Regulation of GDF-11 and myostatin activity by GASP-1 and GASP-2

Abstract

Myostatin (MSTN) and growth and differentiation factor-11 (GDF-11) are highly related TGF-β family members that have distinct biological functions. MSTN is expressed primarily in skeletal muscle and acts to limit muscle growth. GDF-11 is expressed more widely and plays multiple roles, including regulating axial skeletal patterning during development. Several MSTN and GDF-11 binding proteins have been identified, including GDF-associated serum protein-1 (GASP-1) and GASP-2, which are capable of inhibiting the activities of these ligands. Here, we show that GASP-1 and GASP-2 act by blocking the initial signaling event (namely, the binding of the ligand to the type II receptor). Moreover, we show that mice lacking Gasp1 and Gasp2 have phenotypes consistent with overactivity of MSTN and GDF-11. Specifically, we show that Gasp2 −/− mice have posteriorly directed transformations of the axial skeleton, which contrast with the anteriorly directed transformations seen in Gdf11 −/− mice. We also show that both Gasp1 −/− and Gasp2 −/− mice have reductions in muscle weights, a shift in fiber type from fast glycolytic type IIb fibers to fast oxidative type IIa fibers, and impaired muscle regeneration ability, which are the reverse of what are seen in Mstn −/− mice. All of these findings suggest that both GASP-1 and GASP-2 are important modulators of GDF-11 and MSTN activity in vivo.

Variation in the ovine WFIKKN2 gene

“…Haidet et al (2008) found that in vivo viral delivery of a WFIKKN2 expression cassette into adult mice hind-limb and fore-limb muscle significantly increased overall body mass and the mass of the Tibialis anterior, Gastrocnemius, Quadriceps and Triceps muscles. Monestier et al (2012) observed that the over-expression of WFIKKN2 caused obvious increases in muscle mass resulting from hypertrophy rather than hyperplasia in a gain-of-function transgenic mouse model, and Lee and Lee (2013) further confirmed the effect of WFIKKN2 on muscle weight, describing how mice genetically engineered to lack WFIKKN2 had a shift in muscle fibre type from fast glycolytic typeIIb to fast oxidative typeIIa, as well as having impaired muscle regeneration ability. Taken together, this literature suggests that WFIKKN2 may be important in the regulation of muscle mass.…”

“…In the developing human foetus, WFIKKN2 is expressed primarily in skeletal muscle (Trexler et al, 2002), and high levels of expression of WFIKKN2 have also been reported in the skeletal muscle of mice (Hill et al, 2003;Lee and Lee, 2013;Marcelo et al, 2009). Haidet et al (2008) found that in vivo viral delivery of a WFIKKN2 expression cassette into adult mice hind-limb and fore-limb muscle significantly increased overall body mass and the mass of the Tibialis anterior, Gastrocnemius, Quadriceps and Triceps muscles.…”

Alternative Binding Modes Identified for Growth and Differentiation Factor-associated Serum Protein (GASP) Family Antagonism of Myostatin

“…Protein Expression and Purification-CHO cells stably overexpressing myostatin, GASP-1 and GASP-2 were used as previously published (4,19). Myostatin conditioned medium (CM) was concentrated ϳ10-fold using tangential flow and concomitantly buffer exchanged into 50 mM Tris pH 7.4, 500 mM NaCl and applied to a Lentil Lectin-Sepharose 4B (Amersham Biosciences) column.…”

“…GASP-1 and GASP-2-GASP-1 and GASP-2 was expressed and purified as published earlier with some minor modifications (19). Following application to butyl-Sepharose and heparin columns, the heparin eluent containing either GASP-1 or GASP-2 was dialyzed extensively into 50 mM Tris pH 7.4, 20 mM NaCl, 1 mM EDTA, applied to a MonoQ 10/100 GL column and eluted with a linear NaCl gradient.…”

“…The reciprocal effect is observed in mice lacking myostatin (21,22). On the other hand, during embryological development, GASP-2 Ϫ/Ϫ mice had significant impairments in skeletal axial patterning, suggesting that GASP-2 may modulate GDF-11 activity because these defects are seen in GDF-11 Ϫ/Ϫ mice (19,23). Analysis of GASP-2 identified the FS domain as the predominant domain responsible for myostatin binding, whereas the C-terminal domains alone (K2 and netrin-like domain) showed limited binding (17).…”