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1.
Cancer Immunol Res ; 10(7): 871-884, 2022 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-35588154

RESUMO

Expression of the purinergic receptor P2RX7 by CD8+ T cells promotes the generation of memory populations following acute infections. However, data suggest that P2RX7 may limit the efficacy of antitumor responses. Herein, we show that P2RX7 is beneficial for optimal melanoma control in a mouse CD8+ T-cell adoptive transfer model. Tumor-specific P2rx7-/- CD8+ T cells exhibited impaired mitochondrial maintenance and function but did not display signs of overt exhaustion early in the antitumor response. However, as the tumor burden increased, the relative frequency of P2RX7-deficient CD8+ T cells declined within the tumor; this correlated with reduced proliferation, increased apoptosis, and mitochondrial dysfunction. Extending these studies, we found that the transient in vitro stimulation of P2RX7 using the ATP analogue BzATP led to enhanced B16 melanoma control by CD8+ T cells. These findings are in keeping with the concept that extracellular ATP (eATP) sensing by P2RX7 on CD8+ T cells is required for their ability to efficiently eliminate tumors by promoting mitochondrial fitness and underscore the potential for P2RX7 stimulation as a novel therapeutic treatment to enhance tumor immunotherapy.


Assuntos
Linfócitos T CD8-Positivos , Melanoma Experimental , Trifosfato de Adenosina/metabolismo , Animais , Linfócitos T CD8-Positivos/metabolismo , Terapia Baseada em Transplante de Células e Tecidos , Imunoterapia Adotiva , Melanoma Experimental/metabolismo , Melanoma Experimental/terapia , Camundongos , Camundongos Endogâmicos C57BL , Receptores Purinérgicos P2X7/genética , Receptores Purinérgicos P2X7/metabolismo
2.
Cell Metab ; 33(12): 2305-2306, 2021 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-34879235

RESUMO

The metabolic state of T cells strongly influences their effector function and anti-tumor efficacy. St. Paul et al. (2021) report that Tc22, a CD8+ T cell subset with potent anti-tumor activity, upregulates the pantothenate/coenzyme A (CoA) pathway and that treatment with CoA or pantothenate is sufficient to enhance tumor immunotherapy.


Assuntos
Linfócitos T CD8-Positivos , Tutoria , Coenzima A , Imunoterapia , Subpopulações de Linfócitos T
3.
Cell Rep ; 37(5): 109911, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34731632

RESUMO

Suppressive regulatory T cell (Treg) differentiation is controlled by diverse immunometabolic signaling pathways and intracellular metabolites. Here we show that cell-permeable α-ketoglutarate (αKG) alters the DNA methylation profile of naive CD4 T cells activated under Treg polarizing conditions, markedly attenuating FoxP3+ Treg differentiation and increasing inflammatory cytokines. Adoptive transfer of these T cells into tumor-bearing mice results in enhanced tumor infiltration, decreased FoxP3 expression, and delayed tumor growth. Mechanistically, αKG leads to an energetic state that is reprogrammed toward a mitochondrial metabolism, with increased oxidative phosphorylation and expression of mitochondrial complex enzymes. Furthermore, carbons from ectopic αKG are directly utilized in the generation of fatty acids, associated with lipidome remodeling and increased triacylglyceride stores. Notably, inhibition of either mitochondrial complex II or DGAT2-mediated triacylglyceride synthesis restores Treg differentiation and decreases the αKG-induced inflammatory phenotype. Thus, we identify a crosstalk between αKG, mitochondrial metabolism and triacylglyceride synthesis that controls Treg fate.


Assuntos
Diferenciação Celular/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Ácidos Cetoglutáricos/farmacologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Linfócitos T Reguladores/efeitos dos fármacos , Animais , Células Cultivadas , Citocinas/genética , Citocinas/metabolismo , Diacilglicerol O-Aciltransferase/metabolismo , Fibrossarcoma/genética , Fibrossarcoma/imunologia , Fibrossarcoma/metabolismo , Fibrossarcoma/terapia , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Homeostase , Humanos , Imunoterapia Adotiva , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/genética , Mitocôndrias/metabolismo , Fenótipo , Receptores de Antígenos Quiméricos/genética , Receptores de Antígenos Quiméricos/metabolismo , Transdução de Sinais , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/metabolismo , Linfócitos T Reguladores/transplante , Células Th1/efeitos dos fármacos , Células Th1/imunologia , Células Th1/metabolismo
4.
Cell Death Dis ; 12(10): 904, 2021 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-34608126

