Microtubules and the Assembly of the Inflammasome Complex

Inflammasomes are assembled from a pattern-recognition receptor, the adapter protein Asc and caspase-1 to process interleukin-1b (IL-1b) and IL-18 in response to microbial components or damage-associated signals. Recently, it was shown that microtubules might have a central role in the assembly of the NOD, LRR and PYD domain-containing protein 3 (NLRP3) inflammasome. Inhibitors of microtubule polymerisation (such as colchicine and nocodazole) significantly decrease the levels of IL-1b that is produced in response to NLRP3 inflammasome activators. However, microtubules do not contribute to the activation of the NLRP3 inflammasome in a phagocytosis-dependent manner. Instead, they are required in a dynein-dependent manner for the relocalisation of the mitochondria close to the endoplasmic reticulum following stimulation by inducers of the NLRP3 inflammasome.

As a result of this microtubule-dependent process, Asc molecules on the mitochondria came into close proximity and could interact with NLRP3 on the endoplasmic reticulum (ER). NLRP3 activators induce microtubule polymerisation and acetylation, with concomitant binding of dynein to acetylated a-tubulin. As a proposed mechanism, NLRP3 activation leads to mitochondrial dysfunction followed by a decrease of the mitochondrial coenzyme NAD+ concentration, which in turn inactivates the NAD+-dependent a-tubulin deacetylase sirtuin 2. This results in the accumulation of acetylated a-tubulin and the subsequent organelle translocation process.

Mircrotubule Antibodies:

anti-α-Tubulin (acetylated), mAb (TEU318)
anti-Polyglutamylation Modification, mAb (GT335)
anti-Polyglutamylation Modification, mAb (GT335) (Biotin)
anti-Polyglutamate chain (polyE), pAb (IN105)

NLRP3 Inflammasome Activators:

Monosodium Urate
Nigericin . Na
7BIO – Induces necrosis and consequently NLRP3 inflammasome activation.

NLRP3 Inflammasome Inhibitors:

MCC950 . Na – Potent and selective NLRP3 inflammasome inhibitor
Isoliquiritigenin – Inhibits NLRP3-activated Asc oligomerization. Blocks priming and activation step
Glyburide (USP) – NLRP3 inflammasome inhibitor
BAY 11-7082 – NLRP3 inflammasome inhibitors, reducing ATPase activity of the NLRP3 inflammasome
Parthenolide – NLRP3 inflammasome inhibitors, reducing ATPase activity of the NLRP3 inflammasome
Arglabin – NLRP3 inflammasome inhibitor
Vinpocetine – NLRP3 inflammasome inhibitor
3-Hydroxybutyric Acid – NLRP3 inflammasome inhibitors. Prevents potassium efflux, reducing Asc oligomerisation and speck formation
Resveratrol – NLRP3 inflammasome inhibitor

Priming of the NLRP3 Inflammasome: 

The most prominent function of the NLRP3 inflammasome is the processing and activation of
pro-interleukin-1b (pro-IL-1β). Yet most cells do not express pro-IL-1b and thus prior expression of pro-IL-1b is required. This can be achieved by stimulating receptors such as TLRs (e.g. through LPS), NODs, TNF-Rs (e.g. through TNF-a) or IL-1R1 (through IL-1a and IL-1b) that activate NF-kB and initiate pro-IL-1β transcription. This process of proIL-1β induction is called priming (Signal 1). Priming also induces NF-kB-dependent transcription of NLRP3.

An additional stimulus (Signal 2) results in the activation of the NLRP3 inflammasome and subsequent initiation of downstream signalling. In the absence of priming, NLRP3 inflammasome-dependent caspase-1 activation can also be observed, but IL-1β secretion is absent.

Inflammasome ‘Priming’ Activators:

TNF-α, Soluble
TNF-α (human) (multimeric) (rec.)
TNF-α (mouse) (multimeric) (rec.)
Adipogen Life Sciences provide a large selection of research reagents targeted to the various components of the inflammasome, thanks to a long-term collaboration with the Professor Jürg Tschopp group – the team who discovered the inflammasome in 2002.

Caltag Medsystems are the exclusive UK & ROI distributor for Adipogen Life Sciences. For further information about any of their products, or for ordering enquiries please contact office@caltagmedsystems.co.uk. Alternatively, you can give us a call on +44 01280 827460.

Related Articles:

Introduction to Inflammasomes