RESUMEN
The TNFR superfamily of receptors, the major focus of the recent TNFR Superfamily Conference held in June 2019, employ the TNFR-associated factor (TRAF) family of adaptor proteins in key aspects of their signaling pathways. Although many early studies investigated TRAF functions via exogenous overexpression in nonhematopoietic cell lines, it has subsequently become clear that whereas TRAFs share some overlap in function, each also plays unique biologic roles, that can be highly context dependent. This brief review summarizes the current state of knowledge of functions of each of the TRAF molecules that mediate important functions in T lymphocytes: TRAFs 1, 2, 3, 5, and 6. Due to our current appreciation of the contextual nature of TRAF function, our focus is upon findings made specifically in T lymphocytes. Key T cell functions for each TRAF are detailed, as well as future knowledge gaps of interest and importance.
Asunto(s)
Síndromes de Inmunodeficiencia/genética , Receptores del Factor de Necrosis Tumoral/genética , Transducción de Señal/genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Factor de Necrosis Tumoral alfa/genética , Animales , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/patología , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/patología , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Humanos , Síndromes de Inmunodeficiencia/inmunología , Síndromes de Inmunodeficiencia/patología , Memoria Inmunológica , Ratones , Ratones Noqueados , Isoformas de Proteínas/deficiencia , Isoformas de Proteínas/genética , Isoformas de Proteínas/inmunología , Receptores del Factor de Necrosis Tumoral/inmunología , Transducción de Señal/inmunología , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/inmunología , Factor de Necrosis Tumoral alfa/inmunologíaRESUMEN
Anticancer topoisomerase "poisons" exploit the break-and-rejoining mechanism of topoisomerase II (TOP2) to generate TOP2-linked DNA double-strand breaks (DSBs). This characteristic underlies the clinical efficacy of TOP2 poisons, but is also implicated in chromosomal translocations and genome instability associated with secondary, treatment-related, haematological malignancy. Despite this relevance for cancer therapy, the mechanistic aspects governing repair of TOP2-induced DSBs and the physiological consequences that absent or aberrant repair can have are still poorly understood. To address these deficits, we employed cells and mice lacking tyrosyl DNA phosphodiesterase 2 (TDP2), an enzyme that hydrolyses 5'-phosphotyrosyl bonds at TOP2-associated DSBs, and studied their response to TOP2 poisons. Our results demonstrate that TDP2 functions in non-homologous end-joining (NHEJ) and liberates DSB termini that are competent for ligation. Moreover, we show that the absence of TDP2 in cells impairs not only the capacity to repair TOP2-induced DSBs but also the accuracy of the process, thus compromising genome integrity. Most importantly, we find this TDP2-dependent NHEJ mechanism to be physiologically relevant, as Tdp2-deleted mice are sensitive to TOP2-induced damage, displaying marked lymphoid toxicity, severe intestinal damage, and increased genome instability in the bone marrow. Collectively, our data reveal TDP2-mediated error-free NHEJ as an efficient and accurate mechanism to repair TOP2-induced DSBs. Given the widespread use of TOP2 poisons in cancer chemotherapy, this raises the possibility of TDP2 being an important etiological factor in the response of tumours to this type of agent and in the development of treatment-related malignancy.