RESUMO

PHLPP2 is a member of the PHLPP family of phosphatases, known to suppress cell growth by inhibiting proliferation or promoting apoptosis. Oncogenic kinases Akt, S6K, and PKC, and pro-apoptotic kinase Mst1, have been recognized as functional targets of the PHLPP family. However, we observed that, in T-leukemia cells subjected to metabolic stress from glucose limitation, PHLPP2 specifically targets the energy-sensing AMP-activated protein kinase, pAMPK, rather than Akt or S6K. PHLPP2 dephosphorylates pAMPK in several other human cancer cells as well. PHLPP2 and pAMPK interact with each other, and the pleckstrin homology (PH) domain on PHLPP2 is required for their interaction, for dephosphorylating and inactivating AMPK, and for the apoptotic response of the leukemia cells to glucose limitation. Silencing PHLPP2 protein expression prolongs the survival of leukemia cells subjected to severe glucose limitation by promoting a switch to AMPK-mediated fatty acid oxidation for energy generation. Thus, this study reveals a novel role for PHLPP2 in suppressing a survival response mediated through AMPK signaling. Given the multiple ways in which PHLPP phosphatases act to oppose survival signaling in cancers and the pivotal role played by AMPK in redox homeostasis via glucose and fatty acid metabolism, the revelation that AMPK is a target of PHLPP2 could lead to better therapeutics directed both at cancer and at metabolic diseases.


Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Estresse Fisiológico , Apoptose , Linhagem Celular Tumoral , Sobrevivência Celular , Ativação Enzimática , Ácidos Graxos/metabolismo , Glucose/metabolismo , Humanos , Oxirredução , Fosfoproteínas Fosfatases/química , Fosforilação , Ligação Proteica , Domínios Proteicos , RNA Interferente Pequeno/metabolismo
5.
Apoptosis ; 26(1-2): 71-82, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33386492

RESUMO

Leucine-rich alpha-2-glycoprotein-1 (LRG1) has been shown to compete with apoptosis activating factor-1 (Apaf-1) for binding cytochrome c (Cyt c) and could play a role in inhibition of apoptosis. Employing MCF-7 breast cancer cells, we report that intracellular LRG1 does protect against apoptosis. Thus, cells transfected with the lrg1 gene and expressing higher levels of LRG1 were more resistant to hydrogen peroxide-induced apoptosis than parental cells, while cells in which LRG mRNA was knocked down by short hairpin (sh) RNA-induced degradation were more sensitive. The amount of Cyt c co-immunoprecipitated with Apaf-1 from the cytosol of apoptotic cells was inversely related to the level of LRG1 expression. In lrg1-transfected cells partially-glycosylated LRG1 was found in the cytosol and there was an increase in cytosolic Cyt c in live lrg1-transfected cells relative to parental cells. However, apoptosis was not spontaneously induced because Cyt c was bound to LRG1 and not to Apaf-1. Cyt c was the only detectable protein co-immunoprecipitated with LRG1. Following hydrogen peroxide treatment degradation of LRG1 allowed for induction of apoptosis. We propose that intracellular LRG1 raises the threshold of cytoplasmic Cyt c required to induce apoptosis and, thus, prevents onset of the intrinsic pathway in cells where Cyt c release from mitochondria does not result from committed apoptotic signaling. This mechanism of survival afforded by LRG1 is likely to be distinct from its extracellular survival function that has been reported by several research groups.


Assuntos
Fator Apoptótico 1 Ativador de Proteases/metabolismo , Neoplasias da Mama/metabolismo , Neoplasias da Mama/fisiopatologia , Citocromos c/metabolismo , Glicoproteínas/metabolismo , Apoptose , Fator Apoptótico 1 Ativador de Proteases/genética , Neoplasias da Mama/genética , Citosol/metabolismo , Feminino , Glicoproteínas/genética , Humanos , Células MCF-7 , Ligação Proteica
6.
J Clin Invest ; 128(10): 4604-4621, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30106752

