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Błaszczyk M, Kozioł A, Palko-Łabuz A, Środa-Pomianek K, Wesołowska O. Modulators of cellular cholesterol homeostasis as antiproliferative and model membranes perturbing agents. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184163. [PMID: 37172710 DOI: 10.1016/j.bbamem.2023.184163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 04/14/2023] [Accepted: 04/26/2023] [Indexed: 05/15/2023]
Abstract
Cholesterol is an important component of mammalian cell membranes affecting their fluidity and permeability. Together with sphingomyelin, cholesterol forms microdomains, called lipid rafts. They play important role in signal transduction forming platforms for interaction of signal proteins. Altered levels of cholesterol are known to be strongly associated with the development of various pathologies (e.g., cancer, atherosclerosis and cardiovascular diseases). In the present work, the group of compounds that share the property of affecting cellular homeostasis of cholesterol was studied. It contained antipsychotic and antidepressant drugs, as well as the inhibitors of cholesterol biosynthesis, simvastatin, betulin, and its derivatives. All compounds were demonstrated to be cytotoxic to colon cancer cells but not to non-cancerous cells. Moreover, the most active compounds decreased the level of free cellular cholesterol. The interaction of drugs with raft-mimicking model membranes was visualized. All compounds reduced the size of lipid domains, however, only some affected their number and shape. Membrane interactions of betulin and its novel derivatives were characterized in detail. Molecular modeling indicated that high dipole moment and significant lipophilicity were characteristic for the most potent antiproliferative agents. The importance of membrane interactions of cholesterol homeostasis-affecting compounds, especially betulin derivatives, for their anticancer potency was suggested.
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Affiliation(s)
- Maria Błaszczyk
- Department of Biophysics and Neuroscience, Wroclaw Medical University, ul. Chalubinskiego 3a, 50-368 Wroclaw, Poland.
| | - Agata Kozioł
- Department of Biochemistry and Immunochemistry, Wroclaw Medical University, Sklodowskiej-Curie 48/50, 50-369 Wroclaw, Poland.
| | - Anna Palko-Łabuz
- Department of Biophysics and Neuroscience, Wroclaw Medical University, ul. Chalubinskiego 3a, 50-368 Wroclaw, Poland.
| | - Kamila Środa-Pomianek
- Department of Biophysics and Neuroscience, Wroclaw Medical University, ul. Chalubinskiego 3a, 50-368 Wroclaw, Poland.
| | - Olga Wesołowska
- Department of Biophysics and Neuroscience, Wroclaw Medical University, ul. Chalubinskiego 3a, 50-368 Wroclaw, Poland.
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2
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Vit G, Duro J, Rajendraprasad G, Hertz EPT, Holland LKK, Weisser MB, McEwan BC, Lopez‐Mendez B, Sotelo‐Parrilla P, Jeyaprakash AA, Montoya G, Mailand N, Maeda K, Kettenbach A, Barisic M, Nilsson J. Chemogenetic profiling reveals PP2A-independent cytotoxicity of proposed PP2A activators iHAP1 and DT-061. EMBO J 2022; 41:e110611. [PMID: 35695070 PMCID: PMC9289710 DOI: 10.15252/embj.2022110611] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 05/18/2022] [Accepted: 05/19/2022] [Indexed: 01/01/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is an abundant phosphoprotein phosphatase that acts as a tumor suppressor. For this reason, compounds able to activate PP2A are attractive anticancer agents. The compounds iHAP1 and DT-061 have recently been reported to selectively stabilize specific PP2A-B56 complexes to mediate cell killing. We were unable to detect direct effects of iHAP1 and DT-061 on PP2A-B56 activity in biochemical assays and composition of holoenzymes. Therefore, we undertook genome-wide CRISPR-Cas9 synthetic lethality screens to uncover biological pathways affected by these compounds. We found that knockout of mitotic regulators is synthetic lethal with iHAP1 while knockout of endoplasmic reticulum (ER) and Golgi components is synthetic lethal with DT-061. Indeed we showed that iHAP1 directly blocks microtubule assembly both in vitro and in vivo and thus acts as a microtubule poison. In contrast, DT-061 disrupts both the Golgi apparatus and the ER and lipid synthesis associated with these structures. Our work provides insight into the biological pathways perturbed by iHAP1 and DT-061 causing cellular toxicity and argues that these compounds cannot be used for dissecting PP2A-B56 biology.
