LRRFIP2 negatively regulates NLRP3 inflammasome activation in macrophages by promoting Flightless-I-mediated caspase-1 inhibition

Abstract

The NLRP3 inflammasome is the most characterized inflammasome activated by cellular infection or stress, which is responsible for the maturation of proinflammatory cytokines IL-1β and IL-18. The precise molecular mechanism for negative regulation of NLRP3 inflammasome activation needs to be further defined. Here we identify leucine-rich repeat Fli-I-interacting protein 2 (LRRFIP2) as an NLRP3-associated protein and an inhibitor for NLRP3 inflammasome activation. LRRFIP2 binds to NLRP3 via its N terminus upon NLRP3 inflammasome activation, and also interacts with Flightless-I, a pseudosubstrate of caspase-1, via its Coil motif. Knockdown of Flightless-I significantly promotes NLRP3 inflammasome activation. LRRFIP2 enhances the interaction between Flightless-I and caspase-1, facilitating the inhibitory effect of Flightless-I on caspase-1 activation. Furthermore, silencing of Flightless-I abrogates the inhibitory effect of LRRFIP2 on NLRP3 inflammasome. These data demonstrate that LRRFIP2 inhibits NLRP3 inflammasome activation by recruiting the caspase-1 inhibitor Flightless-I, thus outlining a new mechanism for negative regulation of NLRP3 inflammasome.

Aryl hydrocarbon receptor negatively regulates NLRP3 inflammasome activity by inhibiting NLRP3 transcription

“…Mouse peritonitis was induced by intraperitoneal (i.p.) injection of alum 14,17 . Peritoneal exudate cells (PECs) were collected and alum-induced recruitment of inflammatory cells was analysed by flow cytometry.…”

“…The peritoneal fluids were collected and concentrated for ELISA analysis with Amicon Ultra 10K from Millipore. Peritoneal exudates cells (PECs) were analysed by fluorescence-activated cell sorting 14,17 .…”

“…16), LRRFIP2 (ref. 17) and so on. Among these regulators, several molecules are directly inhibiting NLRP3 protein expression to attenuate inflammasome activation, such as plasminogen activator inhibitor type 2 (ref.…”

Molecular mechanisms regulating NLRP3 inflammasome activation

“…ASC, apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain; A20, tumor necrosis factor alpha-induced protein 3; AhR, aryl hydrocarbon receptor; CARD8, caspase recruitment domain; CO, carbon monoxide; IKKa, IkB kinase a; GPSM3, G protein signaling modulator-3; LRRFIP2, leucine-rich repeat Fli-I-interacting protein 2; MNS, 3,4-methylenedioxy-b-nitrostyrene; NF-kB, nuclear factor kappa-light-chain-enhancer of activated B cells; NLRP3, NACHT, LRR, and PYD domains-containing protein 3; NO, nitric oxide; SHP, small heterodimer partner; TRIM30, tripartite-motif protein 30. effect of Flightless-I on caspase-1 activation. 124 In addition, it was recently shown that the orphan nuclear receptor SHP acts as a negative regulator of NLRP3 inflammasome activation through binding with NLRP3 and is also required for translocation of NLRP3 into mitochondria and the maintenance of mitochondrial homeostasis. 107 In SHP-deficient macrophages, mitochondrial ROS generation and cytosolic translocation of mitochondrial DNA were increased significantly.…”

Innate recognition of microbial-derived signals in immunity and inflammation

“…As an NLRP3-binding protein, a member of the family of mammalian NIMA-related kinases (Neks) Nek7 acts downstream of potassium efflux to regulate NLRP3 oligomerization and activation (Groß et al, 2016). Leucine-rich repeat Fli-I-interacting protein 2 (LRRFIP2) negatively regulates NLRP3 inflammasome activation by recruiting the caspase-1 inhibitor Flightless-I (Jin et al, 2013). The recent finding that dopamine D1 receptor (DRD1) signaling cause negative regulation of NLRP3 inflammasome via cAMP, which binds to NLRP3 and promotes its ubiquitination and degradation via MARCH7 .…”