RESUMO

Regulatory T cells (Tregs) are critical for maintaining immune homeostasis. However, current Treg immunotherapies do not optimally treat inflammatory diseases in patients. Understanding the cellular processes that control Treg function may allow for the augmentation of therapeutic efficacy. In contrast to activated conventional T cells, in which protein kinase C-θ (PKC-θ) localizes to the contact point between T cells and antigen-presenting cells, in human and mouse Tregs, PKC-θ localizes to the opposite end of the cell in the distal pole complex (DPC). Here, using a phosphoproteomic screen, we identified the intermediate filament vimentin as a PKC-θ phospho target and show that vimentin forms a DPC superstructure on which PKC-θ accumulates. Treatment of mouse Tregs with either a clinically relevant PKC-θ inhibitor or vimentin siRNA disrupted vimentin and enhanced Treg metabolic and suppressive activity. Moreover, vimentin-disrupted mouse Tregs were significantly better than controls at suppressing alloreactive T cell priming in graft-versus-host disease (GVHD) and GVHD lethality, using a complete MHC-mismatch mouse model of acute GVHD (C57BL/6 donor into BALB/c host). Interestingly, vimentin disruption augmented the suppressor function of PKC-θ-deficient mouse Tregs. This suggests that enhanced Treg activity after PKC-θ inhibition is secondary to effects on vimentin, not just PKC-θ kinase activity inhibition. Our data demonstrate that vimentin is a key metabolic and functional controller of Treg activity and provide proof of principle that disruption of vimentin is a feasible, translationally relevant method to enhance Treg potency.


Assuntos
Células Apresentadoras de Antígenos/imunologia , Doença Enxerto-Hospedeiro/imunologia , Filamentos Intermediários/imunologia , Ativação Linfocitária , Linfócitos T Reguladores/imunologia , Vimentina/imunologia , Animais , Células Apresentadoras de Antígenos/patologia , Modelos Animais de Doenças , Doença Enxerto-Hospedeiro/genética , Doença Enxerto-Hospedeiro/patologia , Humanos , Filamentos Intermediários/genética , Filamentos Intermediários/patologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Proteína Quinase C-theta/genética , Proteína Quinase C-theta/imunologia , Linfócitos T Reguladores/patologia , Vimentina/genética
7.
Nature ; 559(7713): 264-268, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29973721

RESUMO

Extracellular ATP (eATP) is an ancient 'danger signal' used by eukaryotes to detect cellular damage1. In mice and humans, the release of eATP during inflammation or injury stimulates both innate immune activation and chronic pain through the purinergic receptor P2RX72-4. It is unclear, however, whether this pathway influences the generation of immunological memory, a hallmark of the adaptive immune system that constitutes the basis of vaccines and protective immunity against re-infection5,6. Here we show that P2RX7 is required for the establishment, maintenance and functionality of long-lived central and tissue-resident memory CD8+ T cell populations in mice. By contrast, P2RX7 is not required for the generation of short-lived effector CD8+ T cells. Mechanistically, P2RX7 promotes mitochondrial homeostasis and metabolic function in differentiating memory CD8+ T cells, at least in part by inducing AMP-activated protein kinase. Pharmacological inhibitors of P2RX7 provoked dysregulated metabolism and differentiation of activated mouse and human CD8+ T cells in vitro, and transient P2RX7 blockade in vivo ameliorated neuropathic pain but also compromised production of CD8+ memory T cells. These findings show that activation of P2RX7 by eATP provides a common currency that both alerts the nervous and immune system to tissue damage, and promotes the metabolic fitness and survival of the most durable and functionally relevant memory CD8+ T cell populations.


Assuntos
Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/metabolismo , Memória Imunológica , Receptores Purinérgicos P2X7/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Linfócitos T CD8-Positivos/enzimologia , Linfócitos T CD8-Positivos/imunologia , Células Cultivadas , Ativação Enzimática , Feminino , Homeostase , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/fisiologia , Receptores Purinérgicos P2X7/deficiência , Receptores Purinérgicos P2X7/genética
9.
Cell Chem Biol ; 24(10): 1259-1275.e6, 2017 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-28919040

