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

Abstract

Familial Mediterranean fever (FMF) is the most common monogenic autoinflammatory disease worldwide. It is caused by mutations in the inflammasome adaptor Pyrin, but how FMF mutations alter signaling in FMF patients is unknown. Herein, we establish Clostridium difficile and its enterotoxin A (TcdA) as Pyrin-activating agents and show that wild-type and FMF Pyrin are differentially controlled by microtubules. Diverse microtubule assembly inhibitors prevented Pyrin-mediated caspase-1 activation and secretion of IL-1β and IL-18 from mouse macrophages and human peripheral blood mononuclear cells (PBMCs). Remarkably, Pyrin inflammasome activation persisted upon microtubule disassembly in PBMCs of FMF patients but not in cells of patients afflicted with other autoinflammatory diseases. We further demonstrate that microtubules control Pyrin activation downstream of Pyrin dephosphorylation and that FMF mutations enable microtubule-independent assembly of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) micrometer-sized perinuclear structures (specks). The discovery that Pyrin mutations remove the obligatory requirement for microtubules in inflammasome activation provides a conceptual framework for understanding FMF and enables immunological screening of FMF mutations.

Inflammasomes contributing to inflammation in arthritis

“…In line with this possibility, colchicine was found to block the pyrin inflammasome activation by bacterial toxins and infection with Clostridium difficile . In contrast, monocytes from FMF patients with gain‐of‐function mutations in pyrin were resistant to inflammasome inhibition by colchicine . This may suggest an increased efficacy of colchicine in vivo compared to in vitro experiments.…”

Inflammasomes in the pathophysiology of autoinflammatory syndromes

“…Interestingly, PAAND‐associated mutations do not map to the B30.2 domain, where most pathogenic FMF‐associated mutations are found. Furthermore, FMF‐associated MEFV mutations do not seem to affect pyrin phosphorylation levels or 14‐3‐3 binding …”

“…B), but only 14 occur frequently in FMF (E148Q, E167D, T267I, P369S, F479L, I591T, M680I, I692del, M694I, M694V, K695R, V726A, A744S, and R761H). Interestingly, in contrast to the gain‐of‐function mutations in NLRP3, NLRC4, or NLRP1 observed in CAPS and in NLRC4‐ and NLRP1‐associated inflammasomopathies, FMF‐associated MEFV mutations do not lead to constitutive pyrin inflammasome activation and require a specific stimulus, such as low doses of Clostridium difficile toxin B . Most pathogenic MEFV mutations in humans occur in exon 10, which encodes the B30.2 domain.…”

Monogenic autoinflammatory disorders: beyond the periodic fever

“…4,5 Clinical variables of participants in the Eurofever project have been collated 6 and proposed classification guidelines have recently been published, taking into account both clinical features and molecular testing. [10][11][12] In health, pyrin is activated by an event downstream of RhoA inactivation, induced by, for example, bacteria such as Clostridium difficile and Burkholderia cenocepacia. 8,9 The majority of cases of FMF are caused by autosomal recessive mutations in exon 2 or 10 of MEFV that result in a decrease in the activation threshold of the inflammasome forming protein pyrin.…”

“…In this select population, the Yalçinkaya-Ozen criteria yielded higher sensitivity, but lower specificity compared with the other diagnostic criteria. 11,12,22 Renal amyloidosis remains the leading cause of increased mortality in adults with FMF even after the introduction of routine colchicine therapy. 18 The therapeutic effectiveness of the microtubule polymerisation inhibitor colchicine in this population has been reported for decades, 21 with several more recent publications documenting in vitro evidence of effect on pyrin inflammasome formation.…”