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Purification and Characterization of Recombinant Activin Receptor Type IIB Kinase Expressed In Sf9 Cells

Activin Receptor Type IIB (ActRIIB) is a member of the transforming growth factor‐β1 (TGF‐β1) superfamily that has been shown to bind to myostatin/GDF‐8. Upon binding to GDF‐8, ActRIIB receptor recruits the type I receptor ALK4/5, phosphorylates ALK4/5 GS‐rich region and leads to phosphorylation and activation of Smad proteins, which then translocate to the nucleus to regulate gene expression. In mice with dominant negative ActRIIB, they exhibited increase muscle mass and muscle tissue but no phenotypcial abnormality. Disruption of binding between GDF‐8 and ActRIIB receptor by administration of GDF‐8 neutralizing antibody in mice also showed an increase of muscle tissue and muscle strength.