Figure 2: Schema of TGF-β1/Smad pathway and PPARγ. TGF-β1 has several effects on the Smad pathway. TGF-β1 binds type 2 TGF-β receptor (TGF-βRII) which recruits type 1 TGF-β receptors (TGF-βRI). This leads to a heterotetramer that phosphorylates Smad2/Smad3, which then binds to Smad4. The Smad 2-3-4 complex then translocates to the nucleus, where it interacts with various transcription factors to regulate the transcription of target genes (CTGF, COL1A1, and COL1A2). Other non-Smad pathways can occur through PI3K-AKT, p38, and JNK. PTEN inhibits PI3K-AKT and interferes with PPARγ.