis of helminth ES proteins by host epithelial cells and sheds light on the pathways by which this parasite causes one of the most devastating forms of cancer in south-eastern Asia.
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Affiliation(s)
- Sujittra Chaiyadet
- Biomedical Sciences Program, Graduate School, Khon Kaen University, Khon Kaen, Thailand; Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Michael Smout
- Centre for Biodiscovery and Molecular Development of Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Michael Johnson
- Faculty of Science, University of Technology Sydney, Sydney, Australia
| | | | - Lynne Turnbull
- Faculty of Science, University of Technology Sydney, Sydney, Australia
| | - Sasithorn Kaewkes
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Javier Sotillo
- Centre for Biodiscovery and Molecular Development of Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Alex Loukas
- Centre for Biodiscovery and Molecular Development of Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Banchob Sripa
- Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
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Keswani RK, Lazebnik M, Pack DW. Intracellular trafficking of hybrid gene delivery vectors. J Control Release 2015; 207:120-30. [PMID: 25883029 DOI: 10.1016/j.jconrel.2015.04.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 04/10/2015] [Accepted: 04/11/2015] [Indexed: 10/23/2022]
Abstract
Viral and non-viral gene delivery vectors are in development for human gene therapy, but both exhibit disadvantages such as inadequate efficiency, lack of cell-specific targeting or safety concerns. We have recently reported the design of hybrid delivery vectors combining retrovirus-like particles with synthetic polymers or lipids that are efficient, provide sustained gene expression and are more stable compared to native retroviruses. To guide further development of this promising class of gene delivery vectors, we have investigated their mechanisms of intracellular trafficking. Moloney murine leukemia virus-like particles (M-VLPs) were complexed with chitosan (Chi) or liposomes (Lip) comprising DOTAP, DOPE and cholesterol to form the hybrid vectors (Chi/M-VLPs and Lip/M-VLPs, respectively). Transfection efficiency and cellular internalization of the vectors were quantified in the presence of a panel of inhibitors of various endocytic pathways. Intracellular transport and trafficking kinetics of the hybrid vectors were dependent on the synthetic component and used a combination of clathrin- and caveolar-dependent endocytosis and macropinocytosis. Chi/M-VLPs were slower to transfect compared to Lip/M-VLPs due to the delayed detachment of the synthetic component. The synthetic component of hybrid gene delivery vectors plays a significant role in their cellular interactions and processing and is a key parameter for the design of more efficient gene delivery vehicles.
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Affiliation(s)
- Rahul K Keswani
- Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 61801, USA
| | - Mihael Lazebnik
- Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 61801, USA
| | - Daniel W Pack
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, USA; Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40506, USA.
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Hwang ME, Keswani RK, Pack DW. Dependence of PEI and PAMAM Gene Delivery on Clathrin- and Caveolin-Dependent Trafficking Pathways. Pharm Res 2014; 32:2051-9. [PMID: 25511918 DOI: 10.1007/s11095-014-1598-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 12/05/2014] [Indexed: 11/29/2022]
Abstract
PURPOSE Non-viral gene delivery vehicles such as polyethylenimine and polyamidoamine dendrimer effectively condense plasmid DNA, facilitate endocytosis, and deliver nucleic acid cargo to the nucleus in vitro. Better understanding of intracellular trafficking mechanisms involved in polymeric gene delivery is a prerequisite to clinical application. This study investigates the role of clathrin and caveolin endocytic pathways in cellular uptake and subsequent vector processing. METHODS We formed 25-kD polyethylenimine (PEI) and generation 4 (G4) polyamidoamine (PAMAM) polyplexes at N/P 10 and evaluated internalization pathways and gene delivery in HeLa cells. Clathrin- and caveolin-dependent endocytosis inhibitors were used at varying concentrations to elucidate the roles of these important pathways. RESULTS PEI and PAMAM polyplexes were internalized by both pathways. However, the amount of polyplex internalized poorly correlated with transgene expression. While the caveolin-dependent pathway generally led to effective gene delivery with both polymers, complete inhibition of the clathrin-dependent pathway was also deleterious to transfection with PEI polyplexes. Inhibition of one endocytic pathway may lead to an overall increase in uptake via unaffected pathways, suggesting the existence of compensatory endocytic mechanisms. CONCLUSIONS The well-studied clathrin- and caveolin-dependent endocytosis pathways are not necessarily independent, and perturbing one mechanism of trafficking influences the larger trafficking network.
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Affiliation(s)
- Mark E Hwang
- Department of Bioengineering, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA
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Uribe KB, Martín C, Etxebarria A, González-Bullón D, Gómez-Bilbao G, Ostolaza H. Ca2+ influx and tyrosine kinases trigger Bordetella adenylate cyclase toxin (ACT) endocytosis. Cell physiology and expression of the CD11b/CD18 integrin major determinants of the entry route. PLoS One 2013; 8:e74248. [PMID: 24058533 PMCID: PMC3772820 DOI: 10.1371/journal.pone.0074248] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/31/2013] [Indexed: 12/12/2022] Open
Abstract
Humans infected with Bordetella pertussis, the whooping cough bacterium, show evidences of impaired host defenses. This pathogenic bacterium produces a unique adenylate cyclase toxin (ACT) which enters human phagocytes and catalyzes the unregulated formation of cAMP, hampering important bactericidal functions of these immune cells that eventually cause cell death by apoptosis and/or necrosis. Additionally, ACT permeabilizes cells through pore formation in the target cell membrane. Recently, we demonstrated that ACT is internalised into macrophages together with other membrane components, such as the integrin CD11b/CD18 (CR3), its receptor in these immune cells, and GM1. The goal of this study was to determine whether ACT uptake is restricted to receptor-bearing macrophages or on the contrary may also take place into cells devoid of receptor and gain more insights on the signalling involved. Here, we show that ACT is rapidly eliminated from the cell membrane of either CR3-positive as negative cells, though through different entry routes, which depends in part, on the target cell physiology and characteristics. ACT-induced Ca(2+) influx and activation of non-receptor Tyr kinases into the target cell appear to be common master denominators in the different endocytic strategies activated by this toxin. Very importantly, we show that, upon incubation with ACT, target cells are capable of repairing the cell membrane, which suggests the mounting of an anti-toxin cell repair-response, very likely involving the toxin elimination from the cell surface.
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Affiliation(s)
- Kepa B. Uribe
- Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, UPV/EHU, Bilbao, Spain
| | - César Martín
- Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, UPV/EHU, Bilbao, Spain
| | - Aitor Etxebarria
- Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, UPV/EHU, Bilbao, Spain
| | - David González-Bullón
- Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, UPV/EHU, Bilbao, Spain
| | - Geraxane Gómez-Bilbao
- Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, UPV/EHU, Bilbao, Spain
| | - Helena Ostolaza
- Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, UPV/EHU, Bilbao, Spain
- * E-mail:
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Nerve growth factor-induced endocytosis of TWIK-related acid-sensitive K+ 1 channels in adrenal medullary cells and PC12 cells. Pflugers Arch 2013; 465:1051-64. [DOI: 10.1007/s00424-013-1222-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/13/2013] [Accepted: 01/20/2013] [Indexed: 11/27/2022]
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Bachran D, Schneider S, Bachran C, Weng A, Melzig MF, Fuchs H. The endocytic uptake pathways of targeted toxins are influenced by synergistically acting Gypsophila saponins. Mol Pharm 2011; 8:2262-72. [PMID: 21981719 DOI: 10.1021/mp200130j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The expression of the epidermal growth factor (EGF) receptor is upregulated in many human tumors. We developed the targeted toxin SE, consisting of the plant toxin saporin-3 and human EGF. The cytotoxic effect of SE drastically increases in a synergistic manner by a combined treatment with Saponinum album (Spn), a saponin composite from Gypsophila paniculata L. Here we analyzed which endocytic pathways are involved in the uptake of SE and which are mandatory for the Spn-mediated enhancement. We treated HER14 cells (NIH-3T3 cells transfected with human EGF receptor) with either chlorpromazine, dynasore, latrunculin A, chloroquine, bafilomycin A1 or filipin and analyzed the effect on the cytotoxicity of SE alone or in combination with Spn. We demonstrated that SE in combination with Spn enters cells via clathrin- and actin-dependent pathways and the acidification of the endosomes after endocytosis is relevant for the cytotoxicity of SE. Notably, our data suggest that SE without Spn follows a different endocytic uptake pathway. SE cytotoxicity is independent of blocking of clathrin or actin, and the decrease in endosomal pH is irrelevant for SE cytotoxicity. Furthermore, Spn has no influence on the retrograde transport. This work is important for the better understanding of the underlying mechanism of Spn-enhanced cytotoxicity and helps to describe the role of Spn better.
