A Fluorogenic Trehalose Probe for Tracking Phagocytosed Mycobacterium tuberculosis.
Journal of the American Chemical Society
Exploring condensation reaction between aromatic nitriles and amnio thiols to form nanoparticles in cells for imaging the activity of protease and glycosidase.
Angewandte Chemie (International ed. in English)
Tuberculosis (TB) disease is a global epidemic caused by the pathogenic Mycobacterium tuberculosis (Mtb). Tools that can track the replication status of viable Mtb cells within macrophages are vital for the elucidation of host-pathogen interactions. Here, we present a cephalosphorinase-dependent green trehalose (CDG-Tre) fluorogenic probe that enables fluorescence labeling of single live Bacille Calmette-Guérin (BCG) cells within macrophages at concentrations as low as 2 µM. CDG-Tre fluoresces upon activation by BlaC, the ?-lactamase uniquely expressed by Mtb, and the fluorescent product is subsequently incorporated within the bacterial cell wall via trehalose metabolic pathway. CDG-Tre showed high selectivity for mycobacteria over other clinically prevalent species in the Corynebacterineae suborder. The unique labeling strategy of BCG by CDG-Tre provides a versatile tool for tracking Mtb in both pre- and post-phagocytosis and elucidating fundamental physiological and pathological processes related to the mycomembrane.
View details for DOI 10.1021/jacs.0c07700
View details for PubMedID 32813512
Rapid and specific labeling of single live Mycobacterium tuberculosis with a dual-targeting fluorogenic probe
SCIENCE TRANSLATIONAL MEDICINE
2018; 10 (454)
The condensation reaction between 6-hydroxy-2-cyanobenzothiazole (CBT) and cysteine has been shown for various applications such as site-specific protein labelling and in vivo cancer imaging. This report further expands the substrate scope of this reaction by varying the substituents on aromatic nitriles and amino thiols and testing their reactivity and ability to form nanoparticles for cell imaging. The structure-activity relationship study leads to the identification of the minimum structural requirement for the macrocyclization and assembly process in forming nanoparticles. One of the scaffolds made of 2-pyrimidinecarbonitrile and cysteine joined by a benzyl linker was applied to design fluorescent probes to image caspase-3/7 and ?-galactosidase activity in live cells. These results demonstrate the generality of this system for imaging hydrolytic enzymes.
View details for DOI 10.1002/anie.201913314
View details for PubMedID 31828913
Intramolecular substitution uncages fluorogenic probes for detection of metallo-carbapenemase-expressing bacteria.
2017; 8 (11): 7669?74
Tuberculosis (TB) remains a public health crisis and a leading cause of infection-related death globally. Although in high demand, imaging technologies that enable rapid, specific, and nongenetic labeling of live Mycobacterium tuberculosis (Mtb) remain underdeveloped. We report a dual-targeting strategy to develop a small molecular probe (CDG-DNB3) that can fluorescently label single bacilli within 1 hour. CDG-DNB3 fluoresces upon activation of the ?-lactamase BlaC, a hydrolase naturally expressed in Mtb, and the fluorescent product is retained through covalent modification of the Mtb essential enzyme decaprenylphosphoryl-?-d-ribose 2'-epimerase (DprE1). This dual-targeting probe not only discriminates live from dead Bacillus Calmette-Guérin (BCG) but also shows specificity for Mtb over other bacterial species including 43 nontuberculosis mycobacteria (NTM). In addition, CDG-DNB3 can image BCG phagocytosis in real time, as well as Mtb in patients' sputum. Together with a low-cost, self-driven microfluidic chip, we have achieved rapid labeling and automated quantification of live BCG. This labeling approach should find many potential applications for research toward TB pathogenesis, treatment efficacy assessment, and diagnosis.
View details for PubMedID 30111644
Binding studies using Pichia pastoris expressed human aryl hydrocarbon receptor and aryl hydrocarbon receptor nuclear translocator proteins
PROTEIN EXPRESSION AND PURIFICATION
2016; 122: 72-81
Quantitative detection of cells expressing BlaC using droplet-based microfluidics for use in the diagnosis of tuberculosis.
2015; 9 (4): 044120-?
This work reports a novel caging strategy for designing fluorogenic probes to detect the activity of ?-lactamases. The caging strategy uses a thiophenyl linker connected to a fluorophore caged by a good leaving group-dinitrophenyl. The uncaging proceeds in two steps through the sulfa-releasing and subsequent intramolecular substitution. The length of the linker has been examined and optimized to maximize the rate of intramolecular reaction and thus the rate of fluorescence activation. Finally based on this strategy, we prepared a green fluorogenic probe CAT-7 and validated its selectivity for detecting metallo-carbapenemases (VIM-27, IMP-1, NDM-1) in carbapenem-resistant Enterobacteriaceae (CRE) lysates.
View details for PubMedID 29568429
A biomimetic approach for enhancing the in vivo half-life of peptides
Nature Chemical Biology
2015; 11: 793-798
Differential suppression of the aryl hydrocarbon receptor nuclear translocator-dependent function by an aryl hydrocarbon receptor PAS-A-derived inhibitory molecule
2014; 88 (2): 253-265
This paper describes a method for the quantitative detection of cells expressing BlaC, a ?-lactamase naturally expressed by Mycobacterium tuberculosis, intended for the diagnosis of tuberculosis. The method is based on the compartmentalization of bacteria in picoliter droplets at limiting dilutions such that each drop contains one or no cells. The co-encapsulation of a fluorogenic substrate probe for BlaC allows the quantification of bacteria by enumerating the number of fluorescent drops. Quantification of 10 colony forming units per milliliter is demonstrated. Furthermore, the encapsulation of single cell in drops maintains the specificity of the detection scheme even when the concentration of bacteria that do not express BlaC exceeds that expressing BlaC by one million-fold.
View details for DOI 10.1063/1.4928879
View details for PubMedID 26339319
View details for PubMedCentralID PMC4545073
Identification of cyclophilin-40-interacting proteins reveals potential cellular function of cyclophilin-40
2011; 410 (2): 257-265
The aryl hydrocarbon receptor (AhR) heterodimerizes with the aryl hydrocarbon receptor nuclear translocator (Arnt) for transcriptional regulation. We generated three N-terminal deletion constructs of the human AhR of 12-24 kDa in size--namely D1, D2, and D3--to suppress the Arnt function. We observed that all three deletions interact with the human Arnt with similar affinities. D2, which contains part of the AhR PAS-A domain and interacts with the PAS-A domain of Arnt, inhibits the formation of the AhR gel shift complex. D2 suppresses the 3-methylcholanthrene-induced, dioxin response element (DRE)-driven luciferase activity in Hep3B cells and exogenous Arnt reverses this D2 suppression. D2 suppresses the induction of CYP1A1 at both the message and protein levels in Hep3B cells; however, the CYP1B1 induction is not affected. D2 suppresses the recruitment of Arnt to the cyp1a1 promoter but not to the cyp1b1 promoter, partly because the AhR/Arnt heterodimer binds better to the cyp1b1 DRE than to the cyp1a1 DRE. Interestingly, D2 has no effect on the cobalt chloride-induced, hypoxia inducible factor-1 (HIF-1)-dependent expression of vegf, aldolase c, and ldh-a messages. Our data reveal that the flanking sequences of the DRE contribute to the binding affinity of the AhR/Arnt heterodimer to its endogenous enhancers and the function of AhR and HIF-1 can be differentially suppressed by the D2 inhibitory molecule.
View details for DOI 10.1016/j.bcp.2014.01.021
View details for Web of Science ID 000332903600013
View details for PubMedID 24486526
Knockdown of SMYD3 by RNA interference down-regulates c-Met expression and inhibits cells migration and invasion induced by HGF
2009; 280 (1): 78-85
Cyclophilin-40 (CyP40) is part of the immunophilin family and is found in Hsp90-containing protein complexes. We were interested in identifying proteins that interact with CyP40. CyP40-interacting proteins in HeLa cells were identified using the tandem affinity purification approach. Adenovirus expressing human CyP40 protein (Ad-CyP40), fused with streptavidin and calmodulin binding peptides at the N terminus, was generated. Proteins were separated on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel after tandem affinity purification. Here 10 silver-stained protein bands that were enriched in the Ad-CyP40-infected lysate and the corresponding regions in the control lysate were excised, digested by trypsin, and identified by tandem mass spectrometric analysis. Of 11 interacting proteins that were identified, 4 (RACK1, Ku70, RPS3, and NF45) were expressed in rabbit reticulocyte lysate, bacteria, and MCF-7 cells. We confirmed that these proteins interact with CyP40. We observed that RACK1 suppressed the cobalt chloride-induced, hypoxia response element-dependent luciferase activity in MCF-7 cells but not in MCF-7 stable cells expressing approximately 10% of the cellular CyP40 content. In addition, RACK1 reduced the HIF-1? protein accumulation after cobalt chloride treatment, which was not observed when the CyP40 content was down-regulated. Collectively, we conclude that reduction of the HIF-1 ? protein by RACK1 is CyP40-mediated.
View details for DOI 10.1016/j.ab.2010.12.007
View details for Web of Science ID 000287103900013
View details for PubMedID 21146485
Downregulation of survivin and activation of caspase-3 through the PI3K/Akt pathway in ursolic acid-induced HepG2 cell apoptosis
2009; 20 (4): 249-258
We previously reported that over-expression of SMYD3, a histone H3-K4 specific di- and tri-methyltransferase, plays a key role in cell viability, adhesion, migration and invasion. In this study, we investigated the mechanisms underlying these phenomena and found that knocking down SMYD3 expression in tumor cells significantly reduced the biological function of HGF and inhibited carcinoma cells migration and invasion. Due to the fact that the proto-oncogene c-Met encodes the high-affinity receptor for HGF, and the HGF-c-Met signaling plays a critical role in the tumor genesis, we further identified the partial correlation between SMYD3 and c-Met. The results showed that high expression of c-Met accompanied with over-expression of SMYD3. Silencing SMYD3 expression in tumor cells by specific shRNAs down-regulated c-Met gene transcription, while over-expressing SMYD3 induced c-Met transcription. Moreover, we demonstrated here that two SMYD3 binding sites within the c-Met core promoter region were significant in the transactivation of c-Met. The present findings provide significant insights into the epigenetic regulatory mechanisms of oncogene c-Met expression, and develop the strategies that may inhibit the progression of cancer migration and invasion.
View details for DOI 10.1016/j.canlet.2009.02.015
View details for Web of Science ID 000267003500010
View details for PubMedID 19321255
Ursolic acid (UA), a naturally occurring pentacyclic triterpene, is a potent in-vitro anticancer agent, acting through control of growth, apoptosis and differentiation. As the mechanism of its proapoptotic effects on human hepatocellular carcinoma cells has not been extensively studied, we performed an in depth evaluation of the effects of UA on apoptosis in human HepG2 cells. UA was found to inhibit the proliferation of HepG2 cells in a concentration and time-dependent manner. After treatment, cells showed evidence of activation of apoptosis, including the presence of apoptotic bodies and DNA fragmentation. UA-induced apoptosis was accompanied by a significant decrease in bcl-2 and survivin expression, with the corresponding ratio of bax/bcl-2 increased. The treatment with UA also increased the protein level and enzymatic activity of caspase-3. Z-DEVD-fmk, a specific caspase-3 inhibitor, significantly inhibited both the cytotoxic effect and the DNA fragmentation induced by UA, demonstrating the requirement for caspase-3 activity in UA-induced apoptosis. Inactivation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway was also involved, as inhibition of PI3K by LY294002 significantly increased UA-induced apoptosis. Kinetic experiments indicated that UA downregulated PI3K/p85 subunit (PI3K/p85) and phospho-Akt, before downregulating survivin. The further results also confirmed that LY294002 not only downregulated survivin alone, but considerably enhanced the repression of survivin combined with UA. UA therefore seemed to downregulate the expression of survivin by blocking PI3K/Akt. Taken together, the data suggest that the proapoptotic effect of UA on HepG2 cells is mediated by activation of caspase-3, and is highly correlated with inactivation of PI3K/Akt/survivin pathway.
View details for DOI 10.1097/CAD.0b013e328327d476
View details for Web of Science ID 000264676900004
View details for PubMedID 19174695