The activin signaling pathway is one of two branches of Transforming Growth Factor-β family signaling in Drosophila. The binding of an activin family dimer to a heterodimeric serine/threonine kinase receptor complex results in the phosphorylation of Smox, a members of the Smad family. Smox forms a complex with the co-Smad, Med. This complex translocates into the nucleus and regulates the transcription of target genes in concert with other nuclear cofactors. (Adapted from FBrf0236482.)
Notes and selected reviews
Activin signaling is principally considered to be exclusively via the Smad Smox. Mad phosphorylation has been observed in S2 cells (FBrf0155597, FBrf0205031), which has been suggested may represent BMP pathway crosstalk.