TRIM67 interacts with ENAH to regulate the apoptosis and autophagy of lung cancer cells.

The aim of this study was to further clarify the functional mechanism of the triangular 67 (TRIM67) gene in lung cancer cells. We detected the expression of TRIM67 in lung cancer cells by RT-qPCR and Western blot, transfected si-NC, si-TRIM67, and pcDNA-ENAH into the cells. The expression of TRIM67 and ENAH was detected by Western blot and immunofluorescence localization, and CO-IP and GST pull-down experiments verified the interaction. Flow cytometry, Western blot, and transmission electron microscopy (TEM) evaluated the apoptosis and autophagy levels. TRIM67 was highly expressed in lung cancer cell lines. Knockdown of TRIM67 promoted apoptosis and autophagy of A549 and NCI-H1299 cells. TRIM67 interacted with the ENAH protein. ENAH restored the effect of knocking down TRIM67 and further inhibited apoptosis and autophagy of A549 and NCI-H1299 cells. TRIM67 inhibits apoptosis and autophagy of lung cancer cells by interacting with ENAH.

Transmembrane tumor necrosis factor alpha attenuates pressure-overload cardiac hypertrophy via tumor necrosis factor receptor 2.

Tumor necrosis factor-alpha (TNF-α) plays an important pathogenic role in cardiac hypertrophy and heart failure (HF); however, anti-TNF is paradoxically negative in clinical trials and even worsens HF, indicating a possible protective role of TNF-α in HF. TNF-α exists in transmembrane (tmTNF-α) and soluble (sTNF-α) forms. Herein, we found that TNF receptor 1 (TNFR1) knockout (KO) or knockdown (KD) by short hairpin RNA or small interfering RNA (siRNA) significantly alleviated cardiac hypertrophy, heart dysfunction, fibrosis, and inflammation with increased tmTNF-α expression, whereas TNFR2 KO or KD exacerbated the pathological phenomena with increased sTNF-α secretion in transverse aortic constriction (TAC)- and isoproterenol (ISO)-induced cardiac hypertrophy in vivo and in vitro, respectively, indicating the beneficial effects of TNFR2 associated with tmTNF-α. Suppressing TNF-α converting enzyme by TNF-α Protease Inhibitor-1 (TAPI-1) to increase endogenous tmTNF-α expression significantly alleviated TAC-induced cardiac hypertrophy. Importantly, direct addition of exogenous tmTNF-α into cardiomyocytes in vitro significantly reduced ISO-induced cardiac hypertrophy and transcription of the pro-inflammatory cytokines and induced proliferation. The beneficial effects of tmTNF-α were completely blocked by TNFR2 KD in H9C2 cells and TNFR2 KO in primary myocardial cells. Furthermore, we demonstrated that tmTNF-α displayed antihypertrophic and anti-inflammatory effects by activating the AKT pathway and inhibiting the nuclear factor (NF)-κB pathway via TNFR2. Our data suggest that tmTNF-α exerts cardioprotective effects via TNFR2. Specific targeting of tmTNF-α processing, rather than anti-TNF therapy, may be more useful for the treatment of hypertrophy and HF.

Insights into the intestinal toxicity of foodborne mycotoxins through gut microbiota: A comprehensive review.

Mycotoxins, which are fungal metabolites, pose a significant global food safety concern by extensively contaminating food and feed, thereby seriously threatening public health and economic development. Many foodborne mycotoxins exhibit potent intestinal toxicity. However, the mechanisms underlying mycotoxin-induced intestinal toxicity are diverse and complex, and effective prevention or treatment methods for this condition have not yet been established in clinical and animal husbandry practices. In recent years, there has been increasing attention to the role of gut microbiota in the occurrence and development of intestinal diseases. Hence, this review aims to provide a comprehensive summary of the intestinal toxicity mechanisms of six common foodborne mycotoxins. It also explores novel toxicity mechanisms through the "key gut microbiota-key metabolites-key targets" axis, utilizing multiomics and precision toxicology studies with a specific focus on gut microbiota. Additionally, we examine the potential beneficial effects of probiotic supplementation on mycotoxin-induced toxicity based on initial gut microbiota-mediated mycotoxicity. This review offers a systematic description of how mycotoxins impact gut microbiota, metabolites, and genes or proteins, providing valuable insights for subsequent toxicity studies of mycotoxins. Furthermore, it lays a theoretical foundation for preventing and treating intestinal toxicity caused by mycotoxins and advancing food safety practices.

