title: A natural ErbB4 isoform that does not activate phosphoinositide 3-kinase mediates proliferation but not survival or chemotaxis.
abstract: ErbB4 is a member of the epidermal growth factor receptor (ErbB) family that mediates cellular responses activated by neuregulins (NRG) and other epidermal growth factor-like growth factors. Two naturally occurring ErbB4 isoforms, ErbB4 CYT-1 and ErbB4 CYT-2, have previously been identified. Unlike ErbB4 CYT-1, ErbB4 CYT-2 lacks a phosphoinositide 3-kinase (PI3-K)-binding site and is incapable of activating PI3-K. We have now examined the consequences of the inability of this isoform to activate PI3-K on cell proliferation, survival, and chemotaxis in response to NRG-1beta: (i) NRG-1beta stimulated proliferation of cells expressing either ErbB4 CYT-1 or ErbB4 CYT-2. Consistent with the mitogenic responsiveness, analysis of downstream signaling showed that Shc and MAPK were phosphorylated after stimulating either isoform with NRG-1beta. (ii) NRG-1beta protected cells expressing ErbB4 CYT-1 but not cells expressing ErbB4 CYT-2 from starvation-induced apoptosis as measured by effects on cell number and 4', 6-diamidino-2-phenylindole staining. Furthermore, in cells expressing ErbB4 CYT-2, Akt, a protein kinase that mediates cell survival, was not phosphorylated. (iii) NRG-1beta stimulated chemotaxis and membrane ruffling in cells expressing ErbB4 CYT-1 but not in cells expressing ErbB4 CYT-2. In summary, ErbB4 CYT-2 can mediate proliferation but not chemotaxis or survival. These results suggest a novel mechanism by which cellular responses such as chemotaxis and survival may be regulated by the expression of alternative receptor-tyrosine kinase isoforms that differ in their coupling to PI3-K signaling.
authors.affiliation: Medicity Research Laboratories, University of Turku, FIN-20520 Turku, Finland.
authors.forename: V
authors.initials: V
authors.lastname: Kainulainen
authors.forename: M
authors.initials: M
authors.lastname: Sundvall
authors.forename: J A
authors.initials: JA
authors.lastname: Määttä
authors.forename: E
authors.initials: E
authors.lastname: Santiestevan
authors.forename: M
authors.initials: M
authors.lastname: Klagsbrun
authors.forename: K
authors.initials: K
authors.lastname: Elenius
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D017209:Apoptosis; D002455:Cell Division / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology*; D016895:Culture Media, Serum-Free; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020890:Neuregulin-1 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D066247:Receptor, ErbB-4; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D016895:Culture Media, Serum-Free; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D066247:Receptor, ErbB-4; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; C528034:Shc1 protein, mouse; C117467:neuregulin beta; C587690:Erbb4 protein, mouse