K4 Elite
K4 Elite
A 344-amino-acid isoform of the endogenous glycoprotein follistatin, studied as a high-affinity antagonist of myostatin and other TGF-beta superfamily ligands in preclinical models of muscle and tissue biology.
Follistatin is a naturally occurring secreted glycoprotein that binds and neutralizes members of the transforming growth factor-beta (TGF-beta) superfamily, most notably activin and the muscle-regulating factor myostatin (GDF-8). Alternative splicing of the follistatin gene produces two main isoforms; the 344-amino-acid form (FS-344) is the full-length precursor from which the shorter FS-315 isoform is derived.
FS-344 is distinguished in research by its heparin-binding domain, which influences its tissue localization and cell-surface association. Because myostatin acts as a negative regulator of skeletal muscle mass, follistatin's ability to sequester myostatin has made it a focus of muscle-biology and TGF-beta signaling research.
This material is used solely as a laboratory reagent for preclinical and in vitro study.
Follistatin functions by binding target ligands such as myostatin and activin with high affinity, preventing them from engaging their type I and type II serine/threonine kinase receptors. By neutralizing myostatin, follistatin removes a brake on the SMAD signaling pathway that normally restrains muscle-cell growth in experimental models.
The FS-344 isoform's additional heparin-binding sequence promotes association with cell-surface proteoglycans, which researchers have linked to differences in bioavailability and tissue retention compared with the FS-315 isoform.
These describe published preclinical research for informational purposes only and are not directions for use.
Gene-transfer studies in mouse and non-human primate models have delivered follistatin via adeno-associated viral vectors and reported increases in muscle mass; Kota and colleagues (2009) described AAV-follistatin gene delivery producing muscle growth in mice and primates in a laboratory setting.
Foundational work by Lee and McPherron characterized the myostatin-follistatin regulatory relationship, showing that follistatin overexpression in transgenic mice increased muscle mass, establishing follistatin as a myostatin antagonist of research interest.
Combinations examined in the research literature. Descriptive only — not a recommendation to combine compounds.
References are being compiled for this entry.