the inflammasomes guardians of the body
DESCRIPTION
The INFLAMMASOMES Guardians of the Body. Fabio Martinion, Annick Mayor, Jurg Tschopp Annual Reviews Immunology 2009. Marcin Cebula. Innate immunity. Toll like receptors – extracellular sensing (PAMPs, DAMPs) RIG-like helicases (RIG-I, MDA5 viral sensors) – intracelular sensing - PowerPoint PPT PresentationTRANSCRIPT
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The INFLAMMASOMES
Guardians of the BodyFabio Martinion, Annick Mayor, Jurg Tschopp
Annual Reviews Immunology 2009
Marcin Cebula
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Innate immunity Toll like receptors – extracellular sensing (PAMPs, DAMPs)
RIG-like helicases (RIG-I, MDA5 viral sensors) – intracelular sensing
NOD - like receptors – intracellular sensing- microbial products- danger signals- metabolic stress
Some NLR form large cytoplasmatic complexes
INFLAMMASOMES
Link between sensing of microbial products with proteolytic activation of proinflammatory cytokines
IL-1 and IL-18
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Structure of NLR family (I)
Multidomain proteins
1) C-terminal region (Leucin rich repeats 20-30 - LRR)
2 ) NACHT – belongs to STAND family of NTPases
3) N-terminal effector domain
LRR – ligand sensing, autoregulation of NLR signaling, LRR domains are formed by tandem repeats
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Structures of NLR
Two sub familiesI PYD containing NALPs (14 in human)II 5 members of NODs + CIITA
IPAF, and BIR containing NAIP form remaining NLR members
Ligand sensing domain
Responsible for NLR oligomerization
Effector domain
PYD – pyrin domainCARD – caspase recruitment domainFIIND – function to findBIR – baculovirys IAP repeat AD- activation dmain
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No experimental data have convincingly demonstrated direct interaction between LRRs of NLRs and their respective activators, suggesting that sensing of patogens by NLRs may be indirect.
It is believed that the crucial step in NLRs activation lies in the oligomerization of the NACHT domains
Formation of active high molecular wieght complexes - INFLAMMASOMES
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NALPs
NALP1, NALP2, NALP3 are central scafold of caspase-1-activating complex known as INFLAMMASOMES
Have PYD domain NALP1 posses additionaly CADR
domain
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IPAF, NAIP
Evolutionary seperates from other NLRs
IPAF – CARD domain NAIP – BIR damain (often
found in proteins involved in apaptosis
Both form INFLAMMASOMES alone or in combination of both
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CARD-containing NLRs
NOD1,2,4 and CIITA and separated NOD3, NOD5
NOD1 and NOD2 once activated recruits kinase RIP2 through CARD-CARD interaction. Oligomerization of RIP2 in NOD signalosomes activate NFBb
NOD1, NOD2 detects PNG NOD2 detects MDP
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NLRs expression pattern and gene regulation NLRs are expressed in cell and tissues that have role in
immunity such as phagocytes
Epitelial cells - the first barrier
NAIP, IPAF – brain, spleen, lung, liver
Some like NALP5, 8, 4, 7, 10, 11 have restricted expression – germ cells and preimplantation embryos
Regulation – TLR stimulation increases the expression of NLRs (NOD1, NOD2 NALP3)
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In Plants…
NLRs genes have similarities to plant genes involved in immune defenses (R-genes)
Contain: LRR, oligomerization domain NB-ARC, and TIR domain (recruitment domain involved in the TLR and IL-R1 family of immune mediators)
Convergent evolution
No NLR-like proteins in insects
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Prototypical inflammasomes (II)
Biochemistry and diversity if inflammasomes is poorly understood, three prototypes
NALP1 NALP3 IPAF
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Prototypical inflammasomes NALP3
Assumed that PYD of NALPs recruits adaptor ASC (apoptosis assiciated spec-like protein containing caspase recruitment domain)
The CARD within ASK binds and recruits caspase-1 to the inflammasomes
NALP1 has C-terminal extension with CARD that rectuits caspase-5 or second caspase-1 to inflammasomes
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Prototypical inflammasomes IPAF
Direct way of recruitment of caspase-1
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Both IPAF and NALP3 bind ATP/dATP what is necessary for oligomerization of NACHT domain. Signal for this comes from LRR that are proposed to sense activating signal
Both IPAF and NALP3 bind SGT1 and HSP90 and activity of HSP90-SGT1 complex is essential for NALP3 activation (by keeping inflammasomes inactive but competent for activation)
Heterocomplexes – diversity?
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Sensors of Danger signals (III)
How innate immune system discriminate between pathogenic and self nonpathogenic microbes
Matzinger suggest DANGER hypothesis Presentation of an antigen in the context of
danger signal triggrs efficient immune response - not only the foreignnes of antigen
Signals released by damaged or stressed tissues
First evidence found in plansMSU – monosoduim urate crystalsCPPD – calcium pyrophosphate dihydrate crystals
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Sensing extracellular ATP
Extracellular ATP released by damage or cellular stress hydrostatic pressure, hypotonic shock
Danger signal binds to purinoreceptor P2X7 thereby activating NALP3 and caspase-1
Extracellular ATP in vivo my be rapidly hydrolyzed. Other ATP sourses
- insulin containing granules from pancreatic cells- microbial flora and pathogenes
ASC deficient mice demonstrated that ATP mediated caspase-1 activation requires ASC and is therefore dependent on activation of NALP
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Uric Acid – a danger signal involved in gout (Arthritismus)
Uric acid form supernatant of dying cells tiggers adjuvanticity. Uric acid with free sodium in extracellular enviroment form
monosodium urate MSD crystals MSU adjuvanticity depends on NALP3 inflammasome
activation → IL-1 ASC, NALP3 deficient mice have reduced crystal induced IL-1
Examples- Erytrocytes infected with Plasmodium contain high levels of hipoxanthine which is released from damaged cells and converted to uric acid – results in inlamation- DC incubated with alum also release uric acid
Aluminium particles act as adjuvant by augumented production of IL-1 Alum-induced caspase -1 is dependent on NALP3 inflammasome
activation
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Silica and Asbestos Inflamation in the lung
Alveolar macrophages reside on barrier between body and the external enviroment
This phagocytes are important defence against microorganisms, dust particles
Silica, asbestos dust are strong inflamation inducers in the lungs.
