1
|
O'Neil PT, Vasquez-Montes V, Swint-Kruse L, Baldwin MR, Ladokhin AS. Spectroscopic evidence of tetanus toxin translocation domain bilayer-induced refolding and insertion. Biophys J 2021; 120:4763-4776. [PMID: 34555358 PMCID: PMC8595737 DOI: 10.1016/j.bpj.2021.09.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/03/2021] [Accepted: 09/16/2021] [Indexed: 12/21/2022] Open
Abstract
Tetanus neurotoxin (TeNT) is an A-B toxin with three functional domains: endopeptidase, translocation (HCT), and receptor binding. Endosomal acidification triggers HCT to interact with and insert into the membrane, translocating the endopeptidase across the bilayer. Although the function of HCT is well defined, the mechanism by which it accomplishes this task is unknown. To gain insight into the HCT membrane interaction on both local and global scales, we utilized an isolated, beltless HCT variant (bHCT), which retained the ability to release potassium ions from vesicles. To examine which bHCT residues interact with the membrane, we widely sampled the surface of bHCT using 47 single-cysteine variants labeled with the environmentally sensitive fluorophore NBD. At neutral pH, no interaction was observed for any variant. In contrast, all NBD-labeled positions reported environmental change in the presence of acidic pH and membranes containing anionic lipids. We then examined the conformation of inserted bHCT using circular dichroism and intrinsic fluorescence. Upon entering the membrane, bHCT retained predominantly α-helical secondary structure, whereas the tertiary structure exhibited substantial refolding. The use of lipid-attached quenchers revealed that at least one of the three tryptophan residues penetrated deep into the hydrocarbon core of the membrane, suggesting formation of a bHCT transmembrane conformation. The possible conformational topology was further explored with the hydropathy analysis webtool MPEx, which identified a large, potential α-helical transmembrane region. Altogether, the spectroscopic evidence supports a model in which, upon acidification, the majority of TeNT bHCT entered the membrane with a concurrent change in tertiary structure.
Collapse
Affiliation(s)
- Pierce T O'Neil
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas
| | - Victor Vasquez-Montes
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas
| | - Liskin Swint-Kruse
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas
| | - Michael R Baldwin
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri
| | - Alexey S Ladokhin
- Department of Biochemistry and Molecular Biology, The University of Kansas Medical Center, Kansas City, Kansas.
| |
Collapse
|
2
|
Abstract
How protein toxins translocate their catalytic domain across a cell membrane is the least understood step in toxin action. This study utilized a reporter, β-lactamase, that was genetically fused to full-length, nontoxic tetanus toxin (βlac-TT) in discovery-based live-cell assays to study LC translocation. Directed mutagenesis identified a role for K768 in LC translocation. K768 was located between α15 and α16 (termed the cis-loop). Cellular assays showed that K768 did not interfere with other toxin functions, including cell binding, intracellular trafficking, and pore formation. The equivalent K768 is conserved among the clostridial neurotoxin family of proteins as a conserved structural motif. The cis-loop appears to contribute to LC translocation. The clostridial neurotoxins (CNTs) comprise tetanus toxin (TT) and botulinum neurotoxin (BoNT [BT]) serotypes (A to G and X) and several recently identified CNT-like proteins, including BT/En and the mosquito BoNT-like toxin Pmp1. CNTs are produced as single proteins cleaved to a light chain (LC) and a heavy chain (HC) connected by an interchain disulfide bond. LC is a zinc metalloprotease (cleaving soluble N-ethylmaleimide-sensitive factor attachment protein receptors [SNAREs]), while HC contains an N-terminal translocation domain (HCN) and a C-terminal receptor binding domain (HCC). HCN-mediated LC translocation is the least understood function of CNT action. Here, β-lactamase (βlac) was used as a reporter in discovery-based live-cell assays to characterize TT-mediated LC translocation. Directed mutagenesis identified a role for a charged loop (767DKE769) connecting α15 and α16 (cis-loop) within HCN in LC translocation; aliphatic substitution inhibited LC translocation but not other toxin functions such as cell binding, intracellular trafficking, or HCN-mediated pore formation. K768 was conserved among the CNTs. In molecular simulations of the HCN with a membrane, the cis-loop did not bind with the cell membrane. Taken together, the results of these studies implicate the cis-loop in LC translocation, independently of pore formation. IMPORTANCE How protein toxins translocate their catalytic domain across a cell membrane is the least understood step in toxin action. This study utilized a reporter, β-lactamase, that was genetically fused to full-length, nontoxic tetanus toxin (βlac-TT) in discovery-based live-cell assays to study LC translocation. Directed mutagenesis identified a role for K768 in LC translocation. K768 was located between α15 and α16 (termed the cis-loop). Cellular assays showed that K768 did not interfere with other toxin functions, including cell binding, intracellular trafficking, and pore formation. The equivalent K768 is conserved among the clostridial neurotoxin family of proteins as a conserved structural motif. The cis-loop appears to contribute to LC translocation.
