Journal
JOURNAL OF CELLULAR PHYSIOLOGY
Volume 206, Issue 1, Pages 47-57Publisher
WILEY
DOI: 10.1002/jcp.20423
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Funding
- EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT [ZIAHD000184] Funding Source: NIH RePORTER
- EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH &HUMAN DEVELOPMENT [ZIAHD000193, Z01HD000184, Z01HD000193] Funding Source: NIH RePORTER
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ManyG protein coupled receptors (GPCRs) cause phosphorylation of MAP kinases through transactivation of the epidermal growth factor receptor (EGF-R), leading to increased cell survival and growth, motility, and migration. Phosphoinositide 3-kinase (PI3K) is one of the important cell survival signaling molecules activated by EGF-R stimulation. However, the extent to which EGF-R transactivation is essential for GPCR agonist-stimulated PI3K activation is not known. Here we examined the mechanism of PI3K activation that elicits GPCR-mediated ERK1/2 activation by pathways dependent and/or independent of EGF-R transactivation in specific cell types. Immortalized hypothalamic neurons (GT1-7 cells) express endogenous gonadotropin-releasing hormone receptors (GnRH-R) and their stimulation causes marked phosphorylation of ERK1/2 and Akt (Ser473) through transactivation of the EGF-R and recruitment of PI3K. In C9 hepatocytes, agonist activation of AT(1) angiotensin 11 (AT(1)-R), lysophosphaticlic acid (LPA), and EGF receptors caused phosphorylation of Akt through activation of the EGF-R in a PI3K-dependent manner. However, ERK1/2 activation by these agonists in these cells was independent of PI3K activation. In contrast, agonist stimulation of HEK 293 cells stably expressing AT(1)-R caused ERK1/2 phosphorylation thatwas independent of EGF-R transactivation but required PI3K activation. LPA signaling in these cells showed partial and complete dependence on EGF-R and PI3K, respectively. These data indicate that GPCR induced ERK1/2 phosphorylation is dependent or independent of PI3K in specific cell types, and that the involvement of PI3K during ERK1/2 activation is not dependent solely on agonist-induced transactivation of the EGF-R.
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