title: β/δ-PrIT1, a highly insecticidal toxin from the venom of the Brazilian spider Phoneutria reidyi (F.O. Pickard-Cambridge, 1897).
abstract: A potent insecticidal toxin, β/δ-PrIT1, molecular mass of 5598.86 [M+H](+), was characterized from Phoneutria reidyi spider venom. Its partial amino acid sequence showed high similarity with insecticidal spider toxins from the genus Phoneutria. β/δ-PrIT1 was very toxic (LD50 = 4 nmol/g) to flies (Musca domestica), but not to mice (Mus musculus). Kinetic studies showed that (125)I-β/δ-PrIT1 binds to two distinct sites in insect sodium channels, with close affinity (Kd1 = 34.7 pM and Kd2 = 35.1 pM). Its association is rather fast (t1/2(1) = 1.4 min, t1/2(2) = 8.5 min) and its dissociation is a slower process (t1/2(1) = 5.4 min, t1/2(2) = 32.8 min). On rat brain synaptosomes β/δ-PrIT1 partially competed (∼30%) with the beta-toxin (125)I-CssIV, but did not compete with the alpha-toxin of reference (125)I-AaII, nor with the beta-toxin (125)I-TsVII. On cockroach nerve cord synaptosomes, β/δ-PrIT1 did not compete with the anti-insect toxin (125)I-LqqIT1, but it competed (IC50 = 80 pM) with the "alpha-like" toxin (125)I-BomIV. In cockroach neurons, β/δ-PrIT1 inhibited the inactivation of Nav-channels and it shifted the sodium channel activation to hyperpolarizing potentials. These results indicate two different binding sites for β/δ-PrIT1, leading to two different pharmacological responses. β/δ-PrIT1 is one of the most toxic spider toxins to insects without apparent toxicity to mammals, and provide new model for the development of insecticides.
authors.affiliation: Departamento de Farmácia, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Rua da Glória, 187 - Centro, 39100-000 Diamantina, MG, Brazil; Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Leida Calegário
authors.initials: LC
authors.lastname: de Oliveira
authors.affiliation: Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Fabiana V
authors.initials: FV
authors.lastname: Campos
authors.affiliation: Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Avenida Marechal Campos, 1468, 29043-900, Maruípe, Vitória, ES, Brazil.
authors.forename: Suely Gomes
authors.initials: SG
authors.lastname: Figueiredo
authors.affiliation: Centro de Pesquisa e Desenvolvimento "Prof. Carlos Ribeiro Diniz", Fundação Ezequiel Dias, Rua Conde Pereira Carneiro, 80, 30550-010 Belo Horizonte, MG, Brazil.
authors.forename: Marta N
authors.initials: MN
authors.lastname: Cordeiro
authors.affiliation: Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Beatriz R
authors.initials: BR
authors.lastname: Adaime
authors.affiliation: Centro de Pesquisa e Desenvolvimento "Prof. Carlos Ribeiro Diniz", Fundação Ezequiel Dias, Rua Conde Pereira Carneiro, 80, 30550-010 Belo Horizonte, MG, Brazil.
authors.forename: Michael
authors.initials: M
authors.lastname: Richardson
authors.affiliation: Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Adriano M C
authors.initials: AM
authors.lastname: Pimenta
authors.affiliation: Aix-Marseille University, CNRS UMR 7286, CRN2M, School of Medicine, Bd Pierre Dramard, 13916 Marseille Cedex 20, France.
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Martin-Eauclaire
authors.affiliation: Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Paulo S L
authors.initials: PS
authors.lastname: Beirão
authors.affiliation: Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil. Electronic address: melenalima@icb.ufmg.br.
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: De Lima
mesh_terms: D000818:Animals; D001665:Binding Sites; D001938:Brazil; D003058:Cockroaches / Q000166:cytology / Q000187:drug effects; D004175:Diptera / Q000187:drug effects; D005260:Female; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000378:metabolism; D013111:Spider Venoms / Q000737:chemistry / Q000494:pharmacology*; D013112:Spiders / Q000737:chemistry*; D013574:Synaptosomes / Q000378:metabolism*
chemical_list: D007306:Insecticides; D015222:Sodium Channels; D013111:Spider Venoms
keywords: Anti-insect toxins; Phoneutria reidyi; Spider venoms; Voltage-gated sodium channels