Collapse
|
3
|
Noskov AN. [Molecular model of anthrax toxin translocation into target-cells]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2015; 40:399-404. [PMID: 25898749 DOI: 10.1134/s1068162014040098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anthrax toxin is formed from three components: protective antigen (PA), lethal (LF) and edema (EF) factors. PA83 is cleaved by cell surface protease furin to produce a 63-kDa fragment (PA63). PA63 and LF/EF molecules are assembled to anthrax toxin complexes: oligomer PA63 x 7 + LF/EF x 3. Assembly is occurred during of binding with cellular receptor or near surface of target-cell. This toxin complex forms pore and induces receptor-mediated endocytosis. Formed endosome consists extracellular liquid with LF/EF and membrane-associated ferments (H+ and K+/Na+-ATPases) and proteins (receptors and others). H+ concentration is increased into endosome as result of K/Na-ATPase-dependent- activity of H+-ATPase. Difference of potentials (between endosome and intracellular liquid) is increased and LF/EF molecules are moved to pore and bound with PA63-oligomer to PA63 x 7 + LF/EF x 7 and full block pore (ion-selective channel). Endosome is increased in volume and induces increasing of PA63-oligomer pore to.size of effector complex: LF/EF x 7 + PAl7 x 7 = 750 kDa. Effector complex is translocated from endosome to cytosol by means high difference of potentials (H+) and dissociates from PA47 x 7 complex after cleavage of FFD315-sait by intracellular chymotrypsin-like proteases in all 7 molecules PA63. PA47 x 7 complex (strongly fixed in membrane with debris of hydrophobic loops) return into endosome and pore is destroyed. Endosome pH is decreased rapidly and PA47 x 7 complex is destroyed by endosomal/lysosomal proteases. Receptor-mediated endocytosis is ended by endosome recycling in cell-membrane.
Collapse
|
4
|
Noskov AN. [Molecular mechanism of AB5 toxin A-subunit translocation into the target cells]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2013; 39:671-9. [PMID: 25696929 DOI: 10.1134/s1068162013050129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
AB5 toxins are pore-forming protein complexes, which destroy eukaryotic target cells inactivating essential enzyme complexes through protein ADP-ribosylation or glycosylation by enzymatically active A1 subunits. The B-subunit pentamer interacts with the target cell receptor, induces membrane pore formation, and initiates receptor-mediated endocytosis. In the present article, we propose a model of A1-subunit translocation in the form of a globular structure, as opposed to the generally accepted hypothesis of A-subunit unfolding in the acidic milieu of the endosome followed by its transport in the form of unfolded polypeptide and refolding in the cytoplasm. This model is based on physical-chemical processes and explains why an endosome, but not an exosome, is formed. A-subunit translocation into the cytosol is driven by the proton potential difference generated by K/Na- and H(+)-ATPases. After reduction of the disulphide bond between A1 and A2 fragments by intracellular enzymes, B-subunit returns back into the endosome, where they are destroyed by endosomal proteases, and the pore is closed. Endosome integrates into the cellular membrane, and membrane-bound enzymatic complexes (ATPases and others) return back to their initial position. The proposed model of receptor-mediated endocytosis is a universal molecular mechanism of translocation of effector toxin molecule subunits or any other proteins into the target cell, as well as of cell membrane reparation after any cell membrane injury by pore-forming complexes.
