Abstracts - Deutsche Zoologische Gesellschaft

Physiology Symposium 83O PH.5 (Sa) - ENA novel discoidal high-density-lipoprotein in Crustacea – a prototype in lipoproteinarchitecture?Stefanie Stieb, Sven Schenk, Ulrich HoegerInstitut für Zoologie, Abt. I, Johannes Gutenberg-Universität, MainzLipoproteins are the ‚lipid-emulsifiers‘ in animals. The secreted apoproteins complex lipids andform the mature lipoproteins which consist of a lipid and a protein part. According to their densitylipoproteins are classified into four groups: the very low-density (VLDL), low-density (LDL), highdensity(HDL) and the very high-density (VHDL) lipoproteins. In crustaceans, two classes of sexindependent lipoproteins are present: a ß-glycan-binding-protein/HDL, which possesses defensivefunctions besides its role in lipid transport, and the clotting protein/VHDL. These two lipoproteinsare globular in shape with a diameter of ~7 nm and have a lipid content below 20%. However, wehave recently found a third sex-independent lipoprotein present in at least one species of Crustacea,the crayfish Astacus leptodactylus. This novel HDL-type lipoprotein has a high lipid binding capacityof over 60%. It is discoidal in shape with a diameter of about 40 nm. As judged from its morphologyand some biochemical properties (apoprotein composition and stoichiometry, sedimentation coefficient),it shows remarkable similarities with the lipoprotein from a lower invertebrate, the polychaeteNereis virens. These similarities suggest this type of lipoprotein as a prototype in the lipoproteinevolution. It remains enigmatic at present why this lipoprotein found in A. leptodactylus is absent inthe congener A. astacus. Supported by the Deutsche Forschungsgemeinschaft (Ho 889/7-1).O PH.6 (Sa) - ENLipoprotein receptors in the polychaete Nereis virensSven Schenk 1 , Ulrich HoegerInstitut für Zoologie, Abt. I, Johannes Gutenberg-Universität, MainzTransportation of hydrophilic components such as dietary lipids, pigments or hormones through theaqueous body media requires the presence of lipoproteins. After the isolation and characterization ofthe HDL-type lipoprotein from the coelomic fluid of the polychaete Nereis virens, the correspondinglipoprotein receptor was isolated from the membranes of various tissues and cells by affinitychromatography. The functionality of the isolated receptor protein was demonstrated by ligand blotanalysis. The receptor was found to be a monomeric, integral membrane glycoprotein with an apparentmass of ~110 kDa as judged from SDS-PAGE. In ligand blot analysis, however, it showed amass of ~120 kDa. The binding properties showed strong dependence for Ca 2+ and the presence ofdisulfide bonds. Ligand binding was inhibited in the presence of 5 mM suramin. These biochemicalparameters suggest that this receptor is member of the LDLR superfamily, which have been describedin many animal species, although mainly by genetical approaches. The protein was presentin all kinds of cells and tissues such as oocytes, spermatogonia, elaeocytes, muscle and intestine.Biological function was demonstrated by the in-cooperation of fluorescently labeled Nereis lipoproteininto oocytes and eleocytes in vitro. Supported by the DFG (Ho-889/7-1)