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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Direct root contact among neighboring plants influences activity of soil extracellular enzymes

Composition and diversity of vegetation systems can influence soil microbial activity and extracellular enzyme (EE) dynamics, which are crucial for soil carbon (C) accrual and nutrient cycling. Yet, the impact of plant interactions and competition on EE activities remains a notable knowledge gap. This study examines how direct root contact and neighboring plant identity affect the activity and spatial distribution of four key soil EEs: β-glucosidase (BGlu), chitinase, acid phosphatase (AcidP), and alkaline phosphatase (AlkP). Using three-compartment rhizoboxes with switchgrass (Panicum virgatum L.) grown alongside bush clover (Lespedeza capitata Michx.), and black-eyed Susan (Rudbeckia hirta L.), we assessed enzyme activities using zymography under conditions that either allowed or restricted direct root contact by root barriers. Results show that root proliferation and species interactions significantly influenced EE activity. While BGlu and AcidP activities were strongly correlated with root biomass, AlkP activity was consistently higher in the absence of root barriers, indicating a pronounced microbial response to plant interactions via direct/close root contacts. Additionally, soil phosphorus availability modulated enzyme activity, with higher phosphatase activities in low-P soils. Furthermore, these findings highlight the importance of root-root interactions and plant species composition in shaping soil biochemical processes.

enyzme activity↗
DOE OSTI2021

Performance evaluation of a dynamic wall integrated with active insulation and thermal energy storage systems

Thermal energy storage systems in buildings can store cooling/heating energy during non-peak load hours or when renewable energy sources are available for later use when demanded. Using the building envelope as a thermal battery can help to shave the peak load, reduce the burden in electric grids, and enhance the occupant's thermal comfort. Sensible energy storage on wall systems such as thermally activated building systems can provide an active thermal storage strategy. However, most of the stored energy is used through passive means directed by the thermal lag, which can impede the on-demand release of the stored energy. Integrating active insulation systems with building thermal storage systems can increase the flexibility of charging and discharging time and duration. In this study, a wall system equipped with an active insulation system and thermally activated storage system was designed, and its performance on active cooling energy contribution was studied. The performances of energy storage (charging), release (discharging) of the thermal energy storage energy, and the active insulation system were studied separately and together as an integrated system. Results showed that the thermal properties of the thermal energy storage core material and the pipe spacing of both embedded pipes in the thermal energy storage and hydronic pipes used in the active insulation system affected the wall performance the most out of all the tested wall system parameters. During discharging, the heat flux into the wall was as high as 81.92 W/m 2 . This active insulation system's dynamic R-value varied between less than 1ft 2 •°F•h/BTU (0.18 m 2 •K/W) to 98% of the equally thick foam insulation's R-value.

25 ENERGY STORAGE↗
DOE OSTI2019

Reactivity and selectivity descriptors of dioxygen activation routes on metal oxides

The activation of dioxygen at typically isolated two-electron reduced centers can lead to the formation of electrophilic superoxo or peroxo species, providing an essential route to form reactive O 2 -derived species in biological, organometallic, and heterogeneous catalysts. Alternatively, O 2 activation can proceed via outer sphere routes, circumventing the formation of bound peroxo (OO*) species during oxidation catalysis by forming H 2 O 2 (g), which can react with another reduced center to form H 2 O. The electronic and binding properties of metal oxides that determine the relative rates of these activation routes are assessed here by systematic theoretical treatments using density functional theory (DFT). These methods are combined with conceptual frameworks based on thermochemical cycles and crossing potential models to assess the most appropriate descriptors for the activation barriers for each route using Keggin polyoxometalates as illustrative examples. In doing so, we show that inner sphere routes, which form OO* species via O 2 activation on the O-vacancies (*) formed in the reduction part of redox cycles, are mediated by early transition states that only weakly sense the oxide binding properties. Outer sphere routes form H 2 O 2 (g) via O 2 activation on OH pairs (H/OH*) formed by dissociation of H 2 O on O-vacancies; their rates and activation barriers reflect the rates of the first H-atom transfer from H/OH* to O 2 . The activation barriers for this H-transfer step depend on the binding energy of more weakly-bound H-atom in H/OH* pairs (HAE 2 ) and on the ˙OOH-surface interaction energy at its product state ($E_{int}$ 0 ). The $E_{int}$ 0 values are similar among oxides unless a large charge-balancing cation is present and interacts with radical ˙OOH; consequently, HAE 2 acts as an appropriate descriptor of the outer sphere dynamics. HAE 2 also determines the thermodynamics of H 2 O dissociation on O-vacancies, which influence the inner and outer sphere rates by setting the relative coverage of * and H/OH*. So these results, in turn, show that HAE 2 is a complete descriptor of the reactivity and selectivity of oxides for O 2 activation; the O-atoms in more reducible oxides (more negative HAE 2 ) exhibit a greater preference for the inner sphere routes and for the formation of electrophilic OO* intermediates that mediate epoxidation and O-insertion reactions during catalytic redox cycles. Large charge-balancing cations locally modify $E_{int}$ 0 values that determine the outer sphere rates and thus can be used to alter the preference of O-atoms to either inner or outer sphere routes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Phase Diagram of Active Brownian Spheres: Crystallization and the Metastability of Motility-Induced Phase Separation