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Affiliation(s)
- Gianmatteo Vit
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Joana Duro
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Girish Rajendraprasad
- Cell Division and CytoskeletonDanish Cancer Society Research CenterCopenhagenDenmark
| | - Emil P T Hertz
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Lya Katrine Kauffeldt Holland
- Cell Death and Metabolism UnitCenter for Autophagy, Recycling and Disease (CARD)Danish Cancer Society Research Center (DCRC)CopenhagenDenmark
| | - Melanie Bianca Weisser
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Brennan C McEwan
- Department of Biochemistry and Cell BiologyGeisel School of Medicine at Dartmouth CollegeHanoverNHUSA,Norris Cotton Cancer CenterLebanonNHUSA
| | - Blanca Lopez‐Mendez
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | | | | | - Guillermo Montoya
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Niels Mailand
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Kenji Maeda
- Cell Death and Metabolism UnitCenter for Autophagy, Recycling and Disease (CARD)Danish Cancer Society Research Center (DCRC)CopenhagenDenmark
| | - Arminja Kettenbach
- Department of Biochemistry and Cell BiologyGeisel School of Medicine at Dartmouth CollegeHanoverNHUSA
| | - Marin Barisic
- Cell Division and CytoskeletonDanish Cancer Society Research CenterCopenhagenDenmark,Department of Cellular and Molecular MedicineFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Jakob Nilsson
- Novo Nordisk Foundation Center for Protein ResearchFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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3
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Phenothiazines alter plasma membrane properties and sensitize cancer cells to injury by inhibiting annexin-mediated repair. J Biol Chem 2021; 297:101012. [PMID: 34324830 PMCID: PMC8363839 DOI: 10.1016/j.jbc.2021.101012] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 07/18/2021] [Accepted: 07/23/2021] [Indexed: 01/11/2023] Open
Abstract
Repair of damaged plasma membrane in eukaryotic cells is largely dependent on the binding of annexin repair proteins to phospholipids. Changing the biophysical properties of the plasma membrane may provide means to compromise annexin-mediated repair and sensitize cells to injury. Since, cancer cells experience heightened membrane stress and are more dependent on efficient plasma membrane repair, inhibiting repair may provide approaches to sensitize cancer cells to plasma membrane damage and cell death. Here, we show that derivatives of phenothiazines, which have widespread use in the fields of psychiatry and allergy treatment, strongly sensitize cancer cells to mechanical-, chemical-, and heat-induced injury by inhibiting annexin-mediated plasma membrane repair. Using a combination of cell biology, biophysics, and computer simulations, we show that trifluoperazine acts by thinning the membrane bilayer, making it more fragile and prone to ruptures. Secondly, it decreases annexin binding by compromising the lateral diffusion of phosphatidylserine, inhibiting the ability of annexins to curve and shape membranes, which is essential for their function in plasma membrane repair. Our results reveal a novel avenue to target cancer cells by compromising plasma membrane repair in combination with noninvasive approaches that induce membrane injuries.
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Dubinin MV, Semenova AA, Ilzorkina AI, Mikheeva IB, Yashin VA, Penkov NV, Vydrina VA, Ishmuratov GY, Sharapov VA, Khoroshavina EI, Gudkov SV, Belosludtsev KN. Effect of betulin and betulonic acid on isolated rat liver mitochondria and liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183383. [PMID: 32522531 DOI: 10.1016/j.bbamem.2020.183383] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 06/02/2020] [Accepted: 06/03/2020] [Indexed: 01/01/2023]
Abstract
The paper considers the effects of plant triterpenoid betulin and its derivative betulonic acid on rat liver mitochondria and liposomes. It was found that betulonic acid and, to a lesser extent, betulin, activate mitochondrial respiration in states 2 and 4 and inhibit ADP- and DNP-stimulated (uncoupled) respiration. The effect of betulonic acid resulted in a significant decrease of the respiratory control and ADP/O ratios and decrease in Δψ. The effects of both compounds were most pronounced in the case of succinate-fueled mitochondrial respiration. This may include both the possible protonophore effect of betulonic acid and the inhibition of respiratory chain complexes by both compounds. Both agents enhanced H2O2 production in succinate-fueled mitochondria, while betulonic acid exerted an antioxidant effect with NAD-dependent substrates. Betulin was found to induce mitochondrial aggregation, but had no effect on membrane permeability. A similar pattern was found on liposomes. As revealed by the laurdan generalized polarization (GP) technique, betulin increased laurdan GP in lecithin liposomes, indicating a decrease in membrane fluidity. Measurements of GP as a function of fluorescence excitation wavelength gave an ascending line for high concentrations of betulin, which can be interpreted as phase heterogeneity of the lipid/betulin system. High concentrations of betulin (> 60 mol%) was also demonstrated to cause permeabilization of lecithin liposomes. Betulonic acid was much less effective in inducing the aggregation of mitochondria and liposomes and had no effect on membrane permeability. The possible mechanisms of betulin and betulonic acid effect on rat liver mitochondria and liposomes are discussed.
