GDF-8 1mg

Research on myostatin inhibitors requires a positive control -- exogenous myostatin establishes the baseline signaling state that the inhibitor is supposed to reduce. Cell-based screening assays for anti-myostatin compounds need defined myostatin concentrations. Mechanistic studies of SMAD2/3 signaling need controlled myostatin input. Muscle atrophy models sometimes use exogenous myostatin to produce reproducible atrophy in cell culture. In all these contexts, having research-grade myostatin with known activity and purity is important for experimental consistency and interpretation.

Myostatin binds preferentially to ActRIIB (Activin receptor type IIB) and secondarily to ActRIIA. These type II receptors then recruit and activate type I receptors ALK4 or ALK5, which phosphorylate SMAD2 and SMAD3 transcription factors. Phosphorylated SMAD2/3 complex with SMAD4 and translocate to the nucleus, where they drive expression of genes that suppress myogenesis-pathway activity in cited studies -- inhibiting satellite cell proliferation and protein synthesis. This is the canonical pathway, though myostatin also activates MAPK and PI3K pathways to varying degrees.

GDF-8 (myostatin) and GDF-11 are closely related TGF-beta family members with approximately 90% sequence similarity in their mature domains. GDF-11 uses the same receptors (ActRIIA/B and ALK4/5) and produces similar SMAD2/3 signaling. However, GDF-11's physiological roles differ: GDF-11 has roles in axial patterning during development and some cardiac and neural functions that are distinct from myostatin's predominantly muscle-focused activity. There has been debate in the literature about whether GDF-11 is a "rejuvenating factor" in parabiosis experiments -- most evidence now suggests the cardiac effects attributed to GDF-11 may have been an artifact of the assay used. Cross-reactivity with follistatin and ActRIIB-based inhibitors is a consideration for specificity in experiments using either.