[Methodology for adaptive decision--making research on manufacturing process of traditional Chinese medicine based on deep reinforcement learning].

The manufacturing process of traditional Chinese medicine is subject to material fluctuation and other uncertain factors which usually cause non-optimal state and inconsistent product quality. Therefore, it is necessary to design and collect the quality-rela-ted physical parameters, process parameters, and equipment parameters in the whole manufacturing process of traditional Chinese medicine for digitization and modeling of the process. In this paper, a method for non-optimal state identification and self-recovering regulation was developed for active quality control in the manufacturing process of traditional Chinese medicine. Moreover, taking vacuum belt drying process as an example, a DQN algorithm-based intelligent decision model was established and verified and the implementation process was also discussed and studied. Thus, the process parameters-based self-optimization strategy discovery and path planning of optimal process control were rea-lized in this study. The results showed that the deep reinforcement learning-based artificial intelligence technology was helpful to improve the product quality consistency, reduce production cost, and increase benefit.

Alkyne-Tagged Raman Probes for Local Environmental Sensing by Hydrogen-Deuterium Exchange.

Alkyne-tagged Raman probes have shown high promise for noninvasive and sensitive visualization of small biomolecules to understand their functional roles in live cells. However, the potential for alkynes to sense cellular environments that goes beyond imaging remains to be further explored. Here, we report a general strategy for Raman imaging-based local environment sensing by hydrogen-deuterium exchange (HDX) of terminal alkynes (termed alkyne-HDX). We first demonstrate, in multiple Raman probes, that deuterations of the alkynyl hydrogens lead to remarkable shifts of alkyne Raman peaks for about 130 cm-1, providing resolvable signals suited for imaging-based analysis with high specificity. Both our analytical derivation and experimental characterizations subsequently establish that HDX kinetics are linearly proportional to both alkyne pKas and environmental pDs. After validating the quantitative nature of this strategy, we apply alkyne-HDX to sensing local chemical and cellular environments. We establish that alkyne-HDX exhibits high sensitivity to various DNA structures and demonstrates the capacity to detect DNA structural changes in situ from UV-induced damage. We further show that this strategy is also applicable to resolve subtle pD variations in live cells. Altogether, our work lays the foundation for utilizing alkyne-HDX strategy to quantitatively sense the local environments for a broad spectrum of applications in complex biological systems.

[Construction of knowledge base of Chinese medicine manufacturing].

Chinese medicine pharmaceutical industry is in the process of digital and intelligent transformation. Intelligent methods are required for efficient analysis and mining of the valuable information in the history data including literature data, pharmaceutical big data, and expert knowledge. Therefore, it is urgent to establish a knowledge-driven intelligent system of pharmaceutical technologies of Chinese medicine for efficient supplying of high-quality Chinese medicinal products. The present study proposed the construction method of the knowledge base of Chinese medicine manufacturing, which was preliminarily established from literature mining, case-based reasoning, and real-time prediction based on vacuum belt drying process optimization. Integrating the technologies(such as deep learning, case-based reasoning, and simulation modeling), pharmaceutical mechanisms, and big data, the knowledge base of Chinese medicine manufacturing can realize knowledge automation and scientific decision-making. It provides an example for upgrading from experience-based manufacturing to intelligent Chinese medicine manufacturing.

[Moisture content measurement model of whole package of Chinese medicinal materials based on microwave transmission technology].