Collapse
|
5
|
Deciphering Membrane Insertion of the Diphtheria Toxin T Domain by Specular Neutron Reflectometry and Solid-State NMR Spectroscopy. J Mol Biol 2009; 391:872-83. [DOI: 10.1016/j.jmb.2009.06.061] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 06/15/2009] [Accepted: 06/24/2009] [Indexed: 11/23/2022]
|
6
|
Rosconi MP, Zhao G, London E. Analyzing Topography of Membrane-Inserted Diphtheria Toxin T Domain Using BODIPY-Streptavidin: At Low pH, Helices 8 and 9 Form a Transmembrane Hairpin but Helices 5−7 Form Stable Nonclassical Inserted Segments on the cis Side of the Bilayer. Biochemistry 2004; 43:9127-39. [PMID: 15248770 DOI: 10.1021/bi049354j] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Low pH-induced membrane insertion by diphtheria toxin T domain is crucial for A chain translocation into the cytoplasm. To define the membrane topography of the T domain, the exposure of biotinylated Cys residues to the cis and trans bilayer surfaces was examined using model membrane vesicles containing a deeply inserted T domain. To do this, the reactivity of biotin with external and vesicle-entrapped BODIPY-labeled streptavidin was measured. The T domain was found to insert with roughly 70-80% of the molecules in the physiologically relevant orientation. In this orientation, residue 349, located in the loop between hydrophobic helices 8 and 9, was exposed to the trans side of the bilayer, while other solution-exposed residues along the hydrophobic helices 5-9 region of the T domain located near the cis surface. A protocol developed to detect the movement of residues back and forth across the membranes demonstrated that T domain sequences did not rapidly equilibrate between the cis and the trans sides of the bilayer. Binding streptavidin to biotinylated residues prior to membrane insertion only inhibited T domain pore formation for residues in the loop between helices 8 and 9. Pore formation experiments used an approach avoiding interference from transient membrane defects/leakage that may occur upon the initial insertion of protein. Combined, these results indicate that at low pH hydrophobic helices 8 and 9 form a transmembrane hairpin, while hydrophobic helices 5-7 form a nonclassical deeply inserted nontransmembraneous state. We propose that this represents a novel pre-translocation state that is distinct from a previously defined post-translocation state.
Collapse
Affiliation(s)
- Michael P Rosconi
- Department of Biochemistry and Cell Biology, State University of New York at Stony Brook, Stony Brook, New York 11794-5215, USA
| | | | | |
Collapse
|
7
|
Nolan DP, Voorheis HP. Factors that determine the plasma-membrane potential in bloodstream forms of Trypanosoma brucei. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:4615-23. [PMID: 10903493 DOI: 10.1046/j.1432-1327.2000.01477.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The plasma-membrane potential (Delta(psi)p) in bloodstream forms of Trypanosoma brucei was studied using several different radiolabelled probes: 86Rb+ and [14C]SCN- were used to report Delta(psi)p directly because they distribute in easily measured quantities across the plasma membrane only, and [3H]methyltriphenylphosphonium (MePh3P+) was used to report Delta(psi)p only when Delta(psi)m had been abolished with FCCP because it reports the algebraic sum of the two potentials when used alone. The unperturbed Delta(psi)p had a value of -82 mV and was found to be essentially identical with, and determined almost completely by, the potassium diffusion potential, as evidenced by: (a) the lack of effect of valinomycin on the value obtained under appropriate conditions when any of these probes were used; (b) the close agreement of this measured value with that predicted from the measured distribution of K+ across the plasma membrane (-76 mV); (c) the large effect of changes in the extracellular K+ concentration by substitution with Na+ on Delta(psi)p together with the complete lack of effect of substitution of extracellular Na+ by the choline cation or substitution of extracellular Cl- by the gluconate anion on Delta(psi)p. The contribution to Delta(psi)p by electrogenic pumping of Na+/K+-ATPase was found to be small (of the order of 6 mV). H+ was not found to be pumped across the plasma membrane or to contribute to Delta(psi)p.
