Transforming growth factor-β1-induced satellite cell apoptosis in chickens is associated with β1 integrin-mediated focal adhesion kinase activation

Transforming growth factor-beta 1 (TGF-beta 1) induces apoptosis in many types of cells. The cell adhesion receptor, beta 1 integrin subunit, prevents apoptosis and may be involved in TGF-beta 1-induced muscle cell apoptosis. In the current study, chicken primary satellite cells, myogenic precursors, were used to investigate the apoptotic effect of TGF-beta 1 on muscle cells. The data from the current study showed that the addition of exogenous TGF-beta 1 reduced beta 1 integrin expression and altered its localization. Treatment of the satellite cells with TGF-beta 1 increased the number of apoptotic cells indicated by annexin-V using flow cytometry. The number of caspase-positive cells was increased in the TGF-beta 1-treated immunostained cells, which supported that TGF-beta 1 induced satellite cell apoptosis. It has been shown that beta 1 integrin is involved in muscle cell survival. In response to the activation of beta 1 integrin, focal adhesion kinase (FAK) phosphorylates tyrosine at residue 397 and activates cell survival signal transduction. The phosphorylation of FAK was significantly reduced from 30 min to 4 h after TGF-beta 1 treatment during both satellite cell proliferation and differentiation. These data suggested that the apoptotic effect of TGF-beta 1 on satellite cells is likely associated with a beta 1 integrin-mediated FAK signaling pathway during satellite cell proliferation and differentiation.