Altered growth responses of pulmonary artery smooth muscle cells from patients with primary pulmonary hypertension to transforming growth factor-beta(1) and bone morphogenetic proteins.
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BACKGROUND: Mutations in the type II receptor for bone morphogenetic protein (BMPR-II), a receptor member of the transforming growth factor-beta (TGF-beta) superfamily, underlie many cases of familial and sporadic primary pulmonary hypertension (PPH). We postulated that pulmonary artery smooth muscle cells (PASMCs) from patients with PPH might demonstrate abnormal growth responses to TGF-beta superfamily members. METHODS AND RESULTS: For studies of (3)H-thymidine incorporation or cell proliferation, PASMCs (passages 4 to 8) were derived from main pulmonary arteries. In control cells, 24-hour incubation with TGF-beta(1) (10 ng/mL) or bone morphogenetic protein (BMP)-2, -4, and -7 (100 ng/mL) inhibited basal and serum-stimulated (3)H-thymidine incorporation, and TGF-beta(1) and BMPs inhibited the proliferation of serum-stimulated PASMCs. In contrast, TGF-beta(1) stimulated (3)H-thymidine incorporation (200%; P<0.001) and cell proliferation in PASMCs from PPH but not from patients with secondary pulmonary hypertension. In addition, BMPs failed to suppress DNA synthesis and proliferation in PASMCs from PPH patients. Reverse transcription-polymerase chain reaction of PASMC mRNA detected transcripts for type I (TGF-betaRI, Alk-1, ActRI, and BMPRIB) and type II (TGF-betaRII, BMPR-II, ActRII, ActRIIB) receptors. Receptor binding and cross-linking studies with (125)I-TGF-beta(1) confirmed that the abnormal responses in PPH cells were not due to differences in TGF-beta receptor binding. Mutation analysis of PASMC DNA failed to detect mutations in TGF-betaRII and Alk-1 but confirmed the presence of a mutation in BMPR-II in 1 of 5 PPH isolates. CONCLUSIONS: We conclude that PASMCs from patients with PPH exhibit abnormal growth responses to TGF-beta(1) and BMPs and that altered integration of TGF-beta superfamily growth signals may contribute to the pathogenesis of PPH. (+info)
Bone morphogenetic proteins, genetics and the pathophysiology of primary pulmonary hypertension.
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Several recent papers have shown that both familial primary pulmonary hypertension (FPPH) and sporadic primary pulmonary hypertension (PPH) may have a common etiology that is associated with the inheritance and/or spontaneous development of germline mutations in the bone morphogenetic protein receptor (BMPR) type II gene. Because BMPR-II is a ubiquitously expressed receptor for a family of secreted growth factors known as the bone morphogenetic proteins (BMPs), these findings suggest that BMPs play an important role in the maintenance of normal pulmonary vascular physiology. In the present commentary we discuss the implications of these findings in the context of BMP receptor biology, and relate these data to the genetics and pulmonary pathophysiology of patients with PPH. (+info)
The Drosophila BMP type II receptor Wishful Thinking regulates neuromuscular synapse morphology and function.
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Proper synaptic development is critical for establishing all aspects of neural function including learning, memory, and locomotion. Here, we describe the phenotypic consequences of mutations in the wishful thinking (wit) gene, the Drosophila homolog of the vertebrate BMP type II receptor. Mutations in wit result in pharate lethality that can be rescued by expression of a wit transgene in motor neurons but not in muscles. Mutant larvae exhibit small synapses, severe defects in evoked junctional potentials, a lower frequency of spontaneous vesicle release, and an alteration in the ultrastructure of synaptic active zones. These results reveal a novel role for BMP signaling in regulating Drosophila neuromuscular junction synapse assembly and activity and may indicate that similar pathways could govern vertebrate synapse development. (+info)
wishful thinking encodes a BMP type II receptor that regulates synaptic growth in Drosophila.
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We conducted a large-scale screen for Drosophila mutants that have structural abnormalities of the larval neuromuscular junction (NMJ). We recovered mutations in wishful thinking (wit), a gene that positively regulates synaptic growth. wit encodes a BMP type II receptor. In wit mutant larvae, the size of the NMJs is greatly reduced relative to the size of the muscles. wit NMJs have reduced evoked excitatory junctional potentials, decreased levels of the synaptic cell adhesion molecule Fasciclin II, and synaptic membrane detachment at active zones. Wit is expressed by a subset of neurons, including motoneurons. The NMJ phenotype is specifically rescued by transgenic expression of Wit only in motoneurons. Thus, Wit appears to function as a presynaptic receptor that regulates synaptic size at the Drosophila NMJ. (+info)
Recent insights into the pathogenesis and therapeutics of pulmonary hypertension.
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The normal adult pulmonary circulation is a low-pressure, high-capacity circuit. Pulmonary vascular resistance is regulated by alveolar oxygen tension, potassium channels and a variety of locally produced and circulating vasoactive factors. Perturbations of these systems may contribute to the pathogenesis of pulmonary hypertension. Recently, mutations in BMPR2 and ALK-1, genes that encode members of the transforming growth factor-beta (TGF-beta) receptor superfamily, have been found in patients with primary pulmonary hypertension. These observations provide a novel insight into the pathogenesis of primary pulmonary hypertension, and emphasize the importance of the integrity of the TGF-beta receptor family in the maintenance of normal pulmonary vascular structure and function. This review discusses the latest developments in the field of pulmonary vascular biology and the prospects for improving the treatment of pulmonary hypertension. (+info)
Effect of bone morphogenetic protein 2 (BMP2) on oestradiol and inhibin A production by sheep granulosa cells, and localization of BMP receptors in the ovary by immunohistochemistry.
