title: Granularin, a novel molluscan opsonin comprising a single vWF type C domain is up-regulated during parasitation.
abstract: Snails are intermediate hosts to schistosome parasites, some of which are the main cause of human schistosomiasis (bilharzia), and have been used as models for parasite-host interactions for a long time. Here, we have characterized a novel internal defense peptide of the snail Lymnaea stagnalis, of which the relative abundance in brain tissue increases upon infection with the avian schistosome Trichobilharzia ocellata. This protein, named granularin, is secreted by granular cells, which are numerous in the connective tissue surrounding the brain. The protein is unique because it comprises only a single Von Willebrand factor type C domain that is normally found in large transmembrane and secreted extracellular matrix proteins. The granularin gene is twice up-regulated during parasitation. Purified granularin stimulates phagocytosis of foreign particles by blood hemocytes. Together, our data indicate that granularin represents a novel protein that acts as an opsonin in the molluscan internal defense response.
authors.affiliation: Graduate School Neurosciences Amsterdam, Institute of Neuroscience, Department of Molecular and Cellular Neurobiology, Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: August B
authors.initials: AB
authors.lastname: Smit
authors.forename: Marijke
authors.initials: M
authors.lastname: De Jong-Brink
authors.forename: Ka Wan
authors.initials: KW
authors.lastname: Li
authors.forename: Marion M J
authors.initials: MM
authors.lastname: Sassen
authors.forename: Sabine
authors.initials: S
authors.lastname: Spijker
authors.forename: René
authors.initials: R
authors.lastname: Van Elk
authors.forename: Stèphanie
authors.initials: S
authors.lastname: Buijs
authors.forename: Jan
authors.initials: J
authors.lastname: Van Minnen
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Van Kesteren
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D004199:Disease Vectors; D017952:Ganglia, Invertebrate / Q000378:metabolism; D005786:Gene Expression Regulation; D006434:Hemocytes / Q000502:physiology; D006790:Host-Parasite Interactions / Q000235:genetics*; D006801:Humans; D008195:Lymnaea / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000469:parasitology; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009895:Opsonin Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D010587:Phagocytosis; D017434:Protein Structure, Tertiary; D012551:Schistosomatidae / Q000276:immunology / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014841:von Willebrand Factor / Q000737:chemistry
chemical_list: D018076:DNA, Complementary; D009895:Opsonin Proteins; C490698:granularin protein, Lymnaea stagnalis; D014841:von Willebrand Factor