15358595

pubmed:Citation

2

The role of epidermal growth factor receptor (EGFR) tyrosine kinase and its downstream targets in the regulation of the transition from the G0/G1 phase into DNA synthesis in response to ANG II has not been previously investigated in intestinal epithelial IEC-18 cells. ANG II induced a rapid and striking EGFR tyrosine phosphorylation, which was prevented by selective inhibitors of EGFR tyrosine kinase activity (e.g., AG-1478) or by broad-spectrum matrix metalloproteinase (MMP) inhibitor GM-6001. Pretreatment of these cells with either AG-1478 or GM-6001 reduced ANG II-stimulated DNA synthesis by approximately 50%. To elucidate the downstream targets of EGFR, we demonstrated that ANG II stimulated phosphorylation of Akt at Ser473, mTOR at Ser2448, p70S6K1 at Thr389, and S6 ribosomal protein at Ser(235/236). Pretreatment with AG-1478 inhibited Akt, p70S6K1, and S6 ribosomal protein phosphorylation. Inhibition of phosphatidylinositol (PI)3-kinase with LY-294002 or mTOR/p70S6K1 with rapamycin reduced [3H]thymidine incorporation by 50%, i.e., to levels comparable to those achieved by addition of either AG-1478 or GM-6001. Utilizing Akt small-interfering RNA targeted to Akt1 and Akt2, Akt protein knockdown dramatically inhibited p70S6K1 and S6 ribosomal protein phosphorylation. In contrast, AG-1478 or Akt gene silencing exerted no detectable inhibitory effect on ANG II-induced extracellular signal-regulated kinase 1/2 phosphorylation in IEC-18 cells. Taken together, our results demonstrate that EGFR transactivation mediates ANG II-stimulated mitogenesis through the PI3-kinase/Akt/mTOR/p70S6K1 signaling pathway in IEC-18 cells.

eng

IM

MEDLINE

0193-1857

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NLM

G182-94

pubmed-meshheading:15358595-Angiotensin II, pubmed-meshheading:15358595-Animals, pubmed-meshheading:15358595-Cell Line, pubmed-meshheading:15358595-Cell Proliferation, pubmed-meshheading:15358595-DNA, pubmed-meshheading:15358595-Gene Silencing, pubmed-meshheading:15358595-Intestinal Mucosa, pubmed-meshheading:15358595-Phosphatidylinositol 3-Kinases, pubmed-meshheading:15358595-Phosphotransferases (Alcohol Group Acceptor), pubmed-meshheading:15358595-Protein Kinases, pubmed-meshheading:15358595-Protein-Serine-Threonine Kinases, pubmed-meshheading:15358595-Proto-Oncogene Proteins, pubmed-meshheading:15358595-Proto-Oncogene Proteins c-akt, pubmed-meshheading:15358595-Receptor, Epidermal Growth Factor, pubmed-meshheading:15358595-Ribosomal Protein S6 Kinases, 70-kDa, pubmed-meshheading:15358595-Signal Transduction, pubmed-meshheading:15358595-Sirolimus, pubmed-meshheading:15358595-TOR Serine-Threonine Kinases, pubmed-meshheading:15358595-Transcriptional Activation

EGF receptor transactivation mediates ANG II-stimulated mitogenesis in intestinal epithelial cells through the PI3-kinase/Akt/mTOR/p70S6K1 signaling pathway.

Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't