TGF Beta Receptor Dynamics

转化生长因子β生物学中的一个中心悖论是，相同的生长因子如何诱导生长刺激(即间充质细胞)和生长抑制(即上皮细胞)等不同的反应？考虑到转化生长因子在许多正常和病理条件下的关键作用，如果我们希望制定具体的干预策略，解决这个问题是根本的。为此，我们一直在研究一种普遍的假设，即细胞对转化生长因子的反应依赖于运输和信号机制的综合作用。为了支持这一提议，我们已经确定：(I)在极化的上皮细胞中，转化生长因子受体运输到连接复合体附近的基底侧域；(Ii)哺乳动物逆转录复合体通过控制内体循环到质膜递送，通过clathrin、EEA1和Rab11阳性间隔来特异性地维持II型转化生长因子受体的极性；(Iii)分离连接蛋白9(SNX9)，一个已知的运输蛋白，在其典型的质膜作用下游的转化生长因子-β信号转导中具有新的作用；(Iv)已经确定了一种独特的机制，通过该机制可以控制转化生长因子-B信号转导的特异性，并随后用于治疗依赖Smad3的疾病；(V)促纤维化的转化生长因子反应需要PDGF和ErbB受体酪氨酸激酶的协同作用；以及，最重要的是，(Vi)利用肺纤维化的治疗模型，提供临床前数据，通过靶向多个转化生长因子-β调节的通路可以稳定肺功能的生理参数。我们建议使用各种生化、生物学和遗传学方法来扩展这些发现。首先，我们将定义控制转化生长因子受体转运的受体元件和细胞因子，以及逆转聚体在转化生长因子刺激的EMT/迁移中的作用。 由于许多疾病是由于蛋白质分类或运输到特定细胞位置的能力缺陷所致，确定可操作的反式作用因子为改变细胞对转化生长因子的反应提供了潜在的机制。其次，将确定SNX9在调节Smad3依赖表型中的作用，包括肺纤维化和胶质母细胞瘤进展。在发达国家，超过45%的死亡归因于某种慢性纤维增生性疾病，而目前接受化疗的胶质母细胞瘤的中位无进展期和生存期分别为~7个月和15个月，显然需要新的方法。

A central paradox in transforming growth factor beta (TGF-ß) biology is how the same growth factor can induce such divergent responses as growth stimulation (i.e., mesenchymal cells) and growth inhibition (i.e., epithelial cells)? Considering the pivotal role TGF-ß has in a number of normal and pathological conditions, addressing that issue is fundamental if we hope to develop specific intervention strategies. To that end, we have been investigating the general hypothesis that the cellular response to TGF-ß is dependent upon an integrated action of the trafficking and signaling machinery. In support of that proposal, we have determined that (i) in polarized epithelial cells TGF-ß receptors traffic to the basolateral domain, adjacent to the junctional complex; (ii) the mammalian retromer complex specifically maintains type II TGF-ß receptor polarity by controlling recycling endosome to plasma membrane delivery by way of clathrin, EEA1 and Rab11 positive compartments; (iii) sorting nexin 9 (SNX9), a known trafficking protein, has a new role in TGF-ß signaling downstream of its canonical plasma membrane action; (iv) an unique mechanism has been defined by which specificity in TGF-ß signaling can be controlled and subsequently exploited to treat diseases dependent upon Smad3; (v) profibrotic TGF-ß responses require the cooperative action of PDGF and ErbB receptor tyrosine kinases; and, most importantly, (vi) utilizing a treatment model of lung fibrosis, provided preclinical data documenting that physiologic parameters of lung function can be stabilized by targeting multiple TGF-ß regulated pathways. We propose to extend these findings using a variety of biochemical, biological, and genetic approaches. First, the receptor elements and cellular factors controlling TGF-ß receptor trafficking as well as the role of retromer in TGF-ß stimulated EMT/migration will be defined. As a number of diseases result from defects in the ability to sort or transport proteins to defined cellular locales, characterizing the operative trans-acting factors provides potential mechanisms to alter the cellular response to TGF-ß. Second, the role of SNX9 in regulating Smad3-dependent phenotypes including lung fibrosis and glioblastoma progression will be determined. In that upwards of 45% of all deaths in the developed world are attributed to some sort of chronic fibroproliferative disorder, and the median progression-free and survival for glioblastoma with current chemoradiation is ~7 and 15 months, respectively, new approaches are clearly needed.