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Affiliation(s)
- Diana Bachran
- Institut für Laboratoriumsmedizin, Klinische Chemie und Pathobiochemie, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany
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Wiranowska M, Colina LO, Johnson JO. Clathrin-mediated entry and cellular localization of chlorotoxin in human glioma. Cancer Cell Int 2011; 11:27. [PMID: 21838899 PMCID: PMC3204276 DOI: 10.1186/1475-2867-11-27] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2011] [Accepted: 08/12/2011] [Indexed: 12/20/2022] Open
Abstract
Background Chlorotoxin (TM601), a scorpion venom- derived 36-AA peptide, is an experimental drug against recurrent glioma with tumor specificity but unknown route of intracellular distribution. The aim of this study was to evaluate the route of entry and cellular localization of TM601 in glioma cells. Results We have found that in human gliomas, lung carcinoma and normal vascular endothelial cells, TM601 localizes near trans-Golgi while in normal human dermal fibroblasts (NHDF) and astrocytes it is dispersed in the cytoplasm. The uptake of TM601 by U373 glioma cells is rapid, concentration and time dependent, not affected by inhibitors such as filipin (caveolae-dependent endocytosis) and amiloride (non-selective macropinocytosis), but significantly affected by chlorpromazine (clathrin-dependent intracellular transport of coated pits) resulting in intracellular build-up of the drug and clathrin near the Golgi. In contrast, TM601 uptake by NHDF cells was significantly affected by amiloride indicating that macropinocytosis is the dominant uptake route of TM601 in these cells. Conclusions In conclusion, we found a distinct cellular localization pattern and uptake of TM601 by glioma cells differing from that found in normal cells. Further insight into the cellular processing of TM601 should assist in the development of effective anti-glioma therapeutic modalities.
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Affiliation(s)
- Marzenna Wiranowska
- Department Pathology & Cell Biology, College of Medicine, University of South Florida, Tampa FL, USA.
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Inhibition of fibroblast growth factor receptor 1 endocytosis promotes axonal branching of adult sensory neurons. Neuroscience 2011; 188:13-22. [PMID: 21575685 DOI: 10.1016/j.neuroscience.2011.04.064] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 04/26/2011] [Accepted: 04/27/2011] [Indexed: 01/21/2023]
Abstract
Fibroblast growth factors (FGFs) promote axon growth during development and regeneration of the nervous system. Among the four types of FGF receptors (FGFRs), FGFR1 is expressed in adult sensory neurons of dorsal root ganglia (DRG), and overexpression of FGFR1 promotes FGF-2-induced elongative axon growth in vitro. Ligand-induced activation of FGFR1 is followed by endocytosis and lysosomal degradation, which leads to the termination of receptor signaling. We previously reported that the lysosomal inhibitor leupeptin enhances FGF-2-induced elongative axon growth of adult DRG neurons overexpressing FGFR1. To better understand the role of subcellular localization of FGFR1 in axon growth, we analyzed the effects of inhibition of endocytosis of FGFR1 on FGF-2-induced neurite outgrowth in PC12 pheochromocytoma cells and adult DRG neurons. The endocytosis inhibitors methyl-β-cyclodextrin (MβCD) and chlorpromazine enhanced surface localization of FGFR1 in PC12 cells and DRG neurons. Furthermore, MβCD and chlorpromazine increased FGF-2-induced neurite outgrowth of PC12 cells and axonal branching of adult DRG neurons overexpressing FGFR1, whereas MβCD inhibited FGF-2-induced axonal elongation. Analysis of the signaling pathways involved in axon morphology revealed that FGF-2-induced phosphorylation of extracellular signal-regulated kinase (ERK) and Akt was increased by inhibition of FGFR1 endocytosis. Together, our results imply that inhibition of FGFR1 endocytosis by MβCD or chlorpromazine promotes FGF-2-induced axonal branching. The results of this study confirm that internalization of FGFR1 controls axon growth and morphology of adult sensory neurons via selective activation of intracellular signaling pathways.
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Deshpande CN, Harrop SJ, Boucher Y, Hassan KA, Leo RD, Xu X, Cui H, Savchenko A, Chang C, Labbate M, Paulsen IT, Stokes HW, Curmi PMG, Mabbutt BC. Crystal structure of an integron gene cassette-associated protein from Vibrio cholerae identifies a cationic drug-binding module. PLoS One 2011; 6:e16934. [PMID: 21390267 PMCID: PMC3048380 DOI: 10.1371/journal.pone.0016934] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 01/05/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The direct isolation of integron gene cassettes from cultivated and environmental microbial sources allows an assessment of the impact of the integron/gene cassette system on the emergence of new phenotypes, such as drug resistance or virulence. A structural approach is being exploited to investigate the modularity and function of novel integron gene cassettes. METHODOLOGY/PRINCIPAL FINDINGS We report the 1.8 Å crystal structure of Cass2, an integron-associated protein derived from an environmental V. cholerae. The structure defines a monomeric beta-barrel protein with a fold related to the effector-binding portion of AraC/XylS transcription activators. The closest homologs of Cass2 are multi-drug binding proteins, such as BmrR. Consistent with this, a binding pocket made up of hydrophobic residues and a single glutamate side chain is evident in Cass2, occupied in the crystal form by polyethylene glycol. Fluorescence assays demonstrate that Cass2 is capable of binding cationic drug compounds with submicromolar affinity. The Cass2 module possesses a protein interaction surface proximal to its drug-binding cavity with features homologous to those seen in multi-domain transcriptional regulators. CONCLUSIONS/SIGNIFICANCE Genetic analysis identifies Cass2 to be representative of a larger family of independent effector-binding proteins associated with lateral gene transfer within Vibrio and closely-related species. We propose that the Cass2 family not only has capacity to form functional transcription regulator complexes, but represents possible evolutionary precursors to multi-domain regulators associated with cationic drug compounds.
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Affiliation(s)
- Chandrika N. Deshpande
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Stephen J. Harrop
- School of Physics, University of New South Wales, Sydney, New South Wales, Australia
- St Vincent's Centre for Applied Medical Research, Sydney, New South Wales, Australia
| | - Yan Boucher
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Karl A. Hassan
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Rosa Di Leo
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada
| | - Xiaohui Xu
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada
| | - Hong Cui
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada
| | - Alexei Savchenko
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada
| | - Changsoo Chang
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada
| | - Maurizio Labbate
- Institute for the Biotechnology of Infectious Diseases, University of Technology, Sydney, New South Wales, Australia
| | - Ian T. Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - H. W. Stokes
- Institute for the Biotechnology of Infectious Diseases, University of Technology, Sydney, New South Wales, Australia
| | - Paul M. G. Curmi
- School of Physics, University of New South Wales, Sydney, New South Wales, Australia
- St Vincent's Centre for Applied Medical Research, Sydney, New South Wales, Australia
| | - Bridget C. Mabbutt
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
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Li RJ, Ying X, Zhang Y, Ju RJ, Wang XX, Yao HJ, Men Y, Tian W, Yu Y, Zhang L, Huang RJ, Lu WL. All-trans retinoic acid stealth liposomes prevent the relapse of breast cancer arising from the cancer stem cells. J Control Release 2011; 149:281-91. [DOI: 10.1016/j.jconrel.2010.10.019] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 09/01/2010] [Accepted: 10/14/2010] [Indexed: 12/21/2022]
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18
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Zhu D, Yao K, Bo J, Zhang H, Liu L, Dong X, Song L, Leng X. Hydrophilic/lipophilic N-methylene phosphonic chitosan as a promising non-viral vector for gene delivery. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2010; 21:223-229. [PMID: 19680604 DOI: 10.1007/s10856-009-3849-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 08/04/2009] [Indexed: 05/28/2023]
Abstract
Cationic amphiphilic drugs have recently been shown to inhibit receptor recycling by disrupting the assembly-disassembly of clathrin at the plasma membrane and endosomes. It is therefore proposed that amphiphilic and cationic polysaccharide macromolecule, when used as gene delivery vectors, may have potential ability to direct the disassembly process of cell membrane organization, and penetrate across the cell membrane into cell and nucleus. In the current study, N-methylene phosphonic chitosan (NMPCS), an amphiphilic macromolecule, was synthesized by incorporating the methylene phosphonic group into the amino groups of chitosan (CS) using formaldehyde as the coupling agent, and characterized with a FTIR spectrometer. NMPCS/DNA or CS/DNA complexes were prepared using a complex coacervation method, and characterized by agarose gel electrophoresis retardation assay and dynamic light scattering (DLS). MTT assay was employed to evaluate the cytotoxicity of the polymers and pGL3-control luciferase plasmid was utilized as a reporter gene to assess the transgenic efficacy of the polymers. It was demonstrated that NMPCS was able to fully entrap the DNA at N/P ratio of 2:1, whereas CS entrapped the DNA completely at N/P ratio of 1:1. DLS showed that the NMPCS/DNA or CS/DNA complexes were of mean diameters ranging from 110 to 180 nm. Neither NMPCS nor CS induced significant loss of cell viability at the concentrations ranging from 1 to 50 microg/ml, whereas PEI at 5 microg/ml started to result in significantly decreased cell viability. The expression of transgene mediated by NMPCS was much higher (more than 100-folds) than that mediated by CS, indicating that NMPCS was a more efficacious gene ferrying vector than CS.
