Biology subjects

Martin-Sanchez, F.

Publications and source records attributed to Martin-Sanchez, F..

4 recordsLinked to original sources

bioRxiv2023

Pyroptosis leads to loss of centrosomal integrity in macrophages

NLRP3 forms a multiprotein inflammasome complex to initiate the inflammatory response when macrophages sense infection or tissue damage, which leads to caspase-1 activation and maturation and release of the inflammatory cytokines interleukin-1{beta} (IL-1{beta}) and IL-18, and Gasdermin-D (GSDMD) mediated pyroptosis. NLRP3 inflammasome activity must be controlled as unregulated and chronic inflammation underlies inflammatory and autoimmune diseases. Several findings uncovered that NLRP3 inflammasome activity is under the regulation of centrosome localized proteins such as NEK7 and HDAC6, however, whether the centrosome composition or structure is altered during the inflammasome activation is not known. Our data show that levels of the centrosomal scaffold protein pericentrin (PCNT) are reduced upon NLRP3 inflammasome activation via different activators in human and murine macrophages. PCNT loss occurs in the presence of membrane stabilizer punicalagin, suggesting this is not a consequence of membrane rupture. We found that PCNT loss is dependent on NLRP3 and active caspases as MCC950 and pan caspase inhibitor ZVAD prevent its degradation. Moreover, caspase-1 and GSDMD are both required for this NLRP3-mediated PCNT loss because absence of caspase-1 or GSDMD triggers an alternative regulation of PCNT via its cleavage by caspase-3 in response to nigericin stimulation. PCNT degradation occurs in response to nigericin, but also other NLRP3 activators including lysomotropic agent L-Leucyl-L-Leucine methyl ester (LLOMe) and hypotonicity. Our work reveals that the NLRP3 inflammasome activation affects centrosome composition and structure which may deepen our understandings of how activated NLRP3 inflammasomes are involved in the pathogenesis of inflammatory diseases.

immunology↗

bioRxiv2021

NLRP3 activation in response to disrupted endocytic traffic

Inflammation driven by the NLRP3 inflammasome is coordinated through multiple signaling pathways and with a poorly defined regulation by sub-cellular organelles. Here, we tested the hypothesis that NLRP3 senses disrupted endosome trafficking to trigger inflammasome formation and inflammatory cytokine secretion. NLRP3-activating stimuli disrupted endosome trafficking and triggered localization of NLRP3 to vesicles positive for endosome markers and the inositol lipid PtdIns4P. Chemical disruption of endosome trafficking sensitized macrophages to the NLRP3 activator imiquimod driving enhanced inflammasome activation and cytokine secretion. Together these data suggest that NLRP3 is capable of sensing disruptions in the trafficking of endosomal cargoes, and that this may explain in part the spatial activation of the NLRP3 inflammasome complex. These data highlight new mechanisms amenable for the therapeutic targeting of NLRP3. One-Sentence SummaryNLRP3 senses disruptions in endosome trafficking to trigger the formation of an inflammasome complex and initiate an inflammatory response.

immunology↗

bioRxiv2020

Priming Is Dispensable For NLRP3 Inflammasome Activation In Human Monocytes

Interleukin (IL)-1 family of cytokines modulate immune responses during infection and inflammation. IL-18 and IL-1{beta} are members of the IL-1 family, which contribute to inflammatory conditions such as rheumatoid arthritis and Alzheimers disease. IL-18 and IL-1{beta} are produced as inactive precursors that are activated by large macromolecular complexes called inflammasomes upon sensing damage or pathogenic signals. Canonical NLRP3 inflammasome activation is regarded to require a priming step that causes NLRP3 and IL-1{beta} gene upregulation, and also NLRP3 post-translational licencing. A subsequent activation step leads to the assembly of the inflammasome and the cleavage of pro-IL-18 and pro-IL-1{beta} by caspase-1 into their mature forms, allowing their release. Here we show that in primary human monocytes, the initial priming step is dispensable to form an active NLRP3 inflammasome. We found that, in the absence of priming, the NLRP3 activator nigericin caused the processing and release of constitutively expressed IL-18. Another IL-1 family member, IL-37, is constitutively cleaved but the release of its mature form was mediated by inflammasome activation, also in the absence of a priming step. This NLRP3 activation was characterised by ASC oligomerisation as well as caspase-1 and GSDMD cleavage and was blocked by the NLRP3 inhibitor MCC950 and in NLRP3 deficient cells. IL-18 and IL-37 release were impaired in GSDMD deficient THP-1s, suggesting that pyroptosis is required for release of these cytokines. This work highlights the readiness of the NLRP3 inflammasome to assemble in the absence of priming and hence contribute to sterile inflammatory processes in health and disease. Significance StatementThe NLRP3 inflammasome is a driver of inflammation through the processing of Interleukins (IL)-1{beta} and IL-18. Human monocytes coordinate the innate immune response through inflammasome activation following exposure to pathogens and damage signals. We currently think of NLRP3 activation as a 2 step process: priming (NLRP3 gene upregulation and post-translational licencing) and assembly. Here we show that the priming step is dispensable for NLRP3 inflammasome activation in human monocytes. The second signal alone is sufficient for caspase-1 activation, leading to cell death and the release of the constitutively expressed IL-18 and mIL-37. This reveals that in human monocytes, the NLRP3 inflammasome is already licenced and able to quickly assemble to mount an inflammatory response.

immunology↗

bioRxiv2020

ASC oligomer favor caspase-1CARD domain recruitment after intracellular potassium efflux

Signaling through the inflammasome is important for the inflammatory response. Low concentrations of intracellular K+ are associated with the specific oligomerization and activation of the NLRP3 inflammasome, a type of inflammasome involved in sterile inflammation. Subsequent to NLRP3 oligomerization, ASC protein binds and form oligomeric filaments culminating in large protein complexes named ASC specks. ASC specks are also initiated from different inflammasome scaffolds, as AIM2, NLRC4 or Pyrin. ASC oligomers induce the recruitment of caspase-1 through interactions between their respective caspase activation and recruitment domains (CARD), and favoring its activation. So far ASC oligomerization and caspase-1 activation are considered as a K+-independent process. Here we found that ASC oligomers change their structure upon low intracellular K+ independently of NLRP3 and allow the ASCCARD domain to be more accessible for the recruitment of pro-caspase-1CARD domain. Therefore, conditions that decrease intracellular K+ not only drive NLRP3 responses, but also enhance the recruitment of pro-caspase-1 by ASC specks formed by different inflammasomes, indicating that intracellular K+ homeostasis is a key regulatory step for inflammasome regulation.

immunology↗