Collapse
Affiliation(s)
- D P Nolan
- Department of Biochemistry, Trinity College, University of Dublin, Ireland
| | | |
Collapse
|
8
|
van Dalen A, Killian A, de Kruijff B. Delta psi stimulates membrane translocation of the C-terminal part of a signal sequence. J Biol Chem 1999; 274:19913-8. [PMID: 10391938 DOI: 10.1074/jbc.274.28.19913] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
For several proteins in Escherichia coli it has been shown that the protonmotive force (pmf) dependence of translocation can be varied with the signal sequence composition, suggesting an effect of the pmf on the signal sequence. To test this possibility, we analyzed the effect of the membrane potential on translocation of the signal sequence. For this purpose, a precursor peptide was used (SP+7), corresponding to the signal sequence of PhoE with the first seven amino acids of the mature part that can be processed by purified leader peptidase. Translocation was studied in pure lipid vesicles containing leader peptidase, with its active site inside the vesicles. In the presence of a positive inside Delta psi, the amount of processing of SP+7 was significantly higher than without a Delta psi, indicating that the translocation of the cleavage region is stimulated by Delta psi. Replacement of the helix-breaking glycine residue at position -10 in the signal sequence for a leucine abolished the effect of Delta psi on the translocation of the cleavage region. It is concluded that Delta psi directly acts on the wild type signal sequence by stimulating the translocation of its C terminus. We propose that Delta psi acts on the signal sequence by stretching it into a transmembrane orientation.
Collapse
Affiliation(s)
- A van Dalen
- Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| | | | | |
Collapse
|
9
|
Otero AS, Yi XB, Gray MC, Szabo G, Hewlett EL. Membrane depolarization prevents cell invasion by Bordetella pertussis adenylate cyclase toxin. J Biol Chem 1995; 270:9695-7. [PMID: 7730345 DOI: 10.1074/jbc.270.17.9695] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Adenylate cyclase toxin from Bordetella pertussis is a 177-kDa calmodulin-activated enzyme that has the ability to enter eukaryotic cells and convert endogenous ATP into cAMP. Little is known, however, about the mechanism of cell entry. We now demonstrate that intoxication of cardiac myocytes by adenylate cyclase toxin is driven and controlled by the electrical potential across the plasma membrane. The steepness of the voltage dependence of intoxication is comparable with that previously observed for the activation of K+ and Na+ channels of excitable membranes. The voltage-sensitive process is downstream from toxin binding to the cell surface and appears to correspond to the translocation of the catalytic domain across the membrane.
Collapse
Affiliation(s)
- A S Otero
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | | | | | | | | |
Collapse
|
10
|
Thompson WL, Scovill JP, Pace JG. Drugs that show protective effects from ricin toxicity in in vitro protein synthesis assays. NATURAL TOXINS 1995; 3:369-77. [PMID: 8581322 DOI: 10.1002/nt.2620030508] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We used an in-vitro, inhibition of protein synthesis assay (PSI) to test a wide variety of drugs for possible therapeutic use against ricin, a toxic glycoprotein that causes death in animals by inhibiting protein synthesis. Selection of test drugs was based on possible interference with ricin activity at different stages of the toxic process. Most of the drugs tested had no effect on ricin-induced PSI, were toxic when tested alone, or enhanced the toxicity of ricin. The only ones showing protection were galactose, lactose, and several derivatives of these sugars, Brefeldin A (BFA), 3'-azido-3'-deoxythymidine (AZT), and a purine derivative (BM33203). THe sugar derivatives provided 50% protection against a PSI ED99 of ricin (0.1 micrograms/ml). Concentrations of BFA greater than 0.5 micro M caused about 50% PSI by itself, but blocked any further inhibitory effects of ricin. AZT, at optimum concentrations, reached a maximum protection level of about 40% in the presence of an ED99 dose of ricin, while the nucleoside derivative, BM33203 and AZT appeared to have an additive effect, showing up to 80% protection from an ED99 dose of ricin. Drugs showing protection in the PSI cell assay showed no protection from ricin in a cell-free translation assay used to determine if they would block ricin at the protein synthesis site.
