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Functional characterization of bone morphogenetic protein binding sites and Smad1/5 activation in human vascular cells.
Mol Pharmacol. 2008 Feb; 73(2):539-52.MP

Abstract

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 (125)I-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 (125)I-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 (125)I-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 (125)I-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.

Authors+Show Affiliations

Department of Medicine, Box 157, Level 5, Addenbrooke's Hospital, Cambridge, United Kingdom. pdu21@medschl.cam.ac.ukNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17989347

Citation

Upton, Paul D., et al. "Functional Characterization of Bone Morphogenetic Protein Binding Sites and Smad1/5 Activation in Human Vascular Cells." Molecular Pharmacology, vol. 73, no. 2, 2008, pp. 539-52.
Upton PD, Long L, Trembath RC, et al. Functional characterization of bone morphogenetic protein binding sites and Smad1/5 activation in human vascular cells. Mol Pharmacol. 2008;73(2):539-52.
Upton, P. D., Long, L., Trembath, R. C., & Morrell, N. W. (2008). Functional characterization of bone morphogenetic protein binding sites and Smad1/5 activation in human vascular cells. Molecular Pharmacology, 73(2), 539-52.
Upton PD, et al. Functional Characterization of Bone Morphogenetic Protein Binding Sites and Smad1/5 Activation in Human Vascular Cells. Mol Pharmacol. 2008;73(2):539-52. PubMed PMID: 17989347.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Functional characterization of bone morphogenetic protein binding sites and Smad1/5 activation in human vascular cells. AU - Upton,Paul D, AU - Long,Lu, AU - Trembath,Richard C, AU - Morrell,Nicholas W, Y1 - 2007/11/07/ PY - 2007/11/9/pubmed PY - 2008/2/20/medline PY - 2007/11/9/entrez SP - 539 EP - 52 JF - Molecular pharmacology JO - Mol Pharmacol VL - 73 IS - 2 N2 - 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 (125)I-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 (125)I-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 (125)I-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 (125)I-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. SN - 1521-0111 UR - https://www.unboundmedicine.com/medline/citation/17989347/Functional_characterization_of_bone_morphogenetic_protein_binding_sites_and_Smad1/5_activation_in_human_vascular_cells_ L2 - http://molpharm.aspetjournals.org/cgi/pmidlookup?view=long&pmid=17989347 DB - PRIME DP - Unbound Medicine ER -