Heregulin-stimulated Signaling in Rat Pheochromocytoma Cells
EVIDENCE FOR ErbB3 INTERACTIONS WITH Neu/ErbB2 AND p85 (*)
- Daniel C. Gamett(1),
- Tricia Greene(1),
- Allison R. Wagreich(1),
- Hong-Hee Kim(2),
- John G. Koland(2) and
- Richard A. Cerione(1)(§)
- From the (1) Department of Pharmacology, Cornell University, Ithaca, New York 14853-6401 and the
- (2) Department of Pharmacology, University of Iowa, College of Medicine, Iowa City, Iowa 52242-1109
- § To whom correspondence should be addressed.
Abstract
We have reported that overexpression of Neu leads to heregulin-stimulated neurite outgrowth and the tyrosine-phosphorylation of Neu and other cellular proteins in PC12 cells. Considering that Neu/ErbB2 alone is not able to functionally couple to heregulin, we looked for the possible involvement of ErbB3 in these neurite outgrowth and tyrosine phosphorylation responses. We found that heregulin stimulates the tyrosine phosphorylation of endogenous ErbB3 protein in PC12 cells and that this phosphorylation, like that of Neu, is greatly enhanced in cells that overexpress Neu. Furthermore, overexpression of ErbB3 in PC12 cells led to heregulin-stimulated neurite extension. In addition to becoming tyrosine-phosphorylated, Neu/ErbB2 and ErbB3 associate with each other, and each associates with the 85-kDa regulatory subunit (p85) of phosphatidylinositol 3-kinase in a heregulin-dependent manner. Thus, Neu/ErbB2 and ErbB3 appear to cooperate to mediate the heregulin signal in PC12 cells. Like heregulin, epidermal growth factor (EGF) also stimulates the tyrosine phosphorylation of both Neu and ErbB3. However, there are clear differences between the EGF- and heregulin-stimulated phosphorylations of ErbB3. In the heregulin response, two tyrosine-phosphorylated forms of ErbB3 are detected. Of these, only the more quickly migrating form (on SDS-polyacrylamide gel electrophoresis) is found to be associated with Neu, whereas the other, more slowly migrating form is uniquely capable of forming stable complexes with p85. In the EGF response, at least two tyrosine-phosphorylated forms of ErbB3 are detected, but these phosphoproteins have distinctly lower apparent molecular weights compared with the heregulin-stimulated ErbB3 phosphoproteins and do not complex with p85. Thus the formation of a stable ErbB3-p85 complex in PC12 cells is a unique outcome of heregulin signaling that correlates with the differences in cell morphology induced by the activated EGF receptor and the Neu tyrosine kinase.
Footnotes
-
↵* This research was supported by National Institutes of Health Grant GM40654 (to R. A. C.), by Grant 4015 from the Council for Tobacco Research (to R. A. C.), and by USAMRDC Grants DAMD17-94-J-4123 (to R. A. C.) and DAMD17-94-J-4185 (J. G. K.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviation used is:
- EGF
-
epidermal growth factor.
-
- Received February 22, 1995.
- Revision received May 24, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
