Allosteric regulation of protein 14-3-3ζ scaffold by small-molecule editing modulates histone H3 post-translational modifications

Discovery of a Plant 14-3-3 Inhibitor Possessing Isoform Selectivity and In Planta Activity

Synthetic modulators of plant 14-3-3s are promising chemical tools both for understanding the 14-3-3-related signaling pathways and controlling plant physiology. Herein, we describe a novel small-molecule inhibitor for 14-3-3 proteins of Arabidopsis thaliana. The inhibitor was identified from unexpected products in a stock solution in dimethyl sulfoxide (DMSO) of an in-house chemical library. Mass spectroscopy, mutant-based analyses, fluorescence polarization assays, and thermal shift assays revealed that the inhibitor covalently binds to an allosteric site of 14-3-3 with isoform selectivity. Moreover, infiltration of the inhibitor to Arabidopsis leaves suppressed the stomatal aperture. The inhibitor should provide new insight into the design of potent and isoform-selective 14-3-3 modulators.

Astaxanthin Inhibits H2O2-Induced Excessive Mitophagy and Apoptosis in SH-SY5Y Cells by Regulation of Akt/mTOR Activation

Oxidative stress, which damages cellular components and causes mitochondrial dysfunction, occurs in a variety of human diseases, including neurological disorders. The clearance of damaged mitochondria via mitophagy maintains the normal function of mitochondria and facilitates cell survival. Astaxanthin is an antioxidant known to have neuroprotective effects, but the underlying mechanisms remain unclear. This study demonstrated that astaxanthin inhibited H2O2-induced apoptosis in SH-SY5Y cells by ameliorating mitochondrial damage and enhancing cell survival. H2O2 treatment significantly reduced the levels of activated Akt and mTOR and induced mitophagy, while pretreatment with astaxanthin prevented H2O2-induced inhibition of Akt and mTOR and attenuated H2O2-induced mitophagy. Moreover, the inhibition of Akt attenuated the protective effect of astaxanthin against H2O2-induced cytotoxicity. Taken together, astaxanthin might inhibit H2O2-induced apoptosis by protecting mitochondrial function and reducing mitophagy. The results also indicate that the Akt/mTOR signaling pathway was critical for the protection of astaxanthin against H2O2-induced cytotoxicity. The results from the present study suggest that astaxanthin can reduce neuronal oxidative injury and may have the potential to be used for preventing neurotoxicity associated with neurodegenerative diseases.

Targeting 14-3-3ζ by a small-molecule compound AI-34 maintains epithelial barrier integrity and alleviates colitis in mice via stabilizing β-catenin

Aberrant intestinal epithelial barrier function is the primary pathology of Ulcerative colitis (UC), making it a desirable drug target. In this study, our small-molecule compound AI-34 exerted a significant protective effect in an LPS-induced epithelial barrier injury model. In vitro, AI-34 treatment significantly decreased cell permeability, increased transmembrane resistance, and maintained the junctional protein (ZO-1 and E-cadherin) levels in monolayer cells. Using the LiP-small molecule mapping approach (LiP-SMap), we demonstrated that AI-34 binds to 14-3-3ζ. AI-34 promoted the interaction between 14-3-3ζ and β-catenin, decreasing the ubiquitination of β-catenin and thus maintaining intestinal epithelial barrier function. Finally, AI-34 triggered the stabilization of β-catenin mediated by 14-3-3ζ, provoking a significant improvement in the DSS-induced colitis model. Our findings suggest that AI-34 may be a promising candidate for UC treatment.

Verbenalin attenuates hepatic damage and mitochondrial dysfunction in alcohol-associated steatohepatitis by regulating MDMX/PPARα-mediated ferroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Verbenalin is a major compound in Verbena officinalis L. Verbena officinalis L was first recorded in the 'Supplementary Records of Famous Physicians.' Verbenalin (VE) is its active constituent and has been found to have many biological effects, including anti-obesity, anti-inflammatory, and antioxidant activities, removing jaundice, and treating malaria. It could treat lump accumulation, dysmenorrhea, throat obstruction, edema, jaundice, and malaria. Palmitic acid (PA), oleic acid (OA), ethanol, and acetaminophen liver injuries have been proven to benefit from verbenalin.

