title: A new Ig-superfamily member, molluscan defence molecule (MDM) from Lymnaea stagnalis, is down-regulated during parasitosis.
abstract: To survive the attacks of the internal defence system (IDS) of their host, parasites have developed various strategies to manipulate the IDS. We present evidence that the avian schistosome parasite Trichobilharzia ocellata affects gene expression in the granular cells, a cell type of the IDS of the intermediate host, the mollusc Lymnaea stagnalis. From a differential screening, a clone was isolated encoding a protein named molluscan defence molecule (MDM), which encompasses five C2-like immunoglobulin (Ig) domains. The protein shares a domain organization and high amino acid sequence identity with hemolin, an Ig-family member of the insect IDS. Interestingly, both MDM and hemolin have highest sequence identity with neural cell adhesion molecules, but lack the typical fibronectin repeats and motifs for membrane anchors. We find that the expression of the MDM gene is gradually down-regulated during the course of parasitosis to approximately 21% compared to the non-parasitized level, 8 weeks post-infection. Based on our findings, we suggest that MDM is involved in the proper function of the Lymnaea IDS, and that down-regulation of MDM is part of the parasite-induced disabling on non-self recognition.
authors.affiliation: Graduate School Neurosciences Amsterdam, Faculty of Biology, Department of Experimental Zoology, Vrije Universiteit, The Netherlands. Hoek@bio.vu.nl
authors.forename: R M
authors.initials: RM
authors.lastname: Hoek
authors.forename: A B
authors.initials: AB
authors.lastname: Smit
authors.forename: H
authors.initials: H
authors.lastname: Frings
authors.forename: J M
authors.initials: JM
authors.lastname: Vink
authors.forename: M
authors.initials: M
authors.lastname: de Jong-Brink
authors.forename: W P
authors.initials: WP
authors.lastname: Geraerts
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry; D058969:Contactin 2; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D005796:Genes; D006790:Host-Parasite Interactions; D007136:Immunoglobulins; D017403:In Situ Hybridization; D019476:Insect Proteins; D008195:Lymnaea / Q000276:immunology* / Q000469:parasitology; D008969:Molecular Sequence Data; D008978:Mollusk Venoms / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005810:Multigene Family; D011506:Proteins / Q000737:chemistry; D012551:Schistosomatidae / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; D058969:Contactin 2; D029721:Drosophila Proteins; D007136:Immunoglobulins; D019476:Insect Proteins; C099385:MDM protein, Lymnaea stagnalis; D008978:Mollusk Venoms; D011506:Proteins; C061745:Nrg protein, Drosophila; C066846:hemolin