RESUMO

The mechanisms by which cancer cell-intrinsic CYP monooxygenases promote tumor progression are largely unknown. CYP3A4 was unexpectedly associated with breast cancer mitochondria and synthesized arachidonic acid (AA)-derived epoxyeicosatrienoic acids (EETs), which promoted the electron transport chain/respiration and inhibited AMPKα. CYP3A4 knockdown activated AMPKα, promoted autophagy, and prevented mammary tumor formation. The diabetes drug metformin inhibited CYP3A4-mediated EET biosynthesis and depleted cancer cell-intrinsic EETs. Metformin bound to the active-site heme of CYP3A4 in a co-crystal structure, establishing CYP3A4 as a biguanide target. Structure-based design led to discovery of N1-hexyl-N5-benzyl-biguanide (HBB), which bound to the CYP3A4 heme with higher affinity than metformin. HBB potently and specifically inhibited CYP3A4 AA epoxygenase activity. HBB also inhibited growth of established ER+ mammary tumors and suppressed intratumoral mTOR. CYP3A4 AA epoxygenase inhibition by biguanides thus demonstrates convergence between eicosanoid activity in mitochondria and biguanide action in cancer, opening a new avenue for cancer drug discovery.


Assuntos
Biguanidas/metabolismo , Biguanidas/farmacologia , Citocromo P-450 CYP3A/metabolismo , Heme/metabolismo , Mitocôndrias/efeitos dos fármacos , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Biguanidas/química , Neoplasias da Mama/patologia , Domínio Catalítico , Respiração Celular/efeitos dos fármacos , Citocromo P-450 CYP3A/química , Citocromo P-450 CYP3A/deficiência , Citocromo P-450 CYP3A/genética , Receptor alfa de Estrogênio/genética , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Inativação Gênica , Humanos , Células MCF-7 , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Camundongos , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Modelos Moleculares , Transporte Proteico/efeitos dos fármacos
11.
Cell ; 164(5): 884-95, 2016 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-26919427

RESUMO

Ischemic preconditioning is the phenomenon whereby brief periods of sublethal ischemia protect against a subsequent, more prolonged, ischemic insult. In remote ischemic preconditioning (RIPC), ischemia to one organ protects others organs at a distance. We created mouse models to ask if inhibition of the alpha-ketoglutarate (αKG)-dependent dioxygenase Egln1, which senses oxygen and regulates the hypoxia-inducible factor (HIF) transcription factor, could suffice to mediate local and remote ischemic preconditioning. Using somatic gene deletion and a pharmacological inhibitor, we found that inhibiting Egln1 systemically or in skeletal muscles protects mice against myocardial ischemia-reperfusion (I/R) injury. Parabiosis experiments confirmed that RIPC in this latter model was mediated by a secreted factor. Egln1 loss causes accumulation of circulating αKG, which drives hepatic production and secretion of kynurenic acid (KYNA) that is necessary and sufficient to mediate cardiac ischemic protection in this setting.


Assuntos
Prolina Dioxigenases do Fator Induzível por Hipóxia/antagonistas & inibidores , Precondicionamento Isquêmico , Ácidos Cetoglutáricos/metabolismo , Animais , Isquemia/prevenção & controle , Ácido Cinurênico/metabolismo , Fígado/metabolismo , Camundongos , Modelos Animais , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Parabiose
13.
Sci Rep ; 5: 14557, 2015 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-26411306

RESUMO

We showed previously that phosphorylation of Noxa, a 54-residue Bcl-2 protein, at serine 13 (Ser13) inhibited its ability to promote apoptosis through interactions with canonical binding partner, Mcl-1. Using EPR spectroscopy, molecular dynamics (MD) simulations and binding assays, we offer evidence that a structural alteration caused by phosphorylation partially masks Noxa's BH3 domain, inhibiting the Noxa-Mcl-1 interaction. EPR of unphosphorylated Noxa, with spin-labeled amino acid TOAC incorporated within the BH3 domain, revealed equilibrium between ordered and dynamically disordered states. Mcl-1 further restricted the ordered component for non-phosphorylated Noxa, but left the pSer13 Noxa profile unchanged. Microsecond MD simulations indicated that the BH3 domain of unphosphorylated Noxa is housed within a flexible loop connecting two antiparallel ß-sheets, flanked by disordered N- and C-termini and Ser13 phosphorylation creates a network of salt-bridges that facilitate the interaction between the N-terminus and the BH3 domain. EPR showed that a spin label inserted near the N-terminus was weakly immobilized in unphosphorylated Noxa, consistent with a solvent-exposed helix/loop, but strongly constrained in pSer13 Noxa, indicating a more ordered peptide backbone, as predicted by MD simulations. Together these studies reveal a novel mechanism by which phosphorylation of a distal serine inhibits a pro-apoptotic BH3 domain and promotes cell survival.


