Follistatin could promote the proliferation of duck primary myoblasts by activating PI3K/Akt/mTOR signalling

Abstract

FST (follistatin) is essential for skeletal muscle development, but the intracellular signalling networks that regulate FST-induced effects are not well defined. We sought to investigate whether FST promotes the proliferation of myoblasts through the PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B)/mTOR (mammalian target of rapamycin) signalling. In the present study, we transfected the pEGFP-duFST plasmid and added PI3K and mTOR inhibitors to the medium of duck primary myoblasts. Then, we analysed the cellular phenotypic changes that occurred and analysed the expression of target genes. The results showed that FST promoted myoblast proliferation, induced the mRNA expression of PI3K, Akt, mTOR, 70-kDa ribosomal protein S6K (S6 kinase) and the protein expression of phospho-Akt (Thr308), mTOR, phospho-mTOR (serine 2448), phospho-S6K (Ser417), inhibited the mRNA expression of FoxO1, MuRF1 (muscle RING finger-1) and the protein expression of phospho-FoxO1 (Ser256). Moreover, we found that the overexpression of FST could alleviate the inhibitory effect of myoblast proliferation caused by the addition of LY294002, a PI3K inhibitor. Additionally, the overexpression of duck FST also relieved the inhibition of myoblast proliferation caused by the addition of rapamycin (an mTOR inhibitor) through PI3K/Akt/mTOR signalling. In light of the present results, we hypothesize that duck FST could promote myoblast proliferation, which is dependent on PI3K/Akt/mTOR signalling.

Functional role of AKT signaling in bovine early embryonic development: potential link to embryotrophic actions of follistatin

“…TGF-β can induce a physical interaction between the p85 regulatory subunit of PI3K and the TβRII and TβRI receptors converting phosphatidylinositol-4,5-bisphosphate (PIP 2 ) to phosphatidylinositol-3,4,5-triphosphate (PIP 3 ) and subsequently AKT phosphorylation [ 45 – 47 ]. Studies on somatic cell lines indicate that follistatin treatment activates PI3K/AKT signaling pathway [ 48 , 49 ]. In the present studies, follistatin treatment reversed the inhibitory effects of AKT inhibitor treatment on AKT phosphorylation levels at 10 h post treatment, but a follistatin dependent increase in basal AKT phosphorylation was not observed in the absence of AKT inhibitor treatment.…”

Akt-mTOR Signaling Mediates Abnormalities in the Proliferation and Apoptosis of Ovarian Granulosa Cells in Patients with Polycystic Ovary Syndrome

“…The PI3K/Akt/MTOR pathway is an important signaling pathway involved in cell cycle regulation and cell proliferation [15]. S6K1 is an effecter of mTOR and activated by mTOR through phosphorylation [16].…”

MicroRNA-33a negatively regulates myoblast proliferation by targeting IGF1, follistatin and cyclin D1

“…Primary myoblasts were isolated from the leg muscles taken from 13-day-old duck embryos according to the method described previously by Liu et al [20,21]. The myoblasts were cultured in growth medium containing Dulbecco's modified Eagle's medium (DMEM) (Hyclone, U.S.A.) with 10% fetal bovine serum (FBS) (Gibco, U.S.A.) and penicillin (100 U/ml) and streptomycin (100 μg/ml).…”

“…Down-regulation of CCND1 induces cell cycle arrest [17]. FST is an important secretory protein, and its deficiency leads to perinatal death in mice [18] whereas its transgenic form or postnatal overexpression induces muscle hypertrophy and myoblast proliferation [19,20]. By using targetscan software, IGF1, FST and CCND1 were predicted to be the target genes of miR-33a.…”