The hills and valleys of calcium signaling

正Calcium is important for life.Studies over the last several decades have gradually revealed the critical involvement of calcium,especially its ionic form(Ca~(2+)),in every aspect of life forms on earth.Among them,a great deal of work has been done to illustrate how Ca2+levels are regulated in the cytoplasm and how many of the cytosolic enzymes and sig-     

Ca~(2 )-Calmodulin is Involved in Betacyanin Accumulation Induced by Dark in C_3 Halophyte Suaeda salsa

The C_3 halophyte Suaeda salsa was used to investigate the roles of Ca~(2 ),Ca~(2 )channels,and calmodulin(CAM)in betacyaninmetabolism.Seeds of S.salsa were cultured in both the dark and light for 3 days.The fresh weight and betacyanin contentwere much higher in S.salsa seedlings formed in the dark than in seedlings formed in the light.The addition of Ca~(2 )tothe half-strength MS nutrient solution promoted betacyanin accumulation in the dark,whereas Ca~(2 )depletion by EGTAsuppressed the dark-induced betacyanin accumulation in shoots of S.salsa.The Ca~(2 )channel blocker LaCl_3 also inhibiteddark-induced betacyanin accumulation.The highest activity of CaM and the maximum betacyanin content decreased by51% and 45%,respectively,in shoots of S.salsa seedlings treated with the potent CaM antagonist chlorpromazine in thedark.Furthermore,the other CaM antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide(W-7)also inhibited theactivity of CaM and dark-dependent betacyanin accumulation,whereas its less active structural analog N-(6-aminohexyl)-1-naphthalenesulfonamide(W-5)had little effect on the responses to dark of S.salsa seedlings.These results suggest thatCa~(2 ),Ca~(2 )-regulated ion channels,and CaM play an important role in dark-induced betacyanin accumulation in the shootsof the C_3 halophyte S.salsa.     

建设硒学桥梁,助力中国硒学走向世界(英文)

<正>Selenium(Se)was discovered by Swedish chemist Jacob Berzelius(1779-1848)on 1817 and has become one of the most influential natural-occurring trace elements for humans,animals,and even plaints.Till now,it is recognized that two Se-containing amino acids-selenomethionine(SeMet)and selenocysteine(SeCys)are involved in the regulation of two important enzymes families-glutathione peroxidases and thioredoxin reductases.These enzymes play important roles in human physiology,especially in protection from oxidative damage and regulation of intracellular redox state and thyroid hormone metabolism.However,low     

OsHK3 is a crucial regulator of abscisic acid signaling involved in antioxidant defense in rice

In this study, the role of the rice(Oryza sativa L.)histidine kinase Os HK3 in abscisic acid(ABA)-induced antioxidant defense was investigated. Treatments with ABA, H2O2,and polyethylene glycol(PEG) induced the expression of Os HK3 in rice leaves, and H2O2 is required for ABA-induced increase in the expression of Os HK3 under water stress. Subcellular localization analysis showed that Os HK3 is located in the cytoplasm and the plasma membrane. The transient expression analysis and the transient RNA interference test in rice protoplasts showed that Os HK3 is required for ABA-induced upregulation in the expression of antioxidant enzymes genes and the activities of antioxidant enzymes. Further analysis showed that Os HK3 functions upstream of the calcium/calmodulin-dependent protein kinase Os DMI3 and the mitogen-activated protein kinase Os MPK1 to regulate the activities of antioxidant enzymes in ABA signaling. Moreover, Os HK3was also shown to regulate the expression of nicotinamide adenine dinucleotide phosphate oxidase genes, Osrboh B and Osrboh E, and the production of H2O2 in ABA signaling. Our data indicate that Os HK3 play an important role in the regulation of ABA-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling.     

Alpha-latrotoxin Triggers Extracellular Ca^2＋-dependent Exocytosis and Sensitizes Fusion Machinery in Endocrine Cells

α-Latrotoxin from the venom of black widow spider induces and augments neurotransmitterand hormone release by way of extracellular Ca~(2 ) influx and cellular signal transduction pathways.By usingwhole cell current and capacitance recording,the photolysis of card Ca~(2 ),and Ca~(2 ) microfluorometry andamperometry,we investigated the stimulating effect and mechá(?)ism of α-latrotoxin on exocytosis in ratpancreatic β cells,LβT2 cells and latrophilin plasmid-transfected INS-1 cells.Our data indicated that:(1)α-latrotoxin increased cytosolic Ca~(2 ) concentration through the formation of cation-permitting pores and sub-sequent Ca~(2 ) influx with the presence of extracellular Ca~(2 );(2)α-latrotoxin stimulated exocytosis in normalbath solution and its stimulating effect on secretion was eradicated in Ca~(2 )-free bath solution; and (3)α-latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increasedthe response of cells to Ca~(2 ) photolysed by a flash of ultraviolet light.In summary,α-latrotoxin inducedexocytosis by way of Ca~(2 ) influx and accelerated vesicle fusion by the sensitization of fusion machinery.     