Assuntos
Modelos Moleculares , Conformação Proteica , Proteínas Proto-Oncogênicas c-bcl-2/química , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Humanos , Simulação de Dinâmica Molecular , Proteína de Sequência 1 de Leucemia de Células Mieloides/química , Proteína de Sequência 1 de Leucemia de Células Mieloides/metabolismo , Peptídeos , Fosforilação , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Estrutura Secundária de Proteína , Proteínas Recombinantes , Relação Estrutura-Atividade
14.
Mol Biosyst ; 11(7): 1850-6, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25855872

RESUMO

High-resolution characterization of the structure and dynamics of intrinsically disordered proteins (IDPs) remains a challenging task. Consequently, a detailed understanding of the structural and functional features of IDPs remains limited, as very few full-length disordered proteins have been structurally characterized. We have performed microsecond-long molecular dynamics (MD) simulations of Noxa, the smallest member of the large Bcl-2 family of apoptosis regulating proteins, to characterize in atomic-level detail the structural features of a disordered protein. A 2.5 µs MD simulation starting from an unfolded state of the protein revealed the formation of a central antiparallel ß-sheet structure flanked by two disordered segments at the N- and C-terminal ends. This topology is in reasonable agreement with protein disorder predictions and available experimental data. We show that this fold plays an essential role in the intracellular function and regulation of Noxa. We demonstrate that unbiased MD simulations in combination with a modern force field reveal structural and functional features of disordered proteins at atomic-level resolution.


Assuntos
Simulação de Dinâmica Molecular , Proteínas Proto-Oncogênicas c-bcl-2/química , Humanos , Ligação de Hidrogênio , Proteínas Intrinsicamente Desordenadas/química , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Termodinâmica
15.
ACS Chem Biol ; 8(2): 327-35, 2013 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-23102022

RESUMO

Multidrug resistance (MDR) is a major hurdle in the treatment of cancer, and there is a pressing need for new therapies. We have recently developed ethyl 2-amino-6-(3,5-dimethoxyphenyl)-4-(2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate (CXL017), derived from a dual inhibitor of Bcl-2 and SERCA proteins, sHA 14-1, with selective cytotoxicity toward MDR cancer cell lines in vitro. In this study, we present new evidence for its therapeutic potential in treatment of MDR cancers and offer mechanistic insights toward its preferential targeting of drug-resistant cancer. CXL017 selectively suppressed the growth of tumors derived from the MDR cancer cell line, HL60/MX2, in vivo. In addition, even after chronic exposure to CXL017, HL60/MX2 failed to develop stable resistance to CXL017, whereas it acquired >2000-fold resistance to cytarabine (Ara-C), the major first-line chemotherapy for the treatment of acute myeloid leukemia (AML). Remarkably, instead of acquiring further cross-resistance, HL60/MX2 cells exposed to CXL017 were resensitized to standard therapies (10- to 100-fold). Western blotting analyses revealed that CXL017 exposure significantly down-regulated Mcl-1 and Bax and up-regulated Noxa, Bim, Bcl-X(L), SERCA2, and SERCA3 proteins, along with a reduction in endoplasmic reticulum (ER) calcium content. Given the well-established functions of Bcl-2 family proteins and ER calcium in drug resistance, our results suggest that the down-regulation of Mcl-1 and the up-regulation of Noxa and Bim along with the decrease in ER calcium content are likely responsible for CXL017-induced resensitization of MDR cancer cells. These data also demonstrate the unique potential of CXL017 to overcome MDR in cancer treatment.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Benzopiranos/farmacologia , Citarabina/farmacologia , Resistência a Múltiplos Medicamentos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Leucemia Mieloide Aguda/tratamento farmacológico , Protocolos de Quimioterapia Combinada Antineoplásica/química , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Benzopiranos/química , Sobrevivência Celular/efeitos dos fármacos , Citarabina/química , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Células HL-60 , Humanos , Leucemia Mieloide Aguda/patologia , Relação Estrutura-Atividade , Células Tumorais Cultivadas
16.
Carcinogenesis ; 32(7): 964-72, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21317300

