Recruitment and Activation of Raf-1 Kinase by Nitric Oxide-Activated Ras

Nitric oxide (NO) and related species serve as cellular messengers in various physiological and pathological processes. The monomeric G protein, Ras, transduces multiple signaling pathways with varying biological responses. We have previously reported that NO triggers Ras activation and recruitment...

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Bibliographic Details
Published in:Biochemistry (Easton) 2000-08, Vol.39 (32), p.9901-9908
Main Authors: Deora, Ami A, Hajjar, David P, Lander, Harry M
Format: Article
Language:English
Subjects:
Androstadienes - pharmacology
Cell Membrane - metabolism
Cell Nucleus - metabolism
Chromones - pharmacology
DNA-Binding Proteins
Enzyme Activation
ets-Domain Protein Elk-1
Humans
Jurkat Cells
Morpholines - pharmacology
Nitric Oxide - metabolism
Phosphatidylinositol 3-Kinases - antagonists & inhibitors
Phosphorylation
Precipitin Tests
Protein Binding
Proto-Oncogene Proteins - metabolism
Proto-Oncogene Proteins c-raf - metabolism
ras Proteins - metabolism
Signal Transduction
T-Lymphocytes - metabolism
Transcription Factors
Tumor Necrosis Factor-alpha - metabolism
Wortmannin
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Summary:Nitric oxide (NO) and related species serve as cellular messengers in various physiological and pathological processes. The monomeric G protein, Ras, transduces multiple signaling pathways with varying biological responses. We have previously reported that NO triggers Ras activation and recruitment of an effector, phosphatidylinositol 3‘-kinase (PI3K) and Ras-dependent activation of mitogen-activated protein (MAP) kinases which include extracellular signal regulated kinases (ERKs), c-Jun NH2-terminal kinase (JNK), and p38 MAP kinase. In this study, we further defined NO-activated Ras signaling pathways. We have identified Raf-1 as another effector recruited by NO-activated Ras in T lymphocytes. NO activation results in association of Ras and Raf-1 and is biologically significant, as we observe an NO-induced increase in Raf-1 kinase activity. Downstream to Raf-1 kinase lie MAP kinases and their subsequent downstream targets, transcription factors. We found that treatment of T lymphocytes with NO yielded phosphorylation of the transcription factor, Elk-1. This phoshorylation is dependent on NO binding to the cysteine 118 residue of Ras. By further delineating the pathway with pharmacological inhibitors, Elk-1 phosphorylation was also found to be dependent on PI3K and ERK. Moreover, NO triggered an increase in mRNA levels of the proinflammatory cytokine, tumor necrosis factor-α (TNF-α), which was ERK dependent. Thus, we have defined an NO-induced signaling pathway in T lymphocytes arising at the membrane where NO-activated Ras recruits Raf-1 and culminating in the nucleus where Elk-1 is phosphorylated and TNF-α messenger RNA is induced. This NO-activated Ras-mediated signaling pathway may play a critical role in Elk-1-induced transcriptional activation of T lymphocytes, host defense and inflammation.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi992954b