Project description:Defective Fas signaling causes autoimmune lymphoproliferative syndrome (ALPS). While defective apoptosis may impair negative selection and removal of autoreactive B lymphocytes, Fas transmits also non-apoptotic signals. We show herethat transient Fas ligation in CD40L-stimulated human B cells specifically decreased the mTOR axis activation without causing apoptosis. This signal modulation was absent in ALPS patients. Rather, mTOR signaling was enhanced in germinal center (GC) B cells and plasmablasts derived from a ALPS patient lymph node . Mechanistically, transient Fas engagement induced recruitment of DAXX to the activated Fas complex and nuclear exclusion of PTEN. Likewise, Fas stimulation promoted expression of transcripts like MYC and CXCR4, that regulate GC formation and fate decisions of established GC B cells. We suggest that non-apoptotic Fas signaling has a physiological impact on activated B cell fate decisions explaining the effectiveness of mTOR inhibitors in the treatment of ALPS autoimmunity.

2024-04-08 | PXD017601 | Pride

Germline NRAS mutation causes a novel human autoimmune lymphoproliferative syndrome

Project description:The p21 RAS subfamily of small GTPases, including KRAS, HRAS, and NRAS, regulates cell proliferation, cytoskeletal organization and other signaling networks, and is the most frequent target of activating mutations in cancer. Activating germline mutations of KRAS and HRAS cause severe developmental abnormalities leading to Noonan, cardio-facial-cutaneous and Costello syndrome, but activating germline mutations of NRAS have not been reported. Autoimmune lymphoproliferative syndrome (ALPS) is the most common genetic disease of lymphocyte apoptosis and causes autoimmunity as well as excessive lymphocyte accumulation, particularly of CD4-, CD8- ab T cells. Mutations in ALPS typically affect CD95 (Fas/APO-1)-mediated apoptosis, one of the extrinsic death pathways involving tumor necrosis factor receptor (TNFR) superfamily proteins, but certain ALPS individuals have no such mutations. We show here that the salient features of ALPS as well as a predisposition to hematological malignancies can be caused by a heterozygous germline Gly13Asp activating mutation of the NRAS oncogene that does not impair CD95-mediated apoptosis. The increase in active, GTP-bound NRAS augments RAF/MEK/ERK signaling which markedly decreases the pro-apoptotic protein BIM and attenuates intrinsic, nonreceptor-mediated mitochondrial apoptosis. Thus, germline activating mutations in NRAS differ from other p21 Ras oncoproteins by causing selective immune abnormalities without general developmental defects. Our observations on the effects of NRAS activation indicate that RAS-inactivating drugs, such as farnesyl-transferase inhibitors (FTIs) should be examined in human autoimmune and lymphocyte homeostasis disorders. Keywords: NRAS

2008-03-21 | GSE7345 | GEO

iqChoPara

Project description:Chorthippus parallelus (meadow grasshopper)

| PRJEB55932 | ENA