Motility-induced phase separation (MIPS), the phenomenon in which purely repulsive active particles undergo a liquid-gas phase separation, is among the simplest and most widely studied examples of a nonequilibrium phase transition. Here, we show that states of MIPS coexistence are in fact only metastable for three-dimensional active Brownian particles over a very broad range of conditions, decaying at long times through an ordering transition we call active crystallization. At an activity just above the MIPS critical point, the liquid-gas binodal is superseded by the crystal-fluid coexistence curve, with solid, liquid, and gas all coexisting at the triple point where the two curves intersect. Nucleating an active crystal from a disordered fluid, however, requires a rare fluctuation that exhibits the nearly close-packed density of the solid phase. The corresponding barrier to crystallization is surmountable on a feasible timescale only at high activity, and only at fluid densities near maximal packing. The glassiness expected for such dense liquids at equilibrium is strongly mitigated by active forces, so that the lifetime of liquid-gas coexistence declines steadily with increasing activity, manifesting in simulations as a facile spontaneous crystallization at incredibly high activity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Active Fluids Form System-Spanning Filamentary Networks

Recent experimental realizations of liquid-liquid phase separation of active liquid crystals have offered an insight into the interaction between phase separation, ubiquitous in soft matter and biology, and chaotic active flows. Here, in this Letter, we use continuum theory to examine phase separation of an active liquid crystal and a passive fluid and report two new results. First, we provide an analytical derivation of the activity-induced suppression of the phase boundary of the coexistence region—a result first reported in simulations and experiments. We show that the shift in the critical point is a result of the balance between self-stirring active flows and phase-separating diffusive fluxes. Second, we show that this same balance is responsible for dramatically changing the morphology of the phase separated state, resulting in the emergence of a new mixed active phase consisting of a dynamical filamentous active network that invades the entire system area, trapping droplets of passive material. This structure exists even for very low volume fractions of active material. Our work provides an important step towards the goal of understanding how to use activity as a new handle for sculpting interfaces.

active nematics↗
DOE OSTI2023

T cell activation is insufficient to drive SIV disease progression

Resolution of T cell activation and inflammation is a key determinant of the lack of SIV disease progression in African green monkeys (AGMs). Although frequently considered together, T cell activation occurs in response to viral stimulation of acquired immunity, while inflammation reflects innate immune responses to mucosal injury. We dissociated T cell activation from inflammation through regulatory T cell (Treg) depletion with Ontak (interleukin-2 coupled with diphtheria toxin) during early SIV infection of AGMs. This intervention abolished control of T cell immune activation beyond the transition from acute to chronic infection. Ontak had no effect on gut barrier integrity, microbial translocation, inflammation, and hypercoagulation, despite increasing T cell activation. Ontak administration increased macrophage counts yet decreased their activation. Persistent T cell activation influenced SIV pathogenesis, shifting the ramp-up in viral replication to earlier time points, prolonging the high levels of replication, and delaying CD4 + T cell restoration yet without any clinical or biological sign of disease progression in Treg-depleted AGMs. Thus, by inducing T cell activation without damaging mucosal barrier integrity, we showed that systemic T cell activation per se is not sufficient to drive disease progression, which suggests that control of systemic inflammation (likely through maintenance of gut integrity) is the key determinant of lack of disease progression in natural hosts of SIVs.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2001

