Class I and III Phosphatidylinositol 3′-Kinase Play Distinct Roles in TLR Signaling Pathway

Abstract

PI3K involvement has been implicated in the TLR signal pathway. However, the precise roles of the different classes of PI3K in the pathway remain elusive. In this study, we have explored the functions of class I and class III PI3K in the TLR signal pathway using specific kinase mutants and PI3K lipid products. Our results reveal that class III PI3K specifically regulates CpG oligodeoxynucleotide (ODN)-induced cytokine and NO production as well as NF-κB activation, whereas class I PI3K regulates both CpG ODN- and LPS-induced IL-12 production and NF-κB activation. Additional studies of CpG ODN uptake with flow cytometric analysis show that class III PI3K, but not class I, regulates cellular CpG ODN uptake. Furthermore, experiments with MyD88-overexpressing fibroblast cells transfected with dominant-negative mutants of PI3K demonstrate that class III PI3K regulates CpG ODN-mediated signaling upstream of MyD88, while class I PI3K regulation is downstream of MyD88. These results suggest that class I and class III PI3K play distinct roles in not only the uptake of CpG ODN, but also responses elicited by CpG ODN and LPS.

Augmented Lipopolysaccharide-Induced TNF-α Production by Peritoneal Macrophages in Type 2 Diabetic Mice Is Dependent on Elevated Glucose and Requires p38 MAPK

“…PI3K and TLR signaling share several downstream signaling components (22,23,48), however, the role of PI3K in TLR4 signaling, such as LPS is controversial. Several papers (49,50) show that inhibition of PI3K leads to an increase in LPS-induced proinflammatory cytokines such TNF-␣ and tissue factor in monocytes and blood, suggesting that PI3K could be an endogenous inhibitor of LPS-induced cytokines.…”

PI3K/AKT Mediated P53 Down-Regulation Participates in CpG DNA Inhibition of Spontaneous B Cell Apoptosis

“…PI3K and its downstream AKT have been shown to play an important role in promoting cell survival (10,30). CpG DNA/ODN can activate PI3K to regulate a variety of cellular responses (31,32). AKT has been shown to inhibit cell apoptosis in Rat1a fibroblasts in proportion to its kinase activity (33), and it has been reported that CpG DNA inhibits DC (2) and macrophage (34) apoptosis in a PI3K dependent manner.…”

The involvement of hypoxia-inducible factor 1 alpha in Toll-like receptor 7/8-mediated inflammatory response

“…Results of densitometric analysis of the western blot data are expressed as mean values ± SD, where n = 3; *P < 0.01 vs control. by TLR downstream signaling [18]), ERK (known to stimulate NOS activation in macrophages [19]) and PKCd (found to play a role in Nox assembly in zymosanactivated human monocytes [20]) in R848-induced TLR7/8 signaling were investigated. Cells were pretreated with 30 µM Ly294002 (PI3-K inhibitor), 10 µM PD098059 (ERK inhibitor) and 20 µM rottlerin (PKCd inhibitor), followed by 4 h of stimulation with 0.1 µg/ml R848.…”