title: Thrombospondin 1 and thrombospondin 2 are expressed as both homo- and heterotrimers.
abstract: There exist two distinct thrombospondin molecules (designated TSP1 and TSP2) which are encoded by separate genes. TSP1 is a trimeric cell surface and extracellular matrix molecule. Sequence comparison reveals that the 2 cysteines involved in interchain disulfide linkage and trimer assembly in TSP1 are conserved in TSP2 (Laherty, C. D., O'Rourke, K., Wolf, F. W., Katz, R., Seldin, M. F., and Dixit, V. M. (1992) J. Biol. Chem. 267, 3274-3281). Swiss 3T3 fibroblasts express both TSP1 and TSP2, and, therefore, an important question is whether TSP in such cells is expressed as homotrimers or as heterotrimers. We find that Swiss 3T3 cells and epithelial cells transfected with TSP expression vectors express both homo- and heterotrimeric forms of TSP. In addition, homotrimeric TSP2 has a lower affinity for heparin than homotrimeric TSP1. Thus, the heparin affinity of TSP can be modulated by the expression of TSP as homo- or heterotrimers.
authors.affiliation: Department of Pathology, University of Michigan Medical School, Ann Arbor 48109.
authors.forename: K M
authors.initials: KM
authors.lastname: O'Rourke
authors.forename: C D
authors.initials: CD
authors.lastname: Laherty
authors.forename: V M
authors.initials: VM
authors.lastname: Dixit
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000918:Antibody Specificity; D015153:Blotting, Western; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D003545:Cysteine / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005822:Genetic Vectors; D007118:Immunoassay; D037102:Lectins / Q000096:biosynthesis / Q000235:genetics*; D046911:Macromolecular Substances; D008715:Methionine / Q000378:metabolism; D051379:Mice; D010980:Platelet Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D019699:Thrombospondins; D014162:Transfection
chemical_list: D037102:Lectins; D046911:Macromolecular Substances; D010980:Platelet Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D019699:Thrombospondins; D008715:Methionine; D003545:Cysteine