Fibronectin (FN) is known to transduce signal(s) to rescue cells from detachment-induced apoptosis (anoikis) through an integrin-mediated survival pathway. However, the functions of individual FN domains have not been studied in detail. In the present study we investigated whether the interaction of the cell-binding domain of FN with integrin is sufficient to rescue rat embryo fibroblasts (REFs) from detachment-induced apoptosis. REFs attached and spread normally after plating on substrates coated with either intact FN or a FN fragment, FN120, that contains the cell-binding domain but lacks the C-terminal heparin-binding domain, HepII. REFs on FN maintained a well-spread fibroblastic shape and even proliferated in serum-free medium at 20h after plating. In contrast, previously well-spread REFs on FN120 started losing fibroblastic shape with time and detached from FN120-coated plates after approx. 8h. Nuclear condensation indicated apototic cell death. This was due to the decreased activity/stability of focal adhesion kinase (pp125FAK) in the absence of HepII domain. A peptide in the HepII domain [peptide V, WQPPRARI (single-letter amino acid codes)], which has previously been implicated in cytoskeletal organization, rescued apoptotic changes. Consistently, pp125FAK phosphorylation was increased, and both cleavage of pp125FAK and activation of caspase 3 on FN120 were partly blocked by peptide V. Thus the interaction of the cell-binding domain with integrin has a major role in cell survival but is itself not sufficient for cell survival. One or more additional survival signals come from the HepII domain to regulate pp125FAK activity/stability.
Rat embryo fibroblasts require both the cell-binding and the heparin-binding domains of fibronectin for survival
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Jinsook JEONG, Innoc HAN, Yangmi LIM, Jungyean KIM, Ilseon PARK, Anne WOODS, John R. COUCHMAN, Eok-Soo OH; Rat embryo fibroblasts require both the cell-binding and the heparin-binding domains of fibronectin for survival. Biochem J 1 June 2001; 356 (2): 531–537. doi: https://doi.org/10.1042/bj3560531
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