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Affiliation(s)
- Dunwan Zhu
- Tianjin Key Laboratory of Biomedical Materials, Institute of Biomedical Engineering, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, China
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19
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Sohrab S, Petrusca DN, Lockett AD, Schweitzer KS, Rush NI, Gu Y, Kamocki K, Garrison J, Petrache I. Mechanism of alpha-1 antitrypsin endocytosis by lung endothelium. FASEB J 2009; 23:3149-58. [PMID: 19423638 PMCID: PMC2735364 DOI: 10.1096/fj.09-129304] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Accepted: 04/16/2009] [Indexed: 02/02/2023]
Abstract
The integrity of lung alveoli is maintained by proper circulating levels of alpha-1 antitrypsin (A1AT). Next to cigarette smoking, A1AT deficiency is a major risk factor for lung emphysema development. We recently reported that in addition to neutralizing neutrophil elastases in the extracellular compartment, A1AT is internalized by lung endothelial cells and inhibits apoptosis. We hypothesized that the intracellular uptake of A1AT by endothelial cells may be required for its protective function; therefore, we studied the mechanisms of A1AT internalization by primary rat lung microvascular endothelial cells and the effect of cigarette smoke on this process both in vitro and in vivo (in mice). Purified A1AT was taken up intracellularly by endothelial cells in a time-dependent, dose-dependent, and conformer-specific manner and was detected in the cytoplasm of endothelial cells of nondiseased human lung sections. Despite a critical role for caveoli in endothelial cell endocytosis in general, specific inhibition of clathrin-mediated, but not caveoli-mediated, endocytosis profoundly decreased A1AT internalization and reversed the A1AT's antiapoptotic action. Further more, A1AT associated with clathrin heavy chains, but not with caveolin-1 in the plasma membrane fraction of endothelial cells. Interestingly, cigarette smoke exposure significantly inhibited A1AT uptake both in endothelial cells and in the mouse lung and altered the intracellular distribution of clathrin heavy chains. Our results suggest that clathrin-mediated endocytosis regulates A1AT intracellular function in the lung endothelium and may be an important determinant of the serpin's protection against developing cigarette smoke-induced emphysema.
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Affiliation(s)
- Sadaf Sohrab
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Indiana University, Indianapolis, IN 46202, USA
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De Haan L, Hirst TR. Cholera toxin: A paradigm for multi-functional engagement of cellular mechanisms (Review). Mol Membr Biol 2009; 21:77-92. [PMID: 15204437 DOI: 10.1080/09687680410001663267] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Cholera toxin (Ctx) from Vibrio cholerae and its closely related homologue, heat-labile enterotoxin (Etx) from Escherichia coli have become superb tools for illuminating pathways of cellular trafficking and immune cell function. These bacterial protein toxins should be viewed as conglomerates of highly evolved, multi-functional elements equipped to engage the trafficking and signalling machineries of cells. Ctx and Etx are members of a larger family of A-B toxins of bacterial (and plant) origin that are comprised of structurally and functionally distinct enzymatically active A and receptor-binding B sub-units or domains. Intoxication of mammalian cells by Ctx and Etx involves B pentamer-mediated receptor binding and entry into a vesicular pathway, followed by translocation of the enzymatic A1 domain of the A sub-unit into the target cell cytosol, where covalent modification of intracellular targets leads to activation of adenylate cyclase and a sequence of events culminating in life-threatening diarrhoeal disease. Importantly, Ctx and Etx also have the capacity to induce a wide spectrum of remarkable immunological processes. With respect to the latter, it has been found that these toxins activate signalling pathways that modulate the immune system. This review explores the complexities of the cellular interactions that are engaged by these bacterial protein toxins, and highlights some of the new insights to have recently emerged.
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Affiliation(s)
- Lolke De Haan
- Department of Pathology and Microbiology, School of Medical Sciences, University of Bristol, United Kingdom
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21
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Moisescu MG, Leveque P, Verjus MA, Kovacs E, Mir LM. 900 MHz modulated electromagnetic fields accelerate the clathrin-mediated endocytosis pathway. Bioelectromagnetics 2009; 30:222-30. [DOI: 10.1002/bem.20463] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Eisenberg S, Giehl K, Henis YI, Ehrlich M. Differential interference of chlorpromazine with the membrane interactions of oncogenic K-Ras and its effects on cell growth. J Biol Chem 2008; 283:27279-88. [PMID: 18693247 DOI: 10.1074/jbc.m804589200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane anchorage of Ras proteins is important for their signaling and oncogenic potential. K-Ras4B (K-Ras), the Ras isoform most often mutated in human cancers, is the only Ras isoform where a polybasic motif contributes essential electrostatic interactions with the negatively charged cytoplasmic leaflet. Here we studied the effects of the cationic amphiphilic drug chlorpromazine (CPZ) on the membrane association of oncogenic K-Ras(G12V), cell proliferation, and apoptosis. Combining live cell microscopy, FRAP beam size analysis, and cell fractionation studies, we show that CPZ reduces the association of GFP-K-Ras(G12V) with the plasma membrane and increases its exchange between plasma membrane and cytoplasmic pools. These effects appear to depend on electrostatic interactions because the membrane association of another related protein that has a membrane-interacting polybasic cluster (Rac1(G12V)) was also affected, whereas that of H-Ras was not. The weakened association with the plasma membrane led to a higher fraction of GFP-K-Ras(G12V) in the cytoplasm and in internal membranes, accompanied by either cell cycle arrest (PANC-1 cells) or apoptosis (Rat-1 fibroblasts), the latter being in correlation with the targeting of K-Ras(G12V) to mitochondria. In accord with these results, CPZ compromised the transformed phenotype of PANC-1 cells, as indicated by inhibition of cell migration and growth in soft agar.
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Affiliation(s)
- Sharon Eisenberg
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Schumann M, Nakagawa T, Mantey SA, Howell B, Jensen RT. Function of non-visual arrestins in signaling and endocytosis of the gastrin-releasing peptide receptor (GRP receptor). Biochem Pharmacol 2008; 75:1170-85. [PMID: 18199425 PMCID: PMC2265779 DOI: 10.1016/j.bcp.2007.11.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 11/25/2007] [Accepted: 11/26/2007] [Indexed: 11/15/2022]
Abstract
Little is known about the role of arrestins in gastrointestinal hormone/neurotransmitter receptor endocytosis. With other G protein-coupled receptors, arrestins induce G protein-uncoupling and receptor endocytosis. In this study, we used arrestin wild-type and dominant-negative mutant constructs to analyze the arrestin dependence of endocytosis and desensitization of the gastrin-releasing peptide receptor (GRP-R). Co-expression of the GRP-R with wild-type arrestin2 and arrestin3 increased not only GRP-R endocytosis but also GRP-R desensitization in arrestin-overexpressing cells. Co-expression of the dominant-negative mutants V53D-arrestin2 or V54D-arrestin3 reduced GRP-R endocytosis. Notably, different trafficking routes for agonist-activated GRP-R-arrestin2 and GRP-R-arrestin3 complexes were found. Arrestin3 internalizes with GRP-R to intracellular vesicles, arrestin2 splits from the GRP-R and localizes to the cell membrane. Also, the recycling pathway of the GRP-R was different if co-expressed with arrestin2 or arrestin3. Using different GRP-R mutants, the C-terminus and the 2nd intracellular loop of the GRP-R were found to be important for the GRP-R-arrestin interaction and for the difference in GRP receptor trafficking with the two arrestin subtypes. Our results show that both non-visual arrestins play an important role in GRP-R internalization and desensitization.
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Affiliation(s)
- Michael Schumann
- Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1804, USA.