Collapse
Affiliation(s)
- W L Thompson
- Toxicology Division, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA
| | | | | |
Collapse
|
11
|
Menestrina G, Schiavo G, Montecucco C. Molecular mechanisms of action of bacterial protein toxins. Mol Aspects Med 1994; 15:79-193. [PMID: 7984032 DOI: 10.1016/0098-2997(94)90043-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- G Menestrina
- Centro C.N.R. di Fisica degli Stati Aggregati, Povo, Trento, Italy
| | | | | |
Collapse
|
12
|
|
13
|
Neville DM, Scharff J, Srinivasachar K. Anti-T cell immunotoxins: a look at post-endocytotic receptor-mediated routing. J Control Release 1993. [DOI: 10.1016/0168-3659(93)90173-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
14
|
Papini E, Rappuoli R, Murgia M, Montecucco C. Cell penetration of diphtheria toxin. Reduction of the interchain disulfide bridge is the rate-limiting step of translocation in the cytosol. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53890-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
15
|
Chapter 5 Lipid-peptide interactions in model systems: Membrane insertion and translocation of peptides. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0167-7306(08)60234-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
16
|
London E. How bacterial protein toxins enter cells; the role of partial unfolding in membrane translocation. Mol Microbiol 1992; 6:3277-82. [PMID: 1484483 DOI: 10.1111/j.1365-2958.1992.tb02195.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Bacterial protein toxins translocate across membranes by processes that are still mysterious. Studies on diphtheria toxin have shown that partial unfolding processes play a major role in toxin membrane insertion and translocation. Similar unfolding behaviour is seen with other bacterial toxins. The lessons gained from this behaviour allow us to propose novel mechanisms for toxin translocation.
Collapse
Affiliation(s)
- E London
- Department of Biochemistry and Cell Biology, State University of New York, Stony Brook 11794-5215
| |
Collapse
|
17
|
Alakhov VYu, Klinsky EYu, Kolosov MI, Maurer-Fogy I, Moskaleva EYu, Sveshnikov PG, Pozdnyakova LP, Shemchukova OB, Severin ES. Identification of functionally active fragments of staphylococcal enterotoxin B. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:823-8. [PMID: 1425690 DOI: 10.1111/j.1432-1033.1992.tb17353.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
It has been found that staphylococcal enterotoxin B contains a proteolysis-sensitive sequence in the cysteine loop formed by two half-cystines located in the middle of the toxin polypeptide chain. Fragments of the enterotoxin formed as a result of its digestion in this region have been isolated, their N-terminal sequences have been determined and sites of proteolysis have been identified. It has been demonstrated that the N-terminal fragment of staphylococcal enterotoxin B is capable of activating T cell proliferation in the culture of human mononuclear cells practically to the same degree as the intact enterotoxin. The toxin's C-terminal fragment possesses an ability to activate calmodulin-dependent enzymes and is probably the toxicogenic part of the enterotoxin.
