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Cell Biology International (2008) 32, 229234 (Printed in Great Britain)
Three-dimensional matrix induces sustained activation of ERK1/2 via Src/Ras/Raf signaling pathway
Ralica Damianovaa, Nadezhda Stefanovaa, Edna Cukiermanb, Albena Momchilovac and Roumen Pankova*
aDepartment of Cytology, Histology and Embryology, Biological Faculty, Sofia University “St. Kliment Ohridski”, 1164 Sofia, Bulgaria
bDivision of Basic Science, Tumor Cell Biology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
cInstitute of Biophysics, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Research in cell signaling often depends on tissue culture, but the artificial substrates used to grow cells in vitro are likely to distort the conclusions, particularly when adhesion-mediated signaling events are investigated. Studies of signal transduction pathways operating in cells grown in three-dimensional (3D) matrices provide a better system, giving a closer insight of the cell signaling in vivo. We compared the steady-state levels of ERK1/2 activity in primary human fibroblasts, induced by cell-derived 3D fibronectin matrix or fibronectin, coated on flat surfaces. 3D environment caused ERK1/2 stimulation concomitant with a 2.5-fold increase in Ras GTP loading and Src activation. Under these conditions FAK autophosphorylation was suppressed. Treatment with Src inhibitor PP2 abolished these effects indicating that 3D fibronectin matrix activated ERK1/2 through Src/Ras/Raf pathway, bypassing FAK. These observations suggest that within in vivo-like conditions Src may have a leading role in the induction of sustained ERK1/2 activation.
Key words: Three-dimensional matrix, Extracellular matrix, Fibronectin, Src, Ras, ERK.
*Corresponding author: Tel.: +359 2 816 7274.
Received 23 June 2007/13 July 2007; accepted 27 August 2007doi:10.1016/j.cellbi.2007.08.029