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Caspase-4 binds to LPS membranes with positive curvature for non-canonical inflammasome activation

ABSTRACT: The non-canonical inflammasome, consisting of caspase-4 in humans, initiates pyroptosis upon detecting cytosolic lipopolysaccharide (LPS) from Gram-negative bacteria. For its activation, caspase-4 binds the hydrophobic, membrane-embedded lipid A moiety of LPS, but how it accesses lipid A remains unknown. Caspase-4 activation additionally requires guanylate-binding proteins (GBPs), which target the surface of cytosolic bacteria. Here, we report that GBP1 functions as a mechanoenzyme that can deform the LPS-containing outer membrane of bacteria in infected cells, or fragment tubular LPS micelles in vitro. GBP1-induced fragmentation improves the binding of caspase-4 to LPS micelles, mediated by a hydrophobic pocket within caspase-4-CARD, and thereby promotes LPS-induced caspase-4 activation. Finally, we find that caspase-4 specifically binds the tips of LPS micelles, i.e. regions with positive membrane curvature, for its activation. In summary, we propose a unified mechanism for the non-canonical inflammasome, in which GBP-mediated deformation of LPS membranes creates regions of positive curvature that allow caspase-4 to access lipid A, thereby driving caspase oligomerization and activation.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Pavla Vankova

LAB HEAD: Jakub Began

PROVIDER: PXD070731 | Pride | 2026-03-10

REPOSITORIES: Pride

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			Action	DRS
	CARD-His.fasta	Fasta
	CARD-His_PeptideList.csv	Csv
	CARD-His_Results.xlsx	Xlsx
	CARD-His_coiPAnP-N2-200_3Murea-1Mthiourea-200mMtcep_14776.d.zip	Other
	CARD-His_coiPAnP-N2-200_3Murea-1Mthiourea-200mMtcep_14776_SumPeak.csv	Csv

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