TGF Beta Receptor Dynamics

转化生长因子β（TGF-β）生物学中的一个中心矛盾是相同的生长因子如何诱导诸如生长刺激（即，间充质细胞）和生长抑制（即，上皮细胞）？考虑到TGF-β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，解决这个问题是至关重要的。为此，我们一直在调查的一般假设，细胞对TGF-β的反应是依赖于运输和信号机制的综合行动。为了支持该提议，我们已经确定（i）在极化的上皮细胞中，TGF-β受体运输至基底外侧结构域，邻近连接复合物;（ii）哺乳动物逆转录体复合物通过网格蛋白、EEA 1和Rab 11阳性隔室控制再循环内体至质膜递送而特异性地维持II型TGF-β受体极性;（iii）分选连接蛋白9（SNX 9），一种已知的运输蛋白，在其典型质膜作用的TGF-β信号传导下游具有新的作用;（iv）已经定义了一种独特的机制，通过该机制可以控制TGF-β信号传导中的特异性并随后用于治疗依赖于Smad 3的疾病;（v）促纤维化TGF-β应答需要PDGF和ErbB受体酪氨酸激酶的协同作用;并且，最重要的是，（vi）利用肺纤维化的治疗模型，所提供的临床前数据证明肺功能的生理参数可以通过靶向多种TGF-β调节途径来稳定。我们建议使用各种生物化学，生物学和遗传学方法来扩展这些发现。首先，将定义控制TGF-β受体运输的受体元件和细胞因子以及逆转录酶在TGF-β刺激的EMT/迁移中的作用。 由于许多疾病是由将蛋白质分选或转运到限定的细胞区域的能力缺陷引起的，因此表征有效的反式作用因子提供了改变对TGF-β的细胞应答的潜在机制。其次，将确定SNX 9在调节Smad 3依赖性表型（包括肺纤维化和胶质母细胞瘤进展）中的作用。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，并且目前放化疗的胶质母细胞瘤的中位无进展和生存期分别为约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.