Hirai R, Fijita T
The Tokyo Metropolitan Institute of Medical Science, Japan.
Exp Cell Res. 1996 Feb 25;223(1):135-41. doi: 10.1006/excr.1996.0066.
In the signal transduction of transforming growth factor-beta (TGF-beta), the TGF-beta type II receptor (betaR-II) binds TGF-beta, presents the ligand to type I receptor, and forms a heterodimeric receptor complex that functions as an active signaling receptor. We isolated cDNA clones encoding an isoform of human betaR-II from vascular endothelial cells by RT-PCR. The deduced structure of the isoform designated as betaR-IIb contained a 25-amino-acid residue inserted at the extracellular region. The insert exhibited 73% homology to a similar insertion found in a mouse betaR-II variant. BetaR-IIb mRNA was ubiquitously expressed in all human cell lines examined. BetaR-IIb as well as betaR-II stably expressed in betaR-II deficient DR26 cells acted as a functional receptor transducing signals from TGF-beta for growth inhibition and the transcriptional activation of the plasminogen activator inhibitor-1 promoter. These results indicated that the betaR-IIb expressed in mammalian cells functions indistinguishably from in betaR-II. The potential function of betaR-IIb is discussed.
在转化生长因子-β（TGF-β）的信号转导过程中，TGF-β II型受体（βR-II）结合TGF-β，将配体呈递给I型受体，并形成异二聚体受体复合物，该复合物作为活性信号受体发挥作用。我们通过逆转录聚合酶链反应（RT-PCR）从血管内皮细胞中分离出编码人βR-II一种异构体的cDNA克隆。推导的被命名为βR-IIb的异构体结构在细胞外区域含有一个插入的25个氨基酸残基。该插入片段与在小鼠βR-II变体中发现的类似插入片段具有73%的同源性。βR-IIb mRNA在所检测的所有人类细胞系中均有广泛表达。在βR-II缺陷的DR26细胞中稳定表达的βR-IIb以及βR-II作为功能性受体发挥作用，转导来自TGF-β的信号以抑制生长并激活纤溶酶原激活物抑制剂-1启动子的转录。这些结果表明，在哺乳动物细胞中表达的βR-IIb与βR-II的功能没有区别。文中讨论了βR-IIb的潜在功能。
