The cyanobacterial circadian clock has three relatively independent parts: the input path, the core oscillator, and the output path. The core oscillator is composed of three clock proteins: KaiA, KaiB, and KaiC. The interactions among these three proteins generate a rhythmic signal and convey the input signals to the output signals to maintain the accuracy and stability of the oscillation of downstream signals. Based on the cyanobacterial circadian clock and the structure, function, and interaction of the clock proteins of the core oscillator, combining the recent results from our laboratory, this review summarized the recent progresses of the molecular mechanism of KaiA in regulating KaiC's enzymatic activity, mediating phase reset of the oscillator, and competing with CikA for the binding site of KaiB.
Bacterial Proteins ; genetics ; metabolism ; Circadian Clocks ; genetics ; Circadian Rhythm Signaling Peptides and Proteins ; metabolism ; Cyanobacteria ; genetics ; Enzyme Activation ; genetics

Adenosine 5'-monophosphate-activated protein activated protein kinase (AMPK), a heterotrimeric complex, is an important kinase to regulate glycolipid metabolism and energy balance involved in a variety physiological processes in human body. Many research indicated that the function and activity of AMPK were closely related to inflammation, diabetes and cancers. Recent reports show that inhibition of metformin (a first-line drug) on hepatic glucose in patients with hyperglycemia is associated with AMPK pathway, suggesting that targeting AMPK may be one of the effective strategies for the prevention and treatment of a variety of chronic diseases. Here, we review research progress on the structure, activation and regulation of AMPK in glycolipid metabolism to provide an insight into the basic and clinical research of diabetes therapy.
AMP-Activated Protein Kinases ; Adenosine ; Adenosine Monophosphate ; Energy Metabolism ; Enzyme Activation ; Glycolipids ; Humans

OBJECTIVE: To investigate the effects of millimeter wave (MMW) exposure on apoptosis of human melanoma A375 cells and explore the mechanisms. METHODS: Through electromagnetic field calculation we simulated MMW exposure in cells and calculated the specific absorption rate (SAR). The optimal irradiation parameters were determined according to the uniformity and intensity of the SAR. A375 cells were then exposed to MMV for 15, 30, 60, or 90 min, with or without pretreatment with the caspase-3 inhibitor AC-DEVD-fmk (10 μmol/L) for 1 h at 90 min before the exposure. CCK-8 assay was used to assess the changes in the viability and Annexin-V/ PI staining was used to detect the apoptosis of the cells following the exposures; Western blotting was used to detect the expression of caspase-3 in the cells. RESULTS: The results of electromagnetic field calculation showed that for optimal MMV exposure, the incident field needed to be perpendicular to the bottom of the plastic Petri dish with the antenna placed below the dish. CCk-8 assay showed that MMW exposure significantly inhibited the cell viability in a time-dependent manner ( < 0.05); exposures for 15, 30, 60, and 90 min all resulted in significantly increased apoptosis of the cells ( < 0.05). The cells with MMW exposure showed significantly increased expression of caspase-3. The inhibitory effect of MMW on the cell viability was antagonized significantly by pretreatment of the cells with AC-DEVD-fmk ( < 0.05), which increased the cell viability rate from (36.7±0.09)% to (59.8±0.06)% ( < 0.05). CONCLUSIONS 35.2 GHz millimeter wave irradiation induces apoptosis in A375 cells by activating the caspase-3 protein.
Apoptosis ; Caspase 3 ; metabolism ; Caspase Inhibitors ; pharmacology ; Cell Line, Tumor ; Cell Survival ; Electromagnetic Fields ; Enzyme Activation ; Humans ; Magnetic Field Therapy ; Melanoma ; enzymology ; pathology ; therapy ; Time Factors