Analysis of essential histidine residues of maize branching enzymes by chemical modification and site-directed mutagenesis

Incubation of maize branching enzyme, mBEI and mBEII, with 100 μM diethylpyrocarbonate (DEPC) rapidly inactivated the enzymes. Treatment of the DEPC-inactivated enzymes with 100–500 mM hydroxylamine restored the enzyme activities. Spectroscopic data indicated that the inactivation of BE with DEPC was the result of histidine modification. The addition of the substrate amylose or amylopectin retarded the enzyme inactivation by DEPC, suggesting that the histidine residues are important for substrate binding. In maize BEII, conserved histidine residues are in catalytic regions 1 (His320) and 4 (His508). His320 and His508 were individually replaced by Ala via site-directed mutagenesis to probe their role in catalysis. Expression of these mutants inE. coli showed a significant decrease of the activity and the mutant enzymes hadK _m values 10 times higher than the wild type. Therefore, residues His320 and His508 do play an important role in substrate binding.     

The gap junctional intercellular communication is no prerequisite for the stabilization of xenobiotic metabolizing enzyme activities in primary rat liver parenchymal cells in vitro

Summary In primary monocultures of adult rat liver parenchymal cells (PC), the activities of the xenobiotic metabolizing enzymes microsomal epoxide hydrolase (mEH_b), soluble epoxide hydrolase (sEH), glutathione S-transferases (GST), and phenolsulfotransferase (ST) were reduced after 7 d to values below 33% of the initial activities. Furthermore, the gap junctional intercellular communication (GJIC), measured after microinjection by dye transfer, decreased from 90% on Day 1 to undetectable values after 5 d in monoculture. Co-culture of PC with nonparenchymal rat liver epithelial cells (NEC) increased (98% on Day 1) and stabilized (82% on Day 7) the homotypic GJIC of PC. Additionally, most of the measured xenobiotic metabolizing enzyme activities were well stabilized over 1 wk in co-culture. Because GJIC is one of several mechanisms playing an important role in cell differentiation, the importance of GJIC for the stabilization of xenobiotic metabolizing enzymes in PC was investigated. PC in monoculture were, therefore, treated with 2% dimethyl sulfoxide (DMSO), a differentiation promoting factor, and 1,1,1-trichloro-2,2,-bis (p-chlorophenyl) ethane (DDT) (10 μg/ml), a liver tumor promotor and inhibitor of GJIC, was given to co-cultures of PC with NEC. DMSO significantly stabilized (68% on Day 7), while DDT significantly inhibited (8% on Day 7) homotypic GJIC of PC in the respective culture systems. In contrast, the activities of mEH_b, sEH, GST, and ST were not affected in the presence of DMSO or DDT. These results lead to the assumption that the differentiation parameters measured in this study (i.e., homotypic GJIC and the activities of xenobiotic metabolizing enzymes) are independently regulated in adult rat liver PC.     

The role of TRPP2 in agonist-induced gallbladder smooth muscle contraction

TRPP2 channel protein belongs to the superfamily of transient receptor potential(TRP) channels and is widely expressed in various tissues, including smooth muscle in digestive gut. Accumulating evidence has demonstrated that TRPP2 can mediate Ca~(2+) release from Ca~(2+) stores. However, the functional role of TRPP2 in gallbladder smooth muscle contraction still remains unclear. In this study, we used Ca~(2+) imaging and tension measurements to test agonist-induced intracellular Ca~(2+) concentration increase and smooth muscle contraction of guinea pig gallbladder, respectively. When TRPP2 protein was knocked down in gallbladder muscle strips from guinea pig, carbachol(CCh)-evoked Ca~(2+) release and extracellular Ca~(2+) influx were reduced significantly, and gallbladder contractions induced by endothelin 1 and cholecystokinin were suppressed markedly as well. CCh-induced gallbladder contraction was markedly suppressed by pretreatment with U73122, which inhibits phospholipase C to terminate inositol 1,4,5-trisphosphate receptor(IP3) production, and 2-aminoethoxydiphenyl borate(2APB), which inhibits IP3 recepor(IP3R) to abolish IP3R-mediated Ca~(2+) release. To confirm the role of Ca~(2+) release in CCh-induced gallbladder contraction, we used thapsigargin(TG)-to deplete Ca~(2+) stores via inhibiting sarco/endoplasmic reticulum Ca~(2+)-ATPase and eliminate the role of store-operated Ca~(2+) entry on the CCh-induced gallbladder contraction. Preincubation with 2 μmol L~(-1) TG significantly decreased the CCh-induced gallbladder contraction. In addition, pretreatments with U73122, 2APB or TG abolished the difference of the CCh-induced gallbladder contraction between TRPP2 knockdown and control groups. We conclude that TRPP2 mediates Ca~(2+) release from intracellular Ca~(2+) stores, and has an essential role in agonist-induced gallbladder muscle contraction.     

