Biology subjects

Delafontaine, S.

Publications and source records attributed to Delafontaine, 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↗

bioRxiv2024

Autoinflammatory patients with Golgi-trapped CDC42 exhibit intracellular trafficking defects leading to STING hyperactivation

Most autoinflammatory diseases are caused by mutations in innate immunity genes. Recently, four variants in the RHO GTPase CDC42 were discovered in patients affected by syndromes generally characterized by neonatal-onset of cytopenia and auto-inflammation, including hemophagocytic lymphohistiocytosis and rash in the most severe form (NOCARH syndrome). However, the mechanisms responsible for these phenotypes remain largely elusive. Here, we show that the recurrent p.R186C CDC42 variant, which is trapped in the Golgi apparatus, elicits a block in both anterograde and retrograde transports, and endoplasmic reticulum stress. Consequently, it favors STING accumulation in the Golgi in a COPI-dependent manner. This is also observed for the other Golgi-trapped p.*192C*24 CDC42 variant, but not for the p.Y64C and p.C188Y variants that do not accumulate in the Golgi. We demonstrate that the two Golgi-trapped CDC42 variants are the only ones that exhibit overactivation of the STING pathway. Consistent with these results, patients carrying Golgi-trapped CDC42 mutants present very high levels of circulating IFN at the onset of their disease. Thus, we report new mechanistic insights on the impact of the Golgi-trapped CDC42 variants. This increase in STING activation provides a rationale for combination treatments for these severe cases.

immunology↗

bioRxiv2023

Aberrant N-glycosylation in pathogenic variants of adenosine deaminase 2 underlying human ADA2 deficiency

Human deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by pathogenic variants in ADA2 that lead to impaired deaminase activity. Recently, a lysosomal function of ADA2 has been proposed but an intracellular form of the protein has not yet been characterized. Here, we analyze protein expression of mutant ADA2 in human monocyte-derived macrophages from 10 DADA2 patients. We identify an intracellular low-molecular-weight (LMW) form of ADA2 that undergoes glycan trimming by -mannosidases and is absent in DADA2 macrophages. Subcellular fractionation and immunofluorescence microscopy demonstrate that LMW-ADA2 is localized in the lysosomes. By overexpression of 34 ADA2 variants in HEK293T and U-937 cells, we show that absence of LMW-ADA2 strongly correlates with reduced deaminase activity and predicts variant pathogenicity. In conclusion, we describe a previously unreported intracellular hypoglycosylated form of ADA2 and establish the absence of this LMW-ADA2 as a cellular characteristic of DADA2. Thereby, we introduce a protein correlate of the recently described lysosomal form of ADA2. SummaryEhlers et al. demonstrate that mutant ADA2 fails to undergo glycan processing beyond the ER leading to the absence of intracellular low-molecular-weight (LMW) ADA2 in DADA2 patients macrophages. LMW-ADA2 localizes to the lysosomes and can be generated from extracellular wild-type ADA2.

immunology↗