Synthesis, Distribution, and Levels of an Egg Lipoprotein From the Apple Snail Pomacea canaliculata (Mollusca: Gastropoda)

M. DREON, S. LAVARIAS, C.F. GARIN, H. HERAS,* AND R.J. POLLERO
Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CONICET-UNLP, 1900 La Plata, Argentina

ABSTRACT

The site of synthesis of mollusc lipoproteins is hitherto unknown and was investigated for perivitellin 2 (PV2), an egg lipoprotein found in the freshwater snail Pomacea canaliculata. Tissues (albumen gland, gonad–digestive gland complex, and muscle) from vitellogenic females
were incubated in vitro with 14C-leucine at 25°C for 12 hr. At the end of incubation, soluble proteins from tissue homogenates and medium were analyzed for de novo protein synthesis by electrophoresis and HPLC, and radiolabeled proteins were quantified by liquid scintillation. Two albumen gland radiolabeled proteins (67 and 31 kDa) co-migrated with the subunits of PV2, and they represented 6.0% of the total labeled protein in that tissue. Western blot analysis confirmed the presence of PV2 only in the albumen gland. 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 the albumen gland and developing eggs with levels of 26 and 98 mg/g protein, respectively. Therefore, the albumen gland is the only site for PV2 synthesis, and no extra-gland synthesis, circulation, or accumulation could be found. PV2 subunits were further characterized analyzing N-terminal sequences which showed no homology with other proteins.

Journal of experimental zoology (2002), 292:323–330

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