NLRP3 inflammasome Flashcards
what is the NLRP3 inflammasome?
the NLRP3 inflammasome is a signalling scaffold that coordinates the activation of inflammatory mediators in particular in response to endogenous DAMPs released due to reduction in physical activity, increased consumption of processed foods, aging
name and describe the three types of Pathogen Recognition receptors?
- Molecules present in the serum, like C-reactive protein, complement.
- Receptors present on cell surface and on endosome - Toll-like Receptors (TLRs)
- Intracytoplasmic recognition molecules like NOD-Like receptor (NLR) and RIG-like receptor (RLR)
Name the three components of an inflammasome?
a sensor molecule
Adaptor apoptosis-associated speck-like protein containing a CARD (ASC)
effector protease caspase 1
what does activation of the sensor molecule result in?
ASC self-association into a helical fibrillary assembly leading to the formation of a pyroptosome.
NLRP3 inflammasome acts as molecular scaffold for the activation of _ via proximity induced autocatalytic activation
NLRP3 inflammasome acts as molecular scaffold for the activation of procaspase 1 via proximity induced autocatalytic activation
what does active caspase 1 trigger the release of?
caspase 1 triggers the release of IL-1B and IL-18 (proinflammatory cytokines)
name the three important domains in the NLRP3 sensor molecule
NACHT Domain - has ATPase activity, needed for ATP binding for NLRP3 activation.
Leucine Rich Repeat (LRR) domain - for detection of stimuli, thought to induce autoinhibition by folding back onto NACHT domain.
describe NLRP3 inflammasome assembly and function upon stimulation
- NLRP3 oligomerizes via NACHT domains
- NEK7 (kinase) interacts with NLRP3 and oligomerizes NLRP3 into a complex critical for ASC recruitment
- Oligomerized NLRP3 recruits ASC resulting in helical filament formation.
- Assembled ASC recruits procaspase 1 through interactions with CARD
- Proximity-induced caspase 1 undergoes self cleavage and activation is induced.
- caspase 1 cleaves IL-1B and IL-18, these are secreted.
- Gasdermin D (GSDMD) is also cleaved by caspase 1 which inserts into the membrane, forms pores and induces pyroptosis
the quantity of which NLRP3 inflammasome component is the rate-limiting step of its activation?
the quantity of NLRP3 in the cell at rest
what is priming
the first signal which primes the cell by initiating the transcription of the NLRP3 gene, increasing its expression
what receptors need to be engaged for the inflammasome to be primed?
pathogen recognition receptors
what does activation of PRRs lead to
Nuclear factor kappa B (NFKB) activation and NLRP3 gene transcription
what effect does priming with LPS have on macrophage metabolism?
priming with LPS shifts macrophage metabolism from oxidative phosphorylation to glycolysis
what is the second function of priming?
the induction of post-translational modifications of NLRP3 which stabilises the NLRP3
Phosphorylation of _ position of LRR domain inhibits NLRP3 activation
Y861
Phosphorylation of _ in NACHT domain by PKA inhibits, while protein kinase D (activates)
phosphorylation of S295 in NACHT domain by PKA inhibits while PKD activates
what enzyme do bile acids induce and how does this affect NLRP3 inflammasome
bile acids induce PKA which suppresses NLRP3 activation
dephosphorylation at _ inhibits NLRP3 activation by preventing NLRP3 oligomerization and interaction with ASC
dephosphorylation at S198 inhibits NLRP3 activation by preventing NLRP3 oligomerisation with ASC
Name some examples of DAMPs
ATP, cholesterol crystals, urate crystals, alpha-synuclein
Name some examples of PAMPs
LPS, peptidoglycan, Bacterial RNA-DNA hybrid, ssRNA, dsRNA, beta-glucans
Name some examples of PAMPs
LPS, peptidoglycan, Bacterial RNA-DNA hybrid, ssRNA, dsRNA, beta-glucans
what are the unifying factors of NLRP3 activators?
all induce cellular stress, which is sensed by NLRP3
what are the most commonly accepted activating stimuli for NLRP3
K+ Influx through ion channels
cathepsin release following destabilisation of lysosomal membranes
mitochondrial dysfunction (mitochondrial ROS/DNA or cardiolipin)
metabolic changes
what are ionophores?
bacterial pathogenesis factors - efflux of K+ as a method of sensing presence of bacteria