CASP8

Case study 1: Marta Cristaldi, 2023

Cigarette smoking impairs the lung innate immune response making smokers more susceptible to infections and severe symptoms. Dysregulation of cell death is emerging as a key player in chronic inflammatory conditions. CSE caused inhibition of the MyD88-dependent inflammatory response and activation of TRIF/caspase-8/caspase-1 pathway leading to Gasdermin D (GSDMD) cleavage and increased cell permeability. Herein, the researchers tested the hypothesis that activation of caspase-8 by CSE increased pro-inflammatory cell death of LPS-stimulated macrophages. To this purpose, they measured apoptotic and pyroptotic markers as well as the expression/release of pro-inflammatory mediators in hMDMs exposed to LPS and CSE, alone or in combination, for 6 and 24 h.

LPS/CSE-treated hMDMs, but not cells treated with CSE or LPS alone, underwent lytic cell death (LDH release) and displayed apoptotic features (activation of caspase-8 and -3/7, nuclear condensation, and mitochondrial membrane depolarization). And the negative regulator of caspase-8, coded by CFLAR gene, was downregulated by CSE. These findings show that upon exposure to LPS, CS inhibits the TLR4/MyD88 inflammatory response, downregulating the pro-inflammatory genes TNF and IL6 and the anti-apoptotic gene CFLAR, known to counteract caspase-8 activity. CS enhances caspase-8 activation through TLR4/TRIF, with a partial involvement of RIPK1, resulting on the activation of caspase-1/GSDMD axis leading to increased cell permeability and DAMP release through gasdermin pores.

Fig1. Extracellular activity of Caspase-8 and -3/7 (expressed as relative luminescence unit, RLU), were measured after 24 h stimulation.

Fig2. LPS triggers the activation of the axis caspase-8/caspase-3/GSDME in hMDMs exposed to CSE.

Case study 2: Claudia Contadini, 2023

Caspase-8 is a cysteine protease that plays an essential role in apoptosis. Consistently with its canonical proapoptotic function, cancer cells may genetically or epigenetically downregulate its expression. Unexpectedly, Caspase-8 is often retained in cancer, suggesting the presence of alternative mechanisms that may be exploited by cancer cells to their own benefit.

In this study, the researchers investigated the significance of Caspase-8 expression and of its phosphorylation on Y380 in glioblastoma, a brain tumor where both Caspase-8 expression and Src activity are often aberrantly upregulated. Transcriptomic analyses identified inflammatory response as a major target of Caspase-8. Src-dependent phosphorylation of Caspase-8 on Y380 drives the assembly of a multiprotein complex that triggers NFκB activation, thereby inducing the expression of inflammatory and pro-angiogenic factors.

Fig3. Immunoblotting on total protein extracts from U87MG cells stably silenced for Caspase-8 expression (U87shC8#1) and transiently transfected with the empty vector (pcDNA3), Caspase-8-wt (C8-WT) or the catalytically inactive mutant, Caspase-8-C360A (C8-C360A). GAPDH was used as loading control for protein normalization.

Fig4. Immunoblotting on total protein extracts (TOT) and on immunoprecipitated Caspase-8 (IP) from GBMSC83, U87MG and U251 cells treated with Dasatinib 1 μM (DAS) or not (DMSO, CTR) for 16 h. GAPDH and Caspase-8 were used as loading controls for protein normalization.

Fig1. Caspase-8 activity induces apoptosis and inhibits necroptosis. (Jiyi Pang, 2023)

Fig2. The role of caspase-8 in macrophagic differentiation. (Izabela Kostova, 2021)

CASP8 involved in several pathways and played different roles in them. We selected most pathways CASP8 participated on our site, such as p signaling pathway, Apoptosis, Toll-like receptor signaling pathway, which may be useful for your reference. Also, other proteins which involved in the same pathway with CASP8 were listed below. Creative BioMart supplied nearly all the proteins listed, you can search them on our site.

CASP8 has several biochemical functions, for example, cysteine-type endopeptidase activity, cysteine-type endopeptidase activity involved in apoptotic process, cysteine-type endopeptidase activity involved in apoptotic signaling pathway. Some of the functions are cooperated with other proteins, some of the functions could acted by CASP8 itself. We selected most functions CASP8 had, and list some proteins which have the same functions with CASP8. You can find most of the proteins on our site.

CASP8 has direct interactions with proteins and molecules. Those interactions were detected by several methods such as yeast two hybrid, co-IP, pull-down and so on. We selected proteins and molecules interacted with CASP8 here. Most of them are supplied by our site. Hope this information will be useful for your research of CASP8.

FADD