Asunto(s)
Roturas del ADN de Doble Cadena , ADN-Topoisomerasas de Tipo II , Inestabilidad Genómica , Hidrolasas Diéster Fosfóricas , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral , Animales , Daño del ADN/genética , Reparación del ADN por Unión de Extremidades/genética , Reparación del ADN/genética , ADN-Topoisomerasas de Tipo II/genética , ADN-Topoisomerasas de Tipo II/metabolismo , ADN-Topoisomerasas de Tipo II/uso terapéutico , Proteínas de Unión al ADN , Ratones , Hidrolasas Diéster Fosfóricas/deficiencia , Hidrolasas Diéster Fosfóricas/genética , Hidrolasas Diéster Fosfóricas/metabolismo , Recombinación Genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismoRESUMEN
The pro-inflammatory cytokine tumor necrosis factor (TNF) α signals both cell survival and death. The biological outcome of TNFα treatment is determined by the balance between survival factors and Jun NH(2)-terminal kinase (JNK) signaling, which promotes cell death. Here, we show that TRAF7, the most recently identified member of the TNF receptor-associated factors (TRAFs) family of proteins, is essential for activation of JNK following TNFα stimulation. We also show that TRAF6 and TRAF7 promote unconventional polyubiquitination of the anti-apoptotic protein c-FLIP(L) and demonstrate that degradation of c-FLIP(L) also occurs through a lysosomal pathway. RNA interference-mediated depletion of TRAF7 correlates with increased c-FLIP(L) expression level, which, in turn, results in resistance to TNFα cytotoxicity. Collectively, our results indicate an important role for TRAF7 in the activation of JNK following TNFα stimulation and clearly point to an involvement of this protein in regulating the turnover of c-FLIP and, consequently, cell death.
Asunto(s)
Proteína Reguladora de Apoptosis Similar a CASP8 y FADD/metabolismo , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Lisosomas/metabolismo , Poliubiquitina/metabolismo , Proteolisis/efectos de los fármacos , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismo , Factor de Necrosis Tumoral alfa/farmacología , Muerte Celular/efectos de los fármacos , Activación Enzimática/efectos de los fármacos , Regulación de la Expresión Génica/efectos de los fármacos , Técnicas de Silenciamiento del Gen , Células HEK293 , Células HeLa , Humanos , Células Jurkat , Lisosomas/efectos de los fármacos , ARN Interferente Pequeño/genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Ubiquitinación/efectos de los fármacosRESUMEN
Tumor necrosis factor receptor-associated factors (TRAFs) have been discovered and characterized by their capacity to link tumor necrosis factor receptors (TNFR) family proteins to signaling pathways that transduce the cellular effects mediated by TNF family ligands. There are seven known mammalian TRAF proteins (TRAF1-7), that share a domain organization made of a modular structure, characteristic of adaptor proteins whose function is to link structurally dissimilar factors. Functionally, TRAF proteins mediate the assembly of cytoplasmic signal transducers and regulatory molecules downstream of receptors complexes. Despite the similarities in the signaling pathways activated by the different TRAF proteins, each appears to play distinct physiological roles. TRAF7 is the last member of the TRAF family that has been identified. Yet, the functional characterization of TRAF7 presents some aspects still obscure and poorly defined, making this protein arguably the most mysterious member of the family. In fact, recent data indicate that TRAF7 is involved in signal transduction pathways that lead either to activation or repression of NF-κB transcription factor. In addition, TRAF7 regulates activation of cellular stress pathways, as well as unconventional ubiquitination events and differentiation of muscle tissue. In this review, we try to summarize the most recent advances in our understanding of TRAF7 function and the biological processes of this protein is involved in.
Asunto(s)
Transducción de Señal/fisiología , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/fisiología , Animales , Regulación hacia Abajo/fisiología , Humanos , Ratones , Ratones Noqueados , FN-kappa B/antagonistas & inhibidores , FN-kappa B/biosíntesis , Transducción de Señal/genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Regulación hacia Arriba/fisiologíaRESUMEN
Topoisomerase II (Top2) activity involves an intermediate in which the topoisomerase is covalently bound to a DNA double-strand break via a 5'-phosphotyrosyl bond. Although these intermediates are normally transient, they can be stabilized by antitumor agents that act as Top2 "poisons," resulting in the induction of cytotoxic double-strand breaks, and they are implicated in the formation of site-specific translocations that are commonly associated with cancer. Recently, we revealed that TRAF and TNF receptor-associated protein (TTRAP) is a 5'-tyrosyl DNA phosphodiesterase (5'-TDP) that can cleave 5'-phosphotyrosyl bonds, and we denoted this protein tyrosyl DNA phosphodiesterase-2 (TDP2). Here, we have generated TDP2-deleted DT40 cells, and we show that TDP2 is the major if not the only 5'-TDP activity present in vertebrate cells. We also show that TDP2-deleted DT40 cells are highly sensitive to the anticancer Top2 poison, etoposide, but are not hypersensitive to the Top1 poison camptothecin or the DNA-alkyating agent methyl methanesulfonate. These data identify an important mechanism for resistance to Top2-induced chromosome breakage and raise the possibility that TDP2 is a significant factor in cancer development and treatment.
