Dynamics of Energy Metabolism in Carbon Starvation-Induced Fruitlet Abscission in Litchi

Fruit abscission is triggered by multiple changes in endogenous components of the fruit, including energy metabolism. However, it is still unknown how the core energy metabolism pathways are modified during fruit abscission. Here, we investigated the relationship between carbon starvation-induced fruitlet abscission and energy metabolism changes in litchi. The fruitlet abscission of litchi ‘Feizixiao’ was induced sharply by girdling plus defoliation (GPD), a carbon stress treatment. Using liquid chromatography tandem mass spectrometry (LC-MS/MS) targeted metabolomics analysis, we identified a total of 21 metabolites involved in glycolysis, TCA cycle and oxidative phosphorylation pathways. Among them, the content of most metabolites in glycolysis pathways and TCA cycles was reduced, and the activity of corresponding metabolic enzymes such as ATP-dependent phosphofructokinase (ATP-PFK), pyruvate kinase (PK), citrate synthase (CS), succinate thiokinase (SAT), and NAD-dependent malate dehydrogenase (NAD-MDH) was decreased. Consistently, we further showed that the expression of the relative genes (LcPFK2, LcPK2, LcPK4, LcCS1, LcCS2, LcSAT, LcMDH1 and LcMDH2) was also significantly down-regulated. In contrast, the level of ATP, an important metabolite in the oxidative phosphorylation pathway, was elevated in parallel with both higher activity of H+-ATPase and the increased expression level of LcH+-ATPase1. In conclusion, our findings suggest that carbon starvation can induce fruitlet abscission in litchi probably by energy depletion that mediated through both the suppression of the glycolysis pathway and TCA cycle and the enhancement of the oxidative phosphorylation pathway.

Fungicidal Activity of Recombinant Javanicin against Cryptococcus neoformans Is Associated with Intracellular Target(s) Involved in Carbohydrate and Energy Metabolic Processes

The occurrence of Cryptococcus neoformans, the human fungal pathogen that primarily infects immunocompromised individuals, has been progressing at an alarming rate. The increased incidence of infection of C. neoformans with antifungal drugs resistance has become a global concern. Potential antifungal agents with extremely low toxicity are urgently needed. Herein, the biological activities of recombinant javanicin (r-javanicin) against C. neoformans were evaluated. A time-killing assay was performed and both concentration- and time-dependent antifungal activity of r-javanicin were indicated. The inhibitory effect of the peptide was initially observed at 4 h post-treatment and ultimately eradicated within 36 to 48 h. Fungal outer surface alteration was characterized by the scanning electron microscope (SEM) whereas a negligible change with slight shrinkage of external morphology was observed in r-javanicin treated cells. Confocal laser scanning microscopic analysis implied that the target(s) of r-javanicin is conceivably resided in the cell thereby allowing the peptide to penetrate across the membrane and accumulate throughout the fungal body. Finally, cryptococcal cells coped with r-javanicin were preliminarily investigated using label-free mass spectrometry-based proteomics. Combined with microscopic and proteomics analysis, it was clearly elucidated the peptide localized in the intracellular compartment where carbohydrate metabolism and energy production associated with glycolysis pathway and mitochondrial respiration, respectively, were principally interfered. Overall, r-javanicin would be an alternative candidate for further development of antifungal agents.

Towards understanding the novel adhesin function of Candida albicans phosphoglycerate mutase at the pathogen cell surface: some structural analysis of the interactions with human host extracellular matrix proteins

Although many atypical proteinaceous cell wall components that belong to a group of multitasking, "moonlighting" proteins, have been repeatedly identified in numerous pathogenic microorganisms, their novel extracellular functions and secretion mechanisms remain largely unrecognized. In Candida albicans, one of the most common fungal pathogens in humans, phosphoglycerate mutase (Gpm1) - a cytoplasmic enzyme involved in the glycolysis pathway - has been shown to occur on the cell surface and has been identified as a potentially important virulence factor. In this study, we demonstrated tight binding of C. albicans Gpm1 to the candidal cell surface, thus suggesting that the readsorption of soluble Gpm1 from the external environment could be a likely mechanism leading to the presence of this moonlighting protein on the pathogen surface. Several putative Gpm1-binding receptors on the yeast surface were identified. The affinities of Gpm1 to human vitronectin (VTR) and fibronectin (FN) were characterized with surface plasmon resonance measurements, and the dissociation constants of the complexes formed were determined to be in the order of 10–8 M. The internal Gpm1 sequence motifs, directly interacting with VTR (aa 116-158) and FN (aa 138-175) were mapped using chemical crosslinking and mass spectrometry. Synthetic peptides with matching sequences significantly inhibited formation of the Gpm1-VTR and Gpm1-FN complexes. A molecular model of the Gpm1-VTR complex was developed. These results provide the first structural insights into the adhesin function of candidal surface-exposed Gpm1.

