Figure 7.

SERPINA1 regulates the TGF-β signaling pathway through SMAD4. (A) PPI network of SERPINA1 was queried from the BioGRID database. Green nodes represent chemicals, blue nodes represent proteins from the same organism and yellow nodes represent proteins from different organisms. Yellow edges represent protein interactions, blue edges represent chemical interactions and purple edges represent both protein and genetic interactions. (B) SERPINA1 and SMAD4 protein expression were evaluated using western blotting with lysates from AGS cells that were treated with a 72-h transfection of the indicated siRNAs (left panel). Quantification of SERPINA1 and SMAD4 protein. Columns indicate the ratio of SERPINA1 or SMAD4 intensity to GAPDH intensity (right panel, n=3). (C) Western blots of SERPINA1 and SMAD4 proteins in SERPINA1 overexpression vector or control vector-transfected AGS cells (left panel). The relative intensities of the bands were normalized using GAPDH (right panel, n=3). (D) The transcription levels of PAI-1 were measured using reverse transcription quantitative-PCR under the indicated conditions. β-actin was used as an internal control (n=3). *P<0.05, **P<0.01, ***P<0.001. SERPINA1, serpin peptidase inhibitor clade A member 1; SMAD4, SMAD family member 4; PPI, protein-protein interaction; si, small interfering; PAI-1, plasminogen activator inhibitor 1.