Phosphorylation of SMAD2,3 by Activin:Activin Receptor

Activin receptors containing the type II receptors ACVR2A/B (ActRIIA, ActRIIB) and the type I receptors ACVR1B/C (ALK4, ALK7) signal through SMAD2 and SMAD3. The phosphorylated type I receptor (ACVR1B/C) phosphorylates SMAD2 or SMAD3. Homodimers or heterodimers of SMAD2 and SMAD3 bind the co-Smad SMAD4 and the ternary complex (SMAD2/3:SMAD2/3:SMAD4) enters the nucleus and activates expression of target genes.

活化素受体包括II型受体ACVR2A/B（ActRIIA，ActRIIB）和I型受体ACVR1B/C（ALK4，ALK7），它们通过SMAD2和SMAD3进行信号传递。磷酸化的I型受体（ACVR1B/C）磷酸化SMAD2或SMAD3。SMAD2和SMAD3的同源二聚体或异源二聚体与共Smad SMAD4结合，形成的三元复合物（SMAD2/3:SMAD2/3:SMAD4）进入细胞核，从而激活靶基因的表达。