Collapse
Affiliation(s)
- Alakhov VYu
- Research Center of Molecular Diagnostics and Therapy, Moscow, Russia
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Montecucco C, Papini E, Schiavo G, Padovan E, Rossetto O. Ion channel and membrane translocation of diphtheria toxin. FEMS MICROBIOLOGY IMMUNOLOGY 1992; 5:101-11. [PMID: 1384590 DOI: 10.1111/j.1574-6968.1992.tb05892.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Diphtheria toxin is the best studied member of a family of bacterial protein toxins which act inside cells. To reach their cytoplasmic targets, these toxins, which include tetanus and botulinum neurotoxins and anthrax toxin, have to cross the hydrophobic membrane barrier. All of them have been shown to form ion channels across planar lipid bilayer and, in the case of diphtheria toxin, also in the plasma membrane of cells. A relation between the ion channel and the process of membrane translocation has been suggested and two different models have been put forward to account for these phenomena. The two models are discussed on the basis of the available experimental evidence and in terms of the focal points of difference, amenable to further experimental investigations.
Collapse
Affiliation(s)
- C Montecucco
- Centro CNR Biomembrane and Istituto di Patologia Generale, Università di Padova, Italy
| | | | | | | | | |
Collapse
|
19
|
Abstract
A full-length recombinant mutant of diphtheria toxin containing serine in place of a crucial active-site glutamate has been purified and characterized. The serine substitution caused a minor structural alteration in the toxin as measured by trypsinolysis. ADP-ribosyltransferase activity and cytotoxicity of the mutant were both decreased by approximately 500-fold. A similar reduction in cytotoxicity was found when the enzymic fragments of both the wild-type and mutant toxins were introduced into the cytosol of fibroblasts by osmotically lysing pinosomes. The mutation did not alter the binding of the toxin to cell surface receptors and had no apparent effect on membrane translocation. The results suggest that the decreased cytotoxicity of the mutant is solely due to the reduced ADP-ribosyltransferase activity.
Collapse
Affiliation(s)
- D O O'Keefe
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
| |
Collapse
|
20
|
Beaumelle B, Bensammar L, Bienvenüe A. Selective translocation of the A chain of diphtheria toxin across the membrane of purified endosomes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49942-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
21
|
London E. Diphtheria toxin: membrane interaction and membrane translocation. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1113:25-51. [PMID: 1550860 DOI: 10.1016/0304-4157(92)90033-7] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- E London
- Department of Biochemistry and Cell Biology, State University of New York, Stony Brook 11794-5215
| |
Collapse
|
22
|
Affiliation(s)
- I H Madshus
- Department of Biochemistry, Norwegian Radium Hospital, Oslo
| | | |
Collapse
|
23
|
Akeson M, Scharff J, Sharp CM, Neville DM. Evidence that plasma membrane electrical potential is required for vesicular stomatitis virus infection of MDCK cells: a study using fluorescence measurements through polycarbonate supports. J Membr Biol 1992; 125:81-91. [PMID: 1311768 DOI: 10.1007/bf00235799] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We used fluorescence microscopy of Madin-Darby Canine Kidney (MDCK) cells grown on polycarbonate filters to study a possible link between plasma membrane electrical potential (delta psi pm) and infectivity of vesicular stomatitis virus (VSV). Complete substitution of K+ for extracellular Na+ blocks VSV infection of MDCK cells as well as baby hamster kidney (BHK) cells. When we independently perfused the apical and basal-lateral surfaces of high resistance monolayers, high K+ inhibited VSV infection of MDCK cells only when applied to the basal-lateral side; high K+ applied apically had no effect on VSV infection. This morphological specificity correlates with a large decrease in delta psi pm of MDCK cells when high K+ buffer is perfused across the basal-lateral surface. Depolarization of the plasma membrane by 130 mM basal K+ causes a sustained increase of cytosol pH in MDCK cells from 7.3 to 7.5 as reported by the fluorescent dye BCECF. Depolarization also causes a transient increase of cytosol Ca2+ from 70 to 300 nM as reported by the dye Fura-2. Neither increase could explain the block of VSV infectivity by plasma membrane depolarization. One alternative hypothesis is that delta psi pm facilitates membrane translocation of viral macromolecules as previously described for colicins, mitochondrial import proteins, and proteins secreted by Escherichia coli.
