QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: mol.107.041673v1 73/2/539    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Upton, P. D. Articles by Morrell, N. W. Search for Related Content PubMed PubMed Citation Articles by Upton, P. D. Articles by Morrell, N. W.

Functional Characterization of Bone Morphogenetic Protein Binding Sites and Smad1/5 Activation in Human Vascular Cells

Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, England (P.D.U., L.L., N.W.M.); and King's College London, London, England (R.C.)

Mutations in the bone morphogenetic protein (BMP) type II receptor (BMPR2) gene cause familial pulmonary arterial hypertension (FPAH), a disease characterized by excessive smooth muscle and endothelial cell proliferation. However, the specific receptors mediating responses to BMPs in human vascular cells are not known. We show that human pulmonary artery smooth muscle cells (HPASMCs) express high specific ¹²⁵I-BMP4 binding, whereas human microvascular endothelial cells (HMEC-1) and human pulmonary artery endothelial cells (HPAECs) exhibit low binding. BMP4 competes for both high- and low-affinity ¹²⁵I-BMP4 binding sites on HPASMCs, yet BMP2 competes only at the low-affinity binding sites. In addition, BMP4, but not BMP2, induced Smad1/5 phosphorylation at low concentrations in HPASMCs. Conversely, HMEC-1 cells exhibited a single binding site population with equal affinity for BMP2 and BMP4. In both cell types, growth differentiation factor-5 (GDF5), BMP6, and BMP7 stimulated Smad1/5 phosphorylation and competed for ¹²⁵I-BMP4 less efficiently than BMP2 or BMP4. HPAECs exhibited weak Smad responses to BMPs. Expression analysis suggested the low binding in endothelial cells corresponded to lower ALK3 and ALK6 expression. Although transfection of small interfering RNAs (siRNAs) for ALK3 and BMPR-II abrogated Smad1/5 phosphorylation to BMP4, BMP2, and GDF5 in HMEC-1 and HPASMCs, they had little effect on ¹²⁵I-BMP4 binding. ALK6 siRNA did not alter binding or Smad1/5 responses, even to GDF5, a reported ALK6 selective ligand. Therefore, ALK3/BMPR-II is the BMP4/BMP2/GDF5-responsive receptor in human vascular cells, but these studies suggest that a BMP4/GDF5 selective binding protein exists in HPASMCs. These cell-specific differences in BMP responses are important for understanding the pathogenesis of FPAH.

Address correspondence to: Dr. Paul D. Upton, Department of Medicine, Box 157, Level 5, Addenbrooke's Hospital, Cambridge, United Kingdom, CB2 2QQ. E-mail: pdu21{at}medschl.cam.ac.uk

This article has been cited by other articles:

				N. W. Morrell, S. Adnot, S. L. Archer, J. Dupuis, P. Lloyd Jones, M. R. MacLean, I. F. McMurtry, K. R. Stenmark, P. A. Thistlethwaite, N. Weissmann, et al. Cellular and Molecular Basis of Pulmonary Arterial Hypertension J. Am. Coll. Cardiol., June 30, 2009; 54(1_Suppl_S): S20 - S31. [Abstract] [Full Text] [PDF]

				P. D. Upton, R. J. Davies, R. C. Trembath, and N. W. Morrell Bone Morphogenetic Protein (BMP) and Activin Type II Receptors Balance BMP9 Signals Mediated by Activin Receptor-like Kinase-1 in Human Pulmonary Artery Endothelial Cells J. Biol. Chem., June 5, 2009; 284(23): 15794 - 15804. [Abstract] [Full Text] [PDF]

				A. Sobolewski, N. Rudarakanchana, P. D. Upton, J. Yang, T. K. Crilley, R. C. Trembath, and N. W. Morrell Failure of bone morphogenetic protein receptor trafficking in pulmonary arterial hypertension: potential for rescue Hum. Mol. Genet., October 15, 2008; 17(20): 3180 - 3190. [Abstract] [Full Text] [PDF]