Cytosolic LPS-induced caspase-11 oligomerization and activation is regulated by extended synaptotagmin 1

Caspase-11 (Casp-11) is known to induce pyroptosis and defends against cytosol-invading bacterial pathogens, but its regulation remains poorly defined. Here, we identified extended synaptotagmin 1 (E-Syt1), an endoplasmic reticulum protein, as a key regulator of Casp-11 oligomerization and activation. Macrophages lacking E-Syt1 exhibited reduced production of interleukin-1β (IL-1β) and impaired pyroptosis upon cytosolic lipopolysaccharide (LPS) delivery and cytosol-invasive bacterial infection. Moreover, cleavage of Casp-11 and its downstream substrate gasdermin D were significantly diminished in ESyt1−/− macrophages. Upon LPS stimulation, E-Syt1 underwent oligomerization and bound to the p30 domain of Casp-11 via its synaptotagmin-like mitochondrial lipid-binding protein (SMP) domain. E-Syt1 oligomerization and its interaction with Casp-11 facilitated Casp-11 oligomerization and activation. Notably, ESyt1−/− mice were susceptible to infection by cytosol-invading bacteria Burkholderia thailandensis while being resistant to LPS-induced endotoxemia. These findings collectively suggest that E-Syt1 may serve as a platform for Casp-11 oligomerization and activation upon cytosolic LPS sensing. [Display omitted] •E-Syt1 is required for Casp-11 oligomerization and cleavage•E-Syt1 SMP domain interacts with Casp-11’s p30 domain•E-Syt1’s TM domain mediates its oligomerization upon LPS stimulation•Both E-Syt1 TM domain and SMP domain are essential for promoting Casp-11 cleavage Ma et al. discovered that E-Syt1 oligomerizes upon LPS stimulation and interacts with Casp-11’s p30 domain through its SMP domain. E-Syt1 oligomerization and its interaction with Casp-11 promotes Casp-11 oligomerization and cleavage, suggesting E-Syt1 as a platform for Casp-11 activation upon cytosolic LPS sensing.