Bidirectional regulation of Ca~(2+) in exo–endocytosis coupling

正Vesicular exocytosis is a key process involved in neurotransmitter release, whereas vesicle recycling is critical for the homeostasis of plasma membrane structures and the maintenance of neurotransmission. Ca~(2+)regulates several fundamental cellular processes (Zhu et al., 2016; Xiong and Zhu, 2016). Especially, Ca~(2+)influx plays a dual role of triggering vesicular exocytosis and modulating compensatory endocytosis in neurons and endocrine cells. Vesicular exocytosis occurs either by Ca~(2+)-dependent or Ca~(2+)-independent mechanisms (Chai et al., 2017), and local Ca~(2+)signals beneath the plasma membrane plays a critical role in the determination of the fusion pore dilation and fusion     

Assessing the Suitability of Various Physiological Traits to Screen Wheat Genotypes for Salt Tolerance

Success of improving the salt tolerance of genotypes requires effective and reliable screening traits in breeding programs.The objective was to assess the suitability of various physiological traits to screen wheat genotypes for salt tolerance.Thirteen wheat genotypes from Egypt,Germany,Australia and India were grown in soil with two salinity levels(control and150mmol/L NaCl)in a greenhouse.The physiological traits(ion contents in leaves and stems,i.e.Na~ ,Cl~-,K~ ,Ca~(2 )),theratios of K~ /Na~ and Ca~ /Na~ in the leaves and stems,net photosynthesis rate,stomatal conductance,transpiration rate,chlorophyll content(SPAD value),and leaf water relations,were measured at different growth stages.The physiologicaltraits except for Na~ and Cl~-in stems and the leaf transpiration rate at 150 mmol/L NaCI showed a significant genotypicvariation,indicating that the traits that have a significant genotypic variation may be possibly used as screening criteria.According to the analysis of linear regression of the scores of the physiological traits against those of grain yield,however,the physiological traits of Ca~(2 )and Ca~(2 )/Na~ at 45 d and final harvest with the greatest genotypic variation were ranked atthe top.From a practical and economic point of view,SPAD value should be considered to be used as screening criteriaand/or there is a need to develop a quick and practical approach to determine Ca~(2 )in plant tissues.     

The mechanism and function of active DNA demethylation in plants

DNA methylation is a conserved and important epigenetic mark in both mammals and plants.DNA methylation can be dynamically established,maintained,and removed through different pathways.In plants,active DNA demethylation is initiated by the RELEASE OF SILENCING 1(ROS1)family of bifunctional DNA glycosylases/lyases.Accumulating evidence suggests that DNA demethylation is important in many processes in plants.In this review,we summarize recent studies on the enzymes and regulatory factors that have been identified in the DNA demethylation pathway.We also review the functions of active DNA demethylation in plant development as well as biotic and abiotic stress responses.Finally,we highlight those aspects of DNA demethylation that require additional research.     

Effects of the activities of key enzymes involved in starch biosynthesis on the fine structure of amylopectin in developing rice (Oryza sativa L.) endosperms