In view of the relatively low representativeness of manual sampling inspection, and long time-consuming in oven detection of moisture content, which delayed the subsequent production period, this paper proposed a scheme for rapid moisture quantitative detection for Chinese medicinal materials by microwave transmission technology, and took 8 different types of Chinese medicinal mate-rials as examples to analyze the feasibility and reliability of the scheme for the detection results of moisture content of the whole package of Chinese medicine. In the experiment, the least square method was used to establish the measurement model of microwave absorption rate-moisture content for each kind of medicinal material. The results showed that the microwave transmission measurement of moisture content achieved high-precision measurement of the moisture content of Schisandrae Chinensis Fructus, Ziziphi Spinosae Semen, Poria, Pheretima, Lilii Bulbus, Scutellariae Radix, and Galli Gigerii Endothelium Corneum. The measurement model of Ziziphi Spinosae Semen had the highest accuracy, and the R~2 and root mean square error of the validation set were 0.951 5 and 0.15%, respectively. At the same time, this study found that the microwave absorption intensity of animal medicines including Pheretima and Galli Gigerii Endothelium Corneum was much weaker than that of plant medicines such as Schisandrae Chinensis Fructus, but there was also a good linear relationship between microwave absorption and moisture content, which proved the universality of this method. However, this method was not suitable for Phellodendri Chinensis Cortex because its package contained iron wire. For the whole package of medicinal materials with uniform density and no metal inside, the microwave transmission technology for moisture content measurement can be used to detect the moisture content, which is an effective alternative method to detect the moisture content of medicinal materials.

High spatial-resolution imaging of label-free in vivo protein aggregates by VISTA.

Amyloid aggregation, formed by aberrant proteins, is a pathological hallmark for neurodegenerative diseases, including Alzheimer's disease and Huntington's disease. High-resolution holistic mapping of the fine structures from these aggregates should facilitate our understanding of their pathological roles. Here, we achieved label-free high-resolution imaging of the polyQ and the amyloid-beta (Aß) aggregates in cells and tissues utilizing a sample-expansion stimulated Raman strategy. We further focused on characterizing the Aß plaques in 5XFAD mouse brain tissues. 3D volumetric imaging enabled visualization of the whole plaques, resolving both the fine protein filaments and the surrounding components. Coupling our expanded label-free Raman imaging with machine learning, we obtained specific segmentation of aggregate cores, peripheral filaments together with cell nuclei and blood vessels by pre-trained convolutional neural network models. Combining with 2-channel fluorescence imaging, we achieved a 6-color holistic view of the same sample. This ability for precise and multiplex high-resolution imaging of the protein aggregates and their micro-environment without the requirement of labeling would open new biomedical applications.

Toward photoswitchable electronic pre-resonance stimulated Raman probes.

Reversibly photoswitchable probes allow for a wide variety of optical imaging applications. In particular, photoswitchable fluorescent probes have significantly facilitated the development of super-resolution microscopy. Recently, stimulated Raman scattering (SRS) imaging, a sensitive and chemical-specific optical microscopy, has proven to be a powerful live-cell imaging strategy. Driven by the advances of newly developed Raman probes, in particular the pre-resonance enhanced narrow-band vibrational probes, electronic pre-resonance SRS (epr-SRS) has achieved super-multiplex imaging with sensitivity down to 250 nM and multiplexity up to 24 colors. However, despite the high demand, photoswitchable Raman probes have yet to be developed. Here, we propose a general strategy for devising photoswitchable epr-SRS probes. Toward this goal, we exploit the molecular electronic and vibrational coupling, in which we switch the electronic states of the molecules to four different states to turn their ground-state epr-SRS signals on and off. First, we showed that inducing transitions to both the electronic excited state and triplet state can effectively diminish the SRS peaks. Second, we revealed that the epr-SRS signals can be effectively switched off in red-absorbing organic molecules through light-facilitated transitions to a reduced state. Third, we identified that photoswitchable proteins with near-infrared photoswitchable absorbance, whose states are modulable with their electronic resonances detunable toward and away from the pump photon energy, can function as the photoswitchable epr-SRS probes with desirable sensitivity (<1 µM) and low photofatigue (>40 cycles). These photophysical characterizations and proof-of-concept demonstrations should advance the development of novel photoswitchable Raman probes and open up the unexplored Raman imaging capabilities.

