Associations between TGF-beta1 receptors in human bone marrow stromal cells.
Bone marrow stromal cells are required for sustained haemopoiesis. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine present in the bone marrow microenvironment which regulates the expression of several cytokines, cytokine receptors and cell adhesion elements. The TGF-beta receptors type I and II, and endoglin, mediate TGF-beta1 binding to the membrane of human bone marrow stromal cells. [125I]TGF-beta1-affinity labelling experiments showed that three different anti-endoglin monoclonal antibodies co-immunoprecipitated a 68 kD TGF-beta1-labelled polypeptide together with TGF-beta1/endoglin complexes. Here, we have shown that the 68 kD receptor corresponds to the type I receptor, indicating that endoglin and the type I receptor associate on the membrane of these cells upon ligand binding. The expression of endoglin by stromal cells was found to be up-regulated by TGF-beta1, but not by IL-1beta. The association of endoglin with signalling components of the TGF-beta receptor system on the membrane of bone marrow stromal cells might modulate TGF-beta1 access to the signalling pathways, and therefore it could regulate TGF-beta1-mediated stromal cellular responses.
Centro de Investigaciones Biológicas, Departamento de Immunología, Madrid, Spain.
M M
MM
Robledo
M A
MA
Ursa
F
F
Sánchez-Madrid
J
J
Teixidó
D015703:Antigens, CD; D001854:Bone Marrow Cells / Q000378:metabolism*; D002478:Cells, Cultured; D000071063:Endoglin; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; D007375:Interleukin-1; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D019010:Vascular Cell Adhesion Molecule-1