7lvm
CASP8 isoform B DED domainCASP8 isoform B DED domain
Structural highlights
Disease[CASP8_HUMAN] Defects in CASP8 are the cause of caspase-8 deficiency (CASP8D) [MIM:607271]. CASP8D is a disorder resembling autoimmune lymphoproliferative syndrome (ALPS). It is characterized by lymphadenopathy, splenomegaly, and defective CD95-induced apoptosis of peripheral blood lymphocytes (PBLs). It leads to defects in activation of T-lymphocytes, B-lymphocytes, and natural killer cells leading to immunodeficiency characterized by recurrent sinopulmonary and herpes simplex virus infections and poor responses to immunization.[1] Function[CASP8_HUMAN] Most upstream protease of the activation cascade of caspases responsible for the TNFRSF6/FAS mediated and TNFRSF1A induced cell death. Binding to the adapter molecule FADD recruits it to either receptor. The resulting aggregate called death-inducing signaling complex (DISC) performs CASP8 proteolytic activation. The active dimeric enzyme is then liberated from the DISC and free to activate downstream apoptotic proteases. Proteolytic fragments of the N-terminal propeptide (termed CAP3, CAP5 and CAP6) are likely retained in the DISC. Cleaves and activates CASP3, CASP4, CASP6, CASP7, CASP9 and CASP10. May participate in the GZMB apoptotic pathways. Cleaves ADPRT. Hydrolyzes the small-molecule substrate, Ac-Asp-Glu-Val-Asp-|-AMC. Likely target for the cowpox virus CRMA death inhibitory protein. Isoform 5, isoform 6, isoform 7 and isoform 8 lack the catalytic site and may interfere with the pro-apoptotic activity of the complex.[2] [3] Publication Abstract from PubMedOBJECTIVE: Fibroblast-like synoviocytes (FLS) play a pivotal role in rheumatoid arthritis (RA) by contributing to synovial inflammation and progressive joint damage. An imprinted epigenetic state is associated with the FLS aggressive phenotype. We identified CASP8 (encoding for caspase-8) as a differentially marked gene and evaluated its pathogenic role in RA FLSs. METHODS: RA FLS lines were obtained from synovial tissues at arthroplasty and used at passage 5-8. Caspase-8 was silenced using small interfering RNA, and its effect was determined in cell adhesion, migration and invasion assays. Quantitative reverse transcription PCR and western blot were used to assess gene and protein expression, respectively. A caspase-8 selective inhibitor was used determine the role of enzymatic activity on FLS migration and invasion. Caspase-8 isoform transcripts and epigenetic marks in FLSs were analyzed in FLS public databases. Crystal structures of caspase-8B and G were determined. RESULTS: Caspase-8 deficiency in RA FLSs reduced cell adhesion, migration, and invasion independent of its catalytic activity. Epigenetic and transcriptomic analyses of RA FLSs revealed that a specific caspase-8 isoform, variant G, is the dominant isoform expressed (~80% of total caspase-8) and induced by PDGF. The crystal structures of caspase-8 variant G and B were identical except for a unique unstructured 59 amino acid N-terminal domain in variant G. Selective knockdown of caspase-8G was solely responsible for the effects of caspase-8 on calpain activity and cell invasion in FLS. CONCLUSION: Blocking caspase-8 variant G could decrease cell invasion in diseases like RA without the potential deleterious effects of nonspecific caspase-8 inhibition. Caspase-8 Variant G Regulates Rheumatoid Arthritis Fibroblast-Like Synoviocyte Aggressive Behavior.,Ansalone C, Ainsworth RI, Nygaard G, Ai R, Prideaux EB, Hammaker D, Perumal NB, Weichert K, Tung F, Kodandapani L, Sauder JM, Mertsching EC, Benschop RJ, Boyle DL, Wang W, Firestein GS ACR Open Rheumatol. 2021 Dec 28. doi: 10.1002/acr2.11384. PMID:34963199[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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