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Mol. Cell. Biol., 03 1995, 1182-1191, Vol 15, No. 3
D Graus-Porta, RR Beerli and NE Hynes
ErbB-2 becomes rapidly phosphorylated and activated following treatment of
many cell lines with epidermal growth factor (EGF) or Neu differentiation
factor (NDF). However, these factors do not directly bind ErbB-2, and its
activation is likely to be mediated via transmodulation by other members of
the type I/EGF receptor (EGFR)- related family of receptor tyrosine
kinases. The precise role of ErbB-2 in the transduction of the signals
elicited by EGF and NDF is unclear. We have used a novel approach to study
the role of ErbB-2 in signaling through this family of receptors. An
ErbB-2-specific single-chain antibody, designed to prevent transit through
the endoplasmic reticulum and cell surface localization of ErbB-2, has been
expressed in T47D mammary carcinoma cells, which express all four known
members of the EGFR family. We show that cell surface expression of ErbB-2
was selectively suppressed in these cells and that the activation of the
mitogen-activated protein kinase pathway and p70/p85S6K, induction of c-
fos expression, and stimulation of growth by NDF were dramatically
impaired. Activation of mitogen-activated protein kinase and p70/p85S6K and
induction of c-fos expression by EGF were also significantly reduced. We
conclude that in T47D cells, ErbB-2 is a major NDF signal transducer and a
potentiator of the EGF signal. Thus, our observations demonstrate that
ErbB-2 plays a central role in the type I/EGFR-related family of receptors
and that receptor transmodulation represents a crucial step in growth
factor signaling.
Copyright © 1995, American Society for Microbiology
Single-chain antibody-mediated intracellular retention of ErbB-2 impairs Neu differentiation factor and epidermal growth factor signaling
Friedrich Miescher-Institut, Basel, Switzerland.
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