RESUMO
TRAF2 (Tumor necrosis factor receptor-associated factor 2) is a dual function protein, acting as an adaptor protein and a ubiquitin E3 ligase, which plays an essential role in mediating the TNFα-NFκB signal pathway. Dysregulated expression of TRAF2 has been reported in a variety of human cancers. Whether and how TRAF2 regulates the growth of liver cancer cells remains elusive. The goal of this study is to investigate potential dysregulation of TRAF2 and its biological function in liver cancer, and to elucidate the underlying mechanism, leading to validation of TRAF2 as an attractive liver cancer target. Here, we reported TRAF2 is up-regulated in human liver cancer cell lines and tissues, and high TRAF2 expression is associated with a poor prognosis of HCC patients. Proteomics profiling along with Co-immunoprecipitation analysis revealed that p62 is a new substrate of TRAF2, which is subjected to TRAF2-induced polyubiquitination via the K63 linkage at the K420 residue. A strong negative correlation was found between the protein levels of p62 and TRAF2 in human HCC samples. TRAF2 depletion inhibited growth and survival of liver cancer cells both in vitro and in vivo by causing p62 accumulation, which is partially rescued by simultaneous p62 knockdown. Mechanistically, TRAF2-mediated p62 polyubiquitylation activates the mTORC1 by forming the p62-mTORC1-Rag complex, which facilitates the lysosome localization of mTORC1. TRAF2 depletion inhibited mTORC1 activity through the disruption of interaction between p62 and the mTORC1 complex. In conclusion, our study provides the proof-of-concept evidence that TRAF2 is a valid target for liver cancer.
Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Humanos , Carcinoma Hepatocelular/genética , Proliferação de Células , Neoplasias Hepáticas/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Fator 2 Associado a Receptor de TNF/metabolismo , Ubiquitina-Proteína Ligases/metabolismoRESUMO
F-box and WD repeat domain containing 7 (FBXW7) acts as a substrate receptor of SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase and plays crucial roles in the regulation of several cellular processes, including cell growth, division, and differentiation, by targeting diverse key regulators for degradation. However, its role in regulating cellular senescence remains elusive. Here, we found that FBXW7 inactivation by siRNA-based knockdown or CRISPR/Cas9-based knockout induced significant cellular senescence in p53 wild-type cells, but not in p53 mutant or null cells, along with activation of both the p53/p21 and p16INK4a/Rb pathways. Simultaneous p53 inactivation abrogated senescence and cell growth arrest induced by FBXW7 deficiency as well as the alteration of both the p53/p21 and p16INK4a/Rb pathways. Moreover, Fbxw7 deletion accelerated replicative senescence of primary mouse embryonic fibroblasts in a p53-dependent manner. In addition, FBXW7 deletion induced the senescence-associated secretory phenotype to trigger secondary senescence. Importantly, in a radiation-induced senescence mouse model, simultaneous deletion of p53 rescued accelerated senescence and aging caused by Fbxw7 loss. Thus, our study uncovered a novel role for FBXW7 in the regulation of senescence by eliminating p53.
Assuntos
Inibidor p16 de Quinase Dependente de Ciclina , Proteína Supressora de Tumor p53 , Animais , Senescência Celular/genética , Inibidor p16 de Quinase Dependente de Ciclina/genética , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Proteína 7 com Repetições F-Box-WD/genética , Proteína 7 com Repetições F-Box-WD/metabolismo , Fibroblastos/metabolismo , Camundongos , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismoRESUMO
In solid tumors, cancer cells have devised multiple approaches to survival and proliferate in response to glucose starvation that is often observed in solid tumor microenvironments. However, the precise mechanisms are far less known. Herein, we report that glucose deprivation activates 90-kDa ribosomal S6 kinase (p90 RSK), a highly conserved Ser/Thr kinase, and activated p90 RSK promotes cancer cell survival. Mechanistically, activated p90 RSK by glucose deprivation phosphorylates checkpoint kinase 1 (CHK1), a key transducer in checkpoint signaling pathways, at Ser280 and triggers CHK1 ubiquitination mediated by SCFß-TrCP ubiquitin ligase and proteasomal degradation, subsequently suppressing cancer cell apoptosis induced by glucose deprivation. Importantly, we identified an inverse correlation between p90 RSK activity and CHK1 levels within the solid tumor mass, with lower levels of CHK1 and higher activity of p90 RSK in the center of the tumor where low glucose concentrations are often observed. Thus, our study indicates that p90 RSK promotes CHK1 phosphorylation at Ser280 and its subsequent degradation, which allows cancer cells to escape from checkpoint signals under the stress of glucose deprivation, leading to cell survival and thus contributing to tumorigenesis.