The dynamic changes of the activities of enzymes involving in starch biosynthesis, including ADP-glucose pyrophosphorylase (AGPase), soluble starch synthases (SSS), starch branching enzyme (SBE) and starch debranching enzymes (DBE) were studied, and changes of fine structure of amy- lopectin were characterized by isoamylase treatment during rice grain development, using trans anti-waxy gene rice plants. The relationships between the activities of those key enzymes were also analyzed. The amylose synthesis was significantly inhibited in transgenic Wanjing 9522, but the total starch content and final grain weight were less affected as compared with those of non-transgenic Wanjing 9522 rice cultivar. Analyses on the changes of activities of enzymes involving in starch bio- synthesis showed that different enzyme activities were expressed differently during rice endosperm development. Soluble starch synthase is relatively highly expressed in earlier stage of endosperm de- velopment, whilst maximal expression of granule-bound starch synthase (GBSS) occurred in mid-stage of endosperm development. No obvious differences in changes of the activities of AGPase and SBE between two rice cultivars investigated, except the DBEs. Distribution patterns of branches of amy- lopectin changed continually during the development of rice grains and varied between two rice culti- vars. It was suggested that amylopectin synthesis be prior to the synthesis of amylose and different enzymes have different roles in controlling syntheses of branches of amylopectin.     

Tumor necrosis factor a accelerates Hep-2 cells proliferation by suppressing TRPP2 expression

TRPP2, a Ca~(2+)-permeable non-selective cation channel, has been shown to negatively regulate cell cycle, but the mechanism underlying this regulation is unknown. Tumor necrosis factor a(TNF-α) is a proinflammatory cytokine extensively involved in immune system regulation, cell proliferation and cell survival. However, the effects and mechanisms for the role of TNF-αin laryngeal cancer remain unclear. Here, we demonstrated using western blot analyses and intracellular Ca~(2+) concentration measurements that TNF-α treatment suppressed both TRPP2 expression and ATP-induced Ca~(2+) release in a laryngeal cancer cell line(Hep-2). Knockdown of TRPP2 by a specific siRNA significantly decreased ATP-induced Ca~(2+) release and abolished the effect of TNF-α on the ATP-induced Ca~(2+) release. TNF-α treatment also enhanced Hep-2 cell proliferation and growth, as determined using cell counting and flow cytometry cell cycle assays. Moreover, TNF-α treatment down-regulated phosphorylated protein kinase R-like endoplasmic reticulum kinase(p-PERK) and phosphorylated eukaryotic translation initiation factor(p-eIF2α)expression levels, without affecting PERK and eIF2 a expression levels in Hep-2 cells. We concluded that suppressing TRPP2 expression and TRPP2-mediated Ca~(2+) signaling may be one mechanism underlying TNF-α-enhanced Hep-2 cell proliferation.These results offer new insights into the mechanisms of TNF-α-mediated laryngeal cancer cell proliferation, and provide evidences showing a potential role of TNF-α in the development of laryngeal cancer.     

Tyrosine metabolic enzymes from insects and mammals：A comparative perspective

Differences in the metabolism of tyrosine between insects and mammals present an interesting example of molecular evolution. Both insects and mammals possess finetuned systems of enzymes to meet their specific demands for tyrosine metabolites; however, more homologous enzymes involved in tyrosine metabolism have emerged in many insect species. Without knowledge of modem genomics, one might suppose that mammals, which are generally more complex than insects and require tyrosine as a precur sor for important catecholamine neurotransmitters and for melanin, should possess more enzymes to control tyrosine metabolism. Therefore, the question of why insects actually possess more tyrosine metabolic enzymes is quite interesting. It has long been known that insects rely heavily on tyrosine metabolism for cuticle hardening and for innate immune responses, and these evolutionary constraints are likely the key answers to this question. In terms of melanogenesis, mammals also possess a high level of regulation; yet mam malian systems possess more mechanisms for detoxification whereas insects accelerate pathways like melanogenesis and therefore must bear increased oxidative pressure. Our research group has had the opportunity to characterize the structure and function of many key proteins involved in tyrosine metabolism from both insects and mammals. In this mini review we will give a brief overview of our research on tyrosine metabolic enzymes in the scope of an evolutionary perspective of mammals in comparison to insects.     

Assembly and structure of protein phosphatase 2A

Protein phosphatase 2A (PP2A) represents a conserved family of important protein serine/threonine phosphatases in species ranging from yeast to human. The PP2A core enzyme comprises a scaffold subunit and a catalytic subunit. The heterotrimeric PP2A holoenzyme consists of the core enzyme and a variable regulatory subunit. The catalytic subunit of PP2A is subject to reversible methylation, medi-ated by two conserved enzymes. Both the PP2A core and holoenzymes are regulated through interac-tion with a large n...     