AIM OF THE STUDY

To study the effects of verbenalin on the prevention of alcoholic steatohepatitis (ASH) through the regulation of oxidative stress and mitochondrial dysfunction by regulating MDMX (Murine double minute X)/PPARα (Peroxisome proliferator-activated receptor alpha)-mediated ferroptosis.

MATERIAL AND METHODS

C57BL/6 mice treated with alcohol followed by the Gao-Binge protocol were administered verbenalin by gavage simultaneously. The mitochondrial mass and morphology were visualized using TEM. AML-12 cells were stimulated with ethanol to mimic ASH in vitro. Western blotting, co-immunoprecipitation, and kit determination were simultaneously performed. The target protein of verbenalin was identified by molecular docking, and cellular thermal shift assay (CETSA) further confirmed its interactions.

RESULTS

Verbenalin alleviates oxidative stress and ferroptosis in alcohol-associated steatohepatitis. To elucidate the molecular mechanism by which verbenalin inhibits abnormal mitochondrial dysfunction, molecular docking was performed, and MDMX was identified as the target protein of verbenalin. CETSA assays revealed a specific interaction between MDMX and verbenalin. Co-immunoprecipitation demonstrated that PPARα played a critical role in promoting the ability of MDMX to affect ferroptosis. Verbenalin regulates MDMX/PPARα-mediated ferroptosis in AML-12 cells.

CONCLUSION

Verbenalin regulates ferroptosis and highlights the therapeutic potential of verbenalin and ferroptosis inhibition in reducing alcoholic steatohepatitis.

Epigenetic Regulations in Autoimmunity and Cancer: from Basic Science to Translational Medicine

Epigenetics, as a discipline that aims to explain the differential expression of phenotypes arising from the same gene sequence and the heritability of epigenetic expression, has received much attention in medicine. Epigenetic mechanisms are constantly being discovered, including DNA methylation, histone modifications, noncoding RNAs and m6A. The immune system mainly achieves an immune response through the differentiation and functional expression of immune cells, in which epigenetic modification will have an important impact. Because of immune infiltration in the tumor microenvironment, immunotherapy has become a research hotspot in tumor therapy. Epigenetics plays an important role in autoimmune diseases and cancers through immunology. An increasing number of drugs targeting epigenetic mechanisms, such as DNA methyltransferase inhibitors, histone deacetylase inhibitors, and drug combinations, are being evaluated in clinical trials for the treatment of various cancers (including leukemia and osteosarcoma) and autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis). This review summarizes the progress of epigenetic regulation for cancers and autoimmune diseases to date, shedding light on potential therapeutic strategies.

Allosteric Regulation of IGF2BP1 as a Novel Strategy for the Activation of Tumor Immune Microenvironment

Tumor immune microenvironment (TIME) regulators are promising cancer immunotherapeutic targets. IGF2BP1, as a crucial N ⁶-methyladenosine (m⁶A) reader protein, recognizes m⁶A target transcripts, ultimately leading to cancer development. However, currently, the biological function of IGF2BP1 in regulating the TIME is not well-understood. In this study, we report that IGF2BP1 knockdown induces cancer cell apoptosis, thereby significantly not only activating immune cell infiltration including CD4⁺, CD8⁺ T cells, CD56⁺ NK cells, and F4/80⁺ macrophage but also decreasing PD-L1 expression in hepatocellular carcinoma (HCC). Then, chemical genetics identifies a small-molecule cucurbitacin B (CuB), which directly targets IGF2BP1 at a unique site (Cys253) in the KH1-2 domains. This leads to a pharmacological allosteric effect to block IGF2BP1 recognition of m⁶A mRNA targets such as c-MYC, which is highly associated with cell apoptosis and immune response. In vivo, CuB exhibits an obvious anti-HCC effect through inducing apoptosis and subsequently recruits immune cells to tumor microenvironment as well as blocking PD-L1 expression. Collectively, IGF2BP1 may serve as a novel pharmacological allosteric target for anticancer therapeutics via mediating TIME.

