Phosphatidylinositol 3-kinase functions upstream of ras and raf in mediating insulin stimulation of c-fos transcription

Keishi Yamauchi, Kathleen Holt, Jeffrey E. Pessin

Research output: Contribution to journalArticle

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Abstract

Insulin treatment of Chinese hamster ovary (CHO) cells expressing high levels of the insulin receptor (CHO-IR) was found to markedly activate (10-20-fold) transcription of the luciferase reporter gene (Luc) driven by the serum response element (SRE) of the c-fos promoter. SRE-Luc expression was also strongly activated by co-transfection with expression plasmids encoding for either v-Ras or v-Raf. In contrast, insulin-stimulated SRE-Luc activity was inhibited by expression of a negative-dominant Ras (RasAsn-17)- or a negative-dominant Raf (p301-1)-encoding plasmid. Furthermore, the negative-dominant Raf mutant blocked v-Ras activation whereas the negative-dominant Ras mutant had no significant effect on v-Raf activation. Together, these data demonstrate that insulin utilizes the Ras and Raf signaling pathways and that Ras functions upstream of Raf in terms of transcriptional activation of the serum response element. To assess the role of the phosphatidylinositol (PI) 3-kinase in this insulin signaling pathway, CHO-IR cells were co-transfected with the p85 regulatory subunit of the PI 3-kinase. Expression of the p85 subunit inhibited the insulin stimulation of SRE-Luc activity without affecting v-Ras or v-Raf activation. Thus, these data demonstrate that the PI 3-kinase is necessary for insulin signaling of transcriptional events and that, in a linear model of intracellular signaling, the PI 3-kinase functions upstream of both Ras and Raf.

Original languageEnglish (US)
Pages (from-to)14597-14600
Number of pages4
JournalJournal of Biological Chemistry
Volume268
Issue number20
StatePublished - Jul 15 1993
Externally publishedYes

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Phosphatidylinositol 3-Kinase
Serum Response Element
Transcription
Insulin
Cricetulus
Chemical activation
Ovary
Plasmids
Insulin Receptor
Luciferases
Reporter Genes
Transcriptional Activation
Transfection
Linear Models
Genes
Cells

ASJC Scopus subject areas

  • Biochemistry

Cite this

Phosphatidylinositol 3-kinase functions upstream of ras and raf in mediating insulin stimulation of c-fos transcription. / Yamauchi, Keishi; Holt, Kathleen; Pessin, Jeffrey E.

In: Journal of Biological Chemistry, Vol. 268, No. 20, 15.07.1993, p. 14597-14600.

Research output: Contribution to journalArticle

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