Description
Follistatin 315 (FS-315) is a naturally occurring 315-amino acid glycoprotein isoform of follistatin, encoded by the FST gene, and the predominant circulating form found in plasma. It functions as a high-affinity extracellular binding protein for multiple TGF-beta superfamily ligands. This includes activin A, activin B, myostatin (GDF-8), GDF-11, and BMP-7. The neutralization mechanism operates through ligand sequestration rather than receptor antagonism. Two follistatin molecules physically wrap around one TGF-beta ligand dimer, sterically blocking access to ActRII and ALK4 type I and type II serine/threonine kinase receptors and preventing downstream SMAD2/3 phosphorylation. FS-315 is the systemic circulating isoform, distinguishing it from FS-288, which binds cell-surface heparan sulfate proteoglycans and acts as a local tissue sink. This isoform distinction makes FS-315 the appropriate research tool for studying specialty research peptide systemic ligand sequestration biology, while FS-288 addresses local tissue-level TGF-beta regulation.
Chemical Information
- Chemical Name: Follistatin-315 (FST isoform; mature processed glycoprotein)
- Also Known As: FS-315; FST-315
- Compound Class: Endogenous glycoprotein (TGF-beta superfamily antagonist)
- Amino Acid Length: 315 amino acids (mature form, post-signal peptide cleavage)
- Molecular Weight: approximately 35 kDa (glycosylated form; varies by glycosylation state)
- Gene: FST (human follistatin gene)
- Primary Ligands: Activin A, Activin B, Myostatin (GDF-8), GDF-11, BMP-7
- Mechanism Class: Extracellular ligand trap (wrapping/sequestration mechanism)
Applications
- Activin A and activin B sequestration studies in cell-based models. FS-315 provides a defined endogenous-sequence tool for studying how extracellular activin neutralization affects SMAD2/3 phosphorylation and downstream transcriptional responses in target cell populations
- Myostatin pathway biology. FS-315 binds myostatin (GDF-8) and prevents its engagement with ActRIIA and ActRIIB receptors. Used in models studying myostatin-mediated SMAD signaling independently of receptor antagonism approaches; comparison with ACE-031, which uses an ACVR2B-Fc decoy receptor architecture, enables researchers to compare ligand-trap versus receptor-trap strategies for the same pathway
- Isoform comparison research. FS-315 lacks the heparin-binding sequence present in FS-288 (residues 75-86 of the first follistatin domain), making the two isoforms useful as a comparative pair for studying how cell-surface binding versus free circulation affects the spatial and temporal distribution of TGF-beta ligand neutralization in experimental tissue models
- Reproductive biology and FSH regulation. Activin stimulates FSH secretion from pituitary gonadotrophs; follistatin is the primary endogenous activin antagonist in this axis. FS-315 is studied in models examining how systemic activin neutralization affects pituitary-gonadal signaling
- BMP pathway modulation. FS-315 binds BMP-7 and certain other bone morphogenetic proteins. Researchers studying BMP-mediated differentiation in bone and connective tissue cell models use FS-315 to probe how extracellular BMP sequestration alters downstream differentiation programs
Storage and Handling
Store lyophilized protein at -20C for long-term stability. Reconstituted solutions should be stored at 2-8C and used promptly. Avoid repeated freeze-thaw cycles, which can cause aggregation and loss of binding activity in glycoprotein preparations. Protect from light and elevated temperatures. As a glycoprotein, FS-315 is more sensitive to handling conditions than synthetic peptides; refer to the certificate of analysis for batch-specific reconstitution guidance.
Compliance Notice
Follistatin 315 is for laboratory research use only. It is not for human or veterinary use and carries no therapeutic, diagnostic, or clinical indication. This product has not been evaluated by the FDA. By purchasing this product, the buyer confirms that they will follow appropriate institutional safety procedures and use it exclusively for controlled research.
