PKTX, A NEUROTOXIN OF THE SPIDER Phoneutria keyserlingi THAT INTERACTS WITH SODIUM CHANNELS FROM INSECTS

DA COSTA P.R. (1), GOUVÊA DOS SANTOS R. (2), BORGES M.H. (3), RICHARDSON, M.(3), CORDEIRO, M.N.(3), PIMENTA A.M.C.(1), DE LIMA M.E. (1)

(1) Lab. Venenos e Toxinas Animais, Depto. Bioquímica e Imunologia, ICB, UFMG, Belo Horizonte, MG, (2) Lab. Radiobiologia, Centro de Desenvolvimento da Tecnologia Nuclear/CNEN, Belo Horizonte, MG, (3) Centro de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias, Belo Horizonte, MG

Spider venoms contain a multitude of toxins that target membrane receptors and ion channels. PKTx a novel neurotoxin isolated from the spider Phoneutria keyserlingi, was partially sequenced and its primary structure shows similarities with a-like insecticidal toxins isolated from the venoms of spiders of the genus Phoneutria. In preliminary studies, intra-cerebral injections of PKTx in mice (3µg/animal) caused immediate agitation, spastic paralysis, tail elevation and death after 10 minutes. In order to identify and characterize the effects of PKTx, we investigated its toxicity in mice and house flies and we verified its possible interaction with voltage activated sodium channels (Na+v) on mammal and insect synaptosomes. Intra-thoracical injections of PKTx in house flies (Musca domestica) showed elicited movements of legs and mouth parts, extension and contraction of the proboscis, paralysis resulting in loss of ability to fly, and death of 30% of animals (dose level of 500 ng/ animal). Binding studies with radioiodinated toxins were carried out to determine the sites of interaction of PKTx on cockroach (Periplaneta americana) nerve cord synaptosomes. PKTx (5.10-7M) partially competed (42%) with 125I-Bom IV, an a-like toxin from the scorpion Buthus occitanus mardochei, for the binding on the site 3 of Nav channel present on cockroach nerve cord synaptosomes. In conclusion, our results indicate that PKTx interacts with sodium channels of insect excitable cell membranes, probably as the a-like toxins do. Other studies are in development in order to better characterize the interaction of PKTx with insect and mammals nervous system.

KEY WORDS: neurotoxin, Phoneutria keyserlingi, a-like toxin

FINANCIAL SUPPORT: CNPq and FAPEMIG.

CORRESPONDENCE TO: Maria Elena de Lima, Laboratório de Venenos e Toxinas Animais, ICB- UFMG, 55(31)34992659. Email: delima@icb.ufmg.br