Figure 1
From: Transforming growth factor β signaling in uterine development and function
Canonical and non-canonical TGFβ signaling. In the canonical pathway, TGFβ ligands bind to serine/threonine kinase type II and type I receptors and phosphorylate R-SMADs, which form heteromeric complexes with SMAD4 and translocate into the nucleus to regulate gene transcription. The non-canonical pathway generally refers to the SMAD-independent pathway such as PI3K-AKT, ERK1/2, p38, and JNK pathways. Recent studies have identified an “R-SMAD-dependent but SMAD4-independent” non-canonical pathway that regulates miRNA maturation.