Research Overview
Mechanism as a ligand trap
Follistatin does not act on a receptor of its own. It binds activin and related ligands directly, with two follistatin molecules typically wrapping a single activin dimer and occluding both the type I and type II receptor interfaces. The interaction is close to irreversible in practical terms, and the complex is cleared. This ligand-trap architecture is why follistatin is used experimentally as a tool to remove activin or myostatin signalling from a system without disturbing the receptors themselves.
- Skeletal-muscle hypertrophy in rodents following follistatin gene transfer, where large increases in muscle mass have been reported relative to controls.
- Comparative work against other myostatin-pathway interventions, including soluble activin receptor constructs such as ACE-031.
- Reproductive and follicular biology, where follistatin was originally characterised for its suppression of FSH release.
- Fibrosis and wound-remodelling models, where activin signalling contributes to matrix deposition.
- Non-human primate gene-therapy studies exploring durability of expression, which have shaped the current translational picture.
Isoform and formulation notes
Findings are isoform-dependent. FS-288 binds heparan sulfate and remains near the cell surface, whereas FS-315 circulates and behaves differently in vivo; FS-344 is the precursor from which the circulating form is derived. Papers should be read with the specific construct in mind, and recombinant expression system, glycosylation state and tag presence can all affect measured activity.
