title: myo-Inositol hexakisphosphate is a major component of an extracellular structure in the parasitic cestode Echinococcus granulosus.
abstract: myo-Inositol hexakisphosphate (IP(6)) is an abundant intracellular component of animal cells. In this study we describe the presence of extracellular IP(6) in the hydatid cyst wall (HCW) of the larval stage of the cestode parasite Echinococcus granulosus. The HCW comprises an inner cellular layer and an outer, acellular (laminated) layer up to 2 mm in thickness that protects the parasite from host immune cells. A compound, subsequently identified as IP(6), was detected in and purified from an HCW extract on the basis of its capacity to inhibit complement activation. The identification of the isolated compound was carried out by a combination of NMR, MS and TLC. The majority of IP(6) in the HCW was found in the acellular layer, with only a small fraction of the compound being extracted from cells. In the laminated layer, IP(6) was present in association with calcium, and accounted for up to 15% of the total dry mass of the HCW. IP(6) was not detected in any other structures or stages of the parasite. Our results imply that IP(6) is secreted by the larval stage of the parasite in a polarized fashion towards the interface with the host. This is the first report of the secretion of IP(6), and the possible implications beyond the biology of E. granulosus are discussed.
authors.affiliation: Cátedra de Inmunología, Facultad de Química/Ciencias, Universidad de la República, Avenida Alfredo Navarro 3051, piso 2, CP 11600, Montevideo, Uruguay.
authors.forename: Florencia
authors.initials: F
authors.lastname: Irigoín
authors.forename: Fernando
authors.initials: F
authors.lastname: Ferreira
authors.forename: Cecilia
authors.initials: C
authors.lastname: Fernández
authors.forename: Robert B
authors.initials: RB
authors.lastname: Sim
authors.forename: Alvaro
authors.initials: A
authors.lastname: Díaz
mesh_terms: D000818:Animals; D000947:Antigens, Helminth / Q000032:analysis; D002118:Calcium / Q000032:analysis; D002473:Cell Wall / Q000737:chemistry; D002855:Chromatography, Thin Layer; D021984:Cyclophilin A / Q000032:analysis; D004446:Echinococcus / Q000737:chemistry* / Q000254:growth & development; D005110:Extracellular Space / Q000737:chemistry; D015801:Helminth Proteins / Q000032:analysis; D008274:Magnesium / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010833:Phytic Acid / Q000032:analysis* / Q000302:isolation & purification
chemical_list: D000947:Antigens, Helminth; D015801:Helminth Proteins; C406723:P-29 antigen; D010833:Phytic Acid; D021984:Cyclophilin A; D008274:Magnesium; D002118:Calcium