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Affiliation(s)
- Mikhail V Dubinin
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia.
| | - Alena A Semenova
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
| | - Anna I Ilzorkina
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
| | - Irina B Mikheeva
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Institutskaya 3, Pushchino, Moscow Region, 142290, Russia
| | - Valery A Yashin
- Institute of Cell Biophysics, Russian Academy of Sciences, PSCBR RAS, Institutskaya 3, Pushchino, Moscow Region, 142290, Russia
| | - Nikita V Penkov
- Institute of Cell Biophysics, Russian Academy of Sciences, PSCBR RAS, Institutskaya 3, Pushchino, Moscow Region, 142290, Russia
| | - Valentina A Vydrina
- Ufa Institute of Chemistry, Ufa Federal Research Centre of the Russian Academy of Sciences, Prosp. Oktyabrya 71, Ufa, Republic of Bashkortostan, 450054, Russia
| | - Gumer Yu Ishmuratov
- Ufa Institute of Chemistry, Ufa Federal Research Centre of the Russian Academy of Sciences, Prosp. Oktyabrya 71, Ufa, Republic of Bashkortostan, 450054, Russia
| | | | | | - Sergey V Gudkov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilova 38, Moscow, 119991, Russia
| | - Konstantin N Belosludtsev
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia; Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Institutskaya 3, Pushchino, Moscow Region, 142290, Russia
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Pérez-Isidoro R, Costas M. The effect of neuroleptic drugs on DPPC/sphingomyelin/cholesterol membranes. Chem Phys Lipids 2020; 229:104913. [PMID: 32335028 DOI: 10.1016/j.chemphyslip.2020.104913] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 04/10/2020] [Accepted: 04/13/2020] [Indexed: 12/25/2022]
Abstract
The hydrophobic nature of neuroleptic drugs renders that these molecules interact not only with protein receptors, but also with the lipids constituting the membrane bilayer. We present a systematic study of the effect of seven neuroleptic drugs on a biomembrane model composed of DPPC, sphingomyelin, and cholesterol. Differential scanning calorimetry (DSC) measurements were used to monitor the gel-fluid phase transition of the lipid bilayer at three pH values and also as a function of drug concentration. The implementation of a new methodology to mix lipids homogeneously allowed us to assemble bilayers completely free of organic solvents. The seven neuroleptics were: trifluoperazine, haloperidol decanoate, clozapine, quetiapine, olanzapine, aripiprazole, and amisulpride. The DSC results show that the insertion of the drug into the bilayer produces a fluidization and a disordering of the bilayer. The bilayer perturbation is qualitatively the same for all the studied drugs, but quantitatively different. The driving force for the neuroleptic drug to place itself in the lipid bilayer is entropic in nature, signaling to the importance of the size and geometry of the drugs. The drug protonated species produce stronger effects than their non-protonated forms. At high concentrations two of the neuroleptics revert the fluidization effect and another completely abolishes the gel-fluid transition. The DSC data and the associated discussion contribute to the understanding of the interactions between neuroleptic drugs and lipid membranes.
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Affiliation(s)
- R Pérez-Isidoro
- Laboratorio de Bio-fisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, México City 04510, Mexico.
| | - M Costas
- Laboratorio de Bio-fisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, México City 04510, Mexico.
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6
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Belosludtsev KN, Belosludtseva NV, Tenkov KS, Penkov NV, Agafonov AV, Pavlik LL, Yashin VA, Samartsev VN, Dubinin MV. Study of the mechanism of permeabilization of lecithin liposomes and rat liver mitochondria by the antimicrobial drug triclosan. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:264-271. [PMID: 28939382 DOI: 10.1016/j.bbamem.2017.09.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/30/2017] [Accepted: 09/17/2017] [Indexed: 12/22/2022]
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7
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Jiang YW, Gao G, Chen Z, Wu FG. Fluorescence studies on the interaction between chlorpromazine and model cell membranes. NEW J CHEM 2017. [DOI: 10.1039/c7nj00037e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fluorescence quenching of membrane fluorophores and the fluorescence enhancement of chlorpromazine were simultaneously observed during chlorpromazine–lipid membrane interaction.