Assuntos
Quinase 1 do Ponto de Checagem/metabolismo , Glucose/deficiência , Neoplasias/metabolismo , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo , Animais , Linhagem Celular Tumoral , Sobrevivência Celular , Quinase 1 do Ponto de Checagem/química , Ativação Enzimática , Células HEK293 , Humanos , Camundongos , Fosforilação , Proteólise/efeitos dos fármacos , Pteridinas/farmacologia , Ubiquitinação/efeitos dos fármacosRESUMO
The tumor suppressor p53 is activated upon multiple cellular stresses, including DNA damage, oncogene activation, ribosomal stress, and hypoxia, to induce cell cycle arrest, apoptosis, and senescence. Mammalian target of rapamycin (mTOR), an evolutionarily conserved serine/threonine protein kinase, serves as a central regulator of cell growth, proliferation, and survival by coordinating nutrients, energy, growth factors, and oxygen levels. p53 dysfunction and mTOR pathway hyperactivation are hallmarks of human cancer. The balance between response to stresses or commitment to cell proliferation and survival is governed by various regulatory loops between the p53 and mTOR pathways. In this review, we first briefly introduce the tumor suppressor p53 and then describe the upstream regulators and downstream effectors of the mTOR pathway. Next, we discuss the role of p53 in regulating the mTOR pathway through its transcriptional and non-transcriptional effects. We further describe the complicated role of the mTOR pathway in modulating p53 activity. Finally, we discuss the current knowledge and future perspectives on the coordinated regulation of the p53 and mTOR pathways.
RESUMO
DEPTOR plays vital roles in the regulation of cell proliferation and survival by directly modulating the activity of mTORC1/2. However, the physiological role of DEPTOR in lung tumorigenesis, as well as its clinical significance, remains elusive. In this study, we revealed that decreased DEPTOR expression correlated with increased tumor size, poor differentiation, and worse survival in patients with lung cancer. DEPTOR depletion promoted cell proliferation, survival, migration, and invasion in human lung cancer cells. Mechanistically, DEPTOR bound to the kinase domain of EGFR via its PDZ domain to inactivate EGFR signal. Thus, DEPTOR depletion not only directly activated mTORC1/2, but also relieved the inhibition of EGFR to subsequently activate mTOR signals, leading to the induction of cell proliferation and survival. Additionally, activated EGFR-mTOR signals upregulated the expression of ZEB1 and SLUG to induce epithelial-mesenchymal transition, resulting in enhanced migration and invasion. Importantly, Deptor deletion accelerated KrasG12D;p53fl/fl-induced lung tumorigenesis and shortened mouse life span via the activation of EGFR-mTOR signals. Collectively, our study demonstrated that DEPTOR acts as a tumor suppressor in lung tumorigenesis, and its reduction may advance the progression of human lung cancer.
