Rat embryo fibroblasts require both the cell-binding and the heparin-binding domains of fibronectin for survival.
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 20 h after plating. In contrast, previously well-spread REFs on FN120 started losing fibroblastic shape with time and detached from FN120-coated plates after approx. 8 h. 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.
Jeong
J
J
Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Daehyun-dong, Seodaemoon-Gu, Seoul 120-750, South Korea.
Han
I
I
Lim
Y
Y
Kim
J
J
Park
I
I
Woods
A
A
Couchman
J R
JR
Oh
E S
ES
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D053148:Caspase 3; D061945:Caspase Inhibitors; D002470:Cell Survival; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism*; D005353:Fibronectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006493:Heparin / Q000378:metabolism*; D016023:Integrins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction
D061945:Caspase Inhibitors; D005353:Fibronectins; D016023:Integrins; D006493:Heparin; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat; C505410:Casp3 protein, rat; D053148:Caspase 3