Citation

Mourão CB, Heghinian MD, Barbosa EA, Marí F, Bloch C, Restano-Cassulini R, Possani LD, Schwartz EF. Biochemistry 2013; 52(14): 2440-2452.

Copyright

(Copyright © 2013, American Chemical Society)

DOI

10.1021/bi4000035

PMID

23496776

Abstract

Spider venom toxins have raised interest in prospecting new drugs and pesticides. Nevertheless, few studies are carried out with tarantula toxins, especially with species found in Brazil. The present study aimed at the chemical and biological characterization of the first toxin isolated from Acanthoscurria paulensis venom. Ap1a presents 48 amino acid residues and 5457.79 Da. The cloned gene codes for a putative sequence of 23 amino acid residues for the signal peptide and 27 for the pro-peptide. The mature peptide shows 60-84% sequence identity with toxins of HWTX-II family. Different to the structural pattern proposed for these toxins, the disulfide pairing of Ap1a is of the ICK type motif, which is also shared by the U1-TRTX-Bs1a toxin. Ap1a induced a dose-dependent and reversible paralytic effect in Spodoptera frugiperda caterpillars, with an ED50 of 13.0±4.2 µg/g at 8h after injections. In the D. melanogaster Giant Fiber circuit, Ap1a (0.23-4.60 pmol/fly) reduces both the amplitude and frequency of responses from GF-TTM and GF-DLM pathways, suggesting an action at the neuromuscular junction, which is mediated by glutamatergic receptors. It is also lethal to mice (30 µg/animal, intracranial route), inducing effects similar to those reported with i.c.v. administration of NMDA. Ap1a (1 µM) does not alter the response induced by acetylcholine on the rhabdomyosarcoma cells preparation, and shows no significant effects on hNav1.2, hNav1.4, hNav1.5 and hNav1.6 channels. Due to its unique sequence and cysteine assignment into the HWTX-II family, Ap1a is a significant contribution to the structure-function study of this family of toxins.

Language: en