A Caputo-Fabrizio Fractional-Order Model of HIV/AIDS with a Treatment Compartment: Sensitivity Analysis and Optimal Control Strategies.

Although most of the early research studies on fractional-order systems were based on the Caputo or Riemann-Liouville fractional-order derivatives, it has recently been proven that these methods have some drawbacks. For instance, kernels of these methods have a singularity that occurs at the endpoint of an interval of definition. Thus, to overcome this issue, several new definitions of fractional derivatives have been introduced. The Caputo-Fabrizio fractional order is one of these nonsingular definitions. This paper is concerned with the analyses and design of an optimal control strategy for a Caputo-Fabrizio fractional-order model of the HIV/AIDS epidemic. The Caputo-Fabrizio fractional-order model of HIV/AIDS is considered to prevent the singularity problem, which is a real concern in the modeling of real-world systems and phenomena. Firstly, in order to find out how the population of each compartment can be controlled, sensitivity analyses were conducted. Based on the sensitivity analyses, the most effective agents in disease transmission and prevalence were selected as control inputs. In this way, a modified Caputo-Fabrizio fractional-order model of the HIV/AIDS epidemic is proposed. By changing the contact rate of susceptible and infectious people, the atraumatic restorative treatment rate of the treated compartment individuals, and the sexual habits of susceptible people, optimal control was designed. Lastly, simulation results that demonstrate the appropriate performance of the Caputo-Fabrizio fractional-order model and proposed control scheme are illustrated.

[Digital twin based key technologies for intelligent manufacturing of traditional Chinese medicine].

In this paper, we first introduced the concept of digital twin(DT) based key technologies for intelligent manufacturing of traditional Chinese medicine(TCM) and applied DT in two case studies of novel extraction equipment for traditional Chinese medicine and drying equipment for Chinese medicine pills to illustrate the advantages of DT in development of new pharmaceutical technology and optimization of pharmaceutical equipment structure. Furthermore, we discussed the feasibility to adopt DT in the production process of TCM for formation of data-driven real-time optimization of production process and dynamic prediction `of operation and maintenance service. The "ruled" production mode based on data and driven by algorithm was constructed to realize the technical scheme of quality perception, evaluation, prediction, intelligent control and intelligent decision-making in product life cycle.

Cardioprotective Role of Myeloid-Derived Suppressor Cells in Heart Failure.

BACKGROUND: Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that expand in cancer, inflammation, and infection and negatively regulate inflammation and the immune response. Heart failure (HF) is a complex clinical syndrome wherein inflammation induction and incomplete resolution can potentially contribute to HF development and progression. However, the role of MDSCs in HF remains unclear. METHODS: The percentage of MDSCs in patients with HF and in mice with pressure overload-induced HF using isoproterenol infusion or transverse aortic constriction (TAC) was detected by flow cytometry. The effects of MDSCs on isoproterenol- or TAC-induced HF were observed on depleting MDSCs with 5-fluorouracil (50 mg/kg) or gemcitabine (120 mg/kg), transferring purified MDSCs, or enhancing endogenous MDSCs with rapamycin (2 mg·kg-1·d-1). Hypertrophic markers and inflammatory factors were detected by ELISA, real-time polymerase chain reaction, or Western blot. Cardiac functions were determined by echocardiography and hemodynamic analysis. RESULTS: The percentage of human leukocyte antigen-D-related (HLA-DR)-CD33+CD11b+ MDSCs in the blood of patients with HF was significantly increased and positively correlated with disease severity and increased plasma levels of cytokines, including interleukin-6, interleukin-10, and transforming growth factor-ß. Furthermore, MDSCs derived from patients with HF inhibited T-cell proliferation and interferon-γ secretion. Similar results were observed in TAC- and isoproterenol-induced HF in mice. Pharmaceutical depletion of MDSCs significantly exacerbated isoproterenol- and TAC-induced pathological cardiac remodeling and inflammation, whereas adoptive transfer of MDSCs prominently rescued isoproterenol- and TAC-induced HF. Consistently, administration of rapamycin significantly increased endogenous MDSCs by suppressing their differentiation and improved isoproterenol- and TAC-induced HF, but MDSC depletion mostly blocked beneficial rapamycin-mediated effects. Mechanistically, MDSC-secreted molecules suppressed isoproterenol-induced hypertrophy and proinflammatory gene expression in cardiomyocytes in a coculture system. Neutralization of interleukin-10 blunted both monocytic MDSC- and granulocytic MDSC-mediated anti-inflammatory and antihypertrophic effects, but treatment with a nitric oxide inhibitor only partially blocked the antihypertrophic effect of monocytic MDSCs. CONCLUSIONS: Our findings revealed a cardioprotective role of MDSCs in HF by their antihypertrophic effects on cardiomyocytes and anti-inflammatory effects through interleukin-10 and nitric oxide. Pharmacological targeting of MDSCs by rapamycin constitutes a promising therapeutic strategy for HF.

