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Interaction between the Hepatitis B Virus and Cellular FLIP Variants in Viral Replication and the Innate Immune System. Viruses 2022; 14:v14020373. [PMID: 35215970 PMCID: PMC8874586 DOI: 10.3390/v14020373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/28/2022] [Accepted: 02/08/2022] [Indexed: 12/10/2022] Open
Abstract
During viral evolution and adaptation, many viruses have utilized host cellular factors and machinery as their partners. HBx, as a multifunctional viral protein encoded by the hepatitis B virus (HBV), promotes HBV replication and greatly contributes to the development of HBV-associated hepatocellular carcinoma (HCC). HBx interacts with several host factors in order to regulate HBV replication and evolve carcinogenesis. The cellular FADD-like IL-1β-converting enzyme (FLICE)-like inhibitory protein (c-FLIP) is a major factor that functions in a variety of cellular pathways and specifically in apoptosis. It has been shown that the interaction between HBx and c-FLIP determines HBV fate. In this review, we provide a comprehensive and detailed overview of the interplay between c-FLIP and HBV in various environmental circumstances. We describe strategies adapted by HBV to establish its chronic infection. We also summarize the conventional roles of c-FLIP and highlight the functional outcome of the interaction between c-FLIP and HBV or other viruses in viral replication and the innate immune system.
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Tsuchiya Y, Nakabayashi O, Nakano H. FLIP the Switch: Regulation of Apoptosis and Necroptosis by cFLIP. Int J Mol Sci 2015; 16:30321-41. [PMID: 26694384 PMCID: PMC4691174 DOI: 10.3390/ijms161226232] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 12/09/2015] [Accepted: 12/11/2015] [Indexed: 12/11/2022] Open
Abstract
cFLIP (cellular FLICE-like inhibitory protein) is structurally related to caspase-8 but lacks proteolytic activity due to multiple amino acid substitutions of catalytically important residues. cFLIP protein is evolutionarily conserved and expressed as three functionally different isoforms in humans (cFLIPL, cFLIPS, and cFLIPR). cFLIP controls not only the classical death receptor-mediated extrinsic apoptosis pathway, but also the non-conventional pattern recognition receptor-dependent apoptotic pathway. In addition, cFLIP regulates the formation of the death receptor-independent apoptotic platform named the ripoptosome. Moreover, recent studies have revealed that cFLIP is also involved in a non-apoptotic cell death pathway known as programmed necrosis or necroptosis. These functions of cFLIP are strictly controlled in an isoform-, concentration- and tissue-specific manner, and the ubiquitin-proteasome system plays an important role in regulating the stability of cFLIP. In this review, we summarize the current scientific findings from biochemical analyses, cell biological studies, mathematical modeling, and gene-manipulated mice models to illustrate the critical role of cFLIP as a switch to determine the destiny of cells among survival, apoptosis, and necroptosis.
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Affiliation(s)
- Yuichi Tsuchiya
- Department of Biochemistry, Toho University School of Medicine, Tokyo 143-8540, Japan.
| | - Osamu Nakabayashi
- Department of Biochemistry, Toho University School of Medicine, Tokyo 143-8540, Japan.
| | - Hiroyasu Nakano
- Department of Biochemistry, Toho University School of Medicine, Tokyo 143-8540, Japan.
