Follistatin

Follistatin (FST) is a secreted, cysteine-rich glycoprotein that acts as a high-affinity ligand trap rather than a receptor antagonist. Two follistatin molecules wrap around a TGF-beta family ligand dimer and physically occlude both the type I and type II receptor interfaces, neutralising activin A, myostatin and several BMPs.

Isoforms and why they differ

Alternative splicing and proteolysis give three commonly cited forms. FST-288 carries a heparan-sulfate-binding motif and stays bound to the cell surface, so its action is local. FST-315 is the dominant circulating form. FST-344 is the primary translation product, processed to FST-315. A vendor listing of "follistatin-344" therefore describes the precursor construct, and the distinction matters for any experiment where tissue localisation is a variable.

Research context

Rodent work reported substantial increases in muscle mass with follistatin overexpression, and follistatin gene-transfer studies have been run in muscular dystrophy models and small human trials. As with direct myostatin blockade, lean-mass changes have been reported more consistently than functional gains. Follistatin proteins supplied as recombinant research reagents are not stable to gastric passage, which rules out an oral route.

Related terms and material

activin receptor · recombinant. Reference material: Follistatin-344, IGF & muscle peptides. Further reading: what is follistatin-344.