Asunto(s)
Daño del ADN , ADN-Topoisomerasas de Tipo II/metabolismo , Hidrolasas Diéster Fosfóricas/metabolismo , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismo , Animales , Línea Celular Tumoral , Etopósido/farmacología , Humanos , Hidrolasas Diéster Fosfóricas/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficienciaRESUMEN
We have identified the E3 ligase Traf7 as a direct MyoD1 target and show that cell cycle exit-an early event in muscle differentiation-is linked to decreased Traf7 expression. Depletion of Traf7 accelerates myogenesis, in part through downregulation of nuclear factor-κB (NF-κB) activity. We used a proteomic screen to identify NEMO, the NF-κB essential modulator, as a Traf7-interacting protein. Finally, we show that ubiquitylation of NF-κB essential modulator is regulated exclusively by Traf7 activity in myoblasts. Our results suggest a new mechanism by which MyoD1 function is coupled to NF-κB activity through Traf7, regulating the balance between cell cycle progression and differentiation during myogenesis.
Asunto(s)
Desarrollo de Músculos/genética , Proteína MioD/metabolismo , FN-kappa B/metabolismo , Transcripción Genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Animales , Ciclo Celular/genética , Diferenciación Celular/genética , Ciclina D1/metabolismo , Regulación de la Expresión Génica , Quinasa I-kappa B/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Ratones , Mioblastos/citología , Mioblastos/metabolismo , Fosforilación , Unión Proteica , Proteína de Retinoblastoma/metabolismo , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismo , Ubiquitina/metabolismo , UbiquitinaciónRESUMEN
The tumor necrosis factor (TNF) superfamily consists of a wide variety of cell-bound and secreted proteins that regulate numerous cellular processes. In particular, TNF-family proteins regulate the proliferation and death of tumor cells, as well as activated immune cells. This overview discusses the mammalian TNF receptor-associated factors (TRAFs), of which TRAF1, 2, 3, 5, and 6 have been shown to interact directly or indirectly with members of the TNF receptor superfamily. Structural features of TRAF proteins are described along with a discussion of TRAF-interacting proteins and the signaling pathways activated by the TRAF proteins. Finally, we examine the phenotypes observed in TRAF-knockout mice.
Asunto(s)
Receptores del Factor de Necrosis Tumoral/fisiología , Transducción de Señal/fisiología , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/fisiología , Animales , Humanos , Ratones , Ratones Noqueados , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/química , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genéticaRESUMEN
Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) are key adaptor molecules in the TNFR-signaling complexes that promote a wide variety of signaling cascades including cell proliferation, activation, differentiation, and apoptosis. TRAF-interacting protein (TRIP) is required for the inhibitory regulation of TNF-induced NF-kappaB signaling via the TNFR/TRAF-signaling complexes in vitro. TRIP also directly interacts with the familial cylindromatosis tumor suppressor gene (CYLD) and negatively regulates NF-kappaB activation in vitro. However, although there appears to be a relationship between TRIP, the TRAFs and also CYLD as modulators of NF-kappaB signaling in vitro, the functional role of TRIP in vivo is still unclear. To identify the role of TRIP in vivo, we have generated TRIP-deficient mice. Homozygous mouse embryos were found to die shortly after implantation due to proliferation defects and excessive cell death. These results indicate that TRIP is an essential factor during early mouse embryonic development in vivo.
