Growth-regulated cells, such as 3T3 mouse embryo fibroblasts (MEFs), require more than one growth factor for growth, usually the insulin-like growth factor I (IGF-I) in combination with either platelet-derived growth factor or epidermal growth factor. Singly, these growth factors cannot sustain the growth of 3T3 cells. However, if the IGF-I receptor (IGF-IR) is even modestly overexpressed, then IGF-I, by itself, stimulates the growth of MEFs in monolayer and makes them capable of forming colonies in soft agar. The granulin/epithelin precursor (GEP) has been identified as the only growth factor, thus far, that can stimulate by itself the growth of R- cells, a 3T3-like cell line in which the genes for the IGF-IR have been deleted. We have expressed GEP in R- cells and show that these cells can now grow in serum-free medium. GEP, however, cannot replace other functions of the IGF-IR, such as protection from apoptosis (anoikis) or transforming activity (colony formation in soft agar). GEP activates, in R- cells, the two signaling pathways that are known to be sufficient for IGF-I-mediated mitogenesis in cells overexpressing the IGF-IR, the mitogen-activated protein kinase and the phosphatidylinositol 3-kinase pathways. This may explain why GEP, by itself, can replace the IGF-IR for growth in monolayer cultures. It also confirms that, for transformation, other pathways must be activated besides the two pathways that are sufficient for mitogenesis.
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|Anno di pubblicazione:||1999|
|Titolo:||Biological Activities and Signaling Pathways of the Granulin/Epithelin precursor.|
|Autori:||T. ZANOCCO MARANI; T; BATEMAN; A; ROMANO; G; VALENTINIS; B; ZHI-HENG; HE; AND BASERGA; R. BIOLOGICAL ACTIVITIES AND SIGNALING PATHWAYS OF THE GRANULINEPITHELIN PRECURSOR|
|Appare nelle tipologie:||Articolo su rivista|
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