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Buskiewicz IA, Koenig A, Roberts B, Russell J, Shi C, Lee SH, Jung JU, Huber SA, Budd RC. c-FLIP-Short reduces type I interferon production and increases viremia with coxsackievirus B3. PLoS One 2014; 9:e96156. [PMID: 24816846 PMCID: PMC4015977 DOI: 10.1371/journal.pone.0096156] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 04/03/2014] [Indexed: 11/19/2022] Open
Abstract
Cellular FLIP (c-FLIP) is an enzymatically inactive paralogue of caspase-8 and as such can block death receptor-induced apoptosis. However, independent of death receptors, c-FLIP-Long (c-FLIPL) can heterodimerize with and activate caspase-8. This is critical for promoting the growth and survival of T lymphocytes as well as the regulation of the RIG-I helicase pathway for type I interferon production in response to viral infections. Truncated forms of FLIP also exist in mammalian cells (c-FLIPS) and certain viruses (v-FLIP), which lack the C-terminal domain that activates caspase-8. Thus, the ratio of c-FLIPL to these short forms of FLIP may greatly influence the outcome of an immune response. We examined this model in mice transgenically expressing c-FLIPS in T cells during infection with Coxsackievirus B3 (CVB3). In contrast to our earlier findings of reduced myocarditis and mortality with CVB3 infection of c-FLIPL-transgenic mice, c-FLIPS-transgenic mice were highly sensitive to CVB3 infection as manifested by increased cardiac virus titers, myocarditis score, and mortality compared to wild-type C57BL/6 mice. This observation was paralleled by a reduction in serum levels of IL-10 and IFN-α in CVB3-infected c-FLIPS mice. In vitro infection of c-FLIPS T cells with CVB3 confirmed these results. Furthermore, molecular studies revealed that following infection of cells with CVB3, c-FLIPL associates with mitochondrial antiviral signaling protein (MAVS), increases caspase-8 activity and type I IFN production, and reduces viral replication, whereas c-FLIPS promotes the opposite phenotype.
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Affiliation(s)
- Iwona A. Buskiewicz
- Department of Pathology, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
| | - Andreas Koenig
- Department of Medicine, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
| | - Brian Roberts
- Department of Pathology, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
| | - Jennifer Russell
- Department of Medicine, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
| | - Cuixia Shi
- Department of Medicine, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
| | - Sun-Hwa Lee
- Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, California, United States of America.
| | - Jae U. Jung
- Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, California, United States of America.
| | - Sally A. Huber
- Department of Pathology, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
| | - Ralph C. Budd
- Department of Medicine, Vermont Center for Immunology and Infectious Diseases, University of Vermont, Burlington, Vermont, United States of America
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The role of sex differences in autophagy in the heart during coxsackievirus B3-induced myocarditis. J Cardiovasc Transl Res 2013; 7:182-91. [PMID: 24323874 DOI: 10.1007/s12265-013-9525-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 11/20/2013] [Indexed: 12/28/2022]
Abstract
Under normal conditions, autophagy maintains cardiomyocyte health and integrity through turnover of organelles. During stress, oxygen and nutrient deprivation, or microbial infection, autophagy prolongs cardiomyocyte survival. Sex differences in induction of cell death may to some extent explain the disparity between the sexes in many human diseases. However, sex differences in gene expression, which regulate cell death and autophagy, were so far not taken in consideration to explain the sex bias of viral myocarditis. Coxsackievirus B3 (CVB3)-induced myocarditis is a sex-biased disease, with females being substantially less susceptible than males and sex hormones largely determine this bias. CVB3 was shown to induce and subvert the autophagosome for its optimal viral RNA replication. Gene expression analysis on mouse and human, healthy and CVB3-infected, cardiac samples of both sexes, suggests sex differences in autophagy-related gene expression. This review discusses the aspects of sex bias in autophagy induction in cardiomyocytes.
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Buskiewicz IA, Koenig A, Huber SA, Budd RC. Caspase-8 and FLIP regulate RIG-I/MDA5-induced innate immune host responses to picornaviruses. Future Virol 2012; 7:1221-1236. [PMID: 23503762 DOI: 10.2217/fvl.12.115] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Picornaviruses are small, nonenveloped, positive-stranded RNA viruses, which cause a wide range of animal and human diseases, based on their distinct tissue and cell type tropisms. Myocarditis, poliomyelitis, hepatitis and the common cold are the most significant human illnesses caused by picornaviruses. The host response to picornaviruses is complex, and the damage to tissues occurs not only from direct viral replication within infected cells. Picornaviruses exhibit an exceptional ability to evade the early innate immune response, resulting in chronic infection and autoimmunity. This review discusses the detailed aspects of the early innate host response to picornaviruses infection mediated by RIG-I-like helicases, their adaptor, mitochondrial ant iviral signaling protein, innate immune-induced apoptosis, and the role of caspase-8 and its regulatory paralog, FLIP, in these processes.
