MOLECULAR CLONING OF A NOVEL FAMILY OF NEUROTOXINS ACTIVE ON CALCIUM CHANNELS FROM THE VENOM OF THE SPIDER Phoneutria nigriventer

CARDOSO, F.C.; GOMEZ, M.V.; KALAPOTHAKIS, E.

Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil

Introduction:  The spider Phoneutria nigriventeris frequently involved in cases of human envenomation in Central and South of Brazil. It is known to contain in its venom several neurotoxic polypeptides. One of the fractions purified from this venom, designed PhTx3, has been shown to induce a progressive flaccid paralysis in mice when injected intracerebro-ventricularly. These observations are a strong evidence for the action of this fraction on ionic calcium channels. Tx3-6, a polypeptide found in this fraction, produced paralysis only in the hind limbs and gradual decrease in movement and aggression in mice for a period of 24h.

Objectives: Through this evidences, the aim of this work is to clone and characterize the gene coding for the neurotoxin Tx3-6 and also isoforms of this neurotoxins

Methods and Results: Our group has constructed a cDNA library using mRNA isolated from the venom gland of Phoneutria nigriventer. With the aim to isolate the cDNA coding for Tx3-6, we use different approaches of Molecular Biology (PCR, oligonucleotide and cDNA hybridization, etc.). As a result of the screening for Tx3-6, we found an interesting family of polypeptides coding for a new family of neurotoxins. All this toxins reveals the same structure, contain a signal peptide and an intervening propeptide preceding the mature toxin. Besides, these sequences showed us an interesting conserved domain probably involved with the specificity of this toxins by its target, the ionic calcium channels.

Conclusion: The neurotoxin Tx3-6 belongs to a family of interesting neurotoxins that act on ionic calcium channels. Its sequences showed the steps required to form the mature toxins and potential conserved domains probably involved in the specificity and activity of these neurotoxins.

CORRESPONDENCE TO:

Fernanda Caldas Cardoso, Rua Vereador Teixeira Azevedo, nº 30 Apto. 201, Belo Horizonte, MG, CEP: 31170-140, Brasil, Email: fecaldas@icb.ufmg.br