DVL mutations identified from human neural tube defects and Dandy-Walker malformation obstruct the Wnt signaling pathway

Wnt signaling pathways,including the canonical Wnt/β-catenin pathway,planar cell polarity pathway,and Wnt/Ca~(2+) signaling pathway,play important roles in neural development during embryonic stages.The DVL genes encode the hub proteins for Wnt signaling pathways.The mutations in DVL2 and DVL3 were identified from patients with neural tube defects(NTDs),but their functions in the pathogenesis of human neural diseases remain elusive.Here,we sequenced the coding regions of three DVL genes in 176 stillborn or miscarried fetuses with NTDs or Dandy-Walker malformation(DWM) and 480 adult controls from a Han Chinese population.Four rare mutations were identified:DVL1 p.R558 H,DVL1 p.R606 C,DVL2 p.R633 W,and DVL3 p.R222 Q.To assess the effect of these mutations on NTDs and DWM,various functional analyses such as luciferase reporter assay,stress fiber formation,and in vivo teratogenic assay were performed.The results showed that the DVL2 p.R633 W mutation destabilized DVL2 protein and upregulated activities for all three Wnt signalings(Wnt/β-catenin signaling,Wnt/planar cell polarity signaling,and Wnt/Ca~(2+) signaling) in mammalian cells.In contrast,DVL1 mutants(DVL1 p.R558 H and DVL1 p.R606 C) decreased canonical Wnt/β-catenin signaling but increased the activity of Wnt/Ca~(2+)signaling,and DVL3 p.R222 Q only decreased the activity of Wnt/Ca~(2+) signaling.We also found that only the DVL2 p.R633 W mutant displayed more severe teratogenicity in zebrafish embryos than wild-type DVL2.Our study demonstrates that these four rare DVL mutations,especially DVL2 p.R633 W,may contribute to human neural diseases such as NTDs and DWM by obstructing Wnt signaling pathways.     

Nitric oxide reduces hydrogen peroxide accumulation involved in water stress-induced subcellular anti-oxidant defense in maize plants

Nitric oxide （NO） is a bioactive molecule involved in many biological events, and has been reported as pro-oxidant as well as anti-oxidant in plants. In the present study, the sources of NO production under water stress, the role of NO in water stress-induced hydrogen peroxide （H2O2） accumulation and subcellular activities of anti-oxidant enzymes in leaves of maize （Zea mays L.） plants were investigated. Water stress induced defense increases in the generation of NO in maize mesphyll cells and the activity of nitric oxide synthase （NOS） in the cytosolic and microsomal fractions of maize leaves. Water stress-induced defense increases in the production of NO were blocked by pretreatments with inhibitors of NOS and nitrate reductase （NR）, suggesting that NO is produced from NOS and NR in leaves of maize plants exposed to water stress. Water stress also induced increases in the activities of the chloroplastic and cytosolic anti-oxidant enzymes superoxide dismutase （SOD）, ascorbate peroxidase （APX）, and glutathione reductase （GR）, and the increases in the activities of anti-oxidant enzymes were reduced by pretreatments with inhibitors of NOS and NR. Exogenous NO increases the activities of water stress-induced subcellular anti-oxidant enzymes, which decreases accumulation of H2O2. Our results suggest that NOS and NR are involved in water stress-induced NO production and NOS is the major source of NO. The potential ability of NO to scavenge H2O2 is, at least in part, due to the induction of a subcellular anti-oxidant defense.     

Effect of Microwave and He-Ne Laser on Enzyme Activity and Biophoton Emission of Isatis indigotica Fort

The seed embryos of lsatis indigotica Fort were exposed to He-Ne laser (5.23 mW/mm^2, radiated for 5 min) and microwave ( 1.26 mW/mm^2, radiated for 8 s) irradiation to determine the effects of microwave and He-Ne laser pretreatment on enzyme activities, and biophoton emission of cotyledon. Then: (i) changes in the activities of enzymes in L indigotica cotyledon (such as amylase, transaminase, and proteinase) were measured to investigate the effects of He-Ne laser and microwave pretreatment; and (ii) biophoton emission was measured to determine the speed of cell division and metabolism. Results from these experiments indicated that: (i) the activities of amylase, transaminase, and proteinase of the cotyledon pretreated by HeNe laser and microwave were significantly increased; and (ii) the intensity of biophoton emission was enhanced significantly by He-Ne laser and microwave irradiation. These changes suggest that He-Ne laser and microwave pretreatment can improve the inner energy of seeds, lead to an enhancement of cotyledon enzymes, and speed up the metabolism of the cell, resulting in significantly increased biophoton emission. Moreover, the mechanism of action of the effects of laser and microwave radiation on the microcalorimetric parameters, enzyme activities, and biophoton emission of seeds is discussed on the basis of the results obtained.