Biology subjects

Georgin-Lavialle, S.

Publications and source records attributed to Georgin-Lavialle, S..

3 recordsLinked to original sources

bioRxiv2024

C-terminal CDC42 variants in autoinflammatory patients specifically trigger actin defects and NF-kB hyperactivation

BackgroundCDC42 belongs to the RHO GTPases family. Recently, four variants were identified in autoinflammatory patients. One variant affects the N-terminal part of the protein while the three others are located in the C-terminal region. To date, most of the functional defects were only reported for the C-terminal R186C variant. The other three variants are far less characterized at the functional level. ObjectivesWe aimed to investigate whether all four CDC42 variants share common signaling alterations. MethodsWe performed in depth imaging analysis of actin cytoskeleton and NF-{kappa}B nuclear translocation, coupled to flow cytometry in cells from patients or in the monocytic THP-1 cell line. ResultsWe show that the N-terminal Y64C CDC42 variant localizes normally in cells and does not exhibit any defect in actin filaments formation or NF-{kappa}B activation. By contrast, all three C-terminal CDC42 variants have aberrant subcellular localizations and share common functional alterations. They exhibit a strong reduction or complete block in their abilities to polymerize actin filaments. They also show more NF-{kappa}B nuclear translocation and phosphorylation. However, we suggest that there is no causal relationship between these two events. Artificial reduction in cellular actin content using specific pharmacologic drugs is indeed not sufficient to hyperactivate NF-{kappa}B. ConclusionsThis study further extends the spectrum of defects observed in autoinflammatory CDC42 patients, and pinpoints a functional heterogeneity between N- and C-terminal CDC42 variants. We also show that CDC42 patients should not be necessarily classified among actinopathies. Altogether, the functional defects we report here can lead the way towards more personalized therapeutic interventions.

immunology↗

bioRxiv2023

Functional diversity of NLRP3 gain-of-function mutants associated with CAPS autoinflammation.

NLRP3-associated autoinflammatory disease (NLRP3-AID or CAPS) is an heterogenous group of monogenic autoinflammations associated with NLRP3 gain-of-function mutations. The poor functional characterization of most NLRP3 variants is a barrier to diagnosis although patients can be efficiently treated with anti-IL-1 approaches. In addition, while NLRP3 inflammasome is controlled by coordinated priming and activation signals, gain-of-functions of NLRP3 variants have been only investigated in response to priming. Here, we functionally characterize 34 NLRP3 variants in vitro by determining their activity in response to induction, priming and/or activation signals, and their sensitivity to inhibitors. We highlight the functional diversity of the gain-of-function mutants and describe four groups based on their profile of signals required for their activation, that correlate partly with the symptoms severities. We identify a new group of NLRP3 mutants responding to the activation signal without priming, with patients often misdiagnosed. Our results identify key NLRP3 residues controlling the inflammasome activity and sensitivity to inhibitors. The comparison of four inhibitors on the 34 variants identifies inhibitory mechanisms with broader efficiency for future drug design. Altogether, our results provide new insights on NLRP3 activation and an explanatory mechanism for NLRP3-AID heterogeneity, and original tools for NLRP3-AID diagnosis and anti-inflammatory disease drug development. eTOC SummaryFunctional characterization of 34 CAPS-associated NLRP3 variants identifies polymorphisms versus gain-of-function pathogenic mutants, and highlights diversities in the signals controlling their activation and in their sensitivity to inhibitors. This study provides tools for CAPS diagnosis and anti-inflammation drug development and insights on NLRP3 control mechanisms.

immunology↗

bioRxiv2021

Steroid hormone catabolites activate the pyrin inflammasome through a non-canonical mechanism

The pyrin inflammasome acts as a guard of RhoA GTPases and is central to immune defences against RhoA-manipulating pathogens. Pyrin activation proceeds in two steps. Yet, the second step is still poorly understood. Using cells constitutively activated for the pyrin step 1, a chemical screen identified etiocholanolone and pregnanolone, two catabolites of testosterone and progesterone, acting at low concentrations as specific step-2 activators. High concentrations of these metabolites fully and rapidly activated pyrin, in a human-specific, B30.2 domain-dependent manner and without inhibiting RhoA. Mutations in MEFV, encoding pyrin, cause two distinct autoinflammatory diseases (PAAND and FMF). Monocytes from PAAND patients, and to a lower extent from FMF patients, displayed increased responses to these metabolites. This study provides a new perspective on pyrin activation, indicates that endogenous steroid catabolites can drive autoinflammation, through the pyrin inflammasome, and explains the "steroid fever" described in the late 1950s, upon steroid injection in humans.

immunology↗