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Abstract
Excitatory synapses in the mammalian brain contain two types of ligand-gated ion channels: AMPA receptors (AMPARs) and NMDA receptors (NMDARs). AMPARs are responsible for generating excitatory synaptic responses, whereas NMDAR activation triggers long-lasting changes in these responses by modulating the trafficking of AMPARs toward and away from synapses. AMPARs are tetramers composed of four subunits (GluR1-GluR4), which current models suggest govern distinct AMPAR trafficking behavior during synaptic plasticity. Here, we address the roles of GluR2 and GluR3 in controlling the recycling- and activity-dependent endocytosis of AMPARs by using cultured hippocampal neurons prepared from knockout (KO) mice lacking these subunits. We find that synapses and dendritic spines form normally in cells lacking GluR2/3 and that upon NMDAR activation, GluR2/3-lacking AMPARs are endocytosed in a manner indistinguishable from GluR2-containing AMPARs in wild-type (WT) neurons. AMPARs lacking GluR2/3 also recycle to the plasma membrane identically to WT AMPARs. However, because of their permeability to calcium, GluR2-lacking but not WT AMPARs exhibited robust internalization throughout the dendritic tree in response to AMPA application. Dendritic endocytosis of AMPARs also was observed in GABAergic neurons, which express a high proportion of GluR2-lacking AMPARs. These results demonstrate that GluR2 and GluR3 are not required for activity-dependent endocytosis of AMPARs and suggest that the most important property of GluR2 in the context of AMPAR trafficking may be its influence on calcium permeability.
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Bengali Z, Rea JC, Shea LD. Gene expression and internalization following vector adsorption to immobilized proteins: dependence on protein identity and density. J Gene Med 2007; 9:668-78. [PMID: 17533618 PMCID: PMC2659664 DOI: 10.1002/jgm.1058] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Gene delivery by non-specific adsorption of non-viral vectors to protein-coated surfaces can reduce the amount of DNA required, and also increase transgene expression and the number of cells expressing the transgene. The protein on the surface mediates cell adhesion and vector immobilization, and functions to colocalize the two to enhance gene delivery. This report investigates the mechanism and specificity by which the protein coating enhances gene transfer, and determines if the protein coating targets the vector for internalization by a specific pathway. METHODS Proteins (FBS, BSA, fibronectin, collagen I, and laminin) were dried onto culture dishes, followed by PEI/DNA complex adsorption for surface delivery. Reporter genes were employed to characterize transfection as a function of the protein identity and density. Vector immobilization was measured using radiolabeled plasmid, and internalization was quantified in the presence and absence of the endocytosis inhibitors chlorpromazine and genistein. RESULTS Fibronectin coating yielded the greatest expression for PEI/DNA polyplexes, with maximal expression at intermediate protein densities. Expression in control studies with bolus delivery was independent of the protein identity. Substrate binding was independent of the protein identity; however, internalization was greatest on surfaces coated with fibronectin and collagen I. Inhibition of caveolae-mediated endocytosis reduced gene expression more than clathrin-mediated endocytosis. Similarly, inhibition of caveolae-mediated endocytosis significantly reduced the intracellular levels of DNA. CONCLUSIONS Fibronectin at intermediate densities mediated the highest levels of transgene expression, potentially by targeting internalization through caveolae-mediated endocytosis. Substrate modifications, such as the identity and density of proteins, provide an opportunity for modification of biomaterials for enhancing gene expression.
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Affiliation(s)
- Zain Bengali
- Department of Interdepartmental Biological Sciences, Northwestern University, 2145 Sheridan Rd E156, Evanston, IL 60208-3120, USA
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd E156, Evanston, IL 60208-3120, USA
| | - Jennifer C. Rea
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd E156, Evanston, IL 60208-3120, USA
| | - Lonnie D. Shea
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd E156, Evanston, IL 60208-3120, USA
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd E156, Evanston, IL 60208-3120, USA
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL 60611
- Correspondence to: Lonnie D. Shea, Northwestern University, Department of Chemical Engineering, 2145 Sheridan Rd./E156, Evanston, IL 60208-3120, USA. E-mail:
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Regulation of sodium pump endocytosis by cardiotonic steroids: Molecular mechanisms and physiological implications. ACTA ACUST UNITED AC 2007; 14:171-81. [PMID: 17961998 DOI: 10.1016/j.pathophys.2007.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have previously shown that ouabain and other cardiotonic steroids interact with the plasmalemmal Na/K-ATPase and cause a time and dose dependent endocytosis of the Na/K-ATPase. This endocytosis is demonstrable using fluorescence imaging as well as conventional biochemical and biophysical cell separation methods. In proximal tubule cells, this process appears to regulate the density of basolateral Na/K-ATPase expression directly as well as indirectly modulate transepithelial sodium transport. Work with genetic manipulations, as well as pharmacological agents with cell culture models, have demonstrated that the cardiotonic steroid stimulated endocytosis of the plasmalemmal Na/K-ATPase requires caveolin and clathrin as well as the activation of c-Src, transactivation of the EGFR and activation of PI3K. Interestingly c-Src, EGFR and ERK1/2 all appear to be endocytosed along with the plasmalemmal Na/K-ATPase. These observations suggest a close analogy between a subset of plasmalemmal Na/K-ATPase and signaling companions with conventional receptor tyrosine kinases. While further studies are necessary to delineate the role of this endocytosis in the generation as well as the limit of signal transduction through the Na/K-ATPase signal cascade, we propose that it has an important role in the regulation of renal sodium handling as well as other important processes.
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Feofanov A, Sharonov G, Grichine A, Karmakova T, Pljutinskaya A, Lebedeva V, Ruziyev R, Yakubovskaya R, Mironov A, Refregier M, Maurizot JC, Vigny P. Comparative Study of Photodynamic Properties of 13, 15-N-cycloimide Derivatives of chlorin p6¶. Photochem Photobiol 2007. [DOI: 10.1111/j.1751-1097.2004.tb00007.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Kessler CB, Delany AM. Increased Notch 1 expression and attenuated stimulatory G protein coupling to adenylyl cyclase in osteonectin-null osteoblasts. Endocrinology 2007; 148:1666-74. [PMID: 17218421 DOI: 10.1210/en.2006-0443] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Osteonectin, or secreted protein acidic and rich in cysteine, is one of the most abundant noncollagen matrix components in bone. This matricellular protein regulates extracellular matrix assembly and maturation in addition to modulating cell behavior. Mice lacking osteonectin develop severe low-turnover osteopenia, and in vitro studies of osteonectin-null osteoblastic cells showed that osteonectin supports osteoblast formation, maturation, and survival. The present studies demonstrate that osteonectin-null osteoblastic cells have increased expression of Notch 1, a well-documented regulator of cell fate in multiple systems. Furthermore, osteonectin-null cells are more plastic and less committed to osteoblastic differentiation, able to pursue adipogenic differentiation given the appropriate signals. Notch 1 transcripts are down-regulated by inducers of cAMP in both wild-type and osteonectin-null osteoblasts, suggesting that the mutant osteoblasts may have a defect in generation of cAMP in response to stimuli. Indeed, many bone anabolic agents signal through increased cAMP. Wild-type and osteonectin-null osteoblasts generated comparable amounts of cAMP in response to forskolin, a direct stimulator of adenylyl cyclase. However, the ability of osteonectin-null osteoblasts to generate cAMP in response to cholera toxin, a direct stimulator of Gs, was attenuated. These data imply that osteonectin-null osteoblasts have decreased coupling of Gs to adenylyl cyclase. Because osteonectin promotes G protein coupling to an effector, our studies support the concept that low-turnover osteopenia can result from reducing G protein coupled receptor activity.
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Affiliation(s)
- Catherine B Kessler
- Center for Molecular Medicine, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06030, USA
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Chu H, Lee JH, Han SH, Kim SY, Cho NH, Kim IS, Choi MS. Exploitation of the endocytic pathway by Orientia tsutsugamushi in nonprofessional phagocytes. Infect Immun 2006; 74:4246-53. [PMID: 16790799 PMCID: PMC1489698 DOI: 10.1128/iai.01620-05] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Orientia tsutsugamushi, a causative agent of scrub typhus, is an obligate intracellular bacterium that requires the exploitation of the endocytic pathway in the host cell. We observed the localization of O. tsutsugamushi with clathrin or adaptor protein 2 within 30 min after the infection of nonprofessional phagocytes. We have further confirmed that the infectivity of O. tsutsugamushi is significantly reduced by drugs that block clathrin-mediated endocytosis but not by filipin III, an inhibitor that blocks caveola-mediated endocytosis. In the present study, with a confocal microscope, O. tsutsugamushi was sequentially colocalized with the early and late endosomal markers EEA1 and LAMP2, respectively, within 1 h after infection. The colocalization of O. tsutsugamushi organisms with EEA1 and LAMP2 gradually disappeared until 2 h postinfection, and then free O. tsutsugamushi organisms were found in the cytoplasm. When the acidification of endocytic vesicles was blocked by treating the cells with NH(4)Cl or bafilomycin A, the escape of O. tsutsugamushi organisms from the endocytic pathway was severely impaired, and the infectivity of O. tsutsugamushi was drastically reduced. To our knowledge, this is the first report that the invasion of O. tsutsugamushi is dependent on the clathrin-dependent endocytic pathway and the acidification process of the endocytic vesicles in nonprofessional phagocytes.