Endothelial NOS-dependent activation of c-Jun NH(2)- terminal kinase by oxidized low-density lipoprotein

Oxidized low-density lipoprotein (oxLDL) is known to activate a number of signal transduction pathways in endothelial cells. Among these are the c-Jun NH(2)-terminal kinase (JNK), also known as stress-activated protein kinase, and extracellular signal-regulated kinase (ERK). These mitogen-activated protein kinases (MAP kinase) determine cell survival in response to environmental stress. Interestingly, JNK signaling involves redox-sensitive mechanisms and is activated by reactive oxygen and nitrogen species derived from both NADPH oxidases, nitric oxide synthases (NOS), peroxides, and oxidized low-density lipoprotein (oxLDL). The role of endothelial NOS (eNOS) in the activation of JNK in response to oxLDL has not been examined. Herein, we show that on exposure of endothelial cells to oxLDL, both ERK and JNK are activated through independent signal transduction pathways. A key role of eNOS activation through a phosphatidylinositol-3-kinase-dependent mechanism leading to phosphorylation of eNOS is demonstrated for oxLDL-dependent activation of JNK. Moreover, we show that activation of ERK by oxLDL is critical in protection against the cytotoxicity of oxLDL.

Non-NASA Center↗
NASA NTRS2001

YC-1 activation of human soluble guanylyl cyclase has both heme-dependent and heme-independent components

YC-1 [3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole] is an allosteric activator of soluble guanylyl cyclase (sGC). YC-1 increases the catalytic rate of the enzyme and sensitizes the enzyme toward its gaseous activators nitric oxide or carbon monoxide. In other studies the administration of YC-1 to experimental animals resulted in the inhibition of the platelet-rich thrombosis and a decrease of the mean arterial pressure, which correlated with increased cGMP levels. However, details of YC-1 interaction with sGC and enzyme activation are incomplete. Although evidence in the literature indicates that YC-1 activation of sGC is strictly heme-dependent, this report presents evidence for both heme-dependent and heme-independent activation of sGC by YC-1. The oxidation of the sGC heme by 1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one completely inhibited the response to NO, but only partially attenuated activation by YC-1. We also observed activation by YC-1 of a mutant sGC, which lacks heme. These findings indicate that YC-1 activation of sGC can occur independently of heme, but that activation is substantially increased when the heme moiety is present in the enzyme.

NASA Discipline Cardiopulmonary↗
DOE OSTI2025

Insulation Activation and Contamination in Low-Power Experiments

Among the diverse advanced nuclear reactor concepts being developed are designs that expect to operate at much higher temperatures than conventional light-water reactors, and therefore require alternative materials for components capable of withstanding these extreme temperatures. Insulation is one such component where alternative high-temperature industrial composites are being considered. Low-power experiments can provide an opportunity for advancing our understanding of material behavior under irradiation; however, these experiments are not without occupational hazards. The focus of this paper is the potential for activation of insulating composites when exposed to neutron fluence during reactor experiments, and to discuss the subsequent contamination of the testing area. This paper will also discuss practical measures for preventing the creation and inhalation of activated particulate matter (i.e., dust), such as engineering and administrative controls and personal protective equipment. This paper evaluates the suitability of several insulation materials for use in reactor experiments based on their activation from neutron irradiation. The materials considered are Pyrogel XTE by Aspen Aerogel, Cerablanket and Kaowool by Morgan Advanced Materials, Thermo-12 Gold by Johns Manville, and Maxsil CF6-2000 by McAllister Mills. Although these materials are not yet widely used in the nuclear industry, they are common in other industries due to their thermal insulating properties. These materials produce dust while handling that can pose health and safety hazards, which could be further exacerbated by activation. The analysis presented in this paper utilizes a deterministic method developed to predict the activation source term of the provided insulation materials. The method calculates the atomic density of each element within the composites and simulates their exposure to a specified neutron flux density representative of low power experimental conditions. During the irradiation phase and throughout the extensive cooling period, neutron absorptions and nuclear decays are tracked for relevant isotopes. The residual activity within each composite is then assessed to identify the material with the lowest potential radiological hazard to workers. Dust will be created during installation and removal of insulating materials and may also be generated during the experiment. Contamination of surrounding surfaces due to dispersion is highly likely unless preventative measures are taken. The results of this analysis are used to estimate an internal dose from inhalation of activated dust, which is significantly lower than the allowable whole-body dose. However, the risk of internal exposure may increase if the dust becomes a transport vector for nuclear material. The goals of this paper are to enhance the understanding of the potential activation and contamination hazards from the use of these insulating materials in low-power nuclear experiments and to foster safer work environments through informed decision-making and strategic planning. This work ultimately contributes to a broader understanding of how new non-nuclear materials for advanced reactors impact the radiological safety of co-located workers, helping to ensure the responsible management of radioactive materials during installation and decommissioning activities.