Asunto(s)
Pérdida del Embrión/metabolismo , Eliminación de Gen , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismo , Animales , Proliferación Celular , Regulación hacia Abajo/efectos de los fármacos , Pérdida del Embrión/genética , Pérdida del Embrión/patología , Femenino , Genotipo , Ratones , Ratones Noqueados , Células 3T3 NIH , Embarazo , ARN Interferente Pequeño/genética , Factores de Tiempo , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
Insulin-like growth factor I (IGF-I) plays an important role in cell survival, proliferation, and differentiation. Diverse kinases, including AKT/protein kinase B, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK), can be activated by IGF-I. Here, we show that the receptor-interacting protein (RIP), a key mediator of tumor necrosis factor-induced NF-kappaB and JNK activation, plays a key role in IGF-I receptor signaling. IGF-I induced a robust JNK activation in wild type but not RIP null (RIP-/-) mouse embryonic fibroblast cells. Reconstitution of RIP expression in the RIP-/- cells restored the induction of JNK by IGF-I, suggesting that RIP is essential in IGF-I-induced JNK activation. Reconstitution experiments with different RIP mutants further revealed that the death domain and the kinase activity of RIP are not required for IGF-I-induced JNK activation. Interestingly, the AKT and ERK activation by IGF-I was normal in RIP-/- cells. The phosphatidylinositol 3-kinase inhibitor, wortmannin, did not affect IGF-I-induced JNK activation. These results agree with previous studies showing that the IGF-I-induced JNK activation pathway is distinct from that of ERK and AKT activation. Additionally, physical interaction of ectopically expressed RIP and IGF-IRbeta was detected by co-immunoprecipitation assays. More importantly, RIP was recruited to the IGF-I receptor complex during IGF-I-induced signaling. Furthermore, we found that IGF-I-induced cell proliferation was impaired in RIP-/- cells. Taken together, our results indicate that RIP, a key factor in tumor necrosis factor signaling, also plays a pivotal role in IGF-I-induced JNK activation and cell proliferation.
Asunto(s)
Factor I del Crecimiento Similar a la Insulina/fisiología , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Proteínas Serina-Treonina Quinasas/fisiología , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/fisiología , Animales , Muerte Celular/fisiología , Línea Celular , Proliferación Celular , Células Cultivadas , Activación Enzimática/fisiología , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Fibroblastos/enzimología , Fibroblastos/metabolismo , Fibroblastos/fisiología , Humanos , Inmunoprecipitación , Factor I del Crecimiento Similar a la Insulina/metabolismo , Ratones , Fosfatidilinositol 3-Quinasas/fisiología , Proteínas Serina-Treonina Quinasas/deficiencia , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Estructura Terciaria de Proteína/fisiología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptor IGF Tipo 1/fisiología , Proteína Serina-Treonina Quinasas de Interacción con Receptores , Transducción de Señal/fisiología , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/deficiencia , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismoRESUMEN
Pulmonary and serum levels of tumor necrosis factor-alpha (TNF-alpha), are elevated in many lung diseases, causing local inflammation, fever, and multiorgan, including hepatic, dysfunction. Cellular responses to TNF-alpha are determined by recruitment of specific proteins to intracellular receptor signaling complexes. One of these proteins, TNF receptor-associated factor 1 (TRAF1), is highly regulated in pulmonary cells. To determine the effect of reduced pulmonary TRAF1 expression, TRAF1-null (-/-) and control, BALB/c (wild-type), mice were treated intratracheally, intraperitoneally, or intravenously, with TNF-alpha. Despite relatively mild lung injury, intratracheal TNF-alpha-treated TRAF1-/- mice exhibited marked liver injury with an approximate fivefold increase in serum liver enzyme levels as compared to wild-type mice. In addition, serum TNF-alpha levels were strikingly elevated in TRAF1-/- mice. Pretreatment with neutralizing anti-TNFRI antibody significantly reduced liver injury and serum TNF-alpha. Cells isolated by bronchoalveolar lavage from intratracheally treated TRAF1-/- mice produced more TNF-alpha than cells from treated wild-type mice, suggesting that lung cells contributed to elevated serum TNF-alpha. These studies suggest that TRAF1 provides negative feedback for TNF-alpha synthesis and limits TNFRI-mediated systemic effects of TNF-alpha originating in the lung.