PGK1 Promotes NSCLC Progression by Enhancing Aerobic Glycolysis and Activating AKT/ERK Signaling Pathway

Metabolic reprogramming, especially aerobic glycolysis is considered a hallmark of cancer, and is becoming a novel target for cancer therapy. Phosphoglycerate kinase I (PGK1) which is an important enzyme generating the first ATP in glycolysis pathway was already shown can promote some types of cancer development and progression, however, the role of PGK1 in lung cancer development is less reported. The aim of this study was to explore the mechanism of PGK1 in promoting non-small cell lung cancer (NSCLC) development and progression. Gene overexpression or silencing, scratch assay, Trans-well assay, western blot, immunohistochemistry, chromatin immunoprecipitation, real-time quantitative RT-PCR, MTT cell viability assay and mouse xenograft, glucose uptake, lactate secretion, ATP production and Extracellular Acidification Rate (ECAR) seahorse assay were performed to investigate the biological function and the underlying mechanism of PGK1 in NSCLC development. Our study found that PGK1 was high expressed in non-small cell lung cancer tissues, its expression is positive correlated with tumor grade and clinical stage and negative correlated with patients’ overall survival. Importantly, its expression was also associated with clinicopathological characteristics of lung cancer patients. Overexpression PGK1 could not only promote lung epithelial cell and tumor cell migration and proliferation in vitro, but also increase the tumor growth in vivo. Mechanically, PGK1 promotes NSCLC development and progression by activating AKT/ERK signaling pathway and altering aerobic glycolysis pathway. Meanwhile PGK1 was HIF1α downstream target gene and played an essential role in hypoxia-induced shift of glycolysis. In addition, the PGK1 expression was positive correlated with HIF1α expression in NSCLC tissues. Therefore, we concluded that PGK1 could be a biomarker for NSCLC diagnosis and outcome evaluation, and targeting PGK1 should be an innovative strategy for NSCLC therapy in the future.

Annotation of glycolysis, gluconeogenesis, and trehaloneogenesis pathways provide insight into carbohydrate metabolism in the Asian citrus psyllid

Citrus greening disease is caused by the pathogen Candidatus Liberibacter asiaticus, which is transmitted by the Asian citrus psyllid, Diaphorina citri. There is no curative treatment or significant prevention mechanism for this detrimental disease that causes continued economic losses from reduced citrus production. A high quality genome of D. citri is being manually annotated to provide accurate gene models required to identify novel control targets and increase understanding of this pest. Here, we annotated genes involved in glycolysis, gluconeogenesis, and trehaloneogenesis in the D. citri genome, as these are core metabolic pathways and suppression could reduce this pest. Specifically, twenty-five genes were identified and annotated in the glycolysis and gluconeogenesis pathways and seven genes for the trehaloneogenesis pathway. Comparative analysis showed that the glycolysis genes in D. citri are highly conserved compared to orthologs in other insect systems, but copy numbers vary in D. citri. Expression levels of the annotated gene models were analyzed and several enzymes in the glycolysis pathway showed high expression in the thorax. This is consistent with the primary use of glucose by flight muscles located in the thorax. A few of the genes annotated in D. citri have been targeted for gene knockdown as a proof of concept, for RNAi therapeutics. Thus, manual annotation of these core metabolic pathways provides accurate genomic foundations for developing gene-targeting therapeutics to reduce D. citri.

Blood-based untargeted metabolomics in Relapsing-Remitting Multiple Sclerosis revealed the testable therapeutic target

Metabolic aberrations impact the pathogenesis of multiple sclerosis (MS) and possibly can provide clues for new treatment strategies. Using untargeted metabolomics, we measured serum metabolites from 35 relapsing-remitting patients and 14 healthy age-matched controls. Out of 632 known metabolites detected, 60 were significantly altered in relapsing-remitting MS (RRMS). Bioinformatics analysis identified an altered metabotype in RRMS patients, represented by 4 changed metabolic pathways of glycerophospholipid, citrate cycle, sphingolipid, and pyruvate metabolism. Interestingly, the common upstream metabolic pathway feeding these 4 pathways is the glycolysis pathway. Real-time bioenergetic analysis of the patient derived peripheral blood mononuclear cells, showed enhanced glycolysis, supporting the altered metabolic state of immune cells. Experimental autoimmune encephalomyelitis mice treated with the glycolytic inhibitor, 2-deoxy-D-glucose ameliorated the disease progression and inhibited the disease pathology significantly by promoting the anti-inflammatory phenotype of monocytes/macrophage in the central nervous system. Our study suggests that targeting glycolysis offers a potential target for MS.