12 - MGMT OF RADIOACTIVE AND NON-RADIOACTIVE WASTE↗
DOE OSTI2022

Influence of weather on gobbling activity of male wild turkeys

Gobbling activity of Eastern wild turkeys (Meleagris gallopavo silvestris; hereafter, turkeys) has been widely studied, focusing on drivers of daily variation. Weather variables are widely believed to influence gobbling activity, but results across studies are contradictory and often equivocal, leading to uncertainty in the relative contribution of weather variables to daily fluctuations in gobbling activity. Previous works relied on road-based auditory surveys to collect gobbling data, which limits data consistency, duration, and quantity due to logistical difficulties associated with human observers and restricted sampling frames. Development of new methods using autonomous recording units (ARUs) allows researchers to collect continuous data in more locations for longer periods of time, providing the opportunity to delve into factors influencing daily gobbling activity. We used ARUs from 1 March to 31 May to detail gobbling activity across multiple study sites in the southeastern United States during 2014–2018. We used state-space modeling to investigate the effects of weather variables on daily gobbling activity. Our findings suggest rainfall, greater wind speeds, and greater temperatures negatively affected gobbling activity, whereas increasing barometric pressure positively affected gobbling activity. Therefore, when using daily gobbling activity to make inferences relative to gobbling chronology, reproductive phenology, and hunting season frameworks, stakeholders should recognize and consider the potential influences of extended periods of inclement weather.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Design, synthesis, and cytostatic activity of novel pyrazine sorafenib analogs

The current study is focused on a series of sorafenib analogs as potential antitumor agents. We have designed and synthesized nine novel pyrazine analogs 6a–i differing in amide and/or urea regions. Two alternative strategies for the preparation of title compounds were applied. The first strategy involved ether formation between 4-hydroxyphenyl urea 3 and 5-chloro-pyrazine-2-carboxamides 4. In the second strategy, ether functionality was introduced in the molecule before urea moiety and included preparation of 5-(4-aminophenoxy)-N-alkylpyrazine-2-carboxamides 5 and their reaction with 4-chloro-3-(fluoromethyl)phenyl isocyanate. Cytostatic activity of the title compounds was evaluated in vitro against a panel of cancer cell lines. Most of the tested compounds showed strong antiproliferative activity in the low micromolar range. 5-/4-[3-(4-chloro-3-trifluoromethyl-phenyl)-ureido]-phenoxy/-pyrazine-2-carboxylic acid (4-chloro-3-trifluoromethylphenyl)-amide (6g) was the most active compound (IC{sub 50} 0.9–7.5 μM) and showed comparable or stronger activity than sorafenib, but also similar cytotoxicity to normal human fibroblast cells. Two compounds, namely, 5-/4-[3-(4-bromophenyl)-ureido]-phenyloxy/-pyrazine-2-carboxylic acid cyclopentylamide (6c) and 5-/4-[3-(4-chloro-3-trifluoromethyl-phenyl)-ureido]-phenoxy/-pyrazine-2-carboxylic acid cyclopentylamide (6h), exerted cytostatic activities that surpassed the effects observed with sorafenib in three cancer cell lines (HepG2, HeLa, A549, IC{sub 50} 0.6–0.9 μM). Similar to sorafenib, compound 6h proved to be cytotoxic to normal human fibroblast cells, whereas compound 6c did not diminish proliferative capacity of these cells and could be regarded as the most promising derivative. Additional biological studies on the c-Raf activity using Western blot method revealed that antiproliferative activity of 6h could be at least partially attributed to its inhibitory effect on c-Raf activation similar to sorafenib. In contrast, 6c did not inhibit the activity of c-Raf, which implies that other cell signaling pathways govern its antiproliferative effects. Taking into account structural differences between compounds 6c and 6h, it is plausible to believe that the substituent in urea part of the molecule is essential for the interaction with c-Raf.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

