SMAD family member 9 (SMAD9)

SMAD9 or Mothers against decapentaplegic homolog 9 is a polypeptide that, as its name describes, is a homolog of the Drosophila gene: "Mothers against decapentaplegic". It belongs to the SMAD family of proteins, which belong to the TGFbeta superfamily of modulators. Like many other TGFbeta family members, SMAD9 is involved in cell signalling.

When a bone morphogenetic protein binds to a receptor (BMP type 1 receptor kinase) it causes SMAD9 to interact with SMAD anchor for receptor activation (SARA).The binding of ligands causes the phosphorylation of the SMAD9 protein and the dissociation from SARA and the association with SMAD4. It is subsequently transferred to the nucleus where it forms complexes with other proteins and acts as a transcription factor.