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Affiliation(s)
- Hyuk Chu
- Department of Microbiology and Immunology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
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Koh CHV, Cheung NS. Cellular mechanism of U18666A-mediated apoptosis in cultured murine cortical neurons: bridging Niemann-Pick disease type C and Alzheimer's disease. Cell Signal 2006; 18:1844-53. [PMID: 16797161 DOI: 10.1016/j.cellsig.2006.04.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 04/28/2006] [Indexed: 10/24/2022]
Abstract
Neuronal cell death can occur by means of either necrosis or apoptosis. Both necrosis and apoptosis are generally believed to be distinct mechanisms of cell death with different characteristic features distinguished on the basis of their morphological and biochemical properties. The brain is the most cholesterol-rich organ in the body but not much is known about the mechanisms that regulate cholesterol homeostasis in the brain. Recently, several clinical and biochemical studies suggest that cholesterol imbalance in the brain may be a risk factor related to the development of neurological disorders such as Niemann-Pick disease type C (NPC) and Alzheimer's disease (AD). NPC is a fatal juvenile neurodegenerative disorder characterized by premature neuronal death and somatically altered cholesterol metabolism. The main biochemical manifestation in NPC is elevated intracellular accumulation of free cholesterol caused by a genetic deficit in cholesterol trafficking. The pharmacological agent, U18666A (3-beta-[2-(diethylamino)ethoxy]androst-5-en-17-one), is a well-known class-2 amphiphile which inhibits cholesterol transport. Cells treated with this agent accumulate intracellular cholesterol to massive levels, similar to that observed in cells from NPC patients. NPC and AD have some pathological similarities which may share a common underlying cause. AD is one of the most common types of dementia affecting the elderly. However, the molecular mechanisms of neurodegeneration in NPC and AD are largely unknown. This review provides a consolidation of work done using U18666A in the past half century and focuses on the implications of our research findings on the mechanism of U18666A-mediated neuronal apoptosis in primary cortical neurons, which may provide an insight to elucidate the mechanisms of neurodegenerative diseases, particularly NPC and AD, where apoptosis might occur through a similar mechanism.
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Affiliation(s)
- Chor Hui Vivien Koh
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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31
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Aleksandrov DA, Zagryagskaya AN, Pushkareva MA, Bachschmid M, Peters-Golden M, Werz O, Steinhilber D, Sud'ina GF. Cholesterol and its anionic derivatives inhibit 5-lipoxygenase activation in polymorphonuclear leukocytes and MonoMac6 cells. FEBS J 2006; 273:548-57. [PMID: 16420478 DOI: 10.1111/j.1742-4658.2005.05087.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
5-Lipoxygenase (5-LO) is the key enzyme in the biosynthesis of leukotrienes (LTs), biological mediators of host defense reactions and of inflammatory diseases. While the role of membrane binding in the regulation of 5-LO activity is well established, the effects of lipids on cellular activity when added to the medium has not been characterized. Here, we show such a novel function of the most abundant sulfated sterol in human blood, cholesterol sulfate (CS), to suppress LT production in human polymorphonuclear leukocytes (PMNL) and Mono Mac6 cells. We synthesized another anionic lipid, cholesterol phosphate, which demonstrated a similar capacity in suppression of LT synthesis in PMNL. Cholesteryl acetate was without effect. Cholesterol increased the effect of CS on 5-LO product synthesis. CS and cholesterol also inhibited arachidonic acid (AA) release from PMNL. Addition of exogenous AA increased the threshold concentration of CS required to inhibit LT synthesis. The effect of cholesterol and its anionic derivatives can arise from remodeling of the cell membrane, which interferes with 5-LO activation. The fact that cellular LT production is regulated by sulfated cholesterol highlights a possible regulatory role of sulfotransferases/sulfatases in 5-LO product synthesis.
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Affiliation(s)
- Dmitry A Aleksandrov
- A.N. Belozersky Institute of Physicochemical Biology, Moscow State University, Russia
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32
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Shuto T, Kato K, Mori Y, Viriyakosol S, Oba M, Furuta T, Okiyoneda T, Arima H, Suico MA, Kai H. Membrane-anchored CD14 is required for LPS-induced TLR4 endocytosis in TLR4/MD-2/CD14 overexpressing CHO cells. Biochem Biophys Res Commun 2005; 338:1402-9. [PMID: 16263085 DOI: 10.1016/j.bbrc.2005.10.102] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Accepted: 10/16/2005] [Indexed: 10/25/2022]
Abstract
Lipopolysaccharide (LPS) induces inflammatory activation through TLR4 (toll-like receptor-4)/MD-2 (myeloid differentiation-2)/CD14 (cluster of differentiation-14) complex. Although optimal LPS signaling is required to activate our innate immune systems against gram-negative bacterium, excessive amount of LPS signaling develops a detrimental inflammatory response in gram-negative bacterial infections. Downregulation of surface TLR4 expression is one of the critical mechanisms that can restrict LPS signaling. Here, we found that membrane-anchored CD14 is required for LPS-induced downregulation of TLR4 and MD-2 in CHO cells. Moreover, pretreatment of the cells with sterol-binding agent filipin reduced LPS-induced TLR4 downregulation, suggesting the involvement of caveolae-mediated endocytosis pathway. Involvement of caveolae in LPS-induced TLR4 endocytosis was further confirmed by immunoprecipitation. Thus, our data indicate that caveolae-dependent endocytosis pathway is involved in LPS-induced TLR4 downregulation and that this is dependent on membrane-anchored CD14 expression.
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Affiliation(s)
- Tsuyoshi Shuto
- Department of Molecular Medicine, Kumamoto University, Kumamoto 862-0973, Japan
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33
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Inal J, Miot S, Schifferli JA. The complement inhibitor, CRIT, undergoes clathrin-dependent endocytosis. Exp Cell Res 2005; 310:54-65. [PMID: 16112669 DOI: 10.1016/j.yexcr.2005.07.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 07/07/2005] [Accepted: 07/07/2005] [Indexed: 01/22/2023]
Abstract
Complement C2 receptor inhibitor trispanning (CRIT) is a receptor for the second component of complement and is found in various tissues and hemopoietic cells. On binding to CRIT, C2 cannot be activated to potentially form a variant-C3 convertase as it is rendered non-cleavable by C1s. CRIT thus limits the amount of C3 convertase formed on the cell surface. In this study we have shown, using flow cytometry and immunofluorescence microscopy, that human CRIT undergoes endocytosis from the plasma membrane. The endocytosis, possibly ligand mediated, occurs via clathrin-coated pits as it can be inhibited by prior incubation of cells in hypertonic medium or with chlorpromazine, at 37 degrees C. However, inhibition of endocytosis was not possible after treatment with nystatin, or filipin, inhibitors of caveolae/raft-dependent endocytosis. In the presence of C2 alone, CRIT associates with the adapter protein, beta-arrestin-2, and whether in association with C2 or not, then appears in the perinuclear region, but does not appear to be translocated into the nucleus. Apart from the C3aR and C5aR that internalize the anaphylatoxic peptides, this is the first report of the internalization via the clathrin pathway of a receptor for a complement serum protein.
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Affiliation(s)
- Jameel Inal
- University Hospital Basel, Immunonephrology, Department of Research, 4031 Basel, Switzerland.
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Moody TW, Fuselier J, Coy DH, Mantey S, Pradhan T, Nakagawa T, Jensen RT. Camptothecin-somatostatin conjugates inhibit the growth of small cell lung cancer cells. Peptides 2005; 26:1560-6. [PMID: 16112393 DOI: 10.1016/j.peptides.2005.02.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Revised: 02/22/2005] [Accepted: 02/23/2005] [Indexed: 11/20/2022]
Abstract
The effects of camptothecin-somatostatin (CPT-SS) conjugates were investigated on small cell lung cancer (SCLC) cells. CPT was coupled to a SS agonist (SSA), c(Cys-Phe-DTrp-Lys-Thr-Cys)Thr-NH2 using the built in nucleophile assisted-releasing group (L1) N-methyl-aminoethyl-Gly-Dser-Nle-Dtyr-Dser or (L2) aminoethyl-Gly-Dser-Nle-Dtyr-Dser. The resulting CPT-L1-SSA and CPT-L2-SSA inhibited the specific binding of [125I-Tyr11]SS to NCI-H69 cell membranes with IC50 values of 0.2 and 2.1 nM, respectively. [125I]CPT-L1-SSA was internalized by SCLC cells at 37 degrees C but not at 4 degrees C. CPT-L1-SSA and CPT-L2-SSA inhibited in a dose-dependent manner the increase in adenylylcyclase activity caused by 25 microM forskolin. In vitro, 0.3 microM CPT-L1-SSA half-maximally inhibited the clonal growth of SCLC cells and 1 microM CPT-L1-SSA strongly inhibited 3H-thymidine incorporation into DNA and trypan-blue exclusion. These results suggest that CPT conjugated peptides such as CPT-L1-SSA may prove useful for exploring the efficacy of receptor-directed cytotoxicity to inhibit the proliferation of SCLC cells.