10-oxo-12(Z)-octadecenoic acid, a linoleic acid metabolite produced by gut lactic acid bacteria, potently activates PPARγ and stimulates adipogenesis

Our previous study has shown that gut lactic acid bacteria generate various kinds of fatty acids from polyunsaturated fatty acids such as linoleic acid (LA). In this study, we investigated the effects of LA and LA-derived fatty acids on the activation of peroxisome proliferator-activated receptors (PPARs) which regulate whole-body energy metabolism. None of the fatty acids activated PPARδ, whereas almost all activated PPARα in luciferase assays. Two fatty acids potently activated PPARγ, a master regulator of adipocyte differentiation, with 10-oxo-12(Z)-octadecenoic acid (KetoA) having the most potency. In 3T3-L1 cells, KetoA induced adipocyte differentiation via the activation of PPARγ, and increased adiponectin production and insulin-stimulated glucose uptake. These findings suggest that fatty acids, including KetoA, generated in gut by lactic acid bacteria may be involved in the regulation of host energy metabolism. - Highlights: • Most LA-derived fatty acids from gut lactic acid bacteria potently activated PPARα. • Among tested fatty acids, KetoA and KetoC significantly activated PPARγ. • KetoA induced adipocyte differentiation via the activation of PPARγ. • KetoA enhanced adiponectin production and glucose uptake during adipogenesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

In-vitro and in-vivo imaging of MMP activity in cartilage and joint injury

Non-destructive detection of cartilage-degrading activities represents an advance in osteoarthritis (OA) research, with implications in studies of OA pathogenesis, progression, and intervention strategies. Matrix metalloproteinases (MMPs) are principal cartilage degrading enzymes that contribute to OA pathogenesis. MMPSense750 is an in-vivo fluorimetric imaging probe with the potential to continuously and non-invasively trace real-time MMP activities, but its use in OA-related research has not been reported. Our objective is to detect and characterize the early degradation activities shortly after cartilage or joint injury with MMPSense750. We determined the appropriate concentration, assay time, and linear range using various concentrations of recombinant MMPs as standards. We then quantified MMP activity from cartilage explants subjected to either mechanical injury or inflammatory cytokine treatment in-vitro. Finally, we performed in-vivo MMP imaging of a mouse model of post-traumatic OA. Our in-vitro results showed that the optimal assay time was highly dependent on the MMP enzyme. In cartilage explant culture media, mechanical impact or cytokine treatment increased MMP activity. Injured knees of mice showed significantly higher fluorescent signal than uninjured knees. We conclude that MMPSense750 detects human MMP activities and can be used for in-vitro study with cartilage, as well as in-vivo studies of knee injury, and can offering real-time insight into the degradative processes that occurring within the joint before structural changes become evident radiographically. - Highlights: • MMPSense750 is near-infrared fluorescent probe which can detect MMP activity. • MMPSense750 can detect human MMP-3, -9, and -13. • The reaction kinetics with MMPSense750 were different for the three MMPs. • MMPSense750 can visualized real time MMP activity in mouse injured knees. • MMPSense750 is convenient tool to evaluate real-time MMP activity non-invasively.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Characterization of two MODY2 mutations with different susceptibility to activation

Glucokinase plays a key role in glucose sensing in pancreatic beta cells and in liver metabolism. Heterozygous inactivating glucokinase mutations cause the autosomal dominantly inherited MODY2 subtype of maturity-onset diabetes of the young. The goal of this study was to elucidate the pathogenicity of the recently described glucokinase mutants L304P and L315H, located in an alpha-helix and connecting region, respectively, at the outer region of the large domain of glucokinase. Both mutants showed wild-type-like cytosolic localization, but faster protein degradation in insulin-secreting MIN6 cells. However, strongly reduced nuclear/cytoplasmic localization of the mutants was observed in primary hepatocytes suggesting reduced interaction with the liver specific glucokinase regulatory protein. Both mutants displayed a significantly lowered glucokinase activity compared to the wild-type protein. Even though the L315H protein showed the lowest enzymatic activity, this mutant was very sensitive to allosteric activation. The endogenous activator fructose-2,6-bisphosphatase evoked an increase in glucokinase activity for both mutants, but much stronger for L315H compared to L304P. The synthetic activator RO281675 was ineffective against the L304P mutant. Expression of the mutant proteins evoked loss of glucose-induced insulin secretion in MIN6 cells. Administration of RO281675 increased insulin secretion, however, only for the L315H mutant. Thus, a glucokinase activator drug therapy may help MODY2 patients not in general, but seems to be a useful strategy for carriers of the L315H glucokinase mutation. - Highlights: • The GK mutants L304P and L315H display a highly reduced enzymatic activity. • In hepatocytes both mutations lower the nuclear/cytoplasmic localization ratio of GK. • Both mutants inhibit stimulus-secretion coupling in insulin-producing cells. • Activation by fructose-2,6-bisphosphatase and by RO281675 is stronger for L315H. • RO281675 stimulates insulin secretion only for the L315H mutant, not for L304P.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

