Zhao J, Sime P J, Bringas P, Gauldie J, Warburton D
Center for Craniofacial Molecular Biology, Departments of Surgery and Pediatrics, The Children's Hospital Los Angeles Research Institute, University of Southern California Schools of Dentistry and Medicine Los Angeles, CA 90033, USA.
Mech Dev. 1998 Mar;72(1-2):89-100. doi: 10.1016/s0925-4773(98)00019-7.
Although exogenous transforming growth factor-beta (TGF-beta) is known to inhibit branching morphogenesis in mouse embryonic lungs in culture, whether the principal negative function of endogenous TGF-beta signaling resides in lung epithelium or mesenchyme remains unresolved. A recombinant adenovirus was constructed, containing a mutated human TGF-beta type II receptor with a truncated cytoplasmic kinase domain. We examined whether this dominant-negative receptor could abolish epithelium-specific endogenous TGF-beta signaling. We introduced the recombinant adenovirus into lung explants via intra-tracheal micro-injection. This resulted in over-expression of exogenous truncated TGF-beta type II receptor only in airway epithelium, not in mesenchyme, as assessed by mRNA level and protein localization. Blockade of endogenous TGF-beta receptor signaling in epithelial endoderm by the mutated dominant-negative TGF-beta type II receptor resulted in significant (65%) stimulation of epithelial branching morphogenesis, while exogenous TGF-beta no longer downregulated epithelial PCNA immunoreactivity and surfactant protein C (SP-C) expression. Additionally, the mitogenic responses to epidermal growth factor (EGF) and platelet-derived growth factor, PDGF-AA were potentiated by 33 and 31%, respectively. We conclude that epithelium-specific adenovirus-mediated over-expression of a dominant-negative TGF-beta type II receptor completely and specifically abolished the anti-proliferative effects of both endogenous and exogenous TGF-beta. Therefore, epithelium-specific TGF-beta signaling is sufficient to negatively regulate embryonic lung-branching morphogenesis in culture. We speculate that abrogation of TGF-beta signaling stimulates lung morphogenesis by potentiating the inductive and permissive effects of other endogenous peptide growth factors such as EGF and PDGF-AA.
虽然已知外源性转化生长因子-β（TGF-β）可抑制培养的小鼠胚胎肺中的分支形态发生，但内源性TGF-β信号传导的主要负性作用是存在于肺上皮还是间充质中仍未解决。构建了一种重组腺病毒，其包含具有截短细胞质激酶结构域的突变型人TGF-β II型受体。我们研究了这种显性负性受体是否能消除上皮特异性内源性TGF-β信号传导。通过气管内微量注射将重组腺病毒引入肺外植体。通过mRNA水平和蛋白质定位评估，这导致外源性截短的TGF-β II型受体仅在气道上皮中过度表达，而不在间充质中表达。突变的显性负性TGF-β II型受体阻断上皮内胚层中的内源性TGF-β受体信号传导，导致上皮分支形态发生显著（65%）刺激，而外源性TGF-β不再下调上皮增殖细胞核抗原（PCNA）免疫反应性和表面活性蛋白C（SP-C）表达。此外，对表皮生长因子（EGF）和血小板衍生生长因子PDGF-AA的促有丝分裂反应分别增强了33%和31%。我们得出结论，上皮特异性腺病毒介导的显性负性TGF-β II型受体的过度表达完全且特异性地消除了内源性和外源性TGF-β的抗增殖作用。因此，上皮特异性TGF-β信号传导足以在培养中负向调节胚胎肺分支形态发生。我们推测，TGF-β信号传导的废除通过增强其他内源性肽生长因子如EGF和PDGF-AA的诱导和允许作用来刺激肺形态发生。
