title: Association of extracellular matrix proteins fibulin-1 and fibulin-2 with fibronectin in bone marrow stroma.
abstract: Extracellular matrix (ECM) molecules, together with growth factors and stromal cells, regulate haematopoietic cell development in bone marrow (BM). We report here expression of ECM proteins fibulin-1 and fibulin-2 in mouse BM. In other tissues, fibulin-1 and fibulin-2 associate with fibronectin and other ECM proteins. Fibulin-2 has also been found to adhere to cells via beta3 integrins. We studied the association of fibulins with fibronectin in BM stroma. By confocal microscopy, fibulin-1 and fibulin-2 immunostainings were co-localized with fibronectin in the adherent layer of long-term BM cultures. In cell adhesion assays using recombinant proteins, mouse fibulin-2 adhered to human erythroid-megakaryocytic leukaemia cell line HEL. This adhesion was mediated by beta3 integrins. However, HEL cells did not adhere to human fibulin-2. We therefore studied a possible species-specific cell-adhesive activity of mouse fibulin-2 by using mouse megakaryocytes, obtained by culture of BM cells in the presence of thrombopoietin. These megakaryocytes did not adhere to mouse fibulin-2. Our findings suggested that the functional role of fibulin-1 and fibulin-2 in BM stroma is related to binding to the major cell adhesion protein fibronectin, whereas adhesion of mouse fibulin-2 to human cells containing the integrin beta3 chain is not related to an apparent physiological function of the protein.
authors.affiliation: Department of Cell and Molecular Biology, Lund University, Lund, Sweden.
authors.forename: Y C
authors.initials: YC
authors.lastname: Gu
authors.forename: K
authors.initials: K
authors.lastname: Nilsson
authors.forename: H
authors.initials: H
authors.lastname: Eng
authors.forename: M
authors.initials: M
authors.lastname: Ekblom
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000737:chemistry / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D002448:Cell Adhesion; D018920:Coculture Techniques; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000378:metabolism*; D005353:Fibronectins / Q000032:analysis / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D015151:Immunoblotting; D008533:Megakaryocytes / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018613:Microscopy, Confocal; D011485:Protein Binding; D014407:Tumor Cells, Cultured
chemical_list: D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; C060820:fibulin; C084612:fibulin 2