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Pungercar J, Krizaj I. Understanding the molecular mechanism underlying the presynaptic toxicity of secreted phospholipases A2. Toxicon 2007; 50:871-92. [PMID: 17905401 DOI: 10.1016/j.toxicon.2007.07.025] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Revised: 07/13/2007] [Accepted: 07/20/2007] [Indexed: 11/24/2022]
Abstract
An important group of toxins, whose action at the molecular level is still a matter of debate, is secreted phospholipases A(2) (sPLA(2)s) endowed with presynaptic or beta-neurotoxicity. The current belief is that these beta-neurotoxins (beta-ntxs) exert their toxicity primarily due to their extracellular enzymatic action on the plasma membrane of motoneurons at the neuromuscular junction. However, the discovery of several extra- and intracellular proteins, with high binding affinity for snake venom beta-ntxs, has raised the question as to whether this explanation is adequate to account for all the observed phenomena in the process of presynaptic toxicity. The purpose of this review is to critically examine the various published studies, including the most recent results on internalization of a beta-ntx into motor nerve terminals, in order to contribute to a better understanding of the molecular mechanism of beta-neurotoxicity. As a result, we propose that presynaptic neurotoxicity of sPLA(2)s is a result of both extra- and intracellular actions of beta-ntxs, involving enzymatic activity as well as interaction of the toxins with intracellular proteins affecting the cycling of synaptic vesicles in the axon terminals of vertebrate motoneurons.
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Affiliation(s)
- Joze Pungercar
- Department of Molecular and Biomedical Sciences, Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
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Rouault M, Rash LD, Escoubas P, Boilard E, Bollinger J, Lomonte B, Maurin T, Guillaume C, Canaan S, Deregnaucourt C, Schrével J, Doglio A, Gutiérrez JM, Lazdunski M, Gelb MH, Lambeau G. Neurotoxicity and other pharmacological activities of the snake venom phospholipase A2 OS2: the N-terminal region is more important than enzymatic activity. Biochemistry 2006; 45:5800-16. [PMID: 16669624 PMCID: PMC2796912 DOI: 10.1021/bi060217r] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Several snake venom secreted phospholipases A2 (sPLA2s) including OS2 exert a variety of pharmacological effects ranging from central neurotoxicity to anti-HIV activity by mechanisms that are not yet fully understood. To conclusively address the role of enzymatic activity and map the key structural elements of OS2 responsible for its pharmacological properties, we have prepared single point OS2 mutants at the catalytic site and large chimeras between OS2 and OS1, a homologous but nontoxic sPLA2. Most importantly, we found that the enzymatic activity of the active site mutant H48Q is 500-fold lower than that of the wild-type protein, while central neurotoxicity is only 16-fold lower, providing convincing evidence that catalytic activity is at most a minor factor that determines central neurotoxicity. The chimera approach has identified the N-terminal region (residues 1-22) of OS2, but not the central one (residues 58-89), as crucial for both enzymatic activity and pharmacological effects. The C-terminal region of OS2 (residues 102-119) was found to be critical for enzymatic activity, but not for central neurotoxicity and anti-HIV activity, allowing us to further dissociate enzymatic activity and pharmacological effects. Finally, direct binding studies with the C-terminal chimera, which poorly binds to phospholipids while it is still neurotoxic, led to the identification of a subset of brain N-type receptors which may be directly involved in central neurotoxicity.
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Affiliation(s)
- Morgane Rouault
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
| | - Lachlan D. Rash
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
| | - Pierre Escoubas
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
| | - Eric Boilard
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
| | - James Bollinger
- Departments of Chemistry and Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Bruno Lomonte
- Universidad de Costa Rica, Faculdad de Microbiologia, Instituto Clodomiro Picado, San José, Costa Rica
| | - Thomas Maurin
- Laboratoire de Virologie, IFR50, Faculté de Médecine, 06107 Nice cedex 2, France
| | - Carole Guillaume
- USM 0504, Biologie Fonctionnelle des Protozoaires, Laboratoire de Biologie Parasitaire, Museum National d’Histoire Naturelle, 61 rue Buffon, 75231 Paris cedex 05, France
| | - Stéphane Canaan
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, CNRS-UPR 9025, 31 Chemin Joseph-Aiguier, 13402 Marseille cedex 20, France
| | - Christiane Deregnaucourt
- USM 0504, Biologie Fonctionnelle des Protozoaires, Laboratoire de Biologie Parasitaire, Museum National d’Histoire Naturelle, 61 rue Buffon, 75231 Paris cedex 05, France
| | - Joseph Schrével
- USM 0504, Biologie Fonctionnelle des Protozoaires, Laboratoire de Biologie Parasitaire, Museum National d’Histoire Naturelle, 61 rue Buffon, 75231 Paris cedex 05, France
| | - Alain Doglio
- Laboratoire de Virologie, IFR50, Faculté de Médecine, 06107 Nice cedex 2, France
| | - José María Gutiérrez
- Universidad de Costa Rica, Faculdad de Microbiologia, Instituto Clodomiro Picado, San José, Costa Rica
| | - Michel Lazdunski
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
| | - Michael H. Gelb
- Departments of Chemistry and Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Gérard Lambeau
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
- Address correspondence to: Gérard Lambeau, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France, Tel. +33 (0) 4 93 95 77 33; Fax. +33 (0) 4 93 95 77 08;
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Hseu MJ, Yen CH, Tzeng MC. Crocalbin: a new calcium-binding protein that is also a binding protein for crotoxin, a neurotoxic phospholipase A2. FEBS Lett 1999; 445:440-4. [PMID: 10094503 DOI: 10.1016/s0014-5793(99)00177-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Utilizing Marathon-ready cDNA library and a gene-specific primer corresponding to a partial amino acid sequence determined previously, the complete nucleotide sequence for the cDNA of crocalbin, which binds crotoxin (a phospholipase A2) and Ca2+, was obtained by polymerase chain reaction. The open reading frame of the cDNA encodes a novel polypeptide of 315 amino acid residues, including a signal sequence of 19 residues. This protein contains six potential Ca(2+)-binding domains, one N-glycosylation site, and a large amount of acidic amino acid residues. The ability to bind Ca2+ has been ascertained by calcium overlay experiment. Evidenced by sequence similarity in addition, it is concluded that crocalbin is a new member of the reticulocalbin family of calcium-binding proteins.
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Affiliation(s)
- M J Hseu
- Institute of Biological Chemistry, Academia Sinica, National Taiwan University, Taipei
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