Activin A Protein, Human/Mouse/Rat (HEK293, His)

Activin is a member of transforming growth factor-β (TGF-β) superfamily consisting of two inhibin β subunits linked by disulfide bonds. Activin A is expressed widely in various tissues and cells with strong bioactivities and is the mostly studied activin^[1].
The sequence of amino acids in Activin A proteins from different species is very stable, which leads to the conclusion that in the process of evolution, Activin A has been only slightly altered, and that both in humans and in animals, its function is similar.
Activin exists in three basic molecular forms composed of two inhibin β subunits: activin A (βAβA), activin B (βBβB), and activin AB (βAβB). Activin A binds with high affinity to activin type II receptors, which recruit type I receptors and are necessary for the activation of Smad2/3 signaling. The phosphorylated ActRI activates Smad2 and Smad3, which form a complex with Smad4 to translocate to the nucleus. Activin and TGF-β share the same signaling pathway at the level of Smad2/3/4. Activin A exerts a variety of biological functions including regulation of hematopoietic cell proliferation, neuron differentiation, pituitary hormone secretion, and tissue repair. It is also involved in the process of many diseases, for example, inflammation, fibrosis and tumorigenesis^[1][2].
Activin A has pro- and anti-tumorigenic functions depending on the tumor type. In breast, liver and colon cancers, activin signals were revealed to inhibit tumor cell growth. In addition, tumor tissues were revealed to express decreased levels of activin A or increased levels of activin antagonists or demonstrated the downregulation of activin receptors or Smad proteins. Moreover, its roles include embryonic differentiation, trophoblast invasion of the uterine wall in early pregnancy, and fetal/neonate brain protection in hypoxic conditions. Activin A also regulates bone formation and regeneration, enhances joint inflammation in rheumatoid arthritis, and triggers pathogenic mechanisms in the respiratory system^[1][2].

Recombinant Activin A (-1 ng/mL; for 12 and 24 h) inhibits the proliferation of myeloma cell line NS-1 cells and induces NS-1 cell apoptosis. Activin A upregulates the expression of CHOP, GADD34, caspase-3, and caspase-12. Moreover, both Smad3 and p-Smad3 levels are increased with treatment of activin A in NS-1 cells^[1].

Recombinant Activin A (2 ng/1 µL; intratumoral injection; for 6 days) inhibits the growth of solid tumors in tumor-bearing mice with NS-1 cells^[1].