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Mol. Cell. Biol., 12 1995, 6829-6837, Vol 15, No. 12
M Tanaka, R Gupta and BJ Mayer
SH2/SH3 adapters are thought to function in signal transduction pathways by
coupling inputs from tyrosine kinases to downstream effectors such as Ras.
Members of the mitogen-activated protein kinase family are known to be
activated by a variety of mitogenic stimuli, including tyrosine kinases
such as Abl and the epidermal growth factor (EGF) receptor. We have used
activation of the mitogen-activated protein kinase Erk-1 as a model system
with which to examine whether various dominant-negative SH2/SH3 adapters
(Grb2, Crk, and Nck) could block signaling pathways leading to Erk
activation. Activation of Erk-1 by oncogenic Abl was effectively inhibited
by Grb2 with mutations in either its SH2 or SH3 domain or by Crk-1 with an
SH3 domain mutation. The Crk-1 SH2 mutant was less effective, while Nck SH2
and SH3 mutants had little or no effect on Erk activation. These results
suggest that both Crk and Grb2 may contribute to the activation of Erk by
oncogenic Abl, whereas Nck is unlikely to participate in this pathway. Next
we examined whether combinations of these dominant-negative adapters could
inhibit Erk activation more effectively than each mutant alone. When
combinations of Crk-1 and Grb2 mutants were analyzed, the combination of
the Crk-1 SH3 mutant plus the Grb2 SH3 mutant gave a striking synergistic
effect. This finding suggests that in Abl-transformed cells, more than one
class of tyrosine-phosphorylated sites (those that bind the Grb2 SH2 domain
and those that bind the Crk SH2 domain) can lead to Ras
activation.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Differential inhibition of signaling pathways by dominant-negative SH2/SH3 adapter proteins
Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts 02115, USA.
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