PKM2 functions as a histidine kinase to phosphorylate PGAM1 and increase glycolysis shunts in cancer.

Phosphoglycerate mutase 1 (PGAM1) is a key node enzyme that diverts the metabolic reactions from glycolysis into its shunts to support macromolecule biosynthesis for rapid and sustainable cell proliferation. It is prevalent that PGAM1 activity is upregulated in various tumors; however, the underlying mechanism remains unclear. Here, we unveil that pyruvate kinase M2 (PKM2) moonlights as a histidine kinase in a phosphoenolpyruvate (PEP)-dependent manner to catalyze PGAM1 H11 phosphorylation, that is essential for PGAM1 activity. Moreover, monomeric and dimeric but not tetrameric PKM2 are efficient to phosphorylate and activate PGAM1. In response to epidermal growth factor signaling, Src-catalyzed PGAM1 Y119 phosphorylation is a prerequisite for PKM2 binding and the subsequent PGAM1 H11 phosphorylation, which constitutes a discrepancy between tumor and normal cells. A PGAM1-derived pY119-containing cell-permeable peptide or Y119 mutation disrupts the interaction of PGAM1 with PKM2 and PGAM1 H11 phosphorylation, dampening the glycolysis shunts and tumor growth. Together, these results identify a function of PKM2 as a histidine kinase, and illustrate the importance of enzyme crosstalk as a regulatory mode during metabolic reprogramming and tumorigenesis.

Cysteine and homocysteine can be exploited by GPX4 in ferroptosis inhibition independent of GSH synthesis.

Ferroptosis is inhibited by glutathione peroxidase 4 (GPX4), an antioxidant enzyme that uses reduced glutathione (GSH) as a cofactor to detoxify lipid hydroperoxides. As a selenoprotein, the core function of GPX4 is the thiol-dependent redox reaction. In addition to GSH, other small molecules such as cysteine and homocysteine also contain thiols; yet, whether GPX4 can exploit cysteine and homocysteine to directly detoxify lipid hydroperoxides and inhibit ferroptosis has not been addressed. In this study, we found that cysteine and homocysteine inhibit ferroptosis in a GPX4-dependent manner. However, cysteine inhibits ferroptosis independent of GSH synthesis, and homocysteine inhibits ferroptosis through non-cysteine and non-GSH pathway. Furthermore, we used molecular docking and GPX4 activity analysis to study the binding patterns and affinity between GPX4 and GSH, cysteine, and homocysteine. We found that besides GSH, cysteine and homocysteine are also able to serve as substrates for GPX4 though the affinities of GPX4 with cysteine and homocysteine are lower than that with GSH. Importantly, GPX family and the GSH synthetase pathway might be asynchronously evolved. When GSH synthetase is absent, for example in Flexibacter, the fGPX exhibits higher affinity with cysteine and homocysteine than GSH. Taken together, the present study provided the understanding of the role of thiol-dependent redox systems in protecting cells from ferroptosis and propose that GSH might be a substitute for cysteine or homocysteine to be used as a cofactor for GPX4 during the evolution of aerobic metabolism.

ACLY ubiquitination by CUL3-KLHL25 induces the reprogramming of fatty acid metabolism to facilitate iTreg differentiation.

Inducible regulatory T (iTreg) cells play a central role in immune suppression. As iTreg cells are differentiated from activated T (Th0) cells, cell metabolism undergoes dramatic changes, including a shift from fatty acid synthesis (FAS) to fatty acid oxidation (FAO). Although the reprogramming in fatty acid metabolism is critical, the mechanism regulating this process during iTreg differentiation is still unclear. Here we have revealed that the enzymatic activity of ATP-citrate lyase (ACLY) declined significantly during iTreg differentiation upon transforming growth factor ß1 (TGFß1) stimulation. This reduction was due to CUL3-KLHL25-mediated ACLY ubiquitination and degradation. As a consequence, malonyl-CoA, a metabolic intermediate in FAS that is capable of inhibiting the rate-limiting enzyme in FAO, carnitine palmitoyltransferase 1 (CPT1), was decreased. Therefore, ACLY ubiquitination and degradation facilitate FAO and thereby iTreg differentiation. Together, we suggest TGFß1-CUL3-KLHL25-ACLY axis as an important means regulating iTreg differentiation and bring insights into the maintenance of immune homeostasis for the prevention of immune diseases.

Butyrate enhances CPT1A activity to promote fatty acid oxidation and iTreg differentiation.

