First egg protein with a neurotoxic effect on mice

FRASSA,V.; FERNÁNDEZ, P.E.; GALOSI, C.M.; GIMENO, E.; DREON MS,; HERAS, H

Va. Carlos Paz, Argentina

Congreso; XLIV Reunión SAIByBM; 2008

SAIByBM

While many invertebrates sequester toxic compounds to endow eggs with chemical defences, here we show, for the first time to our knowledge, the identification of a neurotoxin of proteic nature, localized inside an egg. Egg extracts from the freshwater apple snail Pomacea canaliculata displayed a neurotoxic effect in mice upon intraperitoneal injection (i.p.) (LD50, 96h 2.3 mg/Kg). Egg protein and total lipids were analysed separately and the only fraction displaying a highly toxic effect (LD50, 96h 0.25 mg/Kg, i.p.) was further purified to homogeneity as an oligomeric glyco-lipoprotein of 400 KDa and 2 subunits, biochemically and immunologically identical to the previously described perivitellin PV2. The neurotoxin was heat sensitive and there was evidence of circulating antibody response to sublethal i.p. dosis on mice. Clinical signs, histopathological and immunocytochemical studies revealed damage mostly in mice spinal cord. Experiments showed cromatolysis and a decreased response to calbindin D-28K associated with a significant increase of TUNEL-positive cells in the dorsal horn neurons. These results suggest that calcium buffering? homeostasis and apoptosis may play a role in the neurological disorders induced by the toxin in mammalian central nervous system. This is the first report of a mollusc neurotoxin genetically encoded outside the cone snail species.