Trapping of CDC42 C-terminal variants in the Golgi drives pyrin inflammasome hyperactivation

Abstract

Mutations in the C-terminal region of the CDC42 gene cause severe neonatal-onset autoinflammation. Effectiveness of IL-1β–blocking therapy indicates that the pathology involves abnormal inflammasome activation; however, the mechanism underlying autoinflammation remains to be elucidated. Using induced-pluripotent stem cells established from patients carrying CDC42R186C, we found that patient-derived cells secreted larger amounts of IL-1β in response to pyrin-activating stimuli. Aberrant palmitoylation and localization of CDC42R186C protein to the Golgi apparatus promoted pyrin inflammasome assembly downstream of pyrin dephosphorylation. Aberrant subcellular localization was the common pathological feature shared by CDC42 C-terminal variants with inflammatory phenotypes, including CDC42*192C*24 that also localizes to the Golgi apparatus. Furthermore, the level of pyrin inflammasome overactivation paralleled that of mutant protein accumulation in the Golgi apparatus, but not that of the mutant GTPase activity. These results reveal an unexpected association between CDC42 subcellular localization and pyrin inflammasome activation that could pave the way for elucidating the mechanism of pyrin inflammasome formation.

A CDC42 Stop-loss Mutation in a Patient with Relapsing Polychondritis and Autoinflammation

“…The specific mutation we found was previously described in a patient with neonatal-onset multisystem inflammatory disease (NOMID), an IL-1-mediated autoinflammatory disease [3]. Recently, functional analysis of this particular mutation showed impaired geranyl-geranylation resulting in Golgirestricted mislocalization of the mutant protein, hyperactivation of the pyrin inflammasome, and subsequent accelerated proteasomal degradation [4,5]. Moreover, we also found extremely rare and severe truncating heterozygous mutations in PANX3 (NM_052959 c.765delC; p.V255fs, gnomAD frequency 3.98 × 10 -6 ) and JDP2 (NM_001135049 c.476dupC; p.T159fs, gnomAD frequency 4.00 × 10 -6 ), which both play a role in cartilage and bone development.…”

Cellular models in autoinflammatory disease research

“…The demonstration of iPS‐derived monocytes and macrophages as adequate alternatives to their primary counterparts has paved the way for the use of these cells to model autoinflammatory diseases. Patient‐derived iPSDMs have been used to recapitulate the autoinflammatory phenotypes of their primary counterparts, such as inflammasome formation and cytokine secretion in FMF, 90,91 and the molecular events leading to pyrin inflammasome activation in the presence of CDC42 mutations 92 . Studies utilising this model system showcase not only the potential of iPS‐based models as an alternative to primary cells, but also some of their unique advantages over primary cell‐based models.…”

Lipidation of small GTPase Cdc42 as regulator of its physiological and pathophysiological functions

“…Recently, Nishitani-Isa and colleagues further analyzed molecular details of autoinflammatory pathology evoked by R186C Cdc42-prenyl mutation. Using induced-pluripotent stem cells (iPSCs)-derived myeloid and macrophages cell lines established from the patients carrying this mutation, they reported that patient-derived cells secreted larger amounts of IL-1β in response to pyrin-activating stimuli ( Nishitani-Isa et al, 2022 ). Noteworthy, pharmacological blockade of palmitoylation released R186C mutant from the Golgi apparatus and damped the IL-1β secretion to the wild-type levels.…”