title: Transthyretin interacts with the lysosome-associated membrane protein (LAMP-1) in circulation.
abstract: LAMP-1 (lysosome-associated membrane protein), a major glycoprotein present in the lysosomal membrane, constitutes up to 50% of total membrane proteins. LAMP-1, expressed at the plasma membrane, is reported to be the major molecule expressing the sialyl-Lewis X antigen. Two forms of LAMP-1 exist; the full-length LAMP-1 [LAMP-1 (+Tail)] has a highly glycosylated lumenal domain, a membrane-spanning domain and a short cytoplasmic tail, and the truncated LAMP-1 [LAMP-1 (-Tail)] contains only the lumenal domain. Soluble LAMP-1 (+/-Tail) has been reported in circulation. LAMP-1 at the cell surface has been shown to interact with E-selectin and galectin and is proposed to function in cell-cell interactions. However, the functional role(s) of soluble LAMP-1 in circulation is unclear. To investigate the functional role of soluble LAMP-1 in circulation, recombinant LAMP-1 (-Tail) and LAMP-1 (+Tail) were produced in HT1080 cells. Two immune-quantification assays were developed to distinguish between the LAMP-1 forms. The interaction and aggregation properties of the different LAMP-1 forms were investigated using the immune-quantification assays. Only LAMP-1 (+Tail) was found to aggregate and interact with plasma proteins. Plasma proteins that interact with LAMP-1 were isolated by affinity chromatography with either the recombinant LAMP-1 (-Tail) or a synthesized peptide consisting of the 14 amino acids of the LAMP-1 cytoplasmic tail. Transthyretin was found to interact with the cytoplasmic tail of LAMP-1. Transthyretin exists as a homotetramer in plasma, as such may play a role in the aggregation of LAMP-1 in circulation.
authors.affiliation: Lysosomal Diseases Research Unit, Department of Genetic Medicine, Women's and Children's Hospital, 72 King William Road, North Adelaide, South Australia 5006, Australia.
authors.forename: Melissa H Y
authors.initials: MH
authors.lastname: Chang
authors.forename: Chi T
authors.initials: CT
authors.lastname: Hua
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Isaac
authors.forename: Tom
authors.initials: T
authors.lastname: Litjens
authors.forename: Greg
authors.initials: G
authors.lastname: Hodge
authors.forename: Litsa E
authors.initials: LE
authors.lastname: Karageorgos
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Meikle
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D015703:Antigens, CD / Q000097:blood / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002793:Cholic Acids / Q000494:pharmacology; D005354:Fibrosarcoma / Q000737:chemistry / Q000235:genetics / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D051907:Lysosomal Membrane Proteins; D011228:Prealbumin / Q000378:metabolism*; D020033:Protein Isoforms / Q000097:blood / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D001798:Blood Proteins; D002793:Cholic Acids; D051907:Lysosomal Membrane Proteins; D011228:Prealbumin; D020033:Protein Isoforms; D011994:Recombinant Proteins; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate