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1.
Hepatology ; 79(2): 323-340, 2024 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-37540188

RESUMO

BACKGROUND AND AIMS: HCC is an aggressive cancer with a poor clinical outcome. Understanding the mechanisms that drive tumor initiation is important for improving treatment strategy. This study aimed to identify functional cell membrane proteins that promote HCC tumor initiation. APPROACH AND RESULTS: Tailor-made siRNA library screening was performed for all membrane protein-encoding genes that are upregulated in human HCC (n = 134), with sphere formation as a surrogate readout for tumor initiation. Upon confirmation of membranous localization by immunofluorescence and tumor initiation ability by limiting dilution assay in vivo, LanC-like protein-1 (LANCL1) was selected for further characterization. LANCL1 suppressed intracellular reactive oxygen species (ROS) and promoted tumorigenicity both in vitro and in vivo. Mechanistically, with mass spectrometry, FAM49B was identified as a downstream binding partner of LANCL1. LANCL1 stabilized FAM49B by blocking the interaction of FAM49B with the specific E3 ubiquitin ligase TRIM21, thus protecting FAM49B from ubiquitin-proteasome degradation. The LANCL1-FAM49B axis suppressed the Rac1-NADPH oxidase-driven ROS production, but this suppression of ROS was independent of the glutathione transferase function of LANCL1. Clinically, HCCs with high co-expression of LANCL1 and FAM49B were associated with more advanced tumor stage, poorer overall survival, and disease-free survival. In addition, anti-LANCL1 antibodies targeting the extracellular N-terminal domain were able to suppress the self-renewal ability, as demonstrated by the sphere formation ability of HCC cells. CONCLUSIONS: Our data showed that LANCL1 is a cell surface protein and a key contributor to HCC initiation. Targeting the LANCL1-FAM49B-Rac1-NADPH oxidase-ROS signaling axis may be a promising therapeutic strategy for HCC.


Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Humanos , Espécies Reativas de Oxigênio/metabolismo , Proteínas de Membrana/metabolismo , Estresse Oxidativo , NADPH Oxidases/metabolismo , Linhagem Celular Tumoral , Receptores Acoplados a Proteínas G/metabolismo
2.
Am J Pathol ; 193(12): 2156-2171, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37673328

RESUMO

A growing body of evidence suggests de novo lipogenesis as a key metabolic pathway adopted by cancers to fuel tumorigenic processes. While increased de novo lipogenesis has also been reported in hepatocellular carcinoma (HCC), understanding on molecular mechanisms driving de novo lipogenesis remains limited. In the present study, the functional role of sortilin, a member of the vacuolar protein sorting 10 protein receptor family, in HCC was investigated. Sortilin was overexpressed in HCC and was associated with poorer survival outcome. In functional studies, sortilin-overexpressing cells conferred tumorigenic phenotypes, namely, self-renewal and metastatic potential, of HCC cells via the cancer secretome. Proteomic profiling highlighted fatty acid metabolism as a potential molecular pathway associated with sortilin-driven cancer secretome. This finding was validated by the increased lipid content and expression of fatty acid synthase (FASN) in HCC cells treated with conditioned medium collected from sortilin-overexpressing cells. The enhanced tumorigenic properties endowed by sortilin-driven cancer secretome were partly abrogated by co-administration of FASN inhibitor C75. Further mechanistic dissection suggested protein stabilization by post-translational modification with O-GlcNAcylation as a major mechanism leading to augmented FASN expression. In conclusion, the present study uncovered the role of sortilin in hepatocarcinogenesis via modulation of the cancer secretome and deregulated lipid metabolism.


Assuntos
Carcinoma Hepatocelular , Lipogênese , Neoplasias Hepáticas , Humanos , Carcinogênese/metabolismo , Carcinogênese/patologia , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patologia , Neoplasias Hepáticas/patologia , Proteômica , Proteínas Proto-Oncogênicas c-akt/metabolismo , Secretoma
3.
Nat Commun ; 14(1): 3564, 2023 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-37322008

RESUMO

Cysteine has been exploited as the binding site of covalent drugs. Its high sensitivity to oxidation is also important for regulating cellular processes. To identify new ligandable cysteines which can be hotspots for therapy and to better study cysteine oxidations, we develop cysteine-reactive probes, N-acryloylindole-alkynes (NAIAs), which have superior cysteine reactivity owing to delocalization of π electrons of the acrylamide warhead over the whole indole scaffold. This allows NAIAs to probe functional cysteines more effectively than conventional iodoacetamide-alkyne, and to image oxidized thiols by confocal fluorescence microscopy. In mass spectrometry experiments, NAIAs successfully capture new oxidized cysteines, as well as a new pool of ligandable cysteines and proteins. Competitive activity-based protein profiling experiments further demonstrate the ability of NAIA to discover lead compounds targeting these cysteines and proteins. We show the development of NAIAs with activated acrylamide for advancing proteome-wide profiling and imaging ligandable cysteines and oxidized thiols.


Assuntos
Cisteína , Compostos de Sulfidrila , Cisteína/metabolismo , Compostos de Sulfidrila/química , Alcinos/química , Proteínas/química , Acrilamidas
4.
Nat Protoc ; 17(7): 1691-1710, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35562423

RESUMO

Hydrogen peroxide (H2O2) is a key member of the reactive oxygen species family of transient small molecules that has broad contributions to oxidative stress and redox signaling. The development of selective and sensitive chemical probes can enable the study of H2O2 biology in cell, tissue and animal models. Peroxymycin-1 is a histochemical activity-based sensing probe that responds to H2O2 via chemoselective boronate oxidation to release puromycin, which is then covalently incorporated into nascent proteins by the ribosome and can be detected by antibody staining. Here, we describe an optimized two-step, one-pot protocol for synthesizing Peroxymycin-1 with improved yields over our originally reported procedure. We also present detailed procedures for applying Peroxymycin-1 to a broad range of biological samples spanning cells to animal tissues for profiling H2O2 levels through histochemical detection by using commercially available anti-puromycin antibodies. The preparation of Peroxymycin-1 takes 9 h, the confocal imaging experiments of endogenous H2O2 levels across different cancer cell lines take 1 d, the dot blot analysis of mouse liver tissues takes 1 d and the confocal imaging of mouse liver tissues takes 3-4 d.


Assuntos
Peróxido de Hidrogênio , Transdução de Sinais , Animais , Corantes Fluorescentes/química , Peróxido de Hidrogênio/análise , Camundongos , Oxirredução , Coloração e Rotulagem
5.
J Hepatol ; 77(2): 383-396, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35227773

RESUMO

BACKGROUND & AIMS: The highly proliferative nature of hepatocellular carcinoma (HCC) frequently results in a hypoxic intratumoural microenvironment, which creates a therapeutic challenge owing to a lack of mechanistic understanding of the phenomenon. We aimed to identify critical drivers of HCC development and progression in the hypoxic microenvironment. METHODS: We performed integrative analysis of multiple transcriptomic and genomic profiles specific for HCC and hypoxia and identified the Ephrin-A3/Eph receptor A2 (EphA2) axis as a clinically relevant and hypoxia-inducible signalling axis in HCC. The functional significance and mechanistic consequences of the Ephrin-A3/EphA2 axis were examined in EFNA3- and EPHA2- knockdown/overexpressing HCC cells. The potential downstream pathways were investigated by transcriptome sequencing, quantitative reverse-transcription PCR, western blotting analysis and metabolomics. RESULTS: EFNA3 was frequently upregulated in HCC and its overexpression was associated with more aggressive tumour behaviours. HIF-1α directly and positively regulated EFNA3 expression under hypoxia. EFNA3 functionally contributed to self-renewal, proliferation and migration in HCC cells. EphA2 was identified as a key functional downstream mediator of EFNA3. Functional characterisation of the Ephrin-A3/EphA2 forward-signalling axis demonstrated a promotion of self-renewal ability and tumour initiation. Mechanistically, the Ephrin-A3/EphA2 axis promoted the maturation of SREBP1 and expression of its transcriptional target, ACLY, was significantly associated with the expression of EFNA3 and hypoxia markers in clinical cohorts. The metabolic signature of EPHA2 and ACLY stable knockdown HCC cells demonstrated significant overlap in fatty acid, cholesterol and tricarboxylic acid cycle metabolite profiles. ACLY was confirmed to mediate the self-renewal function of the Ephrin-A3/EphA2 axis. CONCLUSIONS: Our findings revealed the novel role of the Ephrin-A3/EphA2 axis as a hypoxia-sensitive modulator of HCC cell metabolism and a key contributor to HCC initiation and progression. LAY SUMMARY: Hepatocellular carcinoma (HCC) is a fast-growing tumour; hence, areas of the tumour often have insufficient vasculature and become hypoxic. The presence of hypoxia within tumours has been shown to negatively impact on the survival of patients with tumours, including HCC. Herein, we identified the Ephrin-A3/EphA2 axis as a key functional driver of tumour initiation and progression in response to hypoxia. Additionally, we showed that SREBP1-ACLY-mediated metabolic rewiring was an important downstream effector that induced cancer stemness in response to Ephrin-A3/EphA2 forward-signalling.


Assuntos
Carcinoma Hepatocelular , Efrina-A3 , Neoplasias Hepáticas , Receptor EphA2 , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Efrina-A3/genética , Efrina-A3/metabolismo , Regulação Neoplásica da Expressão Gênica , Humanos , Hipóxia , Neoplasias Hepáticas/patologia , Receptor EphA2/genética , Receptor EphA2/metabolismo , Microambiente Tumoral
6.
J Extracell Biol ; 1(5): e39, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-38939527

RESUMO

MET receptor tyrosine kinase is a cell surface receptor that plays important role in embryonic development and tissue regeneration. Aberrant MET activation has been widely reported in different human cancers, making MET an attractive therapeutic target. The presence of truncated MET within the nucleus (nMET) with potential novel functions poses a great challenge to the current therapeutic strategies against MET surface receptor. Previous work has demonstrated the promoting effect of nMET in aggressive properties of hepatocellular carcinoma (HCC) cells by activating TAK1/NF-κB signalling pathway. Herein, we report the role of nMET in modulating tumour microenvironment and tumour metastasis mediated by extracellular vesicles (EVs). EVs released by nMET overexpressing cells enhanced cell motility and provoked metastasis. Proteomic profiling revealed the enrichment of translational regulatory proteins in EVs derived from nMET overexpressing cells. These proteins include eukaryotic initiation factor (EIF), ribosomal protein small subunit (RPS) and ribosomal protein larger subunit (RPL) gene families. Knockdown of EIF3I, RPS3A and RPL10 diminished the promoting effect of EVs in cell migration invasiveness and metastasis. In conclusion, the findings reveal an unrecognized capacity of nMET to augment HCC through the release of EVs with oncogenic effect. Targeting these translation-related proteins may serve as an alternative treatment for patients with nMET overexpression.

7.
Cell Rep ; 34(4): 108676, 2021 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-33503428

RESUMO

Hypoxia, low oxygen (O2), is a key feature of all solid cancers, including hepatocellular carcinoma (HCC). Genome-wide CRISPR-Cas9 knockout library screening is used to identify reliable therapeutic targets responsible for hypoxic survival in HCC. We find that protein-tyrosine phosphatase mitochondrial 1 (PTPMT1), an important enzyme for cardiolipin (CL) synthesis, is the most significant gene and ranks just after hypoxia-inducible factor (HIF)-1α and HIF-1ß as crucial to hypoxic survival. CL constitutes the mitochondrial membrane and ensures the proper assembly of electron transport chain (ETC) complexes for efficient electron transfer in respiration. ETC becomes highly unstable during hypoxia. Knockout of PTPMT1 stops the maturation of CL and impairs the assembly of ETC complexes, leading to further electron leakage and ROS accumulation at ETC in hypoxia. Excitingly, HCC cells, especially under hypoxic conditions, show great sensitivity toward PTPMT1 inhibitor alexidine dihydrochloride (AD). This study unravels the protective roles of PTPMT1 in hypoxic survival and cancer development.


Assuntos
Cardiolipinas/biossíntese , Neoplasias Hepáticas/metabolismo , PTEN Fosfo-Hidrolase/metabolismo , Animais , Sistemas CRISPR-Cas , Cardiolipinas/genética , Hipóxia Celular/fisiologia , Células HCT116 , Células Hep G2 , Xenoenxertos , Humanos , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Células PC-3 , PTEN Fosfo-Hidrolase/genética
8.
Adv Sci (Weinh) ; 7(21): 2002157, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33173740

RESUMO

In hepatocellular carcinoma (HCC) patients with extrahepatic metastasis, the lung is the most frequent site of metastasis. However, how the lung microenvironment favors disseminated cells remains unclear. Here, it is found that nidogen 1 (NID1) in metastatic HCC cell-derived extracellular vesicles (EVs) promotes pre-metastatic niche formation in the lung by enhancing angiogenesis and pulmonary endothelial permeability to facilitate colonization of tumor cells and extrahepatic metastasis. EV-NID1 also activates fibroblasts, which secrete tumor necrosis factor receptor 1 (TNFR1), facilitate lung colonization of tumor cells, and augment HCC cell growth and motility. Administration of anti-TNFR1 antibody effectively diminishes lung metastasis induced by the metastatic HCC cell-derived EVs in mice. In the clinical perspective, analysis of serum EV-NID1 and TNFR1 in HCC patients reveals their positive correlation and association with tumor stages suggesting the potential of these molecules as noninvasive biomarkers for the early detection of HCC. In conclusion, these results demonstrate the interplay of HCC EVs and activated fibroblasts in pre-metastatic niche formation and how blockage of their functions inhibits distant metastasis to the lungs. This study offers promise for the new direction of HCC treatment by targeting oncogenic EV components and their mediated pathways.

9.
Proc Natl Acad Sci U S A ; 116(37): 18285-18294, 2019 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-31451653

RESUMO

Copper is essential for life, and beyond its well-established ability to serve as a tightly bound, redox-active active site cofactor for enzyme function, emerging data suggest that cellular copper also exists in labile pools, defined as loosely bound to low-molecular-weight ligands, which can regulate diverse transition metal signaling processes spanning neural communication and olfaction, lipolysis, rest-activity cycles, and kinase pathways critical for oncogenic signaling. To help decipher this growing biology, we report a first-generation ratiometric fluorescence resonance energy transfer (FRET) copper probe, FCP-1, for activity-based sensing of labile Cu(I) pools in live cells. FCP-1 links fluorescein and rhodamine dyes through a Tris[(2-pyridyl)methyl]amine bridge. Bioinspired Cu(I)-induced oxidative cleavage decreases FRET between fluorescein donor and rhodamine acceptor. FCP-1 responds to Cu(I) with high metal selectivity and oxidation-state specificity and facilitates ratiometric measurements that minimize potential interferences arising from variations in sample thickness, dye concentration, and light intensity. FCP-1 enables imaging of dynamic changes in labile Cu(I) pools in live cells in response to copper supplementation/depletion, differential expression of the copper importer CTR1, and redox stress induced by manipulating intracellular glutathione levels and reduced/oxidized glutathione (GSH/GSSG) ratios. FCP-1 imaging reveals a labile Cu(I) deficiency induced by oncogene-driven cellular transformation that promotes fluctuations in glutathione metabolism, where lower GSH/GSSG ratios decrease labile Cu(I) availability without affecting total copper levels. By connecting copper dysregulation and glutathione stress in cancer, this work provides a valuable starting point to study broader cross-talk between metal and redox pathways in health and disease with activity-based probes.


Assuntos
Cobre/metabolismo , Transferência Ressonante de Energia de Fluorescência/métodos , Glutationa/metabolismo , Técnicas de Sonda Molecular , Oncogenes/fisiologia , Transportador de Cobre 1/metabolismo , Fluoresceína , Células HEK293 , Células HeLa , Humanos , Processamento de Imagem Assistida por Computador , Neoplasias/metabolismo , Oxirredução , Estresse Oxidativo , Rodaminas , Transdução de Sinais
10.
Nat Chem Biol ; 15(8): 776-785, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31285595

RESUMO

Autophagy is a lysosomal degradation pathway that eliminates aggregated proteins and damaged organelles to maintain cellular homeostasis. A major route for activating autophagy involves inhibition of the mTORC1 kinase, but current mTORC1-targeting compounds do not allow complete and selective mTORC1 blockade. Here, we have coupled screening of a covalent ligand library with activity-based protein profiling to discover EN6, a small-molecule in vivo activator of autophagy that covalently targets cysteine 277 in the ATP6V1A subunit of the lysosomal v-ATPase, which activates mTORC1 via the Rag guanosine triphosphatases. EN6-mediated ATP6V1A modification decouples the v-ATPase from the Rags, leading to inhibition of mTORC1 signaling, increased lysosomal acidification and activation of autophagy. Consistently, EN6 clears TDP-43 aggregates, a causative agent in frontotemporal dementia, in a lysosome-dependent manner. Our results provide insight into how the v-ATPase regulates mTORC1, and reveal a unique approach for enhancing cellular clearance based on covalent inhibition of lysosomal mTORC1 signaling.


Assuntos
Autofagia/efeitos dos fármacos , Alvo Mecanístico do Complexo 1 de Rapamicina/antagonistas & inibidores , ATPases Vacuolares Próton-Translocadoras/metabolismo , Animais , Autofagia/fisiologia , Linhagem Celular , Regulação da Expressão Gênica/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Humanos , Camundongos , Estrutura Molecular , Proteínas Proto-Oncogênicas c-akt , Pirazóis/farmacologia
11.
ACS Chem Biol ; 14(11): 2430-2440, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31059647

RESUMO

Targeted protein degradation has arisen as a powerful strategy for drug discovery allowing the targeting of undruggable proteins for proteasomal degradation. This approach most often employs heterobifunctional degraders consisting of a protein-targeting ligand linked to an E3 ligase recruiter to ubiquitinate and mark proteins of interest for proteasomal degradation. One challenge with this approach, however, is that only a few E3 ligase recruiters currently exist for targeted protein degradation applications, despite the hundreds of known E3 ligases in the human genome. Here, we utilized activity-based protein profiling (ABPP)-based covalent ligand screening approaches to identify cysteine-reactive small-molecules that react with the E3 ubiquitin ligase RNF4 and provide chemical starting points for the design of RNF4-based degraders. The hit covalent ligand from this screen reacted with either of two zinc-coordinating cysteines in the RING domain, C132 and C135, with no effect on RNF4 activity. We further optimized the potency of this hit and incorporated this potential RNF4 recruiter into a bifunctional degrader linked to JQ1, an inhibitor of the BET family of bromodomain proteins. We demonstrate that the resulting compound CCW 28-3 is capable of degrading BRD4 in a proteasome- and RNF4-dependent manner. In this study, we have shown the feasibility of using chemoproteomics-enabled covalent ligand screening platforms to expand the scope of E3 ligase recruiters that can be exploited for targeted protein degradation applications.


Assuntos
Complexos de Coordenação/química , Proteínas Nucleares/metabolismo , Proteólise/efeitos dos fármacos , Bibliotecas de Moléculas Pequenas/química , Fatores de Transcrição/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Proteínas de Ciclo Celular/metabolismo , Complexos de Coordenação/metabolismo , Cisteína/química , Humanos , Ligantes , Simulação de Acoplamento Molecular , Complexo de Endopeptidases do Proteassoma/metabolismo , Ligação Proteica , Domínios Proteicos , Bibliotecas de Moléculas Pequenas/metabolismo , Relação Estrutura-Atividade , Ubiquitinação , Zinco/química
12.
Chem Sci ; 8(3): 1942-1953, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28451309

RESUMO

Gold(iii) porphyrin-PEG conjugates [Au(TPP-COO-PEG5000-OCH3)]Cl (1) and [Au(TPP-CONH-PEG5000-OCH3)]Cl (2) have been synthesized and characterized. Based on the amphiphilic character of the conjugates, they were found to undergo self-assembly into nanostructures with size 120-200 nm and this did not require the presence of other surfactants or components for nano-assembly, unlike most conventional drug nano-formulations. With a readily hydrolyzable ester linkage, chemotherapeutic [Au(TPP-COOH)]+ exhibited triggered release from the conjugate 1 in acidic buffer solution as well as in vitro and in vivo without the formation of toxic side products. The nanostructures of 1 showed higher cellular uptake into cancer cells compared to non-tumorigenic cells, owing to their energy-dependent uptake mechanism. This, together with a generally higher metabolic rate and more acidic nature of cancer cells which can lead to faster hydrolysis of the ester bond, afforded 1 with excellent selectivity in killing cancer cells compared with non-tumorigenic cells in vitro. This was corroborated by fluorescence microscopy imaging and flow cytometric analysis of co-culture model of colon cancer (HCT116) and normal colon (NCM460) cells. In vivo experiments showed that treatment of nude mice bearing HCT116 xenografts with 1 resulted in significant inhibition of tumor growth and, more importantly, minimal systemic toxicity as revealed by histopathological analysis of tissue sections and blood biochemisty. The latter is explained by a lower accumulation of 1 in organs of treated mice at its effective dosage, as compared to that of other gold(iii) porphyrin complexes. Co-assembly of 1 and doxorubicin resulted in encapsulation of doxorubicin by the nanostructures of 1. The nanocomposites demonstrated a strong synergism on killing cancer cells and could overcome efflux pump-mediated drug-resistance in a doxorubicin-resistant ovarian cancer cell line (A2780adr) which was found in cells incubated with doxorubicin alone. Also, the nanocomposites accumulated more slowly in non-tumorigenic cells, resulting in a lower toxicity toward non-tumorigenic cells. These results indicate the potential application of 1 not only as an anti-cancer agent but also as a nanoscale drug carrier for chemotherapy.

13.
Angew Chem Int Ed Engl ; 55(39): 11935-9, 2016 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-27571430

RESUMO

Palladium(II) complexes are generally reactive toward substitution/reduction, and their biological applications are seldom explored. A new series of palladium(II) N-heterocyclic carbene (NHC) complexes that are stable in the presence of biological thiols are reported. A representative complex, [Pd(C^N^N)(N,N'-nBu2 NHC)](CF3 SO3 ) (Pd1 d, HC^N^N=6-phenyl-2,2'-bipyridine, N,N'-nBu2 NHC=N,N'-di-n-butylimidazolylidene), displays potent killing activity toward cancer cell lines (IC50 =0.09-0.5 µm) but is less cytotoxic toward a normal human fibroblast cell line (CCD-19Lu, IC50 =11.8 µm). In vivo anticancer studies revealed that Pd1 d significantly inhibited tumor growth in a nude mice model. Proteomics data and in vitro biochemical assays reveal that Pd1 d exerts anticancer effects, including inhibition of an epidermal growth factor receptor pathway, induction of mitochondrial dysfunction, and antiangiogenic activity to endothelial cells.


Assuntos
Antineoplásicos/uso terapêutico , Complexos de Coordenação/uso terapêutico , Metano/análogos & derivados , Neoplasias/tratamento farmacológico , Paládio/uso terapêutico , Animais , Antineoplásicos/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Complexos de Coordenação/química , Complexos de Coordenação/farmacologia , Humanos , Metano/química , Metano/farmacologia , Metano/uso terapêutico , Camundongos Nus , Neoplasias/patologia , Paládio/química , Paládio/farmacologia
14.
Chem Sci ; 7(5): 3123-3136, 2016 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29997803

RESUMO

A new class of cyclometalated Ir(iii) complexes supported by various bidentate C-deprotonated (C^N) and cis-chelating bis(N-heterocyclic carbene) (bis-NHC) ligands has been synthesized. These complexes display strong emission in deaerated solutions at room temperature with photoluminescence quantum yields up to 89% and emission lifetimes up to 96 µs. A photo-stable complex containing C-deprotonated fluorenyl-substituted C^N shows no significant decomposition even upon irradiation for over 120 h by blue LEDs (12 W). These, together with the strong absorption in the visible region and rich photo-redox properties, allow the bis-NHC Ir(iii) complexes to act as good photo-catalysts for reductive C-C bond formation from C(sp3/sp2)-Br bonds cleavage using visible-light irradiation (λ > 440 nm). A water-soluble complex with a glucose-functionalized bis-NHC ligand catalysed a visible-light-driven radical cyclization for the synthesis of pyrrolidine in aqueous media. Also, the bis-NHC Ir(iii) complex in combination with a cobalt catalyst can catalyse the visible-light-driven CO2 reduction with excellent turnover numbers (>2400) and selectivity (CO over H2 in gas phase: >95%). Additionally, this series of bis-NHC Ir(iii) complexes are found to localize in and stain endoplasmic reticulum (ER) of various cell lines with high selectivity, and exhibit high cytotoxicity towards cancer cells, revealing their potential uses as bioimaging and/or anti-cancer agents.

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