Saposin

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Trichinella Spiralis Secretes A Homologue Of Prosaposin

Journal Title, Volume, Page: 
Molecular and Biochemical Parasitology Volume 135, Issue 1, May 2004, Pages 49-56
Year of Publication: 
2004
Authors: 
Ayman S. Hussein
Department of Biological Sciences, Biochemistry Building, Imperial College London, London SW7 2AZ, UK
Current Affiliation: 
Faculty of Medicine & Health Sciences, Department of Biomedical Sciences, An-Najah National University, Nablus, Palestine
Murray E. Selkirk
Department of Biological Sciences, Biochemistry Building, Imperial College London, London SW7 2AZ, UK
Anne E. Chambers
National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
David Goulding
Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, UK
Marie-Pierre Gares
Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, UK
Celia Vásquez-Lopez
Department of Biological Sciences, Biochemistry Building, Imperial College London, London SW7 2AZ, UK
Teresa Gárate
Instituto de Salud Carlos III, Centro Nacional de Microbiologia, Majadahonda, Madrid, Spain
R.Michael E. Parkhouse
Instituto Gulbenkian de Ciência, PGDB, Apartado 14, 2781-901 Oeiras, Portugal
Kleoniki Gounaris
Department of Biological Sciences, Biochemistry Building, Imperial College London, London SW7 2AZ, UK
Preferred Abstract (Original): 

Infective larvae and adult stage Trichinella spiralis secrete a protein homologous to prosaposin, the precursor of sphingolipid activator proteins (saposins) A–D originally defined in vertebrates. The protein contains four saposin domains, with the six cysteine residues which form the three intramolecular disulphide bonds in close register in each case. It differs substantially from vertebrate prosaposins in the N-terminal prodomain, the region separating saposins A and B, and completely lacks the C-terminal domain which has been demonstrated to be essential for lysosomal targetting in these organisms. The protein is secreted in unprocessed form with an estimated mass of 56 kDa, and contains a single N-linked glycan which is bound by the monoclonal antibody NIM-M1, characteristic of the TSL-1 antigens which are capped by tyvelose (3,6-dideoxy-d-arabinohexose). Immuno-electron microscopy localised the protein to membrane-bound vesicles and more complex multi-lamellar organelles in diverse tissues including the hypodermis, intestine and stichosomes, although it was absent from the dense-core secretory granules typical of the latter. Possible functions of a secreted prosaposin are discussed.

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