Collapse
Affiliation(s)
- M Akeson
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, Maryland 20892
| | | | | | | |
Collapse
|
24
|
Kagan BL. Inositol 1,4,5-trisphosphate directly opens diphtheria toxin channels. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1069:145-50. [PMID: 1932055 DOI: 10.1016/0005-2736(91)90116-p] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP3) is a soluble second messenger, which acts by cooperatively releasing Ca2+ into the cytosol from non-mitochondrial stores, probably by activating Ca(2+)-permeable channels. We demonstrate that submicromolar concentrations of IP3 can directly open the Ca(2+)-permeable diphtheria toxin channel, and that this occurs by IP3 binding to a specific site on the toxin protein. This provides a model for IP3-induced Ca2+ release and suggests that IP3-induced channel opening may play a role in diphtheria intoxication and in protein translocation across membranes.
Collapse
Affiliation(s)
- B L Kagan
- Department of Psychiatry and Biobehavioral Sciences, UCLA Neuropsychiatric Institute, Los Angeles, CA
| |
Collapse
|
25
|
Hudson T, Grillo F. Brefeldin-A enhancement of ricin A-chain immunotoxins and blockade of intact ricin, modeccin, and abrin. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55103-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
26
|
Janicot M, Fouque F, Desbuquois B. Activation of rat liver adenylate cyclase by cholera toxin requires toxin internalization and processing in endosomes. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98773-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
27
|
Chang MP, Wisnieski BJ. Comparison of the intoxication pathways of tumor necrosis factor and diphtheria toxin. Infect Immun 1990; 58:2644-50. [PMID: 2370113 PMCID: PMC258867 DOI: 10.1128/iai.58.8.2644-2650.1990] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The mechanism by which tumor necrosis factor alpha (TNF) initiates tumor cell destruction is unknown. Having established that a brief drop in extracellular pH enhances the killing activity of TNF, our next objective was to explore whether TNF-induced cell death is dependent on endosomal acidification. Diphtheria toxin (DTx), a well-characterized acid-dependent cytotoxin, served as an indicator of the effectiveness of each treatment condition. Studies with lysosomotropic agents demonstrated that the cytotoxic pathway of TNF can operate independently of low pH exposure in contrast to the lethal pathway of DTx. When NH4Cl-treated cells were exposed to TNF at low pH, the level of killing increased two- to threefold over that attained with cells maintained at neutral pH (either with or without NH4Cl). Furthermore, inhibition of metabolic processes by sodium azide in combination with 2-deoxyglucose severely reduced DTx killing but stimulated TNF killing. Despite these differences, TNF and DTx provoked extensive internucleosomal DNA cleavage in prelytic target cells. Inhibitor of nuclear poly(ADP-ribose) transferase also evoked similar levels of cellular resistance to both cytotoxins. Models for DTx- and TNF-induced cytolysis are discussed in view of these new discoveries.
Collapse
Affiliation(s)
- M P Chang
- Department of Microbiology, University of California, Los Angeles 90024
| | | |
Collapse
|
28
|
|
29
|
de Kroon AI, de Gier J, de Kruijff B. Association of synthetic model peptides with phospholipid vesicles induced by a membrane potential. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 981:371-3. [PMID: 2730915 DOI: 10.1016/0005-2736(89)90051-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Hydrophobic model peptides, consisting of 5 or 6 amino acids and carrying a net positive charge at the amino terminus, exhibit a dramatically increased association with large unilamellar egg-PC vesicles upon application of a valinomycin-induced K+ diffusion potential, negative inside. The association of the peptides is largely reversible, apparent from a release of peptide upon dissipation of the membrane potential.
Collapse
Affiliation(s)
- A I de Kroon
- Centre for Biomembranes and Lipid Enzymology, University of Utrecht, The Netherlands
| | | | | |
Collapse
|