Rifamycins, a group of bacterial RNA polymerase inhibitors, are the firstline antimicrobial drugs to treat tuberculosis. In light of the emergence of rifamycinresistant bacteria, development of new RNA polymerase inhibitors that kill rifamycinresistant bacteria with high bioavailability is urgent. Structural analysis of bacterial RNA polymerase in complex with inhibitors by crystallography and cryo-EM indicates that RNA polymerase inhibitors function through five distinct molecular mechanisms:inhibition of the extension of short RNA; competition with substrates; inhibition of the conformational change of the'bridge helix'; inhibition of clamp opening;inhibition of clamp closure. This article reviews the research progress of these five groups of RNA polymerase inhibitors to provide references for the modification of existing RNA polymerase inhibitors and the discovery of new RNA polymerase inhibitors.
Antitubercular Agents ; therapeutic use ; Bacteria ; drug effects ; enzymology ; DNA-Directed RNA Polymerases ; metabolism ; Drug Discovery ; trends ; Drug Resistance, Bacterial ; Enzyme Activation ; drug effects ; Enzyme Inhibitors ; pharmacology ; Humans ; RNA, Bacterial ; Tuberculosis ; drug therapy ; enzymology

AMP-activated protein kinase (AMPK) is a key enzyme in the regulation of cellular energy homeostasis. Recent studies demonstrated that AMPK also plays an important role in the modulation of inflammation, an energy-intensive molecular response. The commonly used AMPK activators include 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and A-769662. In addition, the biological activities of metformin and adiponectin are closely related to activation of AMPK. Numerous studies have shown that these AMPK activators play an effectively protective role in animal models of acute lung injury, asthma, colitis, hepatitis, atherosclerosis and other inflammatory diseases. Therefore, AMPK activators may have promising potential for the prevention and treatment of inflammation related diseases.
AMP-Activated Protein Kinases ; physiology ; Adiponectin ; pharmacology ; Aminoimidazole Carboxamide ; pharmacology ; Animals ; Enzyme Activation ; Inflammation ; enzymology ; Metformin ; pharmacology ; Pyrones ; pharmacology ; Thiophenes ; pharmacology

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) involves dysregulation of the complement system, but whether this also occurs in thrombotic thrombocytopenic purpura (TTP) remains unclear. Although these conditions are difficult to differentiate clinically, TTP can be distinguished by low (<10%) ADAMTS13 activity. The aim was to identify the differences in complement activation products between TTP and aHUS and investigate ADAMTS13 activity as a prognostic factor in aHUS. METHODS: We analyzed patients with thrombotic microangiopathy diagnosed as TTP (N=48) or aHUS (N=50), selected from a Korean registry (N=551). Complement activation products in the plasma samples collected from the patients prior to treatment and in 40 healthy controls were measured by ELISA. RESULTS: The levels of generalized (C3a), alternate (factor Bb), and terminal (C5a and C5b-9) markers were significantly higher (all P<0.01) in the patients than in the healthy controls. Only the factor Bb levels significantly differed (P=0.008) between the two disease groups. In aHUS patients, high normal ADAMTS13 activity (≥77%) was associated with improved treatment response (OR, 6.769; 95% CI, 1.605–28.542; P=0.005), remission (OR, 6.000; 95% CI, 1.693–21.262; P=0.004), exacerbation (OR, 0.242; 95% CI, 0.064–0.916; P=0.031), and disease-associated mortality rates (OR, 0.155; 95% CI, 0.029–0.813; P=0.017). CONCLUSION: These data suggest that complement biomarkers, except factor Bb, are similarly activated in TTP and aHUS patients, and ADAMTS13 activity can predict the treatment response and outcome in aHUS patients.
Atypical Hemolytic Uremic Syndrome ; Biomarkers ; Complement Activation ; Complement System Proteins ; Enzyme-Linked Immunosorbent Assay ; Humans ; Mortality ; Plasma ; Purpura, Thrombotic Thrombocytopenic ; Thrombotic Microangiopathies

