Function
Follistatin (Fs1) is a follicle-stimulating hormone inhibiting substance present in ovarian follicular fluid. Fs1 has affinity for Activin which is neutralized upon binding to Fs1. The interplay between Fs1 and activin represents a regulatory mechanism which affects a variety of cellular processes[1].
Follistatin-like protein (Fstl) is highly homologous to Fs1 and binds activin and myostatin but does not contain a heparin-binding motif. Fst contains 2 follistatin domains - containing 10 Cys residues - while Fs1 contains 3 such domains[2].
Relevance
Fs1 binds myostatin and inhibits its function. Myostatin acts to limit skeletal muscle mass. Thus, the regulation of activin and myostatin by Fs1 may provide therapeutic targets for preserving muscle mass and prevent muscle atrophy and degeneration[3]. Fstl-1 can prevent myocardial ischemia injury by inhibiting apoptosis and inflammatory response and can represent a therpeutic target for post-myocardial infraction[4].
Structural highlights
The 3D structure of the complex between follistatin-like 3 and activin shows the . The between the two proteins include those in the FSTL-3 N-terminal domain and hydrogen bonds in the FSTL-3 follistatin domain[5].
