Pyrin inflammasome activation and RhoA signaling in the autoinflammatory diseases FMF and HIDS

Abstract

Mutations of pyrin and mevalonate kinase (MVK) cause distinct interleukin-1β (IL-1β)-mediated autoinflammatory diseases, familial Mediterranean fever (FMF) and hyperimmunoglobulinemia D syndrome (HIDS). Pyrin forms an inflammasome when mutated or in response to bacterial modification of the GTPase RhoA. Here we show that RhoA activates the serine-threonine kinases PKN1 and PKN2 that bind and phosphorylate pyrin. Phosphorylated pyrin binds 14-3-3 proteins, which block the pyrin inflammasome. The binding of 14-3-3 and PKN proteins to FMF-associated mutant pyrin is substantially decreased, and the constitutive IL-1β release from FMF or HIDS patients’ peripheral blood mononuclear cells is attenuated by activating PKN1 and PKN2. Defects in prenylation, seen in HIDS, lead to RhoA inactivation and consequent pyrin inflammasome activation. These data indicate a previously unsuspected fundamental molecular connection between two seemingly distinct autoinflammatory disorders.

Familial Mediterranean fever mutations lift the obligatory requirement for microtubules in Pyrin inflammasome activation

“…Importantly, the B30.2 domain is absent in the murine Pyrin ortholog, which prompted us to characterize regulation mechanisms of Pyrin activation in peripheral blood mononuclear cells (PBMCs) of healthy donors in parallel with studies in murine bone marrow-derived macrophages (BMDMs). As reported (14,15), TcdB activated the Pyrin inflammasome in our studies ( Fig. S1 A and B).…”

“…Dephosphorylation of Pyrin's intermediate linker domain was recently shown to be required for TcdA-and TcdB-induced inflammasome activation (14,15,19), and introduction of FMF mutations in the B30.2 domain of ectopically expressed Pyrin did not interfere with this process (15). In agreement with these reports, we showed that endogenous Pyrin was not constitutively active in FMF PBMCs but was engaged only after TcdA stimulation or C. difficile infection ( Fig.…”

“…The Pyrin inflammasome responds to infection with Burkholderia cenocepacia (12,13) and the Rho GTPasetargeting toxins Clostridium botulinum toxin C3 and C. difficile cytotoxin B (TcdB) in mouse macrophages (13)(14)(15). Importantly, the B30.2 domain is absent in the murine Pyrin ortholog, which prompted us to characterize regulation mechanisms of Pyrin activation in peripheral blood mononuclear cells (PBMCs) of healthy donors in parallel with studies in murine bone marrow-derived macrophages (BMDMs).…”

“…Although the B30.2 domain is dispensable for Pyrin inflammasome activation, we established here that FMF mutations in this domain nonetheless remove the critical reliance on intact microtubules for Pyrin-based nucleation of ASC specks and inflammasome signaling. Microtubules were recently proposed to control inflammasome activation apically of Pyrin dephosphorylation in response to bacterial RhoA inactivation (14). However, this suggestion is difficult to reconcile with the observation that TcdAinduced Pyrin dephosphorylation continued unhampered in colchicine-pretreated macrophages and 293T cells (Fig.…”

Late ventricular potentials in familial Mediterranean fever with and without AA amyloidosis

“…Chronic inflammation and its sequelae, including anemia, splenomegaly, continuously elevated acute-phase reactants, and amyloidosis may also occur in 30-60% of untreated or treatment-refractory patients (7). The MEditerranean FeVer gene (MEFV) was cloned in 1997, but only recently was it found that the protein encoded by it (pyrin/marenostrin) is a sensor protein of bacterial antigens that is used to promote inflammation (8,9). Mutations in MEFV with enhance this function and allow for episodic and continuous inflammation to occur without interruption and to exert its toll.…”