Recent Advances in the Development of Triose Phosphate Isomerase Inhibitors as Antiprotozoal Agents

Background: Parasitic diseases caused by protozoa such as Chagas disease, leishmaniasis, malaria, African trypanosomiasis, amebiasis, trichomoniasis, and giardiasis are considered serious public health problems in developing countries. Drug-resistance among parasites justifies the search for new therapeutic drugs and the identification of new targets becomes a valuable approach. In this scenario, glycolysis pathway which consists of the conversion of glucose into pyruvate plays an important role in the protozoa energy supply and it is therefore considered as a promising target. In this pathway, triose phosphate isomerase (TIM) plays an essential role in efficient energy production. Furthermore, protozoa TIM show structural differences with human enzyme counterparts suggesting the possibility of obtaining selective inhibitors. Therefore, TIM is considered a valid approach to develop new antiprotozoal agents, inhibiting the glycolysis in the parasite. Objective: In this review, we discuss the drug design strategies, structure-activity relationship, and binding modes of outstanding TIM inhibitors against Trypanosoma cruzi, Trypanosoma brucei, Plasmodium falciparum, Giardia lamblia, Leishmania mexicana, Trichomonas vaginalis, and Entamoeba histolytica. Results: TIM inhibitors showed mainly aromatic systems and symmetrical structure, where the size and type of heteroatom are important for enzyme inhibition. This inhibition is mainly based on the interaction with i) the interfacial region of TIM inducing changes on the quaternary and tertiary structure or ii) with the TIM catalytic region were the main pathways that disabled the catalytic activity of the enzyme. Conclusion: Benzothiazole, benzoxazole, benzimidazole, and sulfhydryl derivatives stand out as TIM inhibitors. In silico and in vitro studies demonstrate that the inhibitors bind mainly at the TIM dimer interface. In this review, the development of new TIM inhibitors as antiprotozoal drugs is demonstrated as an important pharmaceutical strategy that may lead to new therapies for these ancient parasitic diseases.

Metabolomic Characterization Reveals ILF2 and ILF3 Affected Metabolic Adaptions in Esophageal Squamous Cell Carcinoma

Esophageal cancer (EC) is a common malignant disease in eastern countries. However, a study of the metabolomic characteristics associated with other biological factors in esophageal squamous cell carcinoma (ESCC) is limited. Interleukin enhancer binding factor 2 (ILF2) and ILF3, double-stranded RNA-binding proteins, have been reported to contribute to the occurrence and development of various types of malignancy. Nevertheless, the underlying functions of ILF2 and ILF3 in ESCC metabolic reprogramming have never been reported. This study aimed to contribute to the metabolic characterization of ESCC and to investigate the metabolomic alterations associated with ILF2 and ILF3 in ESCC tissues. Here, we identified 112 differential metabolites, which were mainly enriched in phosphatidylcholine biosynthesis, fatty acid metabolism, and amino acid metabolism pathways, based on liquid chromatography–mass spectrometry and capillary electrophoresis–mass spectrometry approaches using ESCC tissues and paired para-cancer tissues from twenty-eight ESCC patients. In addition, ILF2 and ILF3 expression were significantly elevated in EC tissues compared to the histologically normal samples, and closely associated with PI3K/AKT and MAPK signaling pathways in ESCC. Moreover, in ESCC tissues with a high ILF2 expression, several short-chain acyl-carnitines (C3:0, C4:0, and C5:0) related to the BCAA metabolic pathway and long-chain acyl-carnitines (C14:0, C16:0, C16:0-OH, and C18:0) involved in the oxidation of fatty acids were obviously upregulated. Additionally, a series of intermediate metabolites involved in the glycolysis pathway, including G6P/F6P, F1,6BP, DHAP, G3P, and 2,3BPG, were remarkably downregulated in highly ILF3-expressed ESCC tissues compared with the corresponding para-cancer tissues. Overall, these findings may provide evidence for the roles of ILF2 and ILF3 during the process of ESCC metabolic alterations, and new insights into the development of early diagnosis and treatment for ESCC. Further investigation is needed to clarify the underlying mechanism of ILF2 and ILF3 on acyl-carnitines and the glycolysis pathway, respectively.