Rac1 regulates peptidoglycan-induced nuclear factor-κB activation and cyclooxygenase-2 expression in RAW 264.7 macrophages by activating the phosphatidylinositol 3-kinase/Akt pathway

Bing Chang Chen, Ju Chiun Kang, Yen Ta Lu, Ming Jen Hsu, Chiao Chun Liao, Wen Ta Chiu, Fu Lung Yeh, Chien Huang Lin

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Previously, we found that peptidoglycan (PGN), a cell wall component of the gram-positive bacterium Staphylococcus aureus, may activate the Ras/Raf-1/extracellular signal-regulated kinase (ERK) pathway, which in turn initiates IκB kinases α/β (IKKα/β) and nuclear factor-κB (NF-κB) activation, and ultimately induces cyclooxygenase-2 (COX-2) expression in RAW 264.7 macrophages. In this study, we further investigated the roles of Rac1, phosphatidylinositol 3-kinase (PI3K), and Akt in PGN-induced NF-κB activation and COX-2 expression in RAW 264.7 macrophages. PGN-induced COX-2 expression was attenuated by a Rac1 dominant negative mutant (RacN17), PI3K inhibitors (wortmannin and LY 294002), and an Akt inhibitor (1L-6-hydroxymethyl-chiro-inositol2-[(R)-2-O-methyl-3-O-octadecylcarbonate]). PGN-induced PGE 2 release was also inhibited by RacN17. Treatment of RAW 264.7 macrophages with PGN caused the activation of Rac and Akt. PGN-induced Akt activation was inhibited by RacN17, LY 294002, and the Akt inhibitor. Stimulation of RAW 264.7 macrophages with PGN resulted in an increase in IKKα/β phosphorylation and p65 Ser536 phosphorylation; these effects were inhibited by RacN17, LY 294002, an Akt inhibitor, and an Akt dominant negative mutant (AktDN). The PGN-induced increases in κB-luciferase activity were also inhibited by RacN17, wortmannin, LY 294002, an Akt inhibitor, and AktDN. Treatment of macrophages with PGN induced the recruitment of p85α and Rac1 to Toll-like receptor 2 (TLR2) in a time-dependent manner. These results indicate that PGN may activate the Rac1/PI3K/Akt pathway through the recruitment of p85α and Rac1 to TLR2 to mediate IKKα/β activation and p65 phosphorylation, which in turn induces NF-κB transactivation, and ultimately causes COX-2 expression in RAW 264.7 macrophages.

Original languageEnglish
Pages (from-to)1179-1188
Number of pages10
JournalMolecular Immunology
Volume46
Issue number6
DOIs
Publication statusPublished - Mar 2009

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Phosphatidylinositol 3-Kinase
Peptidoglycan
Cyclooxygenase 2
Macrophages
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
Toll-Like Receptor 2
Phosphorylation
Mitogen-Activated Protein Kinase 3
Gram-Positive Bacteria
Cellular Structures
Prostaglandins E
Luciferases
Cell Wall
Transcriptional Activation
Staphylococcus aureus
Phosphotransferases

Keywords

  • Akt
  • Cyclooxygenase-2
  • Nuclear factor-κB
  • Peptidoglycan
  • PI3K
  • Rac1
  • RAW 264.7 macrophages

ASJC Scopus subject areas

  • Molecular Biology
  • Immunology

Cite this

Rac1 regulates peptidoglycan-induced nuclear factor-κB activation and cyclooxygenase-2 expression in RAW 264.7 macrophages by activating the phosphatidylinositol 3-kinase/Akt pathway. / Chen, Bing Chang; Kang, Ju Chiun; Lu, Yen Ta; Hsu, Ming Jen; Liao, Chiao Chun; Chiu, Wen Ta; Yeh, Fu Lung; Lin, Chien Huang.

In: Molecular Immunology, Vol. 46, No. 6, 03.2009, p. 1179-1188.

Research output: Contribution to journalArticle

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abstract = "Previously, we found that peptidoglycan (PGN), a cell wall component of the gram-positive bacterium Staphylococcus aureus, may activate the Ras/Raf-1/extracellular signal-regulated kinase (ERK) pathway, which in turn initiates IκB kinases α/β (IKKα/β) and nuclear factor-κB (NF-κB) activation, and ultimately induces cyclooxygenase-2 (COX-2) expression in RAW 264.7 macrophages. In this study, we further investigated the roles of Rac1, phosphatidylinositol 3-kinase (PI3K), and Akt in PGN-induced NF-κB activation and COX-2 expression in RAW 264.7 macrophages. PGN-induced COX-2 expression was attenuated by a Rac1 dominant negative mutant (RacN17), PI3K inhibitors (wortmannin and LY 294002), and an Akt inhibitor (1L-6-hydroxymethyl-chiro-inositol2-[(R)-2-O-methyl-3-O-octadecylcarbonate]). PGN-induced PGE 2 release was also inhibited by RacN17. Treatment of RAW 264.7 macrophages with PGN caused the activation of Rac and Akt. PGN-induced Akt activation was inhibited by RacN17, LY 294002, and the Akt inhibitor. Stimulation of RAW 264.7 macrophages with PGN resulted in an increase in IKKα/β phosphorylation and p65 Ser536 phosphorylation; these effects were inhibited by RacN17, LY 294002, an Akt inhibitor, and an Akt dominant negative mutant (AktDN). The PGN-induced increases in κB-luciferase activity were also inhibited by RacN17, wortmannin, LY 294002, an Akt inhibitor, and AktDN. Treatment of macrophages with PGN induced the recruitment of p85α and Rac1 to Toll-like receptor 2 (TLR2) in a time-dependent manner. These results indicate that PGN may activate the Rac1/PI3K/Akt pathway through the recruitment of p85α and Rac1 to TLR2 to mediate IKKα/β activation and p65 phosphorylation, which in turn induces NF-κB transactivation, and ultimately causes COX-2 expression in RAW 264.7 macrophages.",
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