RKIP phosphorylation–dependent ERK1 activation stimulates adipogenic lipid accumulation in 3T3-L1 preadipocytes overexpressing LC3

3T3-L1 preadipocytes undergo adipogenesis in response to treatment with dexamethaxone, 1-methyl-3-isobutylxanthine, and insulin (DMI) through activation of several adipogenic transcription factors. Many autophagy-related proteins are also highly activated in the earlier stages of adipogenesis, and the LC3 conjugation system is required for formation of lipid droplets. Here, we investigated the effect of overexpression of green fluorescent protein (GFP)-LC3 fusion protein on adipogenesis. Overexpression of GFP-LC3 in 3T3-L1 preadipocytes using poly-L-lysine-assisted adenoviral GFP-LC3 transduction was sufficient to produce intracellular lipid droplets. Indeed, GFP-LC3 overexpression stimulated expression of some adipogenic transcription factors (e.g., C/EBPα or β, PPARγ, SREBP2). In particular, SREBP2 was highly activated in preadipocytes transfected with adenoviral GFP-LC3. Also, phosphorylation of Raf kinase inhibitory protein (RKIP) at serine 153, consequently stimulating extracellular-signal regulated kinase (ERK)1 activity, was significantly increased during adipogenesis induced by either poly-L-lysine-assisted adenoviral GFP-LC3 transduction or culture in the presence of dexamethasone, 1-methyl-3-isobutylxanthine, and insulin. Furthermore, RKIP knockdown promoted ERK1 and PPARγ activation, and significantly increased the intracellular accumulation of triacylglycerides in DMI-induced adipogenesis. In conclusion, GFP-LC3 overexpression in 3T3-L1 preadipocytes stimulates adipocyte differentiation via direct modulation of RKIP-dependent ERK1 activity. - Highlights: • Overexpression of GFP-LC3 in 3T3-L1 cells produces intracellular lipid droplets. • SREBP2 is highly activated in preadipocytes transfected with adenoviral GFP-LC3. • RKIP phosphorylation at serine 153 is significantly increased during adipogenesis. • RKIP knockdown promotes ERK1 and PPARγ activation during adipogenesis. • RKIP-dependent ERK1 activation increases triacylglycerides in adipocytes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Constitutive androstane receptor activation evokes the expression of glycolytic genes

It is well-known that constitutive androstane receptor (CAR) activation by 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) increases the liver-to-body weight ratio. CAR-mediated liver growth is correlated with increased expression of the pleiotropic transcription factor cMyc, which stimulates cell cycle regulatory genes and drives proliferating cells into S phase. Because glycolysis supports cell proliferation and cMyc is essential for the activation of glycolytic genes, we hypothesized that CAR-mediated up-regulation of cMyc in mouse livers might play a role in inducing the expression of glycolytic genes. The aim of the present study was to examine the effect of long-term CAR activation on glycolytic genes in a mouse model not subjected to metabolic stress. We demonstrated that long-term CAR activation by TCPOBOP increases expression of cMyc, which was correlated with reduced expression of gluconeogenic genes and up-regulation of glucose transporter, glycolytic and mitochondrial pyruvate metabolising genes. These changes in gene expression after TCPOBOP treatment were strongly correlated with changes in levels of glycolytic intermediates in mouse livers. Moreover, we demonstrated a significant positive regulatory effect of TCPOBOP-activated CAR on both mRNA and protein levels of Pkm2, a master regulator of glucose metabolism and cell proliferation. Thus, our findings provide evidence to support the conclusion that CAR activation initiates a transcriptional program that facilitates the coordinated metabolic activities required for cell proliferation. - Highlights: • CAR-mediated liver growth is correlated with increased expression of cMyc. • CAR activation increased the expression of glycolytic genes in mouse livers. • CAR activation increased the level of Pkm2 in mouse livers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

