Mothers against decapentaplegic homolog 2

SMAD2 or Mothers against decapentaplegic homolog 2 is a proteine 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 TGFβ superfamily of modulators. Like many other TGFβ family members SMAD2 is involved in cell signalling. SMAD2 modulates signals of activin and TGFβ's. It interacts with SMAD anchor for receptor activation (SARA).The binding of ligands causes the phosphorylation of the SMAD2 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. SMAD2 is a receptor regulated SMAD (R-SMAD) and is activated by bone morphogenetic protein type 1 receptor kinase.

Nomenclature
The SMAD proteins are homologs of both the drosophila protein, mothers against decapentaplegic (MAD) and the C. elegans protein SMA. The name is a combination of the two. During Drosophila research, it was found that a mutation in the gene, MAD, in the mother, repressed the gene, decapentaplegic, in the embryo. The phrase "Mothers against" was added since mothers often form organizations opposing various issues eg. Mothers Against Drunk Driving or (MADD). The nomenclature for this protein, like that of Sonic hedgehog, has been criticized for its frivolity.