title: HlSRB, a Class B scavenger receptor, is key to the granulocyte-mediated microbial phagocytosis in ticks.
abstract: Ixodid ticks transmit various pathogens of deadly diseases to humans and animals. However, the specific molecule that functions in the recognition and control of pathogens inside ticks is not yet to be identified. Class B scavenger receptor CD36 (SRB) participates in internalization of apoptotic cells, certain bacterial and fungal pathogens, and modified low-density lipoproteins. Recently, we have reported on recombinant HlSRB, a 50-kDa protein with one hydrophobic SRB domain from the hard tick, Haemaphysalis longicornis. Here, we show that HlSRB plays vital roles in granulocyte-mediated phagocytosis to invading Escherichia coli and contributes to the first-line host defense against various pathogens. Data clearly revealed that granulocytes that up-regulated the expression of cell surface HlSRB are almost exclusively involved in hemocyte-mediated phagocytosis for E. coli in ticks, and post-transcriptional silencing of the HlSRB-specific gene ablated the granulocytes' ability to phagocytose E. coli and resulted in the mortality of ticks due to high bacteremia. This is the first report demonstrating that a scavenger receptor molecule contributes to hemocyte-mediated phagocytosis against exogenous pathogens, isolated and characterized from hematophagous arthropods.
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi, Japan.
authors.forename: Kyaw Min
authors.initials: KM
authors.lastname: Aung
authors.forename: Damdinsuren
authors.initials: D
authors.lastname: Boldbaatar
authors.forename: Rika
authors.initials: R
authors.lastname: Umemiya-Shirafuji
authors.forename: Min
authors.initials: M
authors.lastname: Liao
authors.forename: Naotoshi
authors.initials: N
authors.lastname: Tsuji
authors.forename: Xuan
authors.initials: X
authors.lastname: Xuenan
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Aiko
authors.initials: A
authors.lastname: Kume
authors.forename: Remil Linggatong
authors.initials: RL
authors.lastname: Galay
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tanaka
authors.forename: Kozo
authors.initials: K
authors.lastname: Fujisaki
mesh_terms: D000818:Animals; D018955:CD36 Antigens / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005260:Female; D006098:Granulocytes / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D026863:Ixodidae / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D021381:Protein Transport; D011817:Rabbits
chemical_list: D018955:CD36 Antigens