ACTRIIB Extracellular Domain (human, recombinant)

Activin receptor type IIB (ACTRIIB) is a type II activin receptor and member of the TGF-β receptor superfamily.^1,2 It is composed of an extracellular ligand-binding domain, a transmembrane domain, an intracellular kinase domain, and a C-terminal tail.² ACTRIIB is ubiquitously expressed in fetal development with the highest expression in the brain and spinal cord and is enriched in adult skeletal muscle.^3,4 ACTRIIB has several ligands, including activins, growth differentiation factor 8 (GDF8), also known as myostatin, and bone morphogenetic proteins (BMPs).² Upon ligand binding, ACTRIIB forms a complex with type I activin receptors, which results in their activation and signaling via the SMAD pathway. ACTRIIB is involved in hematopoiesis, myogenesis, and bone formation and resorption.⁵ Mutations in the gene encoding ACTRIIB, ACVR2B, are associated with left-right axis malformations.⁶ Formulations containing a fusion protein of the ACTRIIB ligand-binding domain with the Fc of an immunoglobulin have been used as erythroid maturation agents in the treatment of anemia in patients with β-thalassemia or myelodysplastic syndrome (MDS). Cayman’s ACTRIIB Extracellular Domain (human, recombinant) protein can be used for binding assay and cell-based assay applications. This protein consists of 127 amino acids, has a calculated molecular weight of 15 kDa, and a predicted N-terminus of Ser19 after signal peptide cleavage. By SDS-PAGE, under reducing conditions, the apparent molecular mass of the protein is 33-38 kDa due to glycosylation.

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1. Attisano, L., Wrana, J.L., Montalvo, E., et al. Activation of signalling by the activin receptor complex. Mol. Cell. Biol. 16(3), 1066-1073 (1996).

2. Leung, P.C.K., and Peng, C. Activin Receptor Signaling. Encyclopedia of Hormones 17-23 (2003).

3. Hildén, K., Tuuri, T., Erämaa, M., et al. Expression of type II activin receptor genes during differentiation of human K562 cells and cDNA cloning of the human type IIB activin receptor. Blood 83(8), 2163-2170 (1994).

4. Han, H.Q., Zhou, X., Mitch, W.E., et al. Myostatin/activin pathway antagonism: molecular basis and therapeutic potential. Int. J. Biochem. Cell Biol. 45(10), 2333-2347 (2013).

5. Lodberg, A. Principles of the activin receptor signaling pathway and its inhibition. Cytokine Growth Factor Rev. 60, 1-17 (2021).

6. Kosaki, R., Gebbia, M., Kosaki, K., et al. Left-right axis malformations associated with mutations in ACVR2B, the gene for human activin receptor type IIB. Am. J. Med. Genet. 82(1), 70-76 (1999).