RESUMO

Recent studies have implicated multipotential mesenchymal stem cells (MSCs) as an aid to breast cancer cell proliferation and metastasis, partly as a result of the MSCs secretome. As the tumor gets beyond 2 mm in diameter, the stromal cells could undergo starvation due to the lack of sufficient nutrients in solid tumor microenvironment. In this study, we investigated the survival mechanisms used by stressed stromal cells in breast cancers. We used serum-deprived mesenchymal stem cells (SD-MSCs) and MCF-7 breast cancer cells as model system with a hypothesis that stromal cells in the nutrient-deprived core utilize survival mechanisms for supporting surrounding cells. We tested this hypothesis using in vivo tumor xenografts in immunodeficient mice, which indicated that SD-MSCs supported MCF-7 tumor growth by protection from apoptosis. Histochemical assays showed that SD-MSCs-injected tumors exhibited higher cellularity, decreased apoptosis and decreased differentiation. Beclin-1 staining indicated autophagic areas surrounded by actively proliferating cells. Furthermore, in vitro studies demonstrate that SD-MSCs survive using autophagy and secrete paracrine factors that support tumor cells following nutrient/serum deprivation. Western blot and immunocytochemistry analysis of SD-MSCs demonstrated upregulation and perinuclear relocation of autophagy key regulators such as beclin-1, ATG10, ATG12, MAP-LC3 and lysosomes. Electron microscopic analysis detected a time-dependent increase in autophagosome formation and HDAC6 activity assays indicated the upregulation of autophagy. Taken together, these data suggest that under nutrient-deprived conditions that can occur in solid tumors, stromal cells utilize autophagy for survival and also secrete anti-apoptotic factors that can facilitate solid tumor survival and growth.


Assuntos
Autofagia , Células-Tronco Mesenquimais/imunologia , Neoplasias/patologia , Células Estromais/patologia , Animais , Apoptose/imunologia , Linhagem Celular Tumoral , Sobrevivência Celular/imunologia , Células Cultivadas , Meios de Cultura Livres de Soro , Feminino , Humanos , Camundongos , Camundongos SCID , Neoplasias/imunologia
17.
Mol Cell ; 40(5): 823-33, 2010 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-21145489

RESUMO

The BH3-only protein, Noxa, is induced in response to apoptotic stimuli, such as DNA damage, hypoxia, and proteasome inhibition in most human cells. Noxa is constitutively expressed in proliferating cells of hematopoietic lineage and required for apoptosis in response to glucose stress. We show that Noxa is phosphorylated on a serine residue (S(13)) in the presence of glucose. Phosphorylation promotes its cytosolic sequestration and suppresses its apoptotic function. We identify Cdk5 as the Noxa kinase and show that Cdk5 knockdown or expression of a Noxa S(13) to A mutant increases sensitivity to glucose starvation, confirming that the phosphorylation is protective. Both glucose deprivation and Cdk5 inhibition promote apoptosis by dephosphorylating Noxa. Paradoxically, Noxa stimulates glucose consumption and may enhance glucose turnover via the pentose phosphate pathway rather than through glycolysis. We propose that Noxa plays both growth-promoting and proapoptotic roles in hematopoietic cancers with phospho-S(13) as the glucose-sensitive toggle switch controlling these opposing functions.


Assuntos
Apoptose/fisiologia , Quinase 5 Dependente de Ciclina/metabolismo , Glucose/metabolismo , Leucemia/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Linhagem Celular Tumoral , Quinase 5 Dependente de Ciclina/genética , Humanos , Leucemia/enzimologia , Fosforilação , Proteínas Proto-Oncogênicas c-bcl-2/genética
18.
Arch Biochem Biophys ; 494(1): 101-5, 2010 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-19944062

RESUMO

The purpose of this study was to determine the sphingolipid (SL) profile in cells defective in autophagy protein ATG-7 and overall cell death after photodynamic therapy (PDT) with the photosensitizer Pc 4. MCF-7 human breast cancer cells with downregulated ATG-7 and their scrambled controls (Scr) were used. Exposure of ATG-7 knockdown cells to PDT led to increased cell killing. PDT evoked an early (2h) greater global increase in ceramides in ATG-7 defective cells compared to Scr cells. The total increases in dihydroceramide (DHceramide) were significant at 2 and 24h in both cell types post-PDT. The levels of sphingosine-1-phosphate (S1P) and sphingosine were decreased below resting levels at both time points irrespective of the cell type. The data imply that ceramide might be a marker of ATG-7 deficiency in cells sensitized to PDT.