Assuntos
Carcinogênese/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Neoplasias Pulmonares/metabolismo , Pulmão/metabolismo , Transdução de Sinais/fisiologia , Serina-Treonina Quinases TOR/metabolismo , Células A549 , Animais , Carcinogênese/patologia , Linhagem Celular Tumoral , Movimento Celular/fisiologia , Proliferação de Células/fisiologia , Transição Epitelial-Mesenquimal/fisiologia , Receptores ErbB/metabolismo , Humanos , Pulmão/patologia , Neoplasias Pulmonares/patologia , Camundongos , Camundongos Knockout , Regulação para Cima/fisiologiaRESUMO
ß-transducin repeat-containing protein (ß-TrCP), one of the well-characterized F-box proteins, acts as a substrate receptor and constitutes an active SCFß-TrCP E3 ligase with a scaffold protein CUL1, a RING protein RBX1, and an adaptor protein SKP1. ß-TrCP plays a critical role in the regulation of various physiological and pathological processes, including signal transduction, cell cycle progression, cell migration, DNA damage response, and tumorigenesis, by governing burgeoning amounts of key regulators for ubiquitination and proteasomal degradation. Given that a variety of ß-TrCP substrates are well-known oncoproteins and tumor suppressors, and dysregulation of ß-TrCP is frequently identified in human cancers, ß-TrCP plays a vital role in carcinogenesis. In this review, we first briefly introduce the characteristics of ß-TrCP1, ß-TrCP2, and SCFß-TrCP ubiquitin ligase, and then discuss SCFß-TrCP ubiquitin ligase regulated biological processes by targeting its substrates for degradation. Moreover, we summarize the regulation of ß-TrCP1 and ß-TrCP2 at multiple layers and further discuss the various roles of ß-TrCP1 and ß-TrCP2 in human cancer, functioning as either an oncoprotein or a tumor suppressor in a manner dependent of cellular context. Finally, we provide novel insights for future perspectives on the potential of targeting ß-TrCP1 and ß-TrCP2 for cancer therapy.
Assuntos
Carcinogênese/genética , Neoplasias/genética , Ubiquitina-Proteína Ligases/genética , Proteínas Contendo Repetições de beta-Transducina/genética , Proteínas de Transporte/genética , Proteínas Culina/genética , Dano ao DNA/genética , Humanos , Neoplasias/patologia , Proteínas Quinases Associadas a Fase S/genética , Proteínas Ligases SKP Culina F-Box/genética , Transdução de Sinais/genéticaRESUMO
DEP-domain containing mTOR-interacting protein (DEPTOR), a natural mTOR inhibitor, has essential roles in several processes, including cell growth, metabolism, apoptosis, and immunity. DEPTOR expression has been shown to be diversely controlled at transcriptional levels in cell- and context-specific manners. However, whether there is a general mechanism for the regulation of DEPTOR expression remains largely unknown. Here, we report that DEPTOR is a downstream target of the tumor suppressor, p53, whose activity is positively correlated with DEPTOR expression both in vitro in cell cultures and in vivo in mouse tissues. Mechanistically, p53 directly binds to the DEPTOR promoter and transactivates its expression. Depletion of the p53-binding site on the DEPTOR promoter by CRISPR-Cas9 technology decreases DEPTOR expression and promotes cell proliferation and survival by activating AKT signaling. Importantly, inhibition of AKT by small molecular inhibitors or genetic knockdown abrogates the induction of cell growth and survival induced by deletion of the p53-binding region on the DEPTOR promoter. Furthermore, p53, upon activation by the genotoxic agent doxorubicin, induces DEPTOR expression, leading to cancer cell resistance to doxorubicin. Together, DEPTOR is a direct p53 downstream target and contributes to p53-mediated inhibition of cell proliferation, survival, and chemosensitivity.