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Affiliation(s)
- Yao-Wen Jiang
- State Key Laboratory of Bioelectronics
- School of Biological Science and Medical Engineering
- Southeast University
- Nanjing 210096
- P. R. China
| | - Ge Gao
- State Key Laboratory of Bioelectronics
- School of Biological Science and Medical Engineering
- Southeast University
- Nanjing 210096
- P. R. China
| | - Zhan Chen
- Department of Chemistry
- University of Michigan
- Ann Arbor
- USA
| | - Fu-Gen Wu
- State Key Laboratory of Bioelectronics
- School of Biological Science and Medical Engineering
- Southeast University
- Nanjing 210096
- P. R. China
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8
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Abdülrezzak Ü, Erdoğan Z, Silov G, Özdal A, Turhal Ö. Effect of trifluoperazine on Tc-99m sestamibi uptake in patients with advanced nonsmall cell lung cancer. Indian J Nucl Med 2016; 31:103-7. [PMID: 27095857 PMCID: PMC4815380 DOI: 10.4103/0972-3919.178256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
OBJECTIVE The aim of this study was to investigate whether there is an effect of trifluoperazine on Tc-99m methoxyisobutylisonitrile (MIBI) uptake in patients with advanced nonsmall cell lung cancer (NCLC). MATERIALS AND METHODS A total of 23 patients with biopsy-proven advanced NCLC who had no previous history of chemo-radiotherapy, underwent baseline dual phase planar, single photon emission computed tomography and whole body Tc-99m MIBI scintigraphy performed at 20 and 120 min. After oral administration of trifluoperazine (5 mg, 2 times a day, for 5 days), dual phase Tc-99m MIBI scintigraphy was repeated. For each patient, and for both studies, regions of interest were drawn over the tumor area (T) and over the normal lung area (L) on the contralateral side in transverse slices where tumor was visualized clearly. Then, early and delayed T/L ratios and washout rate (WR) were calculated. RESULTS Tc-99m MIBI was accumulated in the cancer tissue in all of the patients. Delayed ratio after the oral administration of trifluoperazine (DR2) was significantly higher (P = 0.039) than delayed ratio before trifluoperazine (DR1). We found no significant differences of early ratio before trifluoperazine (ER1) and early ratio after trifluoperazine (ER2), and washout rate before (WR1) and washout rate after trifluoperazine (WR2). CONCLUSION In patients with advanced NCLC, trifluoperazine treatment in addition to chemotherapy might be useful. However, our results need to be confirmed in larger series of patients.
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Affiliation(s)
- Ümmühan Abdülrezzak
- Department of Nuclear Medicine, Erciyes University School of Medicine, 38010-Kayseri, Turkey
| | - Zeynep Erdoğan
- Department of Nuclear Medicine, Kayseri Training and Research Hospital, 38010-Kayseri, Turkey
| | - Güler Silov
- Department of Nuclear Medicine, Kayseri Training and Research Hospital, 38010-Kayseri, Turkey
| | - Ayşegül Özdal
- Department of Nuclear Medicine, Kayseri Training and Research Hospital, 38010-Kayseri, Turkey
| | - Özgül Turhal
- Department of Nuclear Medicine, Kayseri Training and Research Hospital, 38010-Kayseri, Turkey
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Kuć M, Cieślik-Boczula K, Świątek P, Jaszczyszyn A, Gąsiorowski K, Malinka W. FTIR-ATR study of the influence of the pyrimidine analog of fluphenazine on the chain-melting phase transition of sphingomyelin membranes. Chem Phys 2015. [DOI: 10.1016/j.chemphys.2015.06.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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10
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Phase Separation in Phosphatidylcholine Membrane Caused by the Presence of a Pyrimidine Analogue of Fluphenazine with High Anti-Multidrug-Resistance Activity. J Phys Chem B 2014; 118:3605-15. [DOI: 10.1021/jp410882r] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Phenothiazines inhibit hepatitis C virus entry, likely by increasing the fluidity of cholesterol-rich membranes. Antimicrob Agents Chemother 2013; 57:2571-81. [PMID: 23529728 DOI: 10.1128/aac.02593-12] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Despite recent progress in the development of direct-acting antiviral agents against hepatitis C virus (HCV), more effective therapies are still urgently needed. We and others previously identified three phenothiazine compounds as potent HCV entry inhibitors. In this study, we show that phenothiazines inhibit HCV entry at the step of virus-host cell fusion, by intercalating into cholesterol-rich domains of the target membrane and increasing membrane fluidity. Perturbation of the alignment/packing of cholesterol in lipid membranes likely increases the energy barrier needed for virus-host fusion. A screening assay based on the ability of molecules to selectively increase the fluidity of cholesterol-rich membranes was subsequently developed. One compound that emerged from the library screen, topotecan, is able to very potently inhibit the fusion of liposomes with cell culture-derived HCV (HCVcc). These results yield new insights into HCV infection and provide a platform for the identification of new HCV inhibitors.