Objective To evaluate the antagonistic effects of N-acetylcysteine (NAC) on mitogen-activated protein kinases (MAPK) pathway activation, oxidative stress and inflammatory responses in rats with lung injury induced by fine particulate matter (PM_2.5). Methods Forty eight male Wistar rats were randomly divided into six groups: blank control group (C1), water drip control group (C2), PM_2.5 exposed group (P), low-dose NAC treated and PM_2.5 exposed group (L), middle-dose NAC treated and PM_2.5 exposed group (M), and high-dose NAC treated and PM_2.5 exposed group (H). PM_2.5 suspension (7.5 mg/kg) was administered tracheally once a week for four times. NAC of 125 mg/kg, 250 mg/kg and 500 mg/kg was delivered intragastrically to L, M and H group respectively by gavage (10 ml/kg) for six days before PM_2.5 exposure. The histopathological changes and human mucin 5 subtype AC (MUC5AC) content in lung tissue of rats were evaluated. We investigated IL-6 in serum and bronchoalveolar lavage fluid (BALF) by Enzyme-linked immunosorbent assay (ELISA), MUC5AC in lung tissue homogenate by ELISA, glutathione peroxidase (GSH-PX) in serum and BALF by spectrophotometry, and the expression of p-ERK1/2, p-JNK1/2 and p-p38 proteins by Western blot. All the measurements were analyzed and compared statistically. Results Lung tissue of rats exposed to PM_2.5 showed histological destruction and increased mucus secretion of bronchial epithelial cells. Rats receiving NAC treatment showed less histological destruction and mucus secretion. Of P, L, M and H group, MUC5AC in lung tissue, IL-6 in serum and BALF were higher than controls (C1 and C2) (all P<0.05), with the highest levels found in the P group and a decreasing trend with increase of NAC dose. The activity of GSH-PX in serum and BALF of PM_2.5 exposed rats (P, L, M and H) was lower than that of controls (all P<0.05), with higher activities found in NAC treated rats (L, M, and H), and an increasing trend with increase of NAC dose. The expressions of p-ERK1/2, p-JNK1/2 and p-p38 proteins in PM_2.5 exposed lung tissue (P, L, M and H) was higher than controls (all P<0.05), with decreased levels and dose dependent downregulation found in NAC treated rats. Conclusion NAC can antagonize major MAPK pathway activation, lung oxidative stress and inflammatory injury induced by PM_2.5 in rats.
Acetylcysteine/pharmacology* ; Animals ; Bronchoalveolar Lavage Fluid ; Enzyme Activation/drug effects* ; Glutathione Peroxidase/metabolism* ; Inflammation/pathology* ; Interleukin-6/metabolism* ; Lung/pathology* ; Lung Injury/pathology* ; Male ; Mitogen-Activated Protein Kinases/metabolism* ; Mucin 5AC/metabolism* ; Mucus/metabolism* ; Oxidative Stress/drug effects* ; Particle Size ; Particulate Matter/toxicity* ; Phosphorylation/drug effects* ; Rats, Wistar

Gnaphalium affine D. Don, a medicinal and edible plant, has been used to treat gout in traditional Chinese medicine and popularly consumed in China for a long time. A detailed phytochemical investigation on the aerial part of G. affine led to the isolation of two new esters of caffeoylquinic acid named (-) ethyl 1, 4-di-O-caffeoylquinate (1) and (-) methyl 1, 4-di-O-caffeoylquinate (2), together with 35 known compounds (3-37). Their structures were elucidated by spectroscopic data and first-order multiplet analysis. All the isolated compounds were tested for their xanthine oxidase inhibitory activity with an in vitro enzyme inhibitory screening assay. Among the tested compounds, 1 (IC 11.94 μmol·L) and 2 (IC 15.04 μmol·L) showed a good inhibitory activity. The current results supported the medical use of the plant.
Adenine ; analogs & derivatives ; chemistry ; isolation & purification ; Drugs, Chinese Herbal ; chemistry ; pharmacology ; Enzyme Activation ; drug effects ; Flavonoids ; chemistry ; isolation & purification ; Gnaphalium ; chemistry ; Gout Suppressants ; chemistry ; isolation & purification ; pharmacology ; Hydroxybenzoates ; chemistry ; isolation & purification ; Molecular Structure ; Nuclear Magnetic Resonance, Biomolecular ; Phytochemicals ; chemistry ; isolation & purification ; pharmacology ; Plant Components, Aerial ; chemistry ; Plant Extracts ; chemistry ; isolation & purification ; pharmacology ; Quinic Acid ; analogs & derivatives ; chemistry ; isolation & purification ; Xanthine Oxidase ; antagonists & inhibitors