Assuntos
Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Células A549 , Linhagem Celular Tumoral , Proliferação de Células/fisiologia , Doxorrubicina/farmacologia , Resistencia a Medicamentos Antineoplásicos , Células HCT116 , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/biossíntese , Peptídeos e Proteínas de Sinalização Intracelular/genética , Células MCF-7 , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patologia , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transcrição GênicaRESUMO
Neddylation plays a distinct role in stabilization of a subset of ribosomal proteins. Whether the family of ribosomal proteins S27 (RPS27 and RPS27-like) is subjected to neddylation regulation with associated biological consequence is totally unknown. Here, we report that both family members are subjected to neddylation by MDM2 E3 ubiquitin ligase, and deneddylation by NEDP1. Blockage of neddylation with MLN4924, a small molecule inhibitor of neddylation-activating enzyme, destabilizes RPS27L and RPS27 by shortening their protein half-lives. Biologically, knockdown of RPS27L and RPS27 sensitizes, whereas ectopic expression of RPS27L and RPS27 desensitizes cancer cells to MLN4924-induced apoptosis. Taken together, our study demonstrates that neddylation stabilizes RPS27L and RPS27 to confer the survival of cancer cells.
Assuntos
Endopeptidases/metabolismo , Regulação Neoplásica da Expressão Gênica , Metaloproteínas/metabolismo , Proteínas Nucleares/metabolismo , Processamento de Proteína Pós-Traducional , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteínas Ribossômicas/metabolismo , Linhagem Celular Tumoral , Sobrevivência Celular , Humanos , Proteína NEDD8/metabolismoRESUMO
Topoisomerase II (TOP2)-targeting anticancer chemotherapeutic drugs, termed TOP2 poisons, are widely used and effective in the clinic by stabilizing TOP2-DNA covalent complexes to induce DNA double-strand breaks (DSBs) and ultimately, cause cell death. The stabilized TOP2-DNA complex is known to be degraded by proteasome, whereas the underlying mechanism for instant TOP2ß degradation in response to TOP2 poisons and the subsequent biological consequence remain elusive. Here, we reported that TOP2 poison-induced TOP2ß degradation is mediated by SCFß-TrCP ubiquitin ligase. Specifically, DNA damage signal, triggered by teniposide (VM-26) treatment, activates ATM, cooperating with CK1 to phosphorylate TOP2ß on Ser1134 and Ser1130, respectively, in a canonical degron motif to facilitate ß-TrCP binding and subsequent degradation. Inactivation of ATM, CK1 or SCFß-TrCP by small molecular inhibitors or genetic knockdown/knockout abrogates TOP2ß degradation. Biologically, blockage of TOP2ß degradation in combination with VM-26 treatment impairs DNA damage response and repair, leading to an accelerated cell death via apoptosis. Thus, it appears that TOP2ß degradation is a cellular defensive mechanism to facilitate the exposure of DSBs to trigger DNA damage response and repair. Collectively, our findings reveal a new strategy to improve the efficacy of TOP2 poisons in combination with small-molecule inhibitors against TOP2ß degradation.
RESUMO
Cullin-RING ligases (CRLs), the largest family of E3 ubiquitin ligases, have become an attractive target for drug discovery, primarily due to their ability to regulate the degradation of numerous functionally and structurally diverse proteins, thereby controlling a myriad of biological processes. As the abnormal expressions of CRLs and their substrate proteins are associated with human diseases, elucidating their roles in these physiological and pathological processes will facilitate CRL-targeting drug development for the treatment of these diseases. Notably, these studies are also providing new concepts for the design of potential small-molecule therapeutics targeting CRLs and for the use of CRLs to degrade "undruggable" proteins. In this chapter, we systematically review the development of small molecules that target CRLs and especially emphasize the applications of CRLs in a chemical chimera for protein degradation, termed proteolysis-targeting chimeras (PROTACs).
Assuntos
Proteínas Culina/antagonistas & inibidores , Proteínas Culina/metabolismo , Desenho de Fármacos , Avaliação Pré-Clínica de Medicamentos , Proteólise/efeitos dos fármacos , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/farmacologia , Animais , Doença , HumanosRESUMO
The tumor suppressor p53 plays a critical role in integrating a wide variety of stress responses. Therefore, p53 levels are precisely regulated by multiple ubiquitin ligases. In this study, we report that FBXW7, a substrate recognition component of the SKP1-CUL1-F-box (SCF) E3 ligase, interacts with and targets p53 for polyubiquitination and proteasomal degradation after exposure to ionizing radiation or etoposide. Mechanistically, DNA damage activates ATM to phosphorylate p53 on Ser33 and Ser37, which facilitates the FBXW7 binding and subsequent p53 degradation by SCFFBXW7. Inactivation of ATM or SCFFBXW7 by small molecular inhibitors or genetic knockdown/knockout approaches extends the p53 protein half-life upon DNA damage in an MDM2-independent manner. Biologically, FBXW7 inactivation sensitizes cancer cells to radiation or etoposide by stabilizing p53 to induce cell-cycle arrest and apoptosis. Taken together, our study elucidates a mechanism by which FBXW7 confers cancer cell survival during radiotherapy or chemotherapy via p53 targeting.
