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  • The PYRIN domain-only protein POP2 inhibits inflammasome priming and activation.

The PYRIN domain-only protein POP2 inhibits inflammasome priming and activation.

Nature communications (2017-06-06)
Rojo A Ratsimandresy, Lan H Chu, Sonal Khare, Lucia de Almeida, Anu Gangopadhyay, Mohanalaxmi Indramohan, Alexander V Misharin, David R Greaves, Harris Perlman, Andrea Dorfleutner, Christian Stehlik
ABSTRACT

Inflammasomes are protein platforms linking recognition of microbe, pathogen-associated and damage-associated molecular patterns by cytosolic sensory proteins to caspase-1 activation. Caspase-1 promotes pyroptotic cell death and the maturation and secretion of interleukin (IL)-1β and IL-18, which trigger inflammatory responses to clear infections and initiate wound-healing; however, excessive responses cause inflammatory disease. Inflammasome assembly requires the PYRIN domain (PYD)-containing adaptor ASC, and depends on PYD-PYD interactions. Here we show that the PYD-only protein POP2 inhibits inflammasome assembly by binding to ASC and interfering with the recruitment of ASC to upstream sensors, which prevents caspase-1 activation and cytokine release. POP2 also impairs macrophage priming by inhibiting the activation of non-canonical IκB kinase ɛ and IκBα, and consequently protects from excessive inflammation and acute shock in vivo. Our findings advance our understanding of the complex regulatory mechanisms that maintain a balanced inflammatory response and highlight important differences between individual POP members.

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