Heregulin stimulates mitogenesis and phosphatidylinositol 3-kinase in mouse fibroblasts transfected with erbB2/neu and erbB3.
Heregulin (HRG) is a pluripotent growth factor that can stimulate the growth of some human mammary tumor cells and the differentiation of others. Two members of the epidermal growth factor receptor family of receptor/tyrosine kinases, p180erbB3 and p180erbB4, serve as receptors for the HRG ligand. While HRG appears to be capable of stimulating the autophosphorylation activity of p180erbB4, the co-expression of p185erbB2/neu with p180erbB3 is necessary for the HRG-stimulated tyrosine phosphorylation of both of these receptors. On the basis of the sequences surrounding their putative tyrosine phosphorylation sites, we predict that the different HRG-responsive receptors couple to different intracellular SH2 domain-containing proteins. Hence, the different receptors may mediate different cellular responses to the HRG ligand. In the present study we show that HRG beta 1 is mitogenic for erbB3-transfected DHFR/G8 cells, an NIH3T3 mouse fibroblast derivative that over-expresses p185erbB2/neu. HRG stimulated the incorporation of [3H]thymidine into the DNA of these cells with an EC50 of 70 +/- 7 pM. HRG was not mitogenic for parental DHFR/G8 cells that do not express the ErbB3 protein. Phosphatidylinositol (PI) 3-kinase, an enzyme believed to be important in cellular growth regulation by growth factors and oncogenes, is predicted to couple to tyrosine-phosphorylated ErbB3. We observed that HRG stimulated the association of PI 3-kinase with both p185erbB2/neu and ErbB3 in transfected DHFR/G8 cells, but not in the parental cell line. We conclude that the ErbB3 protein is capable of mediating a proliferative response of fibroblasts to HRG, and that the activation of PI 3-kinase is an integral part of the growth signaling mechanism.
Carraway
K L
KL
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Soltoff
S P
SP
Diamonti
A J
AJ
Cantley
L C
LC
D016475:3T3 Cells; D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D016895:Culture Media, Serum-Free; D003907:Dexamethasone / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006023:Glycoproteins / Q000494:pharmacology*; D006133:Growth Substances / Q000494:pharmacology*; D051379:Mice; D020890:Neuregulin-1; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D010766:Phosphorylation; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D020893:Receptor, ErbB-3; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D002352:Carrier Proteins; D016895:Culture Media, Serum-Free; D003907:Dexamethasone; D066246:ErbB Receptors; D006023:Glycoproteins; D006133:Growth Substances; D020890:Neuregulin-1; D010446:Peptide Fragments; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D011994:Recombinant Proteins; D013936:Thymidine; D014443:Tyrosine; C087230:heregulin beta1