A HaloTag-Based Multicolor Fluorogenic Sensor Visualizes and Quantifies Proteome Stress in Live Cells Using Solvatochromic and Molecular Rotor-Based Fluorophores.

Protein homeostasis, or proteostasis, is essential for cellular fitness and viability. Many environmental factors compromise proteostasis, induce global proteome stress, and cause diseases. The proteome stress sensor is a powerful tool for dissecting the mechanism of cellular stress and finding therapeutics that ameliorate these diseases. In this work, we present a multicolor HaloTag-based sensor (named AgHalo) to visualize and quantify proteome stresses in live cells. The current AgHalo sensor is equipped with three fluorogenic probes that turn on fluorescence when the sensor forms either soluble oligomers or insoluble aggregates upon exposure to stress conditions, both in vitro and in cellulo. In addition, AgHalo probes can be combined with commercially available always-fluorescent HaloTag ligands to enable two-color imaging, allowing for direct visualization of the AgHalo sensor both before and after cells are subjected to stress conditions. Finally, pulse-chase experiments can be performed to discern changes in the cellular proteome in live cells by first forming the AgHalo conjugate and then either applying or removing stress at any desired time point. In summary, the AgHalo sensor can be used to visualize and quantify proteome stress in live cells, a task that is difficult to accomplish using previous always-fluorescent methods. This sensor should be suited to evaluating cellular proteostasis under various exogenous stresses, including chemical toxins, drugs, and environmental factors.

Modulation of Fluorescent Protein Chromophores To Detect Protein Aggregation with Turn-On Fluorescence.

We present a fluorogenic method to visualize misfolding and aggregation of a specific protein-of-interest in live cells using structurally modulated fluorescent protein chromophores. Combining photophysical analysis, X-ray crystallography, and theoretical calculation, we show that fluorescence is triggered by inhibition of twisted-intramolecular charge transfer of these fluorophores in the rigid microenvironment of viscous solvent or protein aggregates. Bioorthogonal conjugation of the fluorophore to Halo-tag fused protein-of-interests allows for fluorogenic detection of both misfolded and aggregated species in live cells. Unlike other methods, our method is capable of detecting previously invisible misfolded soluble proteins. This work provides the first application of fluorescent protein chromophores to detect protein conformational collapse in live cells.

A Molecular Rotor-Based Halo-Tag Ligand Enables a Fluorogenic Proteome Stress Sensor to Detect Protein Misfolding in Mildly Stressed Proteome.

