Brefeldin A–sensitive ER‐Golgi vesicle trafficking contributes to NLRP3‐dependent caspase‐1 activation

Abstract

Endoplasmic reticulum (ER)‐Golgi vesicle trafficking plays a pivotal role in the conventional secretory pathway of many cytokines; however, the precise release mechanism of a major inflammasome mediator, IL‐1β, is not thought to follow the conventional ER‐Golgi route and remains elusive. Here, we found that perturbation of ER‐Golgi trafficking by brefeldin A (BFA) treatment attenuated nucleotide‐binding oligomerization domain‐like receptor family, pyrin–domain–containing 3 (NLRP3) inflammasome activation in mouse bone marrow–derived macrophages (BMDMs). BFA treatment inhibited NLRP3‐mediated inflammasome assembly and caspase‐1 activation but did not block IL‐1β secretion from BMDMs following BFA administration after NLRP3 inflammasome activation. Consistently, short‐hairpin RNA–dependent knockdown of BFA‐inhibited guanine nucleotide‐exchange protein 1 (BIG1), a molecular target of BFA and an initiator of Golgi‐specific vesicle trafficking, abolished NLRP3‐dependent apoptosis‐associated speck‐like protein containing a caspase‐recruitment domain oligomerization and caspase‐1 activation in BMDMs. Similarly, knockdown of Golgi‐specific BFA‐resistance guanine nucleotide exchange factor 1, another target of BFA, clearly attenuated NLRP3‐mediated caspase‐1 activation in BMDMs. Mechanistically, inhibition of BIGl‐mediated vesicle trafficking did not impair NLRP3‐activating signal 2‐promoted events, such as potassium efflux and mitochondrial rearrangement, but caused significant impairment of signal 1‐triggered priming steps, including NF‐κB–mediated pathways. These data suggest that BFA‐targeted vesicle trafficking at the Golgi contributes to activation of the NLRP3 inflammasome signaling.—Hong, S., Hwang, I., Gim, E., Yang, J., Park, S., Yoon, S.‐H., Lee, W.‐W., Yu, J.‐W. Brefeldin A–sensitive ER‐Golgi vesicle trafficking contributes to NLRP3‐dependent caspase‐1 activation. FASEB J. 33, 4547–4558 (2019). http://www.fasebj.org

Right place, right time: localisation and assembly of the NLRP3 inflammasome

“…Following treatment with NLRP3 activators, the levels of diacyl glycerol (DAG) at the Golgi increased and this coincided with the localisation of NLRP3 on MAMs adjacent to the Golgi 20 . Disruption of Golgi integrity with brefeldin A reduced caspase-1 activation, IL-1β secretion and ASC speck formation following NLRP3 inflammasome activation, a result which was corroborated in a subsequent study 94 . This effect was attributed to protein kinase D (PKD), a DAG effector, which phosphorylated NLRP3 at a conserved residue (Ser293) in its NBD domain, allowing its release from MAMs to form an inflammasome complex within the cytosol ( Figure 2).…”

SON DNA‐binding protein mediates macrophage autophagy and responses to intracellular infection

“…This is consistent with our observation that GCA treatment prevents IL‐1β release from AM‐MDMs following treatment with NLRP3 activators or F. tularensis infection. A number of reports show that NLRP3 inflammasome formation depends on trafficking of Golgi‐associated vesicles, although different studies have placed these vesicles at the ER‐Golgi interface [55], between mitochondria‐associated membranes and the Golgi [54], or emerging from a dispersed trans ‐Golgi network [56]. Interestingly, differences are apparent between macrophage models: brefeldin A treatment blocked NLRP3‐mediated caspase‐1 cleavage and IL‐1β release in BMDMs but not in human monocytes or THP‐1 cells, nor did it affect activation of the AIM2 or NLRC4 inflammasomes [55].…”

NLRP3 inflammasome, an immune‐inflammatory target in pathogenesis and treatment of cardiovascular diseases

“…The significant role of Golgi apparatus in NLRP3 inflammasome activation has gradually been recognized. Disruption of ER‐Golgi trafficking inhibited NLRP3 inflammasome assembly and caspase‐1 activation, indicating the involvement of ER‐Golgi vesicle trafficking in NLRP3 activation 11 . Furthermore, NLRP3 inflammasome activation was reported to be accompanied by mitochondrial clustering around the Golgi.…”