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Affiliation(s)
- Iwona A Buskiewicz
- Department of Pathology, Vermont Center for Immunology & Infectious Diseases, University of Vermont, Burlington, VT 05405, USA
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Li H, Tang QZ, Liu C, Moon M, Chen M, Yan L, Bian ZY, Zhang Y, Wang AB, Nghiem MP, Liu PP. Cellular FLICE-inhibitory protein protects against cardiac remodeling induced by angiotensin II in mice. Hypertension 2010; 56:1109-17. [PMID: 20975036 DOI: 10.1161/hypertensionaha.110.157412] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The development of cardiac hypertrophy in response to increased hemodynamic load and neurohormonal stress is initially a compensatory response that may eventually lead to ventricular dilatation and heart failure. Cellular FLICE-inhibitory protein (cFLIP) is a homologue of caspase 8 without caspase activity that inhibits apoptosis initiated by death receptor signaling. Previous studies showed that cFLIP expression was markedly decreased in the ventricular myocardium of patients with end-stage heart failure. However, the critical role of cFLIP on cardiac remodeling remains unclear. To specifically determine the role of cFLIP in pathological cardiac remodeling, we used heterozygote cFLIP(+/-) mice and transgenic mice with cardiac-specific overexpression of the human cFLIP(L) gene. Our results demonstrated that the cFLIP(+/-) mice were susceptible to cardiac hypertrophy and fibrosis through inhibition of mitogen-activated protein kinase kinase-extracellular signal-regulated kinase 1/2 signaling, whereas the transgenic mice displayed the opposite phenotype in response to angiotensin II stimulation. These studies indicate that cFLIP protein is a crucial component of the signaling pathway involved in cardiac remodeling and heart failure.
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Affiliation(s)
- Hongliang Li
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China.
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Abstract
OBJECTIVE Activation of Fas signaling has been associated with the development of cardiomyocyte hypertrophy. In the present study, we investigated the effects of increased expression of c-Flip, a natural modulator of Fas receptor signaling, in a mouse model of cardiac growth response to pressure overload. METHODS A transgenic mouse overexpressing c-Flip in the heart was generated in FVB/N strain. Echocardiographic, hemodynamic, histological and molecular analyses were carried out under basal conditions and after transverse aortic constriction (TAC)-induced pressure overload. RESULTS Overexpression of c-Flip in ventricular heart tissue was functionally silent under basal conditions affecting neither cardiac morphology nor basal cardiac function. Transgenic mice were then subjected to pressure overload by TAC procedure. Under such conditions, c-Flip transgenic mice showed normal left ventricular function with a significantly reduced left ventricular hypertrophy compared with wild-type mice and reduced induction of the cardiac "fetal" gene programme. Further, analysis of intracellular signaling pathways indicated that c-Flip overexpression reduced phosphorylation of both the glycogen synthase kinase 3beta (GSK3 beta) and Akt as compared with controls. Finally, the reduction of the TAC-induced hypertrophy was not accompanied by significant apoptosis increase. CONCLUSION Altogether, these findings indicate c-Flip as a key regulator of the cardiac response to ventricular pressure overload.
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Abstract
Viral myocarditis is an elusive infection of the heart that is currently without an effective or definitive treatment. Viral myocarditis has a complex disease progression that can be divided into early, middle and late phases. Direct cytopathic injury, apoptosis, activation of the innate and adaptive immune system and cardiac remodeling have all been implicated in the pathogenesis of viral myocarditis. Novel treatment approaches are evolving at a rapid pace. The purpose of this review is to provide an update on current research focused on identifying potential treatment options for viral myocarditis.
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Affiliation(s)
- Shelley D Miyamoto
- Department of Pediatric Cardiology, University of Colorado at Denver & Health Sciences Center, The Children’s Hospital, 13123 E. 16th Avenue, B100 Aurora, CO 80045, USA
| | - Roberta L DeBiasi
- Children’s National Medical Center/Children’s Research Institute, Division of Pediatric Infectious Diseases, George Washington University School of Medicine, 111 Michigan Ave NW, Washington DC 20010, USA
| | - Carlin S Long
- Division of Cardiology, University of Colorado at Denver & Health Sciences Center, Box 0960, Denver Health Medical Center, 777 Bannock St, Denver, CO 80204, USA
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