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Affiliation(s)
- Terry W Moody
- DHHS, NIH, NCI Office of the Director, CCR, 31 Center Drive, Bethesda, MD 20892, USA.
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35
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Yamada T, Fialho AM, Punj V, Bratescu L, Gupta TKD, Chakrabarty AM. Internalization of bacterial redox protein azurin in mammalian cells: entry domain and specificity. Cell Microbiol 2005; 7:1418-31. [PMID: 16153242 DOI: 10.1111/j.1462-5822.2005.00567.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Azurin is a member of a group of copper-containing redox proteins called cupredoxins. Different cupredoxins are produced by different aerobic bacteria as agents of electron transfer. Recently, we demonstrated that azurin enters into J774 and several types of cancer cells leading to the induction of apoptosis. We now demonstrate that azurin is internalized in J774 or cancer cells in a temperature-dependent manner. Azurin shows preferential entry into cancer compared with normal cells. An 28-amino-acid fragment of azurin fused to glutathione S-transferase (GST) or the green fluorescent protein (GFP), which are incapable of entering mammalian cells by themselves, can be internalized in J774 or human melanoma or breast cancer cells at 37 degrees C, but not at 4 degrees C. Competition experiments as well as studies with inhibitors such as cytochalasin D suggest that azurin may enter cells, at least in part, by a receptor-mediated endocytic process. The 28-amino-acid peptide therefore acts as a potential protein transduction domain (PTD), and can be used as a vehicle to transport cargo proteins such as GST and GST-GFP fusion proteins. Another member of the cupredoxin family, rusticyanin, that has also been shown to enter J774 and human cancer cells and exert cytotoxicity, does not demonstrate preferential entry for cancer cells and lacks the structural features characteristic of the azurin PTD.
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Affiliation(s)
- Tohru Yamada
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, 60612, USA
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36
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Massol RH, Larsen JE, Fujinaga Y, Lencer WI, Kirchhausen T. Cholera toxin toxicity does not require functional Arf6- and dynamin-dependent endocytic pathways. Mol Biol Cell 2004; 15:3631-41. [PMID: 15146065 PMCID: PMC491824 DOI: 10.1091/mbc.e04-04-0283] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cholera toxin (CT) and related AB(5) toxins bind to glycolipids at the plasma membrane and are then transported in a retrograde manner, first to the Golgi and then to the endoplasmic reticulum (ER). In the ER, the catalytic subunit of CT is translocated into the cytosol, resulting in toxicity. Using fluorescence microscopy, we found that CT is internalized by multiple endocytic pathways. Inhibition of the clathrin-, caveolin-, or Arf6-dependent pathways by overexpression of appropriate dominant mutants had no effect on retrograde traffic of CT to the Golgi and ER, and it did not affect CT toxicity. Unexpectedly, when we blocked all three endocytic pathways at once, although fluorescent CT in the Golgi and ER became undetectable, CT-induced toxicity was largely unaffected. These results are consistent with the existence of an additional retrograde pathway used by CT to reach the ER.
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Affiliation(s)
- Ramiro H Massol
- Department of Cell Biology, Harvard Medical School and The Center for Blood Research for Biomedical Research, Boston, Massachusetts 02115, USA
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Cheung NS, Koh CHV, Bay BH, Qi RZ, Choy MS, Li QT, Wong KP, Whiteman M. Chronic exposure to U18666A induces apoptosis in cultured murine cortical neurons. Biochem Biophys Res Commun 2004; 315:408-17. [PMID: 14766223 DOI: 10.1016/j.bbrc.2004.01.066] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2004] [Indexed: 12/01/2022]
Abstract
Niemann-Pick disease type C (NPC) is a juvenile neurodegenerative disorder characterized by premature neuronal loss and altered cholesterol metabolism. Previous reports applying an 8-h exposure of U18666A, a cholesterol transport-inhibiting agent, demonstrated a dose-dependent reduction in beta-amyloid (Abeta) deposition and secretion in cortical neurons, with no significant cell injury. In the current study, we examined the chronic effect of 24-72h of U18666A treatment on primary cortical neurons and several cell lines. Our results showed caspase-3 activation and cellular injury in U18666A-treated cortical neurons but not in the cell lines, suggesting cell death by apoptosis only occurred in cortical neurons after chronic exposure to U18666A. We also demonstrated through filipin staining the accumulation of intracellular cholesterol in cortical neurons treated with U18666A, indicating the phenotypic mimic of NPC by U18666A. However, additions of 10 and 25microM pravastatin with 0.5microg/ml U18666A significantly attenuated toxicity. Taken together, these data showed for the first time that U18666A induces cell death by apoptosis and suggested an important in vitro model system to study NPC.
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Affiliation(s)
- Nam Sang Cheung
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.
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38
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Feofanov A, Sharonov G, Grichine A, Karmakova T, Pljutinskaya A, Lebedeva V, Ruziyev R, Yakubovskaya R, Mironov A, Refregier M, Maurizot JC, Vigny P. Comparative Study of Photodynamic Properties of 13,15-N-cycloimide Derivatives of Chlorin p6¶. Photochem Photobiol 2004; 79:172-88. [PMID: 15068030 DOI: 10.1562/0031-8655(2004)079<0172:csoppo>2.0.co;2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Comparative study of 13,15-[N-(2-hydroxyethyl)]cycloimide chlorin p6 (2), 13,15-(N-acetoxy)cycloimide chlorin p6 (3), 13,15-(N-hydroxy)cycloimide chlorin p6 methyl ester (4) and 13,15-(N-methoxy)cycloimide chlorin p6 methyl ester (5) together with the previously investigated 13,15-[N-(3-hydroxypropyl)]cycloimide chlorin p6 (1) was performed. The dependence of the key photodynamic properties of 1-5 on the introduced substituents was analyzed. The photoinduced cell-killing activity of 4 is 100- and 280-fold higher than that of chlorin p6 and Photogem, respectively, as estimated on A549 human lung adenocarcinoma cells. The activity is reduced eight times in the order 4 > 5 > 1 > 2 > 3. The intracellular accumulation of 1-5 occurs in cytoplasm in a monomeric form bound to the lipids of cellular membranes. This form of 1, 2, 3, 4 and 5 is characterized by the high quantum yield of singlet oxygen generation, which depends on the introduced substituents, 0.66, 0.59, 0.35, 0.51 and 0.73, respectively. The photostability is two-fold less for 1 and four-fold less for 2, 3 and 5 than for 4. The rates of cellular uptake and efflux of 1-5 vary widely, thus providing the way to optimize the pharmacological properties of the photosensitizer (PS) using the respective substituents. Modifying the substituents, 1-5 were targeted to different cellular organelles. The enhanced accumulation in the Golgi apparatus and mitochondria complemented with diffuse staining of intracellular membranous structures is a property of 1-4. Compound 5 accumulates selectively in the lipid droplets and stains weakly perinuclear structures. Temperature-sensitive mechanisms of transport are responsible for the 1-4 uptake. Diffusion can play a role in the internalization of 5 but not of 1-4. Endocytosis via caveolae, clathrin-dependent and adenosine triphosphate-dependent pathways are not noticeably involved in the 1-5 internalization. Independently from their intracellular localization 1, 4 and 5 are highly efficient near-IR PS, which induce predominantly an apoptotic type of cell death under conditions providing ca 50% level of phototoxicity and necrosis at the 100% level of phototoxicity.