Inducible regulatory T (iTreg) cells play a crucial role in immune suppression and are important for the maintenance of immune homeostasis. Mounting evidence has demonstrated connections between iTreg differentiation and metabolic reprogramming, especially rewiring in fatty acid oxidation (FAO). Previous work showed that butyrate, a specific type of short-chain fatty acid (SCFA) readily produced from fiber-rich diets through microbial fermentation, was critical for the maintenance of intestinal homeostasis and capable of promoting iTreg generation by up-regulating histone acetylation for gene expression as an HDAC inhibitor. Here, we revealed that butyrate could also accelerate FAO to facilitate iTreg differentiation. Moreover, butyrate was converted, by acyl-CoA synthetase short-chain family member 2 (ACSS2), into butyryl-CoA (BCoA), which up-regulated CPT1A activity through antagonizing the association of malonyl-CoA (MCoA), the best known metabolic intermediate inhibiting CPT1A, to promote FAO and thereby iTreg differentiation. Mutation of CPT1A at Arg243, a reported amino acid required for MCoA association, impaired both MCoA and BCoA binding, indicating that Arg243 is probably the responsible site for MCoA and BCoA association. Furthermore, blocking BCoA formation by ACSS2 inhibitor compromised butyrate-mediated iTreg generation and mitigation of mouse colitis. Together, we unveil a previously unappreciated role for butyrate in iTreg differentiation and illustrate butyrate-BCoA-CPT1A axis for the regulation of immune homeostasis.

[Analysis of blood lead level and its influencing factors of workers in one lead acid storage cell enterprise].

OBJECTIVE: To understand the blood lead level and its influencing factors of workers in one lead acid storage cell enterprise in Jiangsu Province. METHODS: An occupational health field investigation was done to this storage cell enterprise at the end of June 2011 to measure the air lead fume (dust) concentration of workplaces. Health-care information of 1364 person-times from 2009 - 2011 was collected, including blood lead level, general state of health, life and health habit. One way ANOVA and ordinal multi-categorical logistic stepwise regression were used to analysis the influencing factors of blood lead level. RESULTS: The lead fume concentration range was 0.008-0.354 mg/m(3) among 12 measuring points, which 7 places were unqualified, while the concentration range of lead dust was 0.023 - 2.432 mg/m(3), 24 out of 27 measuring places were unqualified, both the qualified rate were low. The blood lead concentration of objects was (259.54 ± 106.62) µg/L, among which 96 people (7.04%) who ≥ 400 µg/L should be identified as suspected "observation object", blood lead concentration ≥ 600 µg/L was not found. The blood lead concentration of male (279.76 ± 114.93 µg/L) was significantly higher than female (242.44 ± 95.86) µg/L (t = 6.441, P < 0.01). The proportion of ≥ 400 µg/L in male (11.04%, 69/625) was significantly higher than female (3.65%, 27/739) (χ(2) = 28.237, P < 0.01). The blood lead concentration of workers who exposed to lead fume or dust (265.93 ± 103.70) µg/L was significantly higher than those of not exposed to lead (205.30 ± 115.62) µg/L (t = -6.037, P < 0.01), the blood lead concentration of workers who exposed to lead dust was (267.38 ± 98.02) µg/L significantly higher than those of exposed to lead fume (260.81 ± 121.80) µg/L (t = -2.408, P < 0.05). The proportion of ≥ 400 µg/L in workers who exposed to lead fume (dust) (7.60%, 93/1223) was significantly higher than those of not exposed to lead (2.13%, 3/141) (χ(2) = 4.538, P < 0.05). Ordinal multi-categorical logistic stepwise regression found that the lead fume concentration ≥ 0.03 mg/m(3), lead dust concentration ≥ 0.05 mg/m(3) (OR = 1.59, 95%CI: 1.06 - 2.39), length of service ≥ 3 years (OR = 1.82, 95%CI: 1.12 - 2.98), smoking (OR = 2.06, 95%CI: 1.27 - 3.37) can increase the level of blood lead concentration. CONCLUSIONS: Lead dust concentration of the enterprise exceeded the standard. Workers exposed to lead fume (dust) have more occupational health hazard of lead, of whom the blood lead concentration was high. Higher lead fume (dust) concentration in workplace, longer length of service, smoking were risk factors of high blood lead concentration.

[Detecting the nitrogen oxide in air with portable infrared spectrometer].

OBJECTIVE: To establish a method for rapid detecting nitric oxide (NO) and nitrogen dioxide(NO2) in the workplace air with infrared spectrometer. METHODS: The method of infrared spectrometer was developed to detect nitrogen oxide in laboratory, then applied to detect the concentration of nitrogen oxide in workplace air. The present method was compared with National Standard Methods. RESULTS: NO and NO2 in air were detected simultaneously with the infrared spectrometer, not interfering each other. In standard condition, the minimum detectable concentrations of NO and NO2 were 0.67 and 1.03 mg/m3, the inferior limits of concentrations were 0.67 and 1.03 mg/m3 respectively. When the concentrations of NO and NO2 were 0.67-133.93 mg/m3 and 1.03-102.68 mg/m3, the accuracy and precision of detection were higher. As compared with National Standard Methods, the ratio of the results of two methods was 86.96% and 112.56%. CONCLUSION: The method of infrared spectrometer is a rapid, simple and accurate method for detecting the concentrations of nitrogen oxide in the workplace air.