Technical Articles

Picture the ActRIIB kinase assay as a brake light: the brighter the enzyme activity, the tighter the muscle brake. This article walks through the complete journey of an inhibitor from addition to readout in four acts.

ActRIIB is the type I receptor kinase for myostatin and activin signaling, writing the 'grow less muscle' instruction into the nucleus. This review covers its receptor structure, signaling axis, disease associations and in vitro research tools.

The activin receptor type IIB (ActRIIB) is a pivotal signaling hub in the transforming growth factor-β (TGF-β) superfamily. Far from being a simple receptor, it serves as a "master switch" regulating muscle growth, erythropoiesis, and systemic metabolic homeostasis.

ActRIIB (Activin Receptor Type IIB) is a key signaling receptor in the TGF-β superfamily, serving as the "core negative regulator" of muscle growth and playing a decisive role in muscle atrophy diseases, anemia, and metabolic disorders.

ActRIIB (Activin Type IIB Receptor) and ACTRIIA (Activin Type IIA Receptor) are structurally similar transmembrane receptors belonging to the TGF-β receptor superfamily. They collectively function to receive extracellular "growth regulatory signals," yet exhibit key distinctions in their physiological roles and their value as drug targets.

ALK4 and ActRIIB are a functionally coupled pair of type I and type II transmembrane serine/threonine kinase receptors within the transforming growth factor-beta (TGF-β) superfamily signaling pathway. ActRIIB, as the type II receptor, features an extracellular domain that binds with high affinity to various ligands, including activin, GDF8 (myostatin), and GDF11, and possesses constitutive kinase activity. In contrast, ALK4, as the type I receptor, is strictly dependent on the type II receptor for its activation. Together, in the presence of ligand, they form a stable heterotetrameric signal transduction complex.