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Affiliation(s)
- Alexei Feofanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
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Delcroix JD, Valletta J, Wu C, Howe CL, Lai CF, Cooper JD, Belichenko PV, Salehi A, Mobley WC. Trafficking the NGF signal: implications for normal and degenerating neurons. PROGRESS IN BRAIN RESEARCH 2004; 146:3-23. [PMID: 14699953 DOI: 10.1016/s0079-6123(03)46001-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nerve growth factor (NGF) activates TrkA to trigger signaling events that promote the survival, differentiation and maintenance of neurons. The mechanism(s) that controls the retrograde transport of the NGF signal from axon terminals to neuron cell bodies is not known. The 'signaling endosome' hypothesis stipulates that NGF, TrkA and signaling proteins are retrogradely transported on endocytic vesicles. Here, we provide evidence for the existence of signaling endosomes. Following NGF treatment, clathrin-coated vesicles (CCVs) contain NGF bound to TrkA together with activated signaling proteins of the Ras/pErk1/2 pathway. NGF signals from isolated CCVs through the Erk1/2 pathway. Early endosomes appear to represent a second type of signaling endosomes. We found that NGF induced a sustained activation of Rap1, a small monomeric GTP-binding protein of the Ras family, and that this activation occurred in early endosomes that contain key elements of Rap1/pErk1/2 pathway. We discuss the possibility that the failure of retrograde NGF signaling in a mouse model of Down syndrome (Ts65Dn) may be due to the failure to retrograde transport signaling endosomes. It is important to define further the significance of signaling endosomes in the biology of both normal and degenerating neurons.
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Affiliation(s)
- Jean-Dominique Delcroix
- Department of Neurology and Neurological Sciences and of Pediatrics, Program in Neuroscience, Stanford University, Stanford, CA 94305, USA
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40
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Husain M, Moss B. Intracellular trafficking of a palmitoylated membrane-associated protein component of enveloped vaccinia virus. J Virol 2003; 77:9008-19. [PMID: 12885917 PMCID: PMC167247 DOI: 10.1128/jvi.77.16.9008-9019.2003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The F13L protein of vaccinia virus, an essential and abundant palmitoylated peripheral membrane component of intra- and extracellular enveloped virions, associates with Golgi, endosomal, and plasma membranes in the presence or absence of other viral proteins. In the present study, the trafficking of a fully functional F13L-green fluorescent protein (GFP) chimera in transfected and productively infected cells was analyzed using specific markers and inhibitors. We found that Sar1(H79G), a trans-dominant-negative protein inhibitor of cargo transport from the endoplasmic reticulum, had no apparent effect on the intracellular distribution of F13L-GFP, suggesting that the initial membrane localization occurs at a downstream compartment of the secretory pathway. Recycling of F13L-GFP from the plasma membrane was demonstrated by partial colocalization with FM4-64, a fluorescent membrane marker of endocytosis. Punctate F13L-GFP fluorescence overlapped with clathrin and Texas red-conjugated transferrin, suggesting that endocytosis occurred via clathrin-coated pits. The inhibitory effects of chlorpromazine and trans-dominant-negative forms of dynamin and Eps15 protein on the recycling of F13L-GFP provided further evidence for clathrin-mediated endocytosis. In addition, the F13L protein was specifically coimmunoprecipitated with alpha-adaptin, a component of the AP-2 complex that interacts with Eps15. Nocodazole and wortmannin perturbed the intracellular trafficking of F13L-GFP, consistent with its entry into late and early endosomes through the secretory and endocytic pathways, respectively. The recycling pathway described here provides a mechanism for the reutilization of the F13L protein following its deposition in the plasma membrane during the exocytosis of enveloped virions.
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Affiliation(s)
- Matloob Husain
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0445, USA
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41
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Hall AM, Krishnamoorthy L, Orlow SJ. Accumulation of tyrosinase in the endolysosomal compartment is induced by U18666A. PIGMENT CELL RESEARCH 2003; 16:149-58. [PMID: 12622792 DOI: 10.1034/j.1600-0749.2003.00027.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The 3beta-(2-diethylaminoethoxy)-androstenone HCl (U18666A), progesterone and several cationic amphiphilic drugs have been shown to alter the trafficking of a number of intracellular membrane proteins including CD63/Lamp-3, insulin growth factor 2/mannose 6-phosphate receptor (IGF2/MPR), and the Niemann-Pick C1 gene product (NPC1) as well as ganglioside GM1. We have examined the effects of these compounds on cultured melanocytes at concentrations that have been shown to effectively alter intracellular trafficking. Treatment of melanocytes with U18666A (2.5 micro M) or progesterone (15 micro M) for 96 h decreased melanin content an average of 67% as compared with control without lowering the total cellular tyrosinase activity. Steroidal alkaloids that preferentially act on the Sonic Hedgehog signaling pathway showed no related specificity in their ability to decrease pigmentation. In melanocytes treated with U18666A, tyrosinase accumulates in a compartment that contains both lysosome-associated membrane protein-1 (Lamp 1) and MPR, and stains with filipin, consistent with cholesterol-laden late endosomes/lysosomes. Our results suggest that tyrosinase, like the NPC1 gene product, traverses a U18666A-sensitive trafficking pathway.
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Affiliation(s)
- Andrea M Hall
- The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, NY, USA
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42
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Mahmutefendić H, Kucić N, Lucin P. Distinct pathways for constitutive endocytosis of fully conformed and non-conformed L(d) molecules. Am J Reprod Immunol 2002; 48:87-95. [PMID: 12389597 DOI: 10.1034/j.1600-0897.2002.01134.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
PROBLEM To characterize the constitutive internalization of major histocompatibility complex (MHC) class I molecules, we have studied the expression of completely conformed (full) and unconformed (empty) L(d) molecules on non-polarized murine P815 cells. METHODS OF STUDY Spontaneous endocytosis of L(d) molecules was induced by cycloheximide, an inhibitor of protein synthesis, and their disappearance from the cell surface was determined by flow cytometry. In order to investigate the mechanism of internalization, a palette of inhibitors of endocytosis and vesicular transport was used. RESULTS Inhibitors of clathrine endocytosis did not influence the internalization of L(d) molecules. Inhibitors of caveolar endocytosis and inhibitors of endolysosomal degradation prevented down-regulation of empty, but not of full L(d) molecules. CONCLUSIONS Empty L(d) molecules are internalized mostly by caveolar endocytosis and full L(d) molecules use a different pathway, neither clathrine-mediated nor caveolar. After internalization, full L(d) molecules are probably degraded and empty L(d) molecules recycle between endosomal compartment and the cell surface before they enter into the degradation compartment.
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Affiliation(s)
- Hana Mahmutefendić
- Department of Physiology and Immunology, Medical Faculty, University of Rijeka, Croatia
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43
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Marella M, Lehmann S, Grassi J, Chabry J. Filipin prevents pathological prion protein accumulation by reducing endocytosis and inducing cellular PrP release. J Biol Chem 2002; 277:25457-64. [PMID: 11994310 DOI: 10.1074/jbc.m203248200] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Conversion of the normal membrane-bound prion protein (PrP-sen) to its pathological isoform (PrP-res) is a key event in the pathogenesis of transmissible spongiform encephalopathies. Although the subcellular sites of conversion are poorly characterized, several lines of evidence have suggested the involvement of membrane lipid rafts in the conversion process. Here we report that copper stimulates the endocytosis of PrP-sen via a caveolin-dependent pathway in both microglia and neuroblastoma cells. We show that the polyene antibiotic filipin both limits endocytosis of PrP-sen and dramatically reduces the amount of membrane-bound PrP-sen. This reduction results from a rapid and massive release of full matured PrP-sen into the culture medium. Finally, we demonstrate that filipin is a potent inhibitor of PrP-res formation into chronically infected neuroblastoma cells. Our results reinforce the role of rafts in PrP trafficking and raise the possibility that the release of PrP-sen from the plasma membrane decreases the amount of available substrate PrP-sen at the conversion sites.
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Affiliation(s)
- Mathieu Marella
- Institut de Pharmacologie Moléculaire et Cellulaire, Unité Mixte de Recherche 6097, Centre National de la Recherche Scientifique, 660 Route des Lucioles, 06560 Valbonne, France
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44
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Mitchell JS, Kanca O, McIntyre BW. Lipid microdomain clustering induces a redistribution of antigen recognition and adhesion molecules on human T lymphocytes. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:2737-44. [PMID: 11884440 DOI: 10.4049/jimmunol.168.6.2737] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The study of lipid microdomains in the plasma membrane is a topic of recent interest in leukocyte biology. Many T cell activation and signaling molecules are found to be associated with lipid microdomains and have been implicated in normal T cell function. It has been proposed that lipid microdomains with their associated molecules move by lateral diffusion to areas of cellular interactions to initiate signaling pathways. Using sucrose density gradients we have found that human T cell beta(1) integrins are not normally associated with lipid microdomains. However, cross-linking of GM1 through cholera toxin B-subunit (CTB) causes an enrichment of beta(1) integrins in microdomain fractions, suggesting that cross-linking lipid microdomains causes a reorganization of molecular associations. Fluorescent microscopy was used to examine the localization of various lymphocyte surface molecules before and after lipid microdomain cross-linking. Lymphocytes treated with FITC-CTB reveal an endocytic vesicle that is enriched in TCR and CD59, while beta(1) integrin, CD43, and LFA-3 were not localized in the vesicle. However, when anti-CTB Abs are used to cross-link lipid microdomains, the microdomains are not internalized but are clustered on the cell surface. In this study, CD59, CD43, and beta(1) integrin are all seen to colocalize in a new lipid microdomain from which LFA-3 remains excluded and the TCR is now dissociated. These findings show that cross-linking lipid microdomains can cause a dynamic rearrangement of the normal order of T lymphocyte microdomains into an organization where novel associations are created and signaling pathways may be initiated.