Cellular stress leads to disruption of protein homeostasis (proteostasis) that is associated with global misfolding and aggregation of the endogenous proteome. Monitoring stress-induced proteostasis deficiency remains one of the major technical challenges facing established sensors of this process. Available sensors use solvatochromic fluorophores to detect protein aggregation in forms of soluble oligomers or insoluble aggregates when cells are subjected to severe stress conditions. Misfolded monomers induced by mild stresses, however, remain largely invisible to these sensors. Here, we describe a fluorogenic proteome stress sensor by conjugating a fluorescent molecular rotor with a metastable Halo-tag protein domain that contains a K73T mutation (named AgHalo hereinafter). In nonstressed cells, the AaHalo sensor remains largely folded and the AgHalo•ligand conjugate is fluorescent dark in the folded state. Under various stress conditions, the AgHalo sensor has been established to form both soluble and insoluble aggregates along with metastable proteins of the endogenous cellular proteome. Thus, the AgHalo•ligand conjugate fluoresces strongly when the sensor forms misfolded monomers (a 16-fold increase) or aggregates in both soluble and insoluble forms (a 20-fold increase). Compared to the solvatochromic fluorophore-based sensor, we demonstrate that the molecular rotor-based sensor not only is more effective in detecting mild proteome stress that induces primarily misfolding conformations, but also exhibits a higher fluorescence signal in detecting more severe proteome stress that involves protein aggregates. Thus, the conjugation of a fluorescent molecular rotor to AgHalo further improves the capacity of this sensor to detect conditions of proteome stress. This work highlights the utility of molecular rotor-based fluorophores in direct visualization of the protein aggregation cascade in live cells, providing new methodologies for real-time analyses of cellular proteostasis upon exposure to different types of stress conditions.

Knockdown of CPEB4 expression suppresses cell migration and invasion via Akt pathway in non-small cell lung cancer.

Cytoplasmic polyadenylation element binding protein 4 (CPEB4) could be an important regulator in variety of cancers. However, the biological function and the underlying molecular mechanism of CPEB4 in non-small cell lung cancer (NSCLC) remains unknown. In this study, we investigated the metastasis role of CPEB4 in NSCLC cells, we knocked down CPEB4 using siRNA. Transwell migration assay and cell invasion assay on Matrigel were presented, and cell migration was also determined by scratch-healing assay. ROS generation were determined by fluorescence probe DCFH2-DA. The protein expression was assessed by ELISA and Western blot analysis. LY294002 were used to inhibit PI3 K/Akt signaling. The data showed that knockdown of CPEB4 inhibited the migration and invasion of NSCLC. Moreover, silencing of CPEB4 reduced Snail and MMP-3 expression in vitro. We also indicated that CPEB4 knockdown increased the ROS expression. Furthermore, we found that silencing of CPEB4 decreased pAkt expression. Taken all together, our data demonstrated that silencing of CPEB4 induces ROS generation, thus suppressing the Akt expression, which finally prevents NSCLC cells invasion and migration. Therefore, CPEB4 may regard as a target to inhibit NSCLC invasion and metastasis through Akt pathway.

Executive functioning: perspectives on neurotrophic activity and pharmacology.

Executive functioning is a high-level cognitive ability, regulating other abilities and behaviors to achieve desired goals. A typical executive task can be defined as the capacity to maintain one's attention on the current task, that is, responding only to the correct but not to distractive stimuli. Impairments of executive functions, or executive dysfunctions, have a growing impact on everyday life and academic achievement and are usually an early feature, and one of the core features, in brain injury and memory and behavioral disorders. Furthermore, emerging evidence indicates that memory therapeutics cannot achieve their clinical benefits in cognition if executive dysfunction is not effectively and simultaneously treated. Improvement of executive functions might be achieved through targeting some signaling pathways in the brain, including the brain-derived neurotrophic factor signaling pathways. These agents may be useful either as stand-alone interventions for patients with executive dysfunction and/or psychiatric and memory disorders or as essential adjuncts to drugs that target the underlying pathology in various brain injury and memory and behavioral disorders.

Randomized controlled trial of endostar combined with cisplatin/ pemetrexed chemotherapy for elderly patients with advanced malignant pleural effusion of lung adenocarcinoma.