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The bone morphogenetic proteins (BMPs) have been implicated in the paracrine regulation of ovarian follicular development. In this study, we investigated the expression of the BMP receptors (BMPRs) in sheep ovaries by immunohistochemistry and the effect of BMP2, a natural ligand for these receptors, on granulosa cells cultured in vitro. Ovaries from cyclic ewes were fixed, embedded in paraffin wax and cut into sections. The sections were rehydrated, submitted to microwave antigen retrieval and treated with polyclonal antibodies against BMPR1A, BMPR1B and BMPR2. Strong immunostaining for all three receptors was observed in the granulosa cell layer of follicles from the primary to late antral stages of development. Staining was also present in the oocyte, corpus luteum, ovarian surface epithelium and, to a lesser extent, the theca layer of antral follicles. For functional studies, granulosa cells were obtained from immature follicles 1-3 mm in diameter. The cells were cultured for 6 days in serum-free medium containing 1 ng oFSH-20 ml(-1) in the presence of 0, 3, 10 or 30 ng ml(-1) human recombinant BMP2. The medium was replaced every 2 days and oestradiol and inhibin A concentrations were measured in the spent medium. In the absence of BMP2, oestradiol and inhibin A production increased as the granulosa cells differentiated in vitro. The addition of the highest dose of BMP2 enhanced oestradiol production (P < 0.05) without affecting the proliferation of the cells. It is concluded that BMP receptors are present in sheep ovaries and that BMPs may have a role in the differentiation of granulosa cells by enhancing the action of FSH. (+info)
Primary pulmonary hypertension is associated with reduced pulmonary vascular expression of type II bone morphogenetic protein receptor.
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BACKGROUND: Mutations in the type II receptor for bone morphogenetic protein (BMPR-II), a receptor member of the transforming growth factor-beta (TGF-beta) superfamily, underlie many familial and sporadic cases of primary pulmonary hypertension (PPH). METHODS AND RESULTS: Because the sites of expression of BMPR-II in the normal and hypertensive lung are unknown, we studied the cellular localization of BMPR-II and the related type I and II receptors for TGF-beta by immunohistochemistry in lung sections from patients undergoing heart-lung transplantation for PPH (n=11, including 3 familial cases) or secondary pulmonary hypertension (n=6) and from unused donor lungs (n=4). In situ hybridization was performed for BMPR-II mRNA. Patients were screened for the presence of mutations in BMPR2. In normal lungs, BMPR-II expression was prominent on vascular endothelium, with minimal expression in airway and arterial smooth muscle. In pulmonary hypertension cases, the intensity of BMPR-II immunostaining varied between lesions but involved endothelial and myofibroblast components. Image analysis confirmed that expression of BMPR-II was markedly reduced in the peripheral lung of PPH patients, especially in those harboring heterozygous BMPR2 mutations. A less marked reduction was also observed in patients with secondary pulmonary hypertension. In contrast, there was no difference in level of staining for TGF-betaRII or the endothelial marker CD31. CONCLUSIONS: The cellular localization of BMPR-II is consistent with a role in the formation of pulmonary vascular lesions in PPH, and reduced BMPR-II expression may contribute to the process of vascular obliteration in severe pulmonary hypertension. (+info)
Functional analysis of bone morphogenetic protein type II receptor mutations underlying primary pulmonary hypertension.
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A wide range of mutations in the type II receptor for bone morphogenetic protein (BMPR-II) have been shown to underlie primary pulmonary hypertension. To determine the mechanism of altered BMPR-II function, we employed transient transfection studies in cell lines and primary cultures of pulmonary vascular smooth muscle cells using green fluorescent protein (GFP)-tagged wild-type and mutant BMPR2 constructs and confocal microscopy to localize receptors. Substitution of cysteine residues in the ligand binding or kinase domain prevented trafficking of BMPR-II to the cell surface, and reduced binding of (125)I-BMP4. In addition, transfection of cysteine-substituted BMPR-II markedly reduced basal and BMP4-stimulated transcriptional activity of a BMP/Smad responsive luciferase reporter gene (3GC2wt-Lux), compared with wild-type BMPR-II, suggesting a dominant-negative effect of these mutants on Smad signalling. In contrast, BMPR-II containing non-cysteine substitutions in the kinase domain were localized to the cell membrane, although these also suppressed the activity of 3GC2wt-Lux. Interestingly, BMPR-II mutations within the cytoplasmic tail trafficked to the cell surface, but retained the ability to activate 3GC2wt-Lux. Transfection of mutant, but not wild-type, constructs into a mouse epithelial cell line (NMuMG cells) led to activation of p38(MAPK) and increased serum-induced proliferation compared with the wild-type receptor, which was partly p38(MAPK)-dependent. We conclude that mutations in BMPR-II heterogeneously inhibit BMP/Smad-mediated signalling by diverse molecular mechanisms. However, all mutants studied demonstrate a gain of function involving upregulation of p38(MAPK)-dependent proproliferative pathways. (+info)