This compounds act as activators of NALP3
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and skin inflamations
UV activate NALP3 in keratinocytes Inflammasomes play a role in contact hypersensitivity an inflammatory
disease caused by irritant chemicals penetrating skin and inducing T cell response
Two phases- sensitization (chamicals as adjuvants and foreign hapten)- activation (after reexpousure)
SENSITIZATION phase depends on functional:– caspase-1 IL-1, IL-18
– confirmed role of ASC, NALP3 inflammasome
DNFB (dinitrofluorobenzene) shown to promote release IL-1 in caspase-1 dependent manner in DC and keratinocytes.
Suggestion that inflammasomes may detect such a compound directy or recognise the danger signals produced by irritants
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Reactive oxygen species
ROS production occurs upon expousure of macrophages to:
silica, asbestos, MSU, alum, ATP, toxin nigericin, UV, DNCB
ROS production is signal involved in stress and damage sensing
Knockdown of NADPH oxidaze subunits or use of antioxidants inhibit inflammasome activation by mentioned above compound
It is proposed that ROS is directly sensed by NALP3 or indirectly sensed by cytoplasmic modulators of inflammasome activity
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Sensors of Pathohens (IV)
Extracelular PAMPs and danger signals – TLR, RAGE (receptor for advanced glycation end product)
NLRs samples PAMPs reaching cellular compartments (invasion, degradation products from phagocytosed bacteria, viruses)
Additionaly to PAMPs inflammasomes detects toxins and signals restricted to certain pathogens
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PAMPs & toxins
Mainly bacterial PGNs and nucleic acids (indirect).
PGN is degraded to MDP that is sensed by NLR- NOD2 results in activation of NFB - NALP3 results IL-1 activation via caspase-1 (but NOD2 is required)
Sugesstion that NOD2 and NALP3 can cooperate directly or indirectly as part of the same complex
PORE-FORMING bacterial toxins antivate NALP3 inflammasome- -toxin Staphylococcus aureus- aerolysin Aeromonas hydrophila- listeriolysin O Listeria monocytogenes
-potassium efflux, calcium influx (danger signals)
Antrax lethal toxin activates NALP1
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MDP - Muramyl dipeptide
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IPAF inflamasomme activation by injected
virulent factors Gram negative pathogens that activate IPAF require
type III or type IV secretion system for injection of virulent factors activating IPAF
Mainly flagellin activates IPAF but not only.
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INFLAMMASOME regulators (V)
What are the mechanisms silenting the inflamation iduced by inflammasomes
Factors: proteins that interfere with inflammasome assembly and inflammatory caspase activation
MAIN inflamasome regulators are those containing CARD domain, and those with PYD domain
•Targeted disruption of Pyrin in mice causes increased endotoxin sensitivity and enhanced caspase-1 activation
•But Pyrin overexpression can be proinflamatory
•vPYD defficient poxoviruses – enhanced activation of caspase-1
POPs – poxoviral gene product vPYDs – viral PYD
Pi9 – serpin protease inhibitorvCrmA – cowpox virus-encoded inhibitor of caspase-1
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& inflamatory diseases
Autoinflammatory but not autoimmune disorders
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Inflammasomes & Adjuvanticity
Adjuvants: alum, oil based emulsions TLR agonist ? IL-1 has adjuvant properties. Mice immunization
together with IL-1 results in higher antibody production Inflammasome activators have adjuvant properties
(MDP, MSU) MSU, alum (ASC,NALP3,caspase-1) biases immune
response towards Th2 type via IL-1, IL-18, IL-33
Inflammasomes are important in linking innate immunity to adaptive immunity
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Pyroptosis Apoptosis – silent death
Pyroptosis – „Pyro” Fire Cell death dependent on caspase-1, associated with high inflammatory state
Shigella f. infects colon epitelium, evades phagosome to enter cytosol where tigers death requires caspase-1 but not apoptotic caspase-3
Salmonella induced pyroptosis in infected macrophages (ASC, IPAF) is blocked in IPAF defficient mice
Bacillus anthracis induces pyroptosis dependent on NALP1
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Emerging inflammasomes functions
Research on IL-1 and inflammatory caspases revealed its role as mediators in neurodegenerative disorders, cancer and fertility-associated conditions
Amyloid- in Alzheimer’s disease similary to phagocytosed uric acid crystals, activate NALP3 inflammasome, might be important for inflamation and tissue damage
IL-1 perfusion in rabbit ovary blocks embryo development. Inflammasomes may link innate immunity to reproductive biology
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Thank you
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PAMPs & DAMPs
The Caspase-1 Inflammasome: Apilotof innate immune responseB. Brett Finlay et al. Cell Host & Microbe 2008
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General mechanisms of Inflammasome activation