This allowed us to ask cool new questions (🧵3/3):
-are inflammasomes activated & deactivated in the steady-state?
-is inflammasome silencing critical to prevent disease?
-after a major organ challenge, is it critical to silence inflammasomes to restore homeostasis?
👀 our pre-print for the answers!

Summary: pyroptotic & necroptotic cells assemble F-actin-rich filopodia to ⛳️ their corpses. Filopodia mark corpses for recognition by #DCs, via the corpse antigen sampling receptor, #CLEC9A.
New questions: Does this trigger Ag-specific immunity in #infection, #vaccination & #autoimmunity? 🤯 (12/13)

In clever expts by Inflammasome Lab's Sabrina Burgener, DCs reacted to the calcium-sensitive filopodia of corpses by phosphorylating SYK via #CLEC9A. While #NINJ1-driven #CellExplosion was not needed for filopodial assembly (L; M. Monteleone), it was required to expose F-actin to #CLEC9A🤯. (11/13)

Why do #pyroptotic cells use their final minutes to make #filopodia? Well, #filopodia are rich stores of F-actin under the plasma membrane. Could #CellExplosion during #pyroptosis reveal filopodial F-actin to engage the corpse antigen sampling DC receptor, #CLEC9A/#DNGR1? (10/13) (credit: BioRender)

The killer question: are pyroptotic corpses immunogenic to incoming #DendriticCells? Joon Choi & Jon Kagan
tested this 🙏, finding that DCs ⬆️MHCII & costimulus in response to corpses, if the latter had Ca2+ to make filopodia. These DCs are preparing to present antigen! (9/13)

#HighRes imaging revealed the spectacular morphology of #pyroptosis, with clustered pyroptotic blisters (L, blue) causing asymmetric #CellRupture that blows out a portion of the cell, like a popped balloon (R, SEM by @ariottilab.bsky.social). Filopodia remain, crowning the corpse 👑 (8/13)

Filopodial projections crowed #pyroptotic & #necroptotic corpses, but not #apoptotic corpses - even when apoptosis was triggered by #inflammasome signalling in GSDMD-null cells. So filopodia = a flag that a cell lysed 'under suspicious circumstances' ⛳️ (7/13)
Meme: @arnaudjlegrand.bsky.social

This prompted Mercedes Monteleone from @inflammasomelab.bsky.social to ask whether other effectors of #LyticCellDeath trigger filopodial marks on soon-to-be corpses. #GSDMD, other #gasdermins (#GSDMA, #GSDME) & #MLKL also induce cell assembly of filopodia before cell lysis 😯 (6/13)

Our wonderful collaborators, @danielhfisch.bsky.social
& Jon Kagan showed that while Ca2+ is dispensable for GSDMD-induced #pyroptosis, the GSDMD-Ca2+ signalling axis is sufficient to induce filopodial assembly! (5/13)

Incredibly, minutes before pyroptotic #CellExplosion, cells assemble Myo10-capped #filopodia, which crown the resultant cell corpse. #inflammasome #GSDMD signalling was required for both filopodial assembly & cell death. Might Ca2+ influx via GSDMD pores be involved? 🤔(4/13)

@inflammasomelab.bsky.social star @carolinelholley.bsky.social used a suite of #HighRes #imaging methods to answer these questions, staining the plasma membrane (green) & using an #actin dye that enters via #GSDMD pores during #pyroptosis (purple), to resolve #ExplodingCells (3/13). Watch 👇!

The question: intracellular #microbes potently induce #inflammasomes & #pyroptosis. How does a DC sense that a cell died under 'suspicious circumstances', & needs its corpse antigens sampled? More broadly, how do #inflammasomes enable the transition to #AdaptiveImmunity? (2/13)