Identification of Multi-Target Anti-AD Chemical Constituents From Traditional Chinese Medicine Formulae by Integrating Virtual Screening and In Vitro Validation

Alzheimer's disease (AD) is a neurodegenerative disease that seriously threatens the health of the elderly. At present, no drugs have been proven to cure or delay the progression of the disease. Due to the multifactorial aetiology of this disease, the multi-target-directed ligand (MTDL) approach provides an innovative and promising idea in search for new drugs against AD. In order to find potential multi-target anti-AD drugs from traditional Chinese medicine (TCM) formulae, a compound database derived from anti-AD Chinese herbal formulae was constructed and predicted by the anti-AD multi-target drug prediction platform established in our laboratory. By analyzing the results of virtual screening, 226 chemical constituents with 3 or more potential AD-related targets were collected, from which 16 compounds that were predicted to combat AD through various mechanisms were chosen for biological validation. Several cell models were established to validate the anti-AD effects of these compounds, including KCl, Aβ, okadaic acid (OA), SNP and H₂O₂ induced SH-SY5Y cell model and LPS induced BV2 microglia model. The experimental results showed that 12 compounds including Nonivamide, Bavachromene and 3,4-Dimethoxycinnamic acid could protect model cells from AD-related damages and showed potential anti-AD activity. Furthermore, the potential targets of Nonivamide were investigated by molecular docking study and analysis with CDOCKER revealed the possible binding mode of Nonivamide with its predicted targets. In summary, 12 potential multi-target anti-AD compounds have been found from anti-AD TCM formulae by comprehensive application of computational prediction, molecular docking method and biological validation, which laid a theoretical and experimental foundation for in-depth study, also providing important information and new research ideas for the discovery of anti-AD compounds from traditional Chinese medicine.

First comprehensive analysis of lysine succinylation in paper mulberry (Broussonetia papyrifera)

BACKGROUND

Lysine succinylation is a naturally occurring post-translational modification (PTM) that is ubiquitous in organisms. Lysine succinylation plays important roles in regulating protein structure and function as well as cellular metabolism. Global lysine succinylation at the proteomic level has been identified in a variety of species; however, limited information on lysine succinylation in plant species, especially paper mulberry, is available. Paper mulberry is not only an important plant in traditional Chinese medicine, but it is also a tree species with significant economic value. Paper mulberry is found in the temperate and tropical zones of China. The present study analyzed the effects of lysine succinylation on the growth, development, and physiology of paper mulberry.

RESULTS

A total of 2097 lysine succinylation sites were identified in 935 proteins associated with the citric acid cycle (TCA cycle), glyoxylic acid and dicarboxylic acid metabolism, ribosomes and oxidative phosphorylation; these pathways play a role in carbon fixation in photosynthetic organisms and may be regulated by lysine succinylation. The modified proteins were distributed in multiple subcellular compartments and were involved in a wide variety of biological processes, such as photosynthesis and the Calvin-Benson cycle.

CONCLUSION

Lysine-succinylated proteins may play key regulatory roles in metabolism, primarily in photosynthesis and oxidative phosphorylation, as well as in many other cellular processes. In addition to the large number of succinylated proteins associated with photosynthesis and oxidative phosphorylation, some proteins associated with the TCA cycle are succinylated. Our study can serve as a reference for further proteomics studies of the downstream effects of succinylation on the physiology and biochemistry of paper mulberry.

Protosappanin A Maintains Neuronal Mitochondrial Homeostasis through Promoting Autophagic Degradation of Bax