Assuntos
Autofagia , Ceramidas/metabolismo , Regulação para Baixo , Fármacos Fotossensibilizantes/farmacologia , Enzimas Ativadoras de Ubiquitina/metabolismo , Proteína 7 Relacionada à Autofagia , Linhagem Celular Tumoral , Técnicas de Silenciamento de Genes , Humanos , Fotoquimioterapia , Enzimas Ativadoras de Ubiquitina/genética
19.
Apoptosis ; 15(2): 139-52, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19851871

RESUMO

Previously we reported that serum leucine-rich alpha-2-glycoprotein-1 (LRG) binds cytochrome c (Cyt c; Cummings et al., Apoptosis 11:1121-1129, 2009). Here we show that LRG binding to Cyt c is similar to that of Apaf-1. LRG and Apaf-1 share partial amino acid sequences, compete for binding Cyt c, and are inhibited by modification at lysine 72 in Cyt c. However, in contrast to Apaf-1, LRG acts as a survival factor in vitro rather than a pro-apoptotic factor. By depleting LRG from culture medium we found that LRG protects against a toxic effect of exogenous Cyt c on lymphocytes that would otherwise result in an apoptotic phenotype. LRG, as well as antibodies specific for Cyt c, increased cell viability in the absence of added Cyt c indicating that Cyt c released by dying cells in the cultures is itself toxic. Protection from extracellular Cyt c-induced lymphotoxicity appears to involve an active mechanism rather than steric hindrance of Cyt c. Thus, serum LRG when bound to extracellular Cyt c that is released from apoptotic cells acts as a survival factor for lymphocytes and possibly other cells that are susceptible to the toxic effect of extracellular Cyt c.


Assuntos
Citocromos c/metabolismo , Glicoproteínas/sangue , Linfócitos/citologia , Linfócitos/metabolismo , Sequência de Aminoácidos , Animais , Fator Apoptótico 1 Ativador de Proteases/química , Fator Apoptótico 1 Ativador de Proteases/metabolismo , Ligação Competitiva , Morte Celular , Sobrevivência Celular , Células Cultivadas , Sequência Conservada , Evolução Molecular , Citometria de Fluxo , Glicoproteínas/química , Cavalos , Humanos , Lisina/metabolismo , Camundongos , Modelos Biológicos , Modelos Moleculares , Dados de Sequência Molecular , Fenótipo , Ligação Proteica , Homologia de Sequência de Aminoácidos , Especificidade da Espécie
20.
J Cell Mol Med ; 13(9B): 3687-98, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19298526

RESUMO

Endostatin is a well-characterized endogenous inhibitor of angiogenesis that affects cell proliferation and migration by inhibiting integrin and Wnt-mediated signalling pathways. Here, we show that endothelial cells treated with native and P125A-endostatin activate autophagy. Because autophagy can either be protective or induce programmed cell death, experiments were carried out to understand the signalling pathways leading to autophagy in endothelial cells. P125A-endostatin treatment increased the levels of Beclin 1, a crucial molecule in vesicle nucleation and autophagy. The treatment also reduced the levels of Bcl-2, Bcl-x(L) and beta-catenin; however, progressively increasing amounts of Bcl-2 and Bcl-x(L) were found to be complexed with Beclin 1. Increased beta-catenin and Wnt-mediated signalling reduced Beclin 1 levels and rescued endothelial cells from endostatin-induced autophagy. Finally, knocking down Beclin 1 levels by RNA interference decreased autophagy and accelerated caspase activation in endostatin-treated cells. These studies suggest that endothelial cells may initiate autophagy as a survival response to limit the effects of angiogenesis inhibitors. Thus, interfering with autophagy can potentiate the effects of endostatin by promoting a switch to apoptosis.


Assuntos
Proteínas Reguladoras de Apoptose/metabolismo , Autofagia , Endostatinas/metabolismo , Células Endoteliais/citologia , Regulação da Expressão Gênica , Proteínas de Membrana/metabolismo , beta Catenina/metabolismo , Proteína Beclina-1 , Caspases/metabolismo , Linhagem Celular Tumoral , Endostatinas/farmacologia , Ativação Enzimática , Humanos , Fosfatidilinositol 3-Quinases/metabolismo , Interferência de RNA , Fatores de Tempo , Veias Umbilicais/citologia
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