HDAC6 mediates an aggresome-adore mechanism for NLRP3 and pyrin inflammasome activation

INTRODUCTION

Canonical inflammasomes are multicomponent protein complexes that play key roles in immune surveillance of infections and probability by activating caspase-1, which cleaves interleukin 1? (IL-1?) and the pore-forming protein gasdermin D, main to cytokine maturation and pyroptosis. The nucleotide-binding area, leucine-rich repeat, and pyrin area–containing protein 3 (NLRP3) shall be activated by the bacterial toxin nigericin, extracellular ATP, and diverse particulates similar to monosodium urate (MSU) crystals, alum, silica, and amyloids, whereas the pyrin inflammasome shall be stimulated by the Rho-glucosylation exercise of Clostridium difficile toxin B. One crucial hallmark for inflammasome activation is the formation of a single supramolecular punctum (additionally identified as a speck) per cell. However, the distance and trafficking of such puncta remain unknown.

RATIONALE

To decode the distance and the molecular equipment in inflammasome assembly and activation in macrophages, we aimed to visualize inflammasome assembly by cell imaging complemented by pharmacological inhibition and centered deletion in cells and in mice.

RESULTS

We chanced on that NLRP3 and pyrin inflammasomes are assembled at the centrosome, additionally identified because the microtubule-organizing middle (MTOC), of every cell, which serves as primarily the most significant predicament for caspase-1 activation and IL-1? conversion. Pharmacological inhibitors of microtubule polymerization, dynein ATPase and the dynein adaptor histone deacetylase 6 (HDAC6), and centered deletion or knockdown of Hdac6 compromised the assembly and activation of these inflammasomes. Reconstitution of Hdac6^?/? macrophages showed that the ubiquitin-binding capability of HDAC6, but now not its deacetylase exercise, is required for NLRP3 and pyrin inflammasome activation. In mice, Hdac6 deficiency reduced lipopolysaccharide- and MSU-induced irritation to a identical extent as mutter NLRP3 inhibition, which demonstrates the requirement of HDAC6 and the microtubule retrograde transport equipment for NLRP3 activation. In distinction, AIM2 and NLRC4 inflammasome puncta accomplish now not localize at the MTOC, and these inflammasomes accomplish now not require microtubule retrograde transport for their activation. Thus, our compare revealed a advise mechanism of inflammasome activation for NLRP3 and pyrin.

For the NLRP3 inflammasome, MTOC localization may well facilitate affiliation with the centrosome-localized kinase NEK7 to bolster inflammasome assembly. We chanced on that in Hdac6^?/? macrophages, NLRP3 is trapped as runt speckles at the trans-Golgi network (TGN), a beforehand identified classic predicament for NLRP3 affiliation upon induction by extra than one NLRP3 stimulators. These data suggested that HDAC6-mediated microtubule transport delivers NLRP3 from TGN to the MTOC. The NLRP3 inflammasome shaped at the MTOC colocalizes with LC3b, an autophagy marker, and an autophagy inhibitor enhances NLRP3-induced IL-1? secretion.

CONCLUSION

Our discover about reveals an surprising parallel between HDAC6-dependent assembly of NLRP3 and pyrin inflammasomes and the formation of aggresomes at the MTOC for autophagic degradation of ubiquitinated pathological aggregates. The twin activating and inhibiting roles played by the MTOC localization of NLRP3 and pyrin inflammasomes is liable to be significant for achieving balanced inflammasome law.