crotamine and Necrosis

Biochemically and pharmacologically, myotoxins isolated from snake venoms can be placed in four main groups: myotoxic phospholipases A, low molecular weight basic toxins, cardiotoxins, and hemorrhagic myotoxins. The myotoxic phospholipases A notexin, taipoxin, crotoxin, and Bothrops asper myotoxin induce muscle necrosis by first affecting the integrity of the plasma membrane, thereby inducing a calcium influx that culminates in cell death. The small basic myotoxin crotamine acts on the voltage-sensitive sodium channels of skeletal muscle sarcolemma, inducing a sodium influx which is responsible for depolarization and contraction of skeletal muscle, as well as for vacuolization of sarcoplasmic reticulum. Cardiotoxins are basic membrane-active polypeptides that disorganize the structure of membranes; the myotoxic activity of cardiotoxins results from their ability to disrupt skeletal muscle sarcolemma. Finally, two hemorrhagic toxins (hemorrhagic toxin b and viriditoxin) are myotoxic; apparently, they secondarily to ischemia which develops in muscular tissue as a consequence of the hemorrhagic action of these toxins.

Topics: Animals; Calcium; Cell Membrane; Crotalid Venoms; Crotoxin; Elapid Venoms; Muscle Contraction; Muscles; Naphthols; Necrosis; Snake Venoms; Toxins, Biological

In this work, we isolated the two new crotamine isoforms from the Crotalus durissus cumanensis rattlesnake venom and its "in vitro" neurotoxic, myotoxic and lethality (DL(50)) intracerebroventricular (i.c.v.) effects were characterized. These proteins were named IV-2 and IV-3 and were purified by combination of two chromatographic steps on molecular exclusion chromatography on Superdex 75 and reverse phase HPLC (mu-Bondapack C18). The molecular mass of the crotamine isoforms was 4905.96 Da for isoform IV-2 and 4956.97 Da for IV-3 and, as determined by mass spectrometry, and both contained six Cys residues. Enzymatic hydrolysis followed by de novo sequencing by tandem mass spectrometry was used to determine the primary structure of both isoforms. The positions of five sequenced tryptic peptides, including the N-terminal of the isoform IV-2 and four from isoform IV-3 were deduced by comparison with a homologous protein from the crotamine family. The isoforms IV-2 and IV-3 had a sequence of amino acids of 42 amino acid residues IV-2: YKRCHIKGGH CFPKEKLICI PPSSDIGKMD CPWKRKCCKK RS and pI value 9.54 and IV-3: YKQCHKKGGH CFPKEVLICI PPSSDFGKMD CRWKRKCCKK RS with a pI value of 9.54. This protein showed high molecular amino acid sequence identity with other crotamine-like proteins from Crotalus durissus terrificus. These new crotamine isoforms induced potent blockade of neuromuscular transmission in young chicken biventer cervicis preparation and potent myotoxic effect. In mice, both isoforms induced myonecrosis, upon intramuscular or subcutaneous injections. These activities were modulated by the presence of positively charged amino acid residues. The LD(50) of isoform IV-2 was 0.07 mg/kg and isoform IV-3 was 0.06 mg/kg the animal weight, by i.c.v. route.

Topics: Amino Acid Sequence; Animals; Chickens; Chromatography, High Pressure Liquid; Crotalid Venoms; Crotalus; Mice; Molecular Sequence Data; Myoblasts; Necrosis; Neuromuscular Junction; Peptide Fragments; Protein Isoforms; Sequence Homology, Amino Acid; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization