Cooperative Regulation of NOTCH1 Protein-Phosphatidylinositol 3-Kinase (PI3K) Signaling by NOD1, NOD2, and TLR2 Receptors Renders Enhanced Refractoriness to Transforming Growth Factor-β (TGF-β)- or Cytotoxic T-lymphocyte Antigen 4 (CTLA-4)-mediated Impairment of Human Dendritic Cell Maturation

Devram Sampat Ghorpade,Srini V Kaveri,Jagadeesh Bayry,Kithiganahalli Narayanaswamy Balaji

doi:10.1074/jbc.m111.232413

Abstract

Dendritic cells (DCs) as sentinels of the immune system are important for eliciting both primary and secondary immune responses to a plethora of microbial pathogens. Cooperative stimulation of a complex set of pattern-recognition receptors, including TLR2 and nucleotide-binding oligomerization domain (NOD)-like receptors on DCs, acts as a rate-limiting factor in determining the initiation and mounting of the robust immune response. It underscores the need for "decoding" these multiple receptor interactions. In this study, we demonstrate that TLR2 and NOD receptors cooperatively regulate functional maturation of human DCs. Intriguingly, synergistic stimulation of TLR2 and NOD receptors renders enhanced refractoriness to TGF-β- or CTLA-4-mediated impairment of human DC maturation. Signaling perturbation data suggest that NOTCH1-PI3K signaling dynamics assume critical importance in TLR2- and NOD receptor-mediated surmounting of CTLA-4- and TGF-β-suppressed maturation of human DCs. Interestingly, the NOTCH1-PI3K signaling axis holds the capacity to regulate DC functions by virtue of PKCδ-MAPK-dependent activation of NF-κB. This study provides mechanistic and functional insights into TLR2- and NOD receptor-mediated regulation of DC functions and unravels NOTCH1-PI3K as a signaling cohort for TLR2 and NOD receptors. These findings serve in building a conceptual foundation for the design of improved strategies for adjuvants and immunotherapies against infectious diseases.

Highlights

Responses to a plethora of microbial pathogens
TLR2 and NOD Receptors Cooperatively Regulate Maturation of Human Dendritic cells (DCs)—Immature DCs (0.5 ϫ 106/ml) were cultured with agonists for TLR2, Rv0754 (200 ng/ml), NOD1, and C12-iE-DAP (1 ␮g/ml), or NOD2, muramyl dipeptide (MDP) (1 ␮g/ml) for 48 h, and expression of various surface markers on cells was analyzed by flow cytometry
As a first step, we studied the maturation process of human DCs initiated by engagements of TLR2, NOD1, and NOD2 receptors

Summary

Introduction

Responses to a plethora of microbial pathogens. Cooperative stimulationThoifsaacrotmicplleexhsaest obfepeanttewrni-trhecdorganwitionnbryectehp-e authors. TLR2 triggering by Rv0754 demonstrated significant rescue, cooperative NLR engagement with respective agonists, C12-iE-DAP (NOD1) and MDP (NOD2), significantly surmounted CTLA-4- and TGF-␤-mediated suppression of DC maturation (Fig. 3, A–C and D–F).

Results

Conclusion