Fig. 1

Schematic illustration of BMP signaling pathway. Activation of this pathway occurs when BMP ligand dimers bind to two homologous type II receptors, facilitating the formation of a tetramer with the two type I receptors. The type II receptor kinase, constitutively active, phosphorylates specific serine residues in the type I receptors, leading to their activation. There are four type I BMP receptors: ALK1 (ACVRL1), ALK2 (ACVR1), ALK3 (BMPRIA), and ALK6 (BMPRIB), and three type II BMP receptors: BMP receptor type II (BMPR2), activin type II receptor A (ACVR2A), and activin type II receptor B (ACVR2B). The subsequent steps involve the activation of type I receptors, leading to the phosphorylation of receptor-regulated SMADs (R-SMADs) transcription factors, specifically SMAD1/5/8. In contrast, TGFβ signaling involves SMAD2/3. The R-SMADs form a heteromeric complex with the co-SMAD, SMAD4, and translocate into the nucleus to regulate target gene expression transcriptionally. Created with BioRender.com