Study On The Function Of Two Proteins Interacting With TβRI In TGF - β Signaling Pathway

In recent years transforming growth factor β(TGF-β) is a cytokine which plays an vital role during normal embryogenesis, proliferation, differentiation, apoptosis and migration. TGF beta signaling pathway is composed of Smad dependent and non-Smad dependent pathway. When TGF-P 1 binding to a heterologous tetramer formed by the TβRI and TβRII, the TβRII configuration changes, TβRII autophosphorylated and then phosphorylates TβRI. The TβRI has serine/threonine kinase activity to phosphorylate downstream Smad molecules (R-Smads in; Smad2 and of Smad3). The R-Smads and Smad4 and together with other transcriptional regulatory molecules enter into the nucleus and regulate gene transcription. Non-Smad signaling pathway is not dependent on the expression and regulation of the transcription factor Smad. With the study in depth more and more non-Smad pathways have been reported.TGF-β can lead to auto-ubiquitination of TRAF6 and TRAF6 self-ubiquitination was associated with ubiquitination of TβRI, and then TβRI were cleavaged and accumulated in nucleus. In our previous work we found RanBPM can inhibit the ubiquitination of TRAF6. On this basis, the subject confirmed the association between TβRI and RanBPM by GST pull-down and Co-IP methods and found TβRI, RanBPM and TRAF6 were in a same complex. In indentifying the interaction between truncated constructions of TRAF6 with TβRI and between RanBPM SPRY domain with TβRI, TβRI can interact with N-terminal and carboxy-terminal of TRAF6. The SPRY domain in RanBPM mediates the interaction with TβRI. After mutation of conserved TRAF6 binding sites in TβRI, the interaction between TβRI with RanBPM was disappeared, indicating that the conserved sites in the TβRI which mediated the interaction with TRAF6 were also very important in mediating the association with RanBPM. Overexpression TβRI does not affect the inhibitory effect of RanBPM on TRAF6 ubiquitination and can stabilize the expression of TRAF6. In A549 cells, TβRI were cleavaged and accumulated in nucleus under TGF-beta stimulation and overexpression of RanBPM can inhibit endogenous TβRI accumulation in nucleus.TGF-β can inhibit the growth of epithelial cells. However it is also an active ingredient to promote transition from epithelial to mesenchymal, and to favor the invasion and migration of tumor cells. So it has a dual role in tumorigenesis. Fascinl have a tight relationship with tumor migration and invasion. Once Fascinl was phosphorylated which can inhibit Fascinl combination with Actin, thereby inhibiting the migration and invasion. The previous work of our laboratory proved the interaction between TβRI and Fascin1. This study is about the effect of TGF-beta on epidermal cells EC109. We found TβRI can co-localize with Fascinl and TGF-beta can promote the migration of EC109 cells. But whether TβRI can directely phosphorylate Fascinl and the phosphorylaton site in Fascinl need to be determined in the near future.