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Mol. Cell. Biol., Apr 1996, 1509-1518, Vol 16, No. 4
Q Xiong, JL Chan, CS Zong and LH Wang
Two chimeric receptors, ER1 and ER2, were constructed. ER1 contains the
extracellular and transmembrane (TM) domains derived from epidermal growth
factor receptor and the cytoplasmic domain from c-Ros; ER2 is identical to
ER1 except that its TM domain is derived from c-Ros. Both chimeras can be
activated by epidermal growth factor and are capable of activating or
phosphorylating an array of cellular signaling proteins. Both chimeras
promote colony formation in soft agar with about equal efficiency.
Surprisingly, ER1 inhibits while ER2 stimulates cell growth on monolayer
culture. Cell cycle analysis revealed that all phases, in particular the S
and G2/M phases, of the cell cycle in ER1 cells were elongated whereas G1
phase of ER2 cells was shortened threefold. Comparison of signaling
pathways mediated by the two chimeras revealed several differences. Several
early signaling proteins are activated or phosphorylated to a higher extent
in ER1 than in ER2 cells in response to epidermal growth factor. ER1 is
less efficiently internalized and remains tyrosine phosphorylated for a
longer time than ER2. However, phosphorylation of the 66-kDa She protein,
activation of mitogen activated protein kinase, and induction of c-fos and
c-jun occur either to a lesser extent or for a shorter time in ER1 cells.
Cellular protein phosphorylation patterns are also different in ER1 and ER2
cells. In particular, a 190-kDa Shc-associated protein is tyrosine
phosphorylated in ER2 but not in ER1 cells. Our results indicate that the
TM domains have a profound effect on the signal transduction and biological
activity of those chimeric receptors. The results also imply that sustained
stimulation of ER1 due to its retarded internalization apparently triggers
an inhibitory response that dominantly counteracts the receptor-mediated
mitogenic signals. These two chimeras, expressed at similar levels in the
same cell type but having opposite effects on cell growth, provide an ideal
system to study the mechanism by which a protein tyrosine kinase inhibits
cell growth.
Copyright © 1996, American Society for Microbiology
Two chimeric receptors of epidermal growth factor receptor and c-Ros that differ in their transmembrane domains have opposite effects on cell growth
Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
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