“SYNTHESIS, DISTRIBUTION AND LEVELS OF PERIVITELLIN-2 AN EGG LIPOPROTEIN FROM THE APPLE SNAIL POMACEA CANALICULATA (MOLLUSCA: GASTROPODA)”

DREON, M.S.; LAVARIAS, SABRINA MARIA LUISA; GARIN, C.; HERAS, H.; POLLERO, R.J.

Grahamstown, Sudáfrica

Congreso; 9TH International Congress on Invertebrate Reproduction and Development.; 2001

ISIRD

Pomacea canaliculata is a freshwater snail whose physiology and metabolism are currently under active research. It is a pest for rice crops and the host for the nematode causing eosinophilic meningoencephalitis in humans. Our laboratory has been studying the eggs of the Pomacea canaliculata, and two lipoproteins (perivitellin-1 or ovorubin, and perivitellin-2 (PV 2)) were detected and characterized. The site of synthesis of mollusc lipoproteins is hitherto unknown and was investigated for the egg lipoprotein PV2. Tissues (albumen gland, gonad-hepatopancreas complex and muscle) of vitellogenic females were incubated in vitro at 25 °C for 12h with 14C leucine. At the end of incubation period, soluble proteins from tissue homogenates and medium samples were analyzed for de novo protein synthesis by electrophoresis and HPLC, and radiolabeled proteins were quantified by liquid scincillation. Proteins in all tissues were radiolabelled, but muscle and gonad-hepatopancreas complex did not synthesize PV2, in spite of the fact that total protein synthesis levels were high. Two albumen gland radiolabeled proteins (67 and 31 kDa) comigrated with the subunits of PV2 and represented 6.0 % of the total labeled protein of that tissue. Western blot analysis with polyclonal antibodies confirmed the presence of  PV2 in albumen gland with negative results in gut, gonad-digestive gland complex, muscle, stomach hemolymph and lung. In vivo experiments where adult females were injected with 3H Leucine revealed that PV2 was not present in hemolymph. ELISA analysis in all tissues of the snail confirmed the PV2 presence only in albumen gland and developing eggs with levels of 26 mg/g and 98 mg/g protein, which represent 2.6 and 9.8 % of the total protein, respectively. Therefore, albumen gland is the only site of PV2 synthesis and no extragland synthesis, circulation or accummulation could be found. PV2 subunits were further characterized analyzing N-terminal sequences which showed no homology with other proteins.