Schiemann William P, Blobe Gerard C, Kalume Dario E, Pandey Akhilesh, Lodish Harvey F
Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
J Biol Chem. 2002 Jul 26;277(30):27367-77. doi: 10.1074/jbc.M200148200. Epub 2002 May 20.
Fibulin-5 (FBLN-5; also known as DANCE or EVEC) is an integrin-binding extracellular matrix protein that mediates endothelial cell adhesion; it is also a calcium-dependent elastin-binding protein that scaffolds cells to elastic fibers, thereby preventing elastinopathy in the skin, lung, and vasculature. Transforming growth factor-beta (TGF-beta) regulates the production of cytokines, growth factors, and extracellular matrix proteins by a variety of cell types and tissues. We show here that TGF-beta stimulates murine 3T3-L1 fibroblasts to synthesize FBLN-5 transcript and protein through a Smad3-independent pathway. Overexpression of FBLN-5 in 3T3-L1 cells increased DNA synthesis and enhanced basal and TGF-beta-stimulated activation of ERK1/ERK2 and p38 mitogen-activated protein kinase (MAPK). FBLN-5 overexpression also augmented the tumorigenicity of human HT1080 fibrosarcoma cells by increasing their DNA synthesis, migration toward fibronectin, and invasion through synthetic basement membranes. In stark contrast, FBLN-5 expression was down-regulated in the majority of metastatic human malignancies, particularly in cancers of the kidney, breast, ovary, and colon. Unlike its proliferative response in fibroblasts, FBLN-5 overexpression in mink lung Mv1Lu epithelial cells resulted in an antiproliferative response, reducing their DNA synthesis and cyclin A expression. Moreover, FBLN-5 synergizes with TGF-beta in stimulating AP-1 activity in Mv1Lu cells, an effect that was abrogated by overexpression of dominant-negative versions of either MKK1 or p38 MAPKalpha. Accordingly, both the stimulation and duration of ERK1/ERK2 and p38 MAPK by TGF-beta was enhanced in Mv1Lu cells expressing FBLN-5. Our findings identify FBLN-5 as a novel TGF-beta-inducible target gene that regulates cell growth and motility in a context-specific manner and affects protein kinase activation by TGF-beta. Our findings also indicate that aberrant FBLN-5 expression likely contributes to tumor development in humans.
纤维连接蛋白-5（FBLN-5；也称为DANCE或EVEC）是一种整合素结合细胞外基质蛋白，介导内皮细胞黏附；它也是一种钙依赖性弹性蛋白结合蛋白，可将细胞支架到弹性纤维上，从而预防皮肤、肺和血管系统中的弹性蛋白病。转化生长因子-β（TGF-β）调节多种细胞类型和组织中细胞因子、生长因子和细胞外基质蛋白的产生。我们在此表明，TGF-β通过不依赖Smad3的途径刺激小鼠3T3-L1成纤维细胞合成FBLN-5转录本和蛋白质。FBLN-5在3T3-L1细胞中的过表达增加了DNA合成，并增强了ERK1/ERK2和p38丝裂原活化蛋白激酶（MAPK）的基础激活和TGF-β刺激的激活。FBLN-5过表达还通过增加人HT1080纤维肉瘤细胞的DNA合成、向纤连蛋白的迁移以及通过合成基底膜的侵袭，增强了其致瘤性。与之形成鲜明对比的是，在大多数转移性人类恶性肿瘤中，尤其是在肾癌、乳腺癌、卵巢癌和结肠癌中，FBLN-5表达下调。与它在成纤维细胞中的增殖反应不同，FBLN-5在貂肺Mv1Lu上皮细胞中的过表达导致抗增殖反应，减少了它们的DNA合成和细胞周期蛋白A表达。此外，FBLN-5在刺激Mv1Lu细胞中的AP-1活性方面与TGF-β协同作用，这一效应被MKK1或p38 MAPKα的显性负性版本的过表达所消除。因此，在表达FBLN-5的Mv1Lu细胞中，TGF-β对ERK1/ERK2和p38 MAPK的刺激和持续时间都增强了。我们的研究结果确定FBLN-5为一种新型的TGF-β诱导靶基因，它以一种上下文特异性的方式调节细胞生长和运动，并影响TGF-β对蛋白激酶的激活。我们的研究结果还表明，FBLN-5表达异常可能导致人类肿瘤的发生。