Cerebral ischemia is accompanied by mitochondrial integrity destruction. Thus, reversion of mitochondrial damage holds great potential for cerebral ischemia therapy. As a crucial Bcl-2 family member, pro-apoptotic Bax protein is a main effector of mitochondrial permeabilization and plays an important role in mitochondrial homeostasis. However, there is still a lack of an effective cerebral protective strategy through selectively targeting Bax. In this study, we reported that natural small-molecule protosappanin A (PTA) showed a significant mitochondrial protective effect on oxygen-glucose deprivation/reperfusion (OGD/R)-induced PC12 cells injury through increasing ATP production and maintaining mitochondrial DNA (mtDNA) content. The mechanism study revealed that PTA selectively induced pro-apoptotic protein Bax degradation, without affecting other Bcl-2 family members such as Bcl-2, Bcl-xl, Bad, Puma, Bid, Bim, and Bik. In addition, we found that PTA promoted the association of autophagosomal marker LC3B to Bax for its degradation via an autophagy-dependent manner but not the ubiquitin-proteasome pathway. Collectively, our findings offered a new pharmacological strategy for maintaining mitochondrial function by inducing autophagic degradation of Bax and also provided a novel drug candidate against ischemic neuronal injury.

Online energy-resolved MS boosts the potential of LC-MS towards metabolite characterization of salidroside and tyrosol

Although currently serving as the workhorse for metabolite characterization, one of the most challenging tasks for LC-MS is isomeric differentiation because isomers frequently yield identical quasi-molecular ions and fragmented ion species. Our previous studies have demonstrated that online energy-resolved MS (ER-MS) is an orthogonal technique for MS/MS experiments to facilitate isomeric identification. Herein, attempts were made for the in-depth characterization of the metabolic profiles of an effective natural product named salidroside (SA) in rats using LC coupled with three-dimensional mass spectrometry (LC-3D MS) that was configured by MS¹, MS² and online ER-MS as 1^st, 2^nd, and 3^rd dimensions, respectively. Moreover, the metabolism characterization of its aglycone, namely, tyrosol (Try) was conducted in parallel to aid in proposing metabolic pathways. High-resolution MS¹ and MS² spectra were acquired by IT-TOF-MS, and subsequent data processing provided theoretical formula and sub-structures for each metabolite. Subsequently, online ER-MS was conducted for precursor > product ion transitions-of-interest to offer linkage information among the sub-structures via building breakdown graphs. As a result, ten (M1-10) and nine (M1, M2, and M5-11) metabolites were detected in SA- and Tyr-administrated biological samples, respectively, and their structures were qualitatively identified. Crucial metabolism occurred for either component. SA initially underwent hydrolysis to produce Tyr, and subsequently hydroxylation, oxidation, glucuronidation, and sulfation were observed as the primary metabolic pathways. To summarize, the metabolic fate of SA was understood in depth, and Tyr, as the hydrolytic product, was responsible for the occurrences of most metabolites (M1, M2, and M5-10). More importantly, identification confidences of the metabolites were significantly advanced by LC-3D MS, suggesting that it is eligible to serve as an integral part of the analyst's toolbox.

(+)- and (-)-Corydecumbenines A and B, two pairs of novel quaternary protoberberine alkaloid cycloadduct enantiomers with anti-neuroinflammatory and neuroprotective activities from the rhizomes of Corydalis decumbens

Two novel Diels-Alder [4 + 2] cycloadducts of quaternary protoberberine alkaloids and fumaric acid monoanion, corydecumbenines A and B (1 and 2), and six known isoquinoline analogues (3-8) were isolated from the rhizomes of Corydalis decumbens. The planar structures of 1 and 2 were elucidated by extensive spectroscopic analysis including UV, IR, HRESIMS, 1D and 2D NMR. Chiral chromatography of 1 and 2 afforded two pairs of enantiomers (+)-corydecumbenine A (1a), (-)-corydecumbenine A (1b), (+)-corydecumbenine B (2a), and (-)-corydecumbenine B (2b), respectively, and their absolute configurations were determined by single-crystal X-ray crystallography and comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1b and 2b exhibited significant nitric oxide (NO) inhibitory activities in lipopolysaccharide (LPS)-stimulated BV-2 cells with IC₅₀ values of 11.6 and 16.2 μM, respectively, comparable to the positive control indomethacin (IC₅₀ = 10.3 μM), and they could also decrease the level of interleukin (IL)-1β in BV-2 cells in a dose-dependent manner. Most of the isolates showed neuroprotective effects against the injury of OGD/R-induced PC12 cells at 20 μM.