Assuntos
Proteína 7 com Repetições F-Box-WD/metabolismo , Neoplasias/radioterapia , Proteína Supressora de Tumor p53/metabolismo , Células A549 , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Pontos de Checagem do Ciclo Celular/efeitos da radiação , Linhagem Celular Tumoral , Dano ao DNA , Células HCT116 , Células HEK293 , Humanos , Neoplasias/metabolismo , Neoplasias/patologia , Fosforilação , Tolerância a Radiação , Radioterapia , Análise de SobrevidaRESUMO
The DEPTOR-mTORC1/2 axis has been shown to play an important, but a context dependent role in the regulation of proliferation and the survival of various cancer cells in cell culture settings. The in vivo role of DEPTOR in tumorigenesis remains elusive. Here we showed that the levels of both DEPTOR protein and mRNA were substantially decreased in human prostate cancer tissues, which positively correlated with disease progression. DEPTOR depletion accelerated proliferation and survival, migration, and invasion in human prostate cancer cells. Mechanistically, DEPTOR depletion not only activated both mTORC1 and mTORC2 signals to promote cell proliferation and survival, but also induced an AKT-dependent epithelial-mesenchymal transition (EMT) and ß-catenin nuclear translocation to promote cell migration and invasion. Abrogation of mTOR or AKT activation rescued the biological consequences of DEPTOR depletion. Importantly, in a Deptor-KO mouse model, Deptor knockout accelerated prostate tumorigenesis triggered by Pten loss via the activation of mTOR signaling. Collectively, our study demonstrates that DEPTOR is a tumor suppressor in the prostate, and its depletion promotes tumorigenesis via the activation of mTORC1 and mTORC2 signals. Thus, DEPTOR reactivation via a variety of means would have therapeutic potential for the treatment of prostate cancer.
Assuntos
Carcinogênese , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Alvo Mecanístico do Complexo 2 de Rapamicina/metabolismo , Neoplasias da Próstata/patologia , Transdução de Sinais , Animais , Movimento Celular , Proliferação de Células , Sobrevivência Celular , Técnicas de Silenciamento de Genes , Heterozigoto , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/deficiência , Peptídeos e Proteínas de Sinalização Intracelular/genética , Masculino , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Camundongos , Invasividade Neoplásica , PTEN Fosfo-Hidrolase/deficiência , PTEN Fosfo-Hidrolase/genética , Neoplasias da Próstata/metabolismoRESUMO
ß-transducin repeat-containing protein (ß-TrCP), one of the best-characterized substrate recognition components of the SKP1-CUL1-F-box (SCF) E3 ligase, has two distinct paralogs, ß-TrCP1 and ß-TrCP2, expressed in mammals. Through governing the ubiquitination and degradation of numerous key regulators, ß-TrCP1/2 regulates various cellular physiological and pathological processes. However, whether and how these two proteins cross talk and whether they regulate cell autophagy and proliferation in different manners is completely unknown. Herein, we report that ß-TrCP1 and ß-TrCP2 are the physiological substrates of SCF E3 ligase and target each other for degradation that is dependent on their ß-TrCP degron sequences. Furthermore, glucose deprivation activates AMPK kinase to phosphorylate ß-TrCP1 and promotes the subsequent ubiquitination and degradation of ß-TrCP1 by ß-TrCP2, but does not promote ß-TrCP2 degradation by ß-TrCP1. Finally, we found that ß-TrCP2, not ß-TrCP1, preferentially degrades DEPTOR and REDD1, the inhibitors of mTORC1, to activate mTORC1, leading to autophagy inhibition and cell growth. Thus, our study demonstrates that ß-TrCP1 and ß-TrCP2 mutually target each other for degradation and that ß-TrCP2 acts as a dominant paralog in the regulation of cell autophagy and growth, which might be a promising anticancer target.
