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Transforming growth factor-β1-induced satellite cell apoptosis in chickens is associated with β1 integrin-mediated focal adhesion kinase activation¹

X. Li^*, D. C. McFarland and S. G. Velleman^*,2

^* Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691; and Department of Animal and Range Sciences, South Dakota State University, Brookings 57007

² Corresponding author: velleman.1{at}osu.edu

Transforming growth factor-β1 (TGF-β1) induces apoptosis in many types of cells. The cell adhesion receptor, β1 integrin subunit, prevents apoptosis and may be involved in TGF-β1-induced muscle cell apoptosis. In the current study, chicken primary satellite cells, myogenic precursors, were used to investigate the apoptotic effect of TGF-β1 on muscle cells. The data from the current study showed that the addition of exogenous TGF-β1 reduced β1 integrin expression and altered its localization. Treatment of the satellite cells with TGF-β1 increased the number of apoptotic cells indicated by annexin-V using flow cytometry. The number of caspase-positive cells was increased in the TGF-β1-treated immunostained cells, which supported that TGF-β1 induced satellite cell apoptosis. It has been shown that β1 integrin is involved in muscle cell survival. In response to the activation of β1 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-β1 treatment during both satellite cell proliferation and differentiation. These data suggested that the apoptotic effect of TGF-β1 on satellite cells is likely associated with a β1 integrin-mediated FAK signaling pathway during satellite cell proliferation and differentiation.

Key Words: apoptosis • β1 integrin • transforming growth factor-β1 • focal adhesion kinase • satellite cell

¹ Salary and research support to SGV were provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University, and the Midwest Poultry Consortium (St. Paul, MN) to SGV and DCM.