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Affiliation(s)
- Jason S Mitchell
- Department of Immunology, University of Texas, M. D. Anderson Cancer Center, Houston, TX 77030, USA
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45
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Harris J, Werling D, Hope JC, Taylor G, Howard CJ. Caveolae and caveolin in immune cells: distribution and functions. Trends Immunol 2002; 23:158-64. [PMID: 11864845 DOI: 10.1016/s1471-4906(01)02161-5] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Caveolae are small, cholesterol-rich, hydrophobic membrane domains, characterized by the presence of the protein caveolin and involved in several cellular processes, including clathrin-independent endocytosis, the regulation and transport of cellular cholesterol, and signal transduction. Recently, caveolae have been identified as providing a novel route by which several pathogens are internalized by antigen-presenting cells and as centers for signal transduction. Here, we review the distribution and role of caveolae and caveolin in mammalian immune cells.
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Affiliation(s)
- James Harris
- Sir William Dunn School of Pathology, South Parks Road, OX1 3RE, Oxford, UK.
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Jin M, Park J, Lee S, Park B, Shin J, Song KJ, Ahn TI, Hwang SY, Ahn BY, Ahn K. Hantaan virus enters cells by clathrin-dependent receptor-mediated endocytosis. Virology 2002; 294:60-9. [PMID: 11886265 DOI: 10.1006/viro.2001.1303] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The cellular entry of Hantaan virus (HTN) occurs through interactions with beta(3) integrins as cellular receptors. However, the process of HTN infection following attachment to the cell surface is not well understood. Our data indicate that overexpression of a dominant-negative mutant dynamin inhibits HTN internalization and that compounds that block clathrin- but not caveolae-dependent endocytosis also reduce HTN infectivity. In addition, we show that HTN colocalizes with the clathrin heavy chain but not with caveolae. At the early phase of infection HTN colocalizes with EEA-1, an early endosome marker, and later, HTN colocalizes with LAMP-1, a lysosome marker. Cells treated with lysosomotropic agents are largely resistant to infection, suggesting that a low-pH-dependent step is required for HTN infection. These findings demonstrate that HTN enters cells via the clathrin-coated pit pathway and uses low-pH-dependent intracellular compartments for infectious entry.
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Affiliation(s)
- Mirim Jin
- Division of Life Science and Graduate School of Biotechnology, Korea University, 1, 5-ka, Anam-Dong, Sungbuk-Gu, Seoul 136-701, Korea
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47
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Howe CL, Valletta JS, Rusnak AS, Mobley WC. NGF signaling from clathrin-coated vesicles: evidence that signaling endosomes serve as a platform for the Ras-MAPK pathway. Neuron 2001; 32:801-14. [PMID: 11738027 DOI: 10.1016/s0896-6273(01)00526-8] [Citation(s) in RCA: 280] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The target-derived neurotrophic factor "nerve growth factor" (NGF) signals through TrkA to promote the survival, differentiation, and maintenance of neurons. How the NGF signal in axon terminals is conveyed to the cell body is unknown. The "signaling endosome hypothesis" envisions that NGF-TrkA complexes are internalized at the axon terminal and retrogradely transported to the cell body. Following NGF treatment, we found that clathrin-coated vesicles contained NGF bound to TrkA together with activated signaling proteins of the Ras-MAP kinase pathway. Evidence that these vesicles could signal was their ability in vitro to activate Elk, a downstream target of Erk1/2. Our results point to the existence of a population of signaling endosomes derived from clathrin-coated membranes in NGF-treated cells.
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Affiliation(s)
- C L Howe
- Department of Neurology, Stanford University Medical Center, 1201 Welch Road, MSLS P211, Stanford, CA 94305, USA.
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48
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Shogomori H, Futerman AH. Cholesterol depletion by methyl-beta-cyclodextrin blocks cholera toxin transport from endosomes to the Golgi apparatus in hippocampal neurons. J Neurochem 2001; 78:991-9. [PMID: 11553673 DOI: 10.1046/j.1471-4159.2001.00489.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We recently demonstrated that although cholera toxin (CT) is found in detergent-insoluble domains/rafts at the cell surface of cultured hippocampal neurons, it is internalized via a raft-independent mechanism. Thus, cholesterol depletion by methyl-beta-cyclodextrin (MbetaCD) did not affect the rate of CT internalization from the plasma membrane, but did affect the rate of CT degradation, which occurs in lysosomes. In the current study, we analyze which step of CT intracellular transport is inhibited by MbetaCD. Whereas pre-incubation with MbetaCD completely blocked CT degradation, it had no effect on the degradation of wheat germ agglutinin (WGA) or bovine serum albumin (BSA), which are internalized by receptor-mediated and fluid phase endocytosis, respectively. Brefeldin A also completely blocked CT degradation but had no effect on WGA or BSA degradation. In contrast, MbetaCD did not affect CT degradation, or CT-mediated cAMP generation, when added to neurons after CT had been transported to the Golgi apparatus. We conclude that CT transport from endosomes to the Golgi apparatus is cholesterol-dependent, whereas CT transport from the Golgi apparatus to lysosomes is cholesterol-independent.
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Affiliation(s)
- H Shogomori
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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Shogomori H, Futerman AH. Cholera toxin is found in detergent-insoluble rafts/domains at the cell surface of hippocampal neurons but is internalized via a raft-independent mechanism. J Biol Chem 2001; 276:9182-8. [PMID: 11113142 DOI: 10.1074/jbc.m009414200] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
A number of studies have demonstrated that cholera toxin (CT) is found in detergent-insoluble, cholesterol-enriched domains (rafts) in various cells, including neurons. We now demonstrate that even though CT is associated with these domains at the cell surface of cultured hippocampal neurons, it is internalized via a raft-independent mechanism, at both early and late stages of neuronal development. CT transport to the Golgi apparatus, and its subsequent degradation, is inhibited by hypertonic medium (sucrose), and by chlorpromazine; the former blocks clathrin recruitment, and the latter causes aberrant endosomal accumulation of clathrin. Moreover, both internalization of the transferrin receptor (Tf-R), which occurs via a clathrin-dependent mechanism, and CT internalization, are inhibited to a similar extent by sucrose. In contrast, the cholesterol-binding agents filipin and methyl-beta-cyclodextrin have no effect on the rate of CT or Tf-R internalization. Finally, once internalized, CT becomes more detergent-soluble, and chlorpromazine treatment renders internalized CT completely detergent-soluble. We propose two models to explain how, despite being detergent-insoluble at the cell surface, CT is nevertheless internalized via a raft-independent mechanism in hippocampal neurons.
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Affiliation(s)
- H Shogomori
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Naim R, Iida T, Takahashi A, Honda T. Monodansylcadaverine inhibits cytotoxicity of Vibrio parahaemolyticus thermostable direct hemolysin on cultured rat embryonic fibroblast cells. FEMS Microbiol Lett 2001; 196:99-105. [PMID: 11267763 DOI: 10.1111/j.1574-6968.2001.tb10548.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The mechanism of action of Vibrio parahaemolyticus thermostable direct hemolysin (TDH) on cultured cells still remains unclear. We show that addition of osmotic stabilizers, such as polyethylene glycol and dextran, could not protect cultured rat embryonic fibroblast cells (Rat-1) against cytotoxicity induced by TDH, unlike their protection against the hemolytic activity of TDH. By contrast, 100 microM monodansylcadaverine, as well as the presence of 1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) in medium, protected the cells against cytotoxicity of TDH. Binding of TDH to Rat-1 cells and intracellular localization of TDH were affected by monodansylcadaverine and EGTA as analyzed by flow cytometry and confocal microscopy. On the hemolytic activity of TDH, monodansylcadaverine and EGTA had no effect. These results suggest that the mechanism of cytotoxicity of TDH on Rat-1 cells was different from that of hemolytic activity of TDH on red blood cells.
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Affiliation(s)
- R Naim
- Department of Bacterial Infection, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
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