Assuntos
Autofagia , Proteínas Contendo Repetições de beta-Transducina/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Glucose/deficiência , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Proteólise , Especificidade por Substrato , Fatores de Transcrição , Ubiquitina-Proteína Ligases/metabolismo , UbiquitinaçãoRESUMO
The ATR/CHK1 pathway is a key effector of cellular response to DNA damage and therefore is a critical regulator of genomic stability. While the ATR/CHK1 pathway is often inactivated by mutations, CHK1 itself is rarely mutated in human cancers. Thus, cellular levels of CHK1 likely play a key role in the maintenance of genomic stability and preventing tumorigenesis. Glucose deprivation is observed in many solid tumors due to high glycolytic rates of cancer cells and insufficient vascularization, yet cancer cells have devised mechanisms to survive in conditions of low glucose. Although CHK1 degradation through the ubiquitin-proteasome pathway following glucose deprivation has been previously reported, the detailed molecular mechanisms remain elusive. Here, we show that CHK1 is ubiquitinated and degraded upon glucose deprivation by the Skp1-Cullin-F-box (ß-TrCP) E3 ubiquitin ligase. Specifically, CHK1 contains a ß-TrCP recognizable degron domain, which is phosphorylated by AMPK in response to glucose deprivation, allowing for ß-TrCP to recognize CHK1 for subsequent ubiquitination and degradation. Our results provide a novel mechanism by which glucose metabolism regulates a DNA damage effector, and imply that glucose deprivation, which is often found in solid tumor microenvironments, may enhance mutagenesis, clonal expansion, and tumor progression by triggering CHK1 degradation.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Quinase 1 do Ponto de Checagem/metabolismo , Glucose/deficiência , Ubiquitinação , Proteínas Contendo Repetições de beta-Transducina/metabolismo , Sequência de Aminoácidos , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Estabilidade Enzimática/efeitos dos fármacos , Células HEK293 , Humanos , Fosforilação/efeitos dos fármacos , Ligação Proteica/efeitos dos fármacos , Domínios Proteicos , Proteólise/efeitos dos fármacos , Estaurosporina/farmacologia , Ubiquitinação/efeitos dos fármacos , Proteínas Contendo Repetições de beta-Transducina/químicaRESUMO
Breast cancer is a common type of cancer among female cancer patients and the main cause of cancer-related deaths. During the last decades, targeted therapies for breast cancer have been rapidly developing. Among them, MLN4924, a first-in-class NEDD8-activating enzyme (NAE) inhibitor, has performed antitumor activity by inactivating the cullin-RING ligases and causing the accumulation of their substrates to induce apoptosis in a number of studies. In this study, we found that MLN4924 activates the AKT pathway in both HER2-positive and triple-negative breast cancer (TNBC) cell lines. Given that AKT signaling is responsible for tumor progression and drug resistance in some types of cancers, we hypothesized that the AKT inhibitor may synergistically enhance the tumor suppression capability in breast cancer by MLN4924. To demonstrate the sensitizing effect, MK-2206 was chosen as the adjuvant treatment, and cell growth, migration and apoptosis were detected. The results showed that MLN4924 treatment inhibited cell growth and migration and induced apoptosis in both SK-BR3 and MDA-MB231 breast cancer cell lines. More importantly, the combined treatment of MLN4924 and MK-2206 indeed caused stronger cytotoxicity and inhibition of migration and a much higher induction of apoptosis compared with MLN4924 treatment alone. Our study provides the proof-of-concept evidence for strategic drug combination of MLN4924 with an AKT inhibitor for maximal killing of breast cancer cells via the enhancement of apoptosis.