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Zhou Y, Cho KJ, Plowman SJ, Hancock JF. Nonsteroidal anti-inflammatory drugs alter the spatiotemporal organization of Ras proteins on the plasma membrane. J Biol Chem 2012; 287:16586-95. [PMID: 22433858 DOI: 10.1074/jbc.m112.348490] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ras proteins on the inner leaflet of the plasma membrane signal from transient nanoscale proteolipid assemblies called nanoclusters. Interactions between the Ras lipid anchors and plasma membrane phospholipids, cholesterol, and actin cytoskeleton contribute to the formation, stability, and dynamics of Ras nanoclusters. Many small biological molecules are amphiphilic and capable of intercalating into membranes and altering lipid immiscibility. In this study we systematically examined whether amphiphiles such as indomethacin influence Ras protein nanoclustering in intact plasma membrane. We found that indomethacin, a nonsteroidal anti-inflammatory drug, induced profound and complex effects on Ras spatial organization, all likely related to liquid-ordered domain stabilization. Indomethacin enhanced the clustering of H-Ras.GDP and N-Ras.GTP in cholesterol-dependent nanoclusters. Indomethacin also abrogated efficient GTP-dependent lateral segregation of H- and N-Ras between cholesterol-dependent and cholesterol-independent clusters, resulting in mixed heterotypic clusters of Ras proteins that normally are separated spatially. These heterotypic Ras nanoclusters showed impaired Raf recruitment and kinase activation resulting in significantly compromised MAPK signaling. All of the amphiphilic anti-inflammatory agents we tested had similar effects on Ras nanoclustering and signaling. The potency of these effects correlated with the membrane partition coefficients of the individual agents and was independent of COX inhibition. This study shows that biological amphiphiles have wide-ranging effects on plasma membrane heterogeneity and protein nanoclustering, revealing a novel mechanism of drug action that has important consequences for cell signaling.
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Affiliation(s)
- Yong Zhou
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
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13
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Singh DK, Shentu TP, Enkvetchakul D, Levitan I. Cholesterol regulates prokaryotic Kir channel by direct binding to channel protein. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1808:2527-33. [PMID: 21798234 PMCID: PMC3156940 DOI: 10.1016/j.bbamem.2011.07.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 07/07/2011] [Accepted: 07/09/2011] [Indexed: 12/11/2022]
Abstract
Cholesterol is a major regulator of a variety of ion channels but the mechanisms underlying cholesterol sensitivity of ion channels are still poorly understood. The key question is whether cholesterol regulates ion channels by direct binding to the channel protein or by altering the physical environment of lipid bilayer. In this study, we provide the first direct evidence that cholesterol binds to prokaryotic Kir channels, KirBac1.1, and that cholesterol binding is essential for its regulatory effect. Specifically, we show that cholesterol is eluted together with the KirBac1.1 protein when separated on an affinity column and that the amount of bound cholesterol is proportional to the amount of the protein. We also show that cholesterol binding to KirBac1.1 is saturable with a K(D) of 390μM. Moreover, there is clear competition between radioactive and non-radioactive cholesterol for the binding site. There is no competition, however, between cholesterol and 5-Androsten 3β-17 β-diol, a sterol that we showed previously to have no effect on KirBac1.1 function. Finally, we show that cholesterol-KirBac1.1 binding is significantly inhibited by trifluoperazine, known to inhibit cholesterol binding to other proteins, and that inhibition of cholesterol-KirBac1.1 binding results in full recovery of the channel activity. Collectively, results from this study indicate that cholesterol-induced suppression of KirBac1.1 activity is mediated by direct interaction between cholesterol and the channel protein.
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Affiliation(s)
- Dev K Singh
- Department of Medicine, University of Illinois, Chicago, IL 60612, USA.
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