Efficient coupling with phosphatidylinositol 3-kinase, but not phospholipase C gamma or GTPase-activating protein, distinguishes ErbB-3 signaling from that of other ErbB/EGFR family members.
Recombinant expression of a chimeric EGFR/ErbB-3 receptor in NIH 3T3 fibroblasts allowed us to investigate cytoplasmic events associated with ErbB-3 signal transduction upon ligand activation. An EGFR/ErbB-3 chimera was expressed on the surface of NIH 3T3 transfectants as two classes of receptors possessing epidermal growth factor (EGF) binding affinities comparable to those of the wild-type EGF receptor (EGFR). EGF induced autophosphorylation in vivo of the chimeric receptor and DNA synthesis of EGFR/ErbB-3 transfectants with a dose response similar to that of EGFR transfectants. However, the ErbB-3 and EGFR cytoplasmic domains exhibited striking differences in their interactions with several known tyrosine kinase substrates. We demonstrated strong association of phosphatidylinositol 3-kinase activity with the chimeric receptor upon ligand activation comparable in efficiency with that of the platelet-derived growth factor receptor, while the EGFR exhibited a 10- to 20-fold-lower efficiency in phosphatidylinositol 3-kinase recruitment. By contrast, both phospholipase C gamma and GTPase-activating protein failed to associate with or be phosphorylated by the ErbB-3 cytoplasmic domain under conditions in which they coupled with the EGFR. In addition, though certain signal transmitters, including Shc and GRB2, were recruited by both kinases, EGFR and ErbB-3 elicited tyrosine phosphorylation of distinct sets of intracellular substrates. Thus, our findings show that ligand activation of the ErbB-3 kinase triggers a cytoplasmic signaling pathway that hitherto is unique within this receptor subfamily.
Fedi
P
P
Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892.
Pierce
J H
JH
di Fiore
P P
PP
Kraus
M H
MH
D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism
D020690:GTPase-Activating Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D066246:ErbB Receptors; D010738:Type C Phospholipases