Assuntos
Neoplasias da Mama/enzimologia , Neoplasias da Mama/patologia , Ciclopentanos/farmacologia , Compostos Heterocíclicos com 3 Anéis/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Pirimidinas/farmacologia , Enzimas Ativadoras de Ubiquitina/antagonistas & inibidores , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Feminino , Humanos , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/efeitos dos fármacos , Enzimas Ativadoras de Ubiquitina/metabolismoRESUMO
Apoptosis and autophagy mutually regulate various cellular physiological and pathological processes. The crosstalk between autophagy and apoptosis is multifaceted and complicated. Elucidating the molecular mechanism of their crosstalk will advance the therapeutic applications of autophagy for treating cancer and other diseases. NOXA, a BH3-only member of the BCL-2 family, was reported to induce apoptosis and promote autophagy. Here, we report that autophagy regulates apoptosis by targeting NOXA for degradation. Inhibiting autophagy increases NOXA protein levels by extending the protein half-life. NOXA accumulation effectively suppresses tumor cell growth by inducing apoptosis, which is further enhanced when p53 is present. Mechanistically, NOXA is hijacked by p62 as autophagic cargo, and its three lysine residues at the C-terminus are necessary for NOXA degradation in lysosomes. Taken together, our study demonstrates that NOXA serves as a bridge in the crosstalk between autophagy and apoptosis and implies that autophagy inhibitors could be an effective therapy for cancer, especially wild-type p53-containing cancer.
Assuntos
Lisina/química , Proteínas Proto-Oncogênicas c-bcl-2/química , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Células A549 , Apoptose , Autofagia , Linhagem Celular Tumoral , Células HCT116 , Células HEK293 , Meia-Vida , Humanos , Domínios Proteicos , ProteóliseRESUMO
Proteolysis-targeting chimeric molecules (PROTACs) represent an emerging technique that is receiving much attention for therapeutic intervention. The mechanism is based on the inhibition of protein function by hijacking a ubiquitin E3 ligase for protein degradation. The hetero-bifunctional PROTACs contain a ligand for recruiting an E3 ligase, a linker, and another ligand to bind with the protein targeted for degradation. Thus, PROTACs have profound potential to eliminate "undruggable" protein targets, such as transcription factors and non-enzymatic proteins, which are not limited to physiological substrates of the ubiquitin-proteasome system. These findings indicate great prospects for PROTACs in the development of therapeutics. However, there are several limitations related to poor stability, biodistribution, and penetrability in vivo. This review provides an overview of the main PROTAC-based approaches that have been developed and discusses the promising opportunities and considerations for the application of this technology in therapies and drug discovery.
Assuntos
Descoberta de Drogas/métodos , Proteínas/metabolismo , Animais , Humanos , Proteólise , Fatores de Transcrição/metabolismo , Ubiquitina-Proteína Ligases/metabolismoRESUMO
Cullin-RING ligases (CRLs), the largest E3 ubiquitin ligase family, promote ubiquitination and degradation of various cellular key regulators involved in a broad array of physiological and pathological processes, including cell cycle progression, signal transduction, transcription, cardiomyopathy, and tumorigenesis. Autophagy, an intracellular catabolic reaction that delivers cytoplasmic components to lysosomes for degradation, is crucial for cellular metabolism and homeostasis. The dysfunction of autophagy has been proved to associate with a variety of human diseases. Recent evidences revealed the emerging roles of CRLs in the regulation of autophagy. In this review, we will focus mainly on recent advances in our understandings of the regulation of autophagy by CRLs and the cross-talk between CRLs and autophagy, two degradation systems. We will also discuss the pathogenesis of human diseases associated with the dysregulation of CRLs and autophagy. Finally, we will discuss current efforts and future perspectives on basic and translational research on CRLs and autophagy.