Hyperphosphorylated tau is the major protein component of neurofibrillary tangles in the brains of patients with Alzheimer's disease (AD). However, the mechanism underlying tau hyperphosphorylation is not fully understood. Here, we demonstrated that exogenously expressed wild-type human tau40 was detectable in the phosphorylated form at multiple AD-associated sites in cytoplasmic and nuclear fractions from HEK293 cells. Among these sites, tau phosphorylated at Thr205 and Ser214 was almost exclusively found in the nuclear fraction at the conditions used in the present study. With the intracellular tau accumulation, the Ca concentration was significantly increased in both cytoplasmic and nuclear fractions. Further studies using site-specific mutagenesis and pharmacological treatment demonstrated that phosphorylation of tau at Thr205 increased nuclear Ca concentration with a simultaneous increase in the phosphorylation of Ca/calmodulin-dependent protein kinase IV (CaMKIV) at Ser196. On the other hand, phosphorylation of tau at Ser214 did not significantly change the nuclear Ca/CaMKIV signaling. Finally, expressing calmodulin-binding protein-4 that disrupts formation of the Ca/calmodulin complex abolished the okadaic acid-induced tau hyperphosphorylation in the nuclear fraction. We conclude that the intracellular accumulation of phosphorylated tau, as detected in the brains of AD patients, can trigger nuclear Ca/CaMKIV signaling, which in turn aggravates tau hyperphosphorylation. Our findings provide new insights for tauopathies: hyperphosphorylation of intracellular tau and an increased Ca concentration may induce a self-perpetuating harmful loop to promote neurodegeneration.
Alzheimer Disease ; metabolism ; pathology ; Calcium ; metabolism ; Calcium-Calmodulin-Dependent Protein Kinase Type 4 ; metabolism ; Cell Nucleus ; metabolism ; Enzyme Activation ; physiology ; HEK293 Cells ; Humans ; Neurons ; metabolism ; pathology ; Phosphorylation ; Signal Transduction ; physiology ; tau Proteins ; metabolism

Peroxynitrite is a highly reactive nitrogen species and a potent inducer of apoptosis and necrosis in somatic cells. Peroxynitrite-induced nitrosative stress has emerged as a major cause of impaired sperm function; however, its ability to trigger cell death has not been described in human spermatozoa. The objective here was to characterize biochemical and morphological features of cell death induced by peroxynitrite-mediated nitrosative stress in human spermatozoa. For this, spermatozoa were incubated with and without (untreated control) 3-morpholinosydnonimine (SIN-1), in order to generate peroxynitrite. Sperm viability, mitochondrial permeability transition (MPT), externalization of phosphatidylserine, DNA oxidation and fragmentation, caspase activation, tyrosine nitration, and sperm ultrastructure were analyzed. The results showed that at 24 h of incubation with SIN-1, the sperm viability was significantly reduced compared to untreated control (P < 0.001). Furthermore, the MPT was induced (P < 0.01) and increment in DNA oxidation (P < 0.01), DNA fragmentation (P < 0.01), tyrosine nitration (P < 0.0001) and ultrastructural damage were observed when compared to untreated control. Caspase activation was not evidenced, and although phosphatidylserine externalization increased compared to untreated control (P < 0.001), this process was observed in <10% of the cells and the gradual loss of viability was not characterized by an important increase in this parameter. In conclusion, peroxynitrite-mediated nitrosative stress induces the regulated variant of cell death known as MPT-driven necrosis in human spermatozoa. This study provides a new insight into the pathophysiology of nitrosative stress in human spermatozoa and opens up a new focus for developing specific therapeutic strategies to better preserve sperm viability or to avoid cell death.
Adult ; Caspases/metabolism* ; Cell Death ; Enzyme Activation ; Humans ; Male ; Mitochondria/pathology* ; Necrosis ; Nitrosative Stress/physiology* ; Permeability ; Peroxynitrous Acid/pharmacology* ; Phosphatidylserines/metabolism* ; Spermatozoa/ultrastructure*