PURPOSE: To evaluate the clinical efficacy and safety of endostar combined with cisplatin/pemetrexed (CP) chemotherapy for elderly patients with advanced malignant pleural effusion (MPE) of lung adenocarcinoma. METHODS: A total of 128 lung adenocarcinoma patients with MPE were randomly divided into two groups. Patients in the treatment group were treated with pemetrexed 500 mg/m2, i.v., d 1, cisplatin intracavitary administration with a total dose of 75 mg/m2, d 2, 5 and 8, and endostar intracavitary administration 45 mg, d 1, 4 and 7. Patients in the control group were treated with chemotherapy alone (pemetrexed and cisplatin and mode of administration were the same as for the treatment group. RESULTS: The effective rates (ER) of the treatment group and control group were 81.82 and 64.52%, respectively (x2=4.906, p=0.027). The MPE control rates (DCRs) were 93.94 and 79.03%, respectively (x2=6.168, p=0.013). The control rate of the treatment group was higher compared with the control group (p<0.05), especially during the first period when it was 54.55% (p=0.019); in addition, the recurrence rate was lower (9.68 vs 30.61%, p=0.005). Dyspnea, mood and overall health improved significantly in the treatment group patients. No statistically significant differences in side effects between the groups were noticed. CONCLUSION: Intracavity endostar combined with intracavitary and i.v. pemetrexed and cisplatin had a significant effect on advanced MPE of lung adenocarcinoma. In addition, the quality of life (QoL) was significantly improved and the side effects were tolerable.

The Cation-π Interaction Enables a Halo-Tag Fluorogenic Probe for Fast No-Wash Live Cell Imaging and Gel-Free Protein Quantification.

The design of fluorogenic probes for a Halo tag is highly desirable but challenging. Previous work achieved this goal by controlling the chemical switch of spirolactones upon the covalent conjugation between the Halo tag and probes or by incorporating a "channel dye" into the substrate binding tunnel of the Halo tag. In this work, we have developed a novel class of Halo-tag fluorogenic probes that are derived from solvatochromic fluorophores. The optimal probe, harboring a benzothiadiazole scaffold, exhibits a 1000-fold fluorescence enhancement upon reaction with the Halo tag. Structural, computational, and biochemical studies reveal that the benzene ring of a tryptophan residue engages in a cation-π interaction with the dimethylamino electron-donating group of the benzothiadiazole fluorophore in its excited state. We further demonstrate using noncanonical fluorinated tryptophan that the cation-π interaction directly contributes to the fluorogenicity of the benzothiadiazole fluorophore. Mechanistically, this interaction could contribute to the fluorogenicity by promoting the excited-state charge separation and inhibiting the twisting motion of the dimethylamino group, both leading to an enhanced fluorogenicity. Finally, we demonstrate the utility of the probe in no-wash direct imaging of Halo-tagged proteins in live cells. In addition, the fluorogenic nature of the probe enables a gel-free quantification of fusion proteins expressed in mammalian cells, an application that was not possible with previously nonfluorogenic Halo-tag probes. The unique mechanism revealed by this work suggests that incorporation of an excited-state cation-π interaction could be a feasible strategy for enhancing the optical performance of fluorophores and fluorogenic sensors.

AgHalo: A Facile Fluorogenic Sensor to Detect Drug-Induced Proteome Stress.

Drug-induced proteome stress that involves protein aggregation may cause adverse effects and undermine the safety profile of a drug. Safety of drugs is regularly evaluated using cytotoxicity assays that measure cell death. However, these assays provide limited insights into the presence of proteome stress in live cells. A fluorogenic protein sensor is reported to detect drug-induced proteome stress prior to cell death. An aggregation prone Halo-tag mutant (AgHalo) was evolved to sense proteome stress through its aggregation. Detection of such conformational changes was enabled by a fluorogenic ligand that fluoresces upon AgHalo forming soluble aggregates. Using 5 common anticancer drugs, we exemplified detection of differential proteome stress before any cell death was observed. Thus, this sensor can be used to evaluate drug safety in a regime that the current cytotoxicity assays cannot cover and be generally applied to detect proteome stress induced by other toxins.