cDNA LIBRARIES AND TRANSCRIPTOME: UNRAVELING NEW TOXINS AND UNDERSTANDING THE MECHANISMS OF ENVENOMATION

HO, P.L.(1)

(1)Centro de Biotecnologia, Instituto Butantan, 05503-900, São Paulo, SP, Brazil

A global panorama of transcriptional activity in the venom glands would correlate with its venom composition. The comprehension of the venom composition is fundamental for the mechanisms of envenomation. We have constructed a cDNA library from the Bothrops insularis venom gland and 677 expressed sequence tags (ESTs) were generated from 610 aleatory clones. The sequences were clusterized and 297 resulted cluster sequences were compared with the databanks. Toxin sequences corresponded to 56%, being the metalloproteases (23%) and bradykinin-potentiating peptides (11%) the major toxin components. A new toxin structure-related to Vascular Endothelial Growth Factor was also identified and characterized (JBC276:39836, 2001) that might contribute to venom dissemination and to hypotension observed in the envenomed animals. In order to understand the role of metaloproteases, since they are the major transcript components in the venom gland as revealed by this project, we hypothesized that they would be able to act on plasminogen in order to generate the anti-angiogenic factor angiostatin or angiostatin-like molecules. This result was confirmed and may account for the poor and incomplete regenerative response observed in the damaged tissue upon Viperidae snake bite envenomings (BBRC 294:879, 2002), besides the other actions described for this class of enzymes. The results obtained here allowed us to identify the major toxins from B. insularis venom gland, the description of new toxins and also to a better understanding of the mechanisms of envenomation that affects locally and systemically. In collaborative projects, this approach is being applied now to other venom glands, from the spider Loxosceles laeta, the tick Amblyomma cajennense, the fish  Thalossopherinae nattereri, the caterpillar Lonomia obliqua and others.

Support: FAPESP, CNPq, Fundação Butantan

CORRESPONDENCE TO:

HO, P.L., Centro de Biotecnologia, Instituto Butantan, 05503-900, São Paulo, SP, Brazil. Email: hoplee@usp.br