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Mol. Cell. Biol., Feb 1995, 1102-1109, Vol 15, No. 2
S Roche, M Koegl, MV Barone, MF Roussel and SA Courtneidge
The Src family of protein tyrosine kinases have been implicated in the
response of cells to several ligands. These include platelet-derived growth
factor (PDGF), epidermal growth factor (EGF), and colony stimulating factor
type 1 (CSF-1, in macrophages and in fibroblasts engineered to express the
receptor). We recently described a microinjection approach which we used to
demonstrate that Src family kinases are required for PDGF-induced S phase
entry of fibroblasts. We now use this approach to ask whether other ligands
also require Src kinases to stimulate cells to replicate DNA. An antibody
specific for the carboxy terminus of Src, Fyn, and Yes (anti-cst.1)
inhibited Src kinase activity in vitro and caused morphological reversion
of Src transformed cells in vivo. Microinjection of this antibody was used
to demonstrate that Src kinases were required for both CSF-1 and EGF to
drive cells into the S phase. Expression of a kinase-inactive form of Src
family kinases also prevented EGF- and CSF-1-stimulated DNA synthesis.
However, even though the Src family kinases were necessary for both PDGF-
and EGF-induced DNA synthesis in Swiss 3T3 cells, the responses to two
other potent growth factors for these cells, lysophosphatidic acid and
bombesin, were unaffected by the neutralizing antibodies. Therefore, some
but not all growth factors required functional Src family kinases to
transmit mitogenic responses.
Copyright © 1995, American Society for Microbiology
DNA synthesis induced by some but not all growth factors requires Src family protein tyrosine kinases
Differentiation Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
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