Modulation of Gene Expression via Disruption Of NF-kB Signaling by a

Bacterial Small Molecule

Kravchenko et al. Science 2008

Paulina Blazejewska

Innate Immunity & Pathogen

Innate Immunity0-4 hours

Two phases of the innate response

InfectionRecognition:nonspecific & specific effectors

Removal

Early inducedInnate response4-96 hours

Infection Recognition:microbial-associatedmolecular patterns

Recognition:microbial-associatedmolecular patterns

Inflammation/effector cells

Removal

Conserved receptor e.g. TLR4

LPS

NFκB IkB

IkB kinase (IKK) activity

IκBα & RelA P

proinflammatory cytokines e.g. TNFαp38 protein kinase pathway

Pathogen elimination Bacteremia & persistant infection

C12 ?

TLR4-independentmechanism

Objectives

1. What is the strategy used by pathogens to attenuate the innate immune system ?

2. How to maintain local persistent infection ?

Experimental approach

- Comparison the macrophages response and the phosphorylation of p38 after infection with Salmonella typhimurium , Staphylococcus aureus or Pseudomonas aeruginosa

- Biochemical effect of LPS and C12 and their combination

- C12 in the late stage of LPS stimulation

- Role of C12 in mice

Comparison the macrophages response and the phosphorylation of p38 after infection with S. typhimurium , S. aureus or P. aeruginosa

- similar amount of p-p38

- upon activation with S. typhimurium and S. aureus the patterns of IκBα degradation and resynthesis were comparable

- substantial delay in IκBα resynthesis after infection with P. aeruginosa

- P. aeruginosa deficient in lasL (C12 synthesis) showed the normal profile in IκBα

C12 affects the NFκB pathway in macrophages

Experimental approach

- Comparison the macrophages response and the phosphorylation of p38 after infection with Salmonella typhimurium , Staphylococcus aureus or Pseudomonas aeruginosa

- Biochemical effect of LPS and C12 and their combination

- C12 in the late stage of LPS stimulation

- Role of C12 in mice

Biochemical effect of LPS and C12 and their combination

- C12 impairs the expression and phosphorylation of IκBα

- C12 modulates the phosphorylation of RelA but not expression

- IκBβ degradation was disrupted in the presence of C12

- p-IκBβ remains bound to RelA in the absence of IκBα

C12 reduces the early phase of IKK activation by LPS

Experimental approach

- Comparison the macrophages response and the phosphorylation of p38 after infection with Salmonella typhimurium , Staphylococcus aureus or Pseudomonas aeruginosa

- Biochemical effect of LPS and C12 and their combination

- C12 in the late stage of LPS stimulation

- Role of C12 in mice

C12 in the late stage of LPS stimulation

- the addition of C12 to the macrophages (pretreated with LPS) resulted in rapid reduction of p-IκBα and p-RelA

- C12 also impairs other NFkB-regulated genes

- C12 acts as a general modulator of the NFkB pathway

Experimental approach

- Comparison the macrophages response and the phosphorylation of p38 after infection with Salmonella typhimurium , Staphylococcus aureus or Pseudomonas aeruginosa

- Biochemical effect of LPS and C12 and their combination

- C12 in the late stage of LPS stimulation

- Role of C12 in mice

Role of C12 in mice

- LPS-induced responses were suppressed by C12

What is a mammalian C12 receptor?

- inhibition of TNF by C12 in LPS-stimulated leukocytes may be beneficial for the survival of both pathogen and host

- C12 mediated disruption of NFkB attenuates TLR-4-dependent innate responses – promoting persistent infection with P. aeruginosa

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