ABSTRACT
Death effector domains (DEDs) are protein-protein interaction domains initially identified in proteins such as FADD, FLIP and caspase-8 involved in regulating apoptosis. Subsequently, these proteins have been shown to have important roles in regulating other forms of cell death, including necroptosis, and in regulating other important cellular processes, including autophagy and inflammation. Moreover, these proteins also have prominent roles in innate and adaptive immunity and during embryonic development. In this article, we review the various roles of DED-containing proteins and discuss recent developments in our understanding of DED complex formation and regulation. We also briefly discuss opportunities to therapeutically target DED complex formation in diseases such as cancer.
Subject(s)
Adaptor Proteins, Signal Transducing/chemistry , Caspase 8/chemistry , Fas-Associated Death Domain Protein/chemistry , Gene Expression Regulation, Neoplastic , Neoplasms/genetics , Adaptor Proteins, Signal Transducing/genetics , Adaptor Proteins, Signal Transducing/metabolism , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/therapeutic use , Apoptosis/drug effects , Autophagy/drug effects , Caspase 8/genetics , Caspase 8/metabolism , Clinical Trials as Topic , Fas-Associated Death Domain Protein/genetics , Fas-Associated Death Domain Protein/metabolism , Humans , Mice , Models, Molecular , Neoplasms/drug therapy , Neoplasms/metabolism , Neoplasms/pathology , Protein Binding , Protein Interaction Domains and Motifs , Signal TransductionABSTRACT
Death receptor activation triggers recruitment of FADD, which via its death effector domain (DED) engages the DEDs of procaspase 8 and its inhibitor FLIP to form death-inducing signalling complexes (DISCs). The DEDs of FADD, FLIP and procaspase 8 interact with one another using two binding surfaces defined by α1/α4 and α2/α5 helices, respectively. Here we report that FLIP has preferential affinity for the α1/α4 surface of FADD, whereas procaspase 8 has preferential affinity for FADD's α2/α5 surface. These relative affinities contribute to FLIP being recruited to the DISC at comparable levels to procaspase 8 despite lower cellular expression. Additional studies, including assessment of DISC stoichiometry and functional assays, suggest that following death receptor recruitment, the FADD DED preferentially engages FLIP using its α1/α4 surface and procaspase 8 using its α2/α5 surface; these tripartite intermediates then interact via the α1/α4 surface of FLIP DED1 and the α2/α5 surface of procaspase 8 DED2.
Subject(s)
CASP8 and FADD-Like Apoptosis Regulating Protein/metabolism , Caspase 8/metabolism , Fas-Associated Death Domain Protein/metabolism , Blotting, Western , Chromatography, Gel , HCT116 Cells , Humans , Immunoprecipitation , Protein BindingABSTRACT
Non-small cell lung carcinoma remains by far the leading cause of cancer-related deaths worldwide. Overexpression of FLIP, which blocks the extrinsic apoptotic pathway by inhibiting caspase-8 activation, has been identified in various cancers. We investigated FLIP and procaspase-8 expression in NSCLC and the effect of HDAC inhibitors on FLIP expression, activation of caspase-8 and drug resistance in NSCLC and normal lung cell line models. Immunohistochemical analysis of cytoplasmic and nuclear FLIP and procaspase-8 protein expression was carried out using a novel digital pathology approach. Both FLIP and procaspase-8 were found to be significantly overexpressed in tumours, and importantly, high cytoplasmic expression of FLIP significantly correlated with shorter overall survival. Treatment with HDAC inhibitors targeting HDAC1-3 downregulated FLIP expression predominantly via post-transcriptional mechanisms, and this resulted in death receptor- and caspase-8-dependent apoptosis in NSCLC cells, but not normal lung cells. In addition, HDAC inhibitors synergized with TRAIL and cisplatin in NSCLC cells in a FLIP- and caspase-8-dependent manner. Thus, FLIP and procaspase-8 are overexpressed in NSCLC, and high cytoplasmic FLIP expression is indicative of poor prognosis. Targeting high FLIP expression using HDAC1-3 selective inhibitors such as entinostat to exploit high procaspase-8 expression in NSCLC has promising therapeutic potential, particularly when used in combination with TRAIL receptor-targeted agents.
Subject(s)
CASP8 and FADD-Like Apoptosis Regulating Protein/metabolism , Carcinoma, Non-Small-Cell Lung/enzymology , Caspase 8/metabolism , Blotting, Western , CASP8 and FADD-Like Apoptosis Regulating Protein/genetics , Carcinoma, Non-Small-Cell Lung/genetics , Caspase 8/genetics , Cell Survival/genetics , Cell Survival/physiology , Flow Cytometry , Humans , In Vitro Techniques , Retrospective StudiesABSTRACT
"Not Me, Not Now" is an abstinence oriented, adolescent pregnancy prevention integrated communications program developed by Monroe County, NY. The evaluation utilized a cross-sectional time series approach in the analysis of items from several waves of youth surveys administered to two different age groups: (1) a survey of 7th and 8th graders on awareness, attitudes and intended behavior, and (2) the Youth Risk Behavior Survey administered to 9th through 12th graders. The trends found in the surveys demonstrated high levels of awareness of the program, changing attitudes and intended behaviors consistent with the program's messages. Analysis of pregnancy rates for 15-17 year-olds in the county were compared to reductions found in similar geographic areas. Pregnancy rates in Monroe County declined faster than in comparison areas. The authors conclude that there is a strong likelihood that the program had independent effect on the outcome of pregnancies in the population exposed to the program.
Subject(s)
Family Planning Services , Health Education , Pregnancy in Adolescence , Adolescent , Adolescent Behavior/psychology , Child , Coitus , Female , Health Knowledge, Attitudes, Practice , Humans , Male , New York , Pregnancy , Pregnancy Rate , Program Evaluation , Sexual AbstinenceSubject(s)
Critical Care/psychology , Death , Grief , Parents/psychology , Adolescent , Female , Humans , MaleABSTRACT
High-resolution mass spectrometry (HRMS), hybrid tandem mass spectrometry (MS/MS) (EBqQ), and photoelectron-photoion coincidence (PEPICO) experiments were conducted to examine a possible ortho-ortho effect resulting in a novel [M - 35](+) fragment ion in 2-alkyl-4, 6-dinitrophenols. For compounds having ethyl or larger alkyl substituents, [M35](+) was observed only when [M - 18](+) ions were present, with the ortho nitro group being involved in the reaction to [M- 35](+). For [M - 18](+) and [M - 35](+), HRMS results were consistent with losses of H2O and H2O + OH, respectively, whereas MS/MS results indicated a sequential reaction due to metastable dissociations. The appearance energy determined by PEPICO for [M - 35](+) was found to be greater than the appearance energy for [M - 18](+), thus supporting a sequential reaction. 69-75).
