Stockwell B R, Schreiber S L
Howard Hughes Medical Institute, Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138, USA.
Curr Biol. 1998 Jun 18;8(13):761-70. doi: 10.1016/s0960-9822(98)70299-4.
Transforming growth factor Beta (TGF-Beta) arrests many cell types in the G1 phase of the cell and upregulates plasminogen activator inhibitor 1 (PAI-1). The type 1 (TGF-Beta RI) an II (TGF-Beta RII) TGF-Beta receptors mediate these and other effects of TGF-Beta on target cells. TGF-Beta initially binds to TGF-Beta RII and subsequently TGF-Beta RI is recruited to form a heteromeric complex. TGF-Beta RI phosphorylates the downstream effectors Smad2 and Smad3, leading to their translocation into the nucleus. Here, we explored the role of receptor oligomerization in TGF-Beta signaling.
We constructed fusion proteins containing receptor cytoplasmic tails linked to binding domains for small-molecule dimerizers. In COS-1 cells, recruitment of a soluble TGF-Beta RII tail to a myristoylated TGF-Beta RI tail promoted Smad2 nuclear translocation. In mink lung cells, homo-oligomerization of a myristoylated TGF-Beta Ri tail in presence of a myristoylated TGF-Beta RII tail activated the PAI-1 promoter. Oligomerization of an acidic mutant of the TGF-Beta RI tail in absence of TGF-Beta RII activated the PAI-A promoter and inhibited the growth of mink lung cells.
Non-toxic, small molecules designed to oligomerize cytoplasmic tails of TGF-Beta receptors at the plasma membrane can activate TGF-Beta signaling. Although TGF-Beta normally signals through two receptors that are both necessary for signaling, in one small-molecule system, a dimerizer activates signaling through a single type of receptor that is sufficient to induce TGF-Beta signaling. These methods of activating TGF-Beta signaling could be extended to signaling pathways of other TGF-Beta superfamily members such as activin and the bone morphogenetic proteins.
转化生长因子β（TGF-β）可使许多细胞类型停滞于细胞周期的G1期，并上调纤溶酶原激活物抑制剂1（PAI-1）。1型（TGF-βRI）和2型（TGF-βRII）TGF-β受体介导TGF-β对靶细胞的这些及其他效应。TGF-β最初与TGF-βRII结合，随后TGF-βRI被招募形成异源复合物。TGF-βRI使下游效应分子Smad2和Smad3磷酸化，导致它们转位至细胞核。在此，我们探讨了受体寡聚化在TGF-β信号传导中的作用。
我们构建了包含与小分子二聚体结合域相连的受体胞质尾的融合蛋白。在COS-1细胞中，将可溶性TGF-βRII尾募集至肉豆蔻酰化的TGF-βRI尾可促进Smad2核转位。在貂肺细胞中，在肉豆蔻酰化的TGF-βRII尾存在的情况下，肉豆蔻酰化的TGF-βRI尾的同源寡聚化激活了PAI-1启动子。在不存在TGF-βRII的情况下，TGF-βRI尾的酸性突变体的寡聚化激活了PAI-1启动子并抑制了貂肺细胞的生长。
设计用于在质膜上使TGF-β受体的胞质尾寡聚化的无毒小分子可激活TGF-β信号传导。尽管TGF-β通常通过两种对信号传导都必需的受体进行信号传导，但在一个小分子系统中，二聚体通过单一类型的受体激活信号传导，该受体足以诱导TGF-β信号传导。这些激活TGF-β信号传导的方法可扩展至其他TGF-β超家族成员如激活素和骨形态发生蛋白的信号传导途径。
