Effect of gangliosides on binding, internalization and cytotoxic activity of ricin

“…Ricin was purified from R. communis seeds according to [8]. Ricin A-chain was isolated as previously described [8]. The toxin A-subunit preparation was additionally purified from RTB on Sepharose 4B with fixed asialofetuin.…”

Section: Isolation Of Toxins and Their Subunitsmentioning

confidence: 99%

Immunotoxins containing A‐chain of mistletoe lectin I are more active than immunotoxins with ricin A‐chain

et al. 1996

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“…However, the latter method revealed the presence of an additional binding site of lower affinity which was not sensed by the fluorescent lipid probes. Neither did the anthrylvinyl labeled lipids respond to binding of Re to glycolipids present on the cell surface [11]. It thus appears that while binding of the peptide to its proteinaceous receptor induces notice-able changes in the domain organization of surrounding lipids, binding of the same ligand to glycolipids is not able to initiate such changes.…”

Section: R B Molecules/cellsmentioning

confidence: 91%

Lipid domain reorganization and receptor events Results obtained with new fluorescent lipid probes

Bergel'son¹

1992

FEBS Letters

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Binding of a ligand to the extracellular site of a membrane receptor involves conformational changes not only of the extracellular and cytoplasmic sites but also of the membrane-spanning segments of the receptor protein. The lipids forming the environment of the trans-membrane receptor segments, being flexible and mobile, must follow the shape changes of the receptor molecule to some extent. For this reason ligandreceptor binding itself can be expected to result in changes of the packing of lipid molecules surrounding the receptor. Since lipids are organized in a cooperative manner such changes may affect large areas of the membrane and hence can be registered by physical methods. It has been stated repeatedly that binding of various ligands including hormones, antibodies or lectins to membrane-associated receptors is accompanied by fluidity changes of the target membrane [1][2][3].The aim of this article is to summarize recent evidence suggesting that in highly heterogeneous biological membranes containing numerous metastable lipid domains and/or clusters conformational changes of membrane-associated proteins may result not only in global fluidity changes but also in alterations of the supramolecular lipid domain organization. Frequently such changes can be tbllowed by using, as fluorescent probe, analogs of natural membrane phospholipids or glycolipids bearing, at the end of one of the fatty acyl chains, a 9.anthrylvinyl (AV) group ( cells, and in the latter case may reside for a relatively long time in the plasma membrane without internalization [7].In comparison to most other fluorophores used in membrane research, the AV group displays important advantages. It causes little disturbance because it is nonpolar, flat, and relatively compact. When attached to the fatty acyl chain at an appropriate distance from the head group the AV-fluorophores reside uniformly and exclusively in the center of the bilayer where the host lipids are packed most loosely, and affect neither the mobility nor the orientation and conformation of the major part of the molecules of the surrounding host lipids including their head groups [8]. The AV-group is characterized also by high quantum yields and very short fluorescence lifetimes [9]. The latter property makes the AV-fluorophore suitable for fluorescence polarization measurements. Moreover, in phospholipid bilayers the restricted rotational diffusion of the AVlabeled lipid molecules is of the same time scale as the fluorescence decay. Therefore even subtle changes in the fluidity of the probes microenvironment produce considerable changes in the polarization of fluorescence. The fluorescent parameters of the AV-group (,~ 365 nm, A,~m 430 rim; high extinction coefficient) make it also a highly efficient acceptor for resonance energy transfer (RET) from nearby tryptophans. Since the distance that RET can occur over is as long as 5 nm while RET efficiency depends on the sixth power of the donoracceptor distance, RET measurements with AV-labeled lipids permits the following of even e...

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“…Ricin was extracted from Ricinus communis seeds together with ricin agglutinin and subsequently isolated and purified [18]. Isolated A-and B-subunits were also prepared as previously described [18].…”

Section: Isolation Of Toxins and Subunitsmentioning

confidence: 99%

Comparison between the Mechanisms of Action of Plant Toxins Ricin and Viscumin on the Stage of Intracellular Dissociation

Tonevitsky¹,

Агапов²,

Chelnokova

et al. 2011

Arzneimittelforschung

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Pharmacological effects of mistletoe extracts are determined by the concentration of three toxic lectins: mistletoe lectin I (MLI, or viscumin), MLII, MLIII. These proteins, as well as ricin, belong to ribosome-inactivating proteins type 2 (RIP2). However, the extracts from the plant Ricinus communis, containing ricin, are highly toxic. Ricin is about 30 times more effective in cell culture than viscumin. The dissociation of subunits and the transmembrane transport of catalytic subunit into the cytoplasm are needed to obtain the cytotoxic effect of RIP2. In this paper, hybridomas producing monoclonal antibodies against catalytic subunits of ricin and viscumin are described. Monoclonal antibodies against different epitopes, including one localized in intra-subunit area of catalytic subunits of ricin and viscumin, do not inhibit the enzymatic activity of these proteins in cell-free system. These hybridomas are resistant to the cytotoxic action of native toxins. Protective effect of antibodies are about the same for both toxins, though the dissociation of the subunits of ricin is more effective. The causes of the differences in activity of plant toxins as pharmacological agents, and the importance of above mentioned epitopes for neutralizing antibodies at the clinical applications of mistletoe extracts are discussed.

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Effect of gangliosides on binding, internalization and cytotoxic activity of ricin

Cited by 20 publications

References 13 publications

Immunotoxins containing A‐chain of mistletoe lectin I are more active than immunotoxins with ricin A‐chain

Immunotoxins containing A‐chain of mistletoe lectin I are more active than immunotoxins with ricin A‐chain

Lipid domain reorganization and receptor events Results obtained with new fluorescent lipid probes

Comparison between the Mechanisms of Action of Plant Toxins Ricin and Viscumin on the Stage of Intracellular Dissociation

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