SUMOylation represses the transcriptional activity of the Unfolded Protein Response transducer ATF6

Highlights: • The UPR transducer ATF6 is modified through SUMOylation under ER stress as a feedback regulation. • SUMOylation of ATF6 is mediated through SUMO-1 and PIAS1. • SUMOylation represses the transcriptional activity of ATF6. • Expression of misfolded human cystic fibrosis transmembrane conductance regulator leads to ATF6 SUMOylation. The Unfolded Protein Response (UPR) is a cascade of intracellular stress signaling from the endoplasmic reticulum (ER) that protect the cells from the stress caused by accumulation of unfolded or misfolded proteins in the ER. Activating transcription factor 6 (ATF6) is one of primary UPR transducers that remodels the stressed cells through transcriptional regulation. Although the activation mechanism and biological roles of ATF6 have been well studied, the understanding of the negative or feedback regulation of ATF6 remains elusive. In this report, we showed that ATF6 protein can be modified by small ubiquitin-like modification (SUMOylation) and that the transcriptional activity of ATF6 is negatively regulated by SUMOylation. We identified that SUMOylation of ATF6 is significantly increased in the cells expressing misfolded cystic fibrosis transmembrane conductance regulator (CFTR) encoded by the mutant human CFTR gene (dF508CFTR). Further analyses revealed two highly conserved SUMOylation motifs within the trans-activation domain of ATF6 protein of human, mouse, or rat specie. The human ATF6 protein can be SUMOylated mediated through the small ubiquitin-like modifier protein 1 (SUMO-1) and E3 SUMO-protein ligase 1 (PIAS1) at the conserved sumoylation residue Lys{sup 149} that is located at the N-terminal of the activated form of ATF6 protein. Bimolecular fluorescence complementation (BiFC) analysis confirmed that the activated ATF6 protein can be SUMOylated and that the ATF6 sumoylation occurs in the nuclei. Moreover, trans-activation reporter analysis demonstrated that SUMOylation of the ATF6 protein at the conserved residue Lys{sup 149} represses the transcriptional activity of ATF6. In summary, our study revealed a negative regulation of the UPR transducer ATF6 through post-translational SUMOylation. The information from this study will not only increase our understanding of the fine-tuning regulation of the UPR signaling but will also be informative to the modulation of the UPR for therapeutic benefits.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Characterization of the oxidative protein folding activity of a unique plant oxidoreductase, Arabidopsis protein disulfide isomerase-11

Highlights: • AtPDI11 is a unique protein disulfide isomerase that has no ortholog in animals or yeast. • AtPDI11 has oxidoreductase activity in vitro that is much lower than hPDI. • The active site in the a' domain of AtPDI11 is critical for its oxidative folding activity. • AtPDI11 is present in four redox forms in vivo, which are determined by the active site cysteines. • AtPDI11 is required for plant growth under reducing conditions. Protein disulfide isomerases (PDIs) can catalyze disulfide bond formation in nascent secretory proteins and membrane proteins and can introduce correct disulfide bonds into substrate proteins containing mispaired disulfides. The functions of mammalian PDIs have been extensively studied; however, relative to mammalian PDIs, the systematic characterization of PDIs for their oxidoreductase activity in plants is still lacking. Arabidopsis protein disulfide isomerases-11 (AtPDI11), with the structure of a-a'-D, has no ortholog in animals or yeast. In this study, we demonstrated that AtPDI11 has oxidoreductase activity in vitro using a GSSG/GSH-mediated oxidative protein folding system. Moreover, the active site in the a' domain of AtPDI11 is critical for its oxidative folding activity. AtPDI11 is present in four redox forms in vivo, which are determined by the active site cysteines (Cys52 and Cys55 in the a domain, and Cys171 and Cys174 in the a' domain). Genetic evidence suggests that AtPDI11 is required for plant growth under reducing conditions. Our work provides an example for studying the oxidoreductase function of other plant PDIs.

60 APPLIED LIFE SCIENCES↗