NOD2 and TLR2 Signal via TBK1 and PI31 to Direct Cross-Presentation and CD8 T Cell Responses.

Gennaro Prota,Vincenzo Cerundolo,Alison Simmons,Ji-Li Chen,Tessa Steevels,Daniele Muraro,Marie-Laëtitia Thézénas,Daniele Corridoni,Seiji Shiraishi,Thomas Chapman,Uzi Gileadi,Nicola Ternette

doi:10.3389/fimmu.2019.00958

Abstract

NOD2 and TLR2 recognize components of bacterial cell wall peptidoglycan and direct defense against enteric pathogens. CD8+ T cells are important for immunity to such pathogens but how NOD2 and TLR2 induce antigen specific CD8+ T cell responses is unknown. Here, we define how these pattern recognition receptors (PRRs) signal in primary dendritic cells (DCs) to influence MHC class I antigen presentation. We show NOD2 and TLR2 phosphorylate PI31 via TBK1 following activation in DCs. PI31 interacts with TBK1 and Sec16A at endoplasmic reticulum exit sites (ERES), which positively regulates MHC class I peptide loading and immunoproteasome stability. Following NOD2 and TLR2 stimulation, depletion of PI31 or inhibition of TBK1 activity in vivo impairs DC cross-presentation and CD8+ T cell activation. DCs from Crohn's patients expressing NOD2 polymorphisms show dysregulated cross-presentation and CD8+ T cell responses. Our findings reveal unidentified mechanisms that underlie CD8+ T cell responses to bacteria in health and in Crohn's.

Highlights

NOD2 and TLR2 are pattern recognition receptors (PRRs) that recognize conserved components of peptidoglycan (PGN) found in bacterial cell walls [1, 2]
Utilizing information obtained from a quantitative phosphoproteomic analysis comparing NOD2 and TLR2 signaling in human dendritic cells (DCs), we discovered that NOD2 in combination with TLR2 phosphorylates PI31
We examined mutated peptides for serine, serine, FIGURE 2 | TANK-binding kinase-1 (TBK1) mediates NOD2 and TLR2 mediated PI31 phosphorylation. (A) Constructs were transfected into HEK293 cells expressing human NOD2 and cells stimulated with MDP for 30 min

Summary

Introduction

NOD2 and TLR2 are pattern recognition receptors (PRRs) that recognize conserved components of peptidoglycan (PGN) found in bacterial cell walls [1, 2]. Both PRRs activate intracellular signaling pathways in antigen presenting cells (APCs) that drive pro-inflammatory and antimicrobial adaptive responses. Both receptors are important for clearance of bacterial pathogens such as Salmonella typhimurium, Shigella flexneri, and Mycobacterium tuberculosis [3,4,5]. NOD2 is the NOD2/TLR2-Driven Cross-Presentation strongest associated Crohn’s susceptibility gene and Crohn’s disease patients who express NOD2 polymorphisms display loss of function for induction of NOD2 effector genes and NOD2/TLR2 specific genes [7, 10,11,12,13,14,15]

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