Amino Acids L-glutamine Research Articles

Density and coefficients of Jones–Dole equation for viscosity measurement of l-isoleucine, l-proline, and l-glutamine in aqueous KCl solution at 298.15–323.15 K

The present studies reported the experimental data on thermophysical properties such as density and viscosity of aqueous solutions of different amino acids namely l-isoleucine, l-proline, and l-glutamine in 1.5 mol/L KCl solution at different temperatures ranging from 298.15 to 323.15 K. Hence, the aim of this study is to investigate interactions between amino acids and KCl solution at dilute concentrations. For understanding amino acid and KCl solution interactions, we will investigate ion–ion and ion–solvent interactions. It has been observed that the density and viscosity rise with amino acid concentration and decrease with temperature. Using the Jones–Dole equation, the viscosity A and B coefficients have been determined. The viscosity B-coefficient values for all the three amino acids in aqueous electrolyte system are depicted as positive. The positive values of B-coefficient indicate a strong alignment of the solvent molecules with solute molecules. The amino acid l-glutamine acts as a structure breaker solute. This structure breaking effect of l-glutamine on solvent may be attributed to the domination of hydrophilic nature of amide group. l-isoleucine and l-proline act as structure maker in electrolyte system.

Amyloid Mimicking Assemblies Formed by Glutamine, Glutamic Acid, and Aspartic Acid.

The aggregation of amino acids into amyloid-like structures is a critical phenomenon for understanding the pathophysiology of various diseases, including inborn errors of metabolism (IEMs) associated with amino acid imbalances. Previous studies have primarily focused on self-assembly of aromatic amino acids, leading to a limited understanding of nonaromatic, polar amino acids in this context. To bridge this gap, our study investigates the self-assembly and aggregation behavior of specific nonaromatic charged and uncharged polar amino acids l-glutamine (Gln), l-aspartic acid (Asp), and l-glutamic acid (Glu), which have not been reported widely in the context of amyloid aggregation. Upon aging these amino acids under controlled conditions, we observed the formation of uniform, distinct aggregates, with Gln forming fibrillar gel-like structures and Glu exhibiting fibrous globular morphologies. Computational simulations validated these findings, identifying Gln as the most potent in forming stable aggregates, followed by Glu and Asp. These simulations elucidated the driving forces behind the distinct morphologies and stabilities of the aggregates. Thioflavin T assays were employed to confirm the amyloid-like nature of these aggregates, suggesting their potential cytotoxic impact. To assess toxicity, we performed in vitro studies on neural cell lines and in vivo experiments in Caenorhabditis elegans (C. elegans), which demonstrated measurable cytotoxic effects, corroborated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and heat shock survival assays. Importantly, this study fills a critical gap in our understanding on the role of nonaromatic amino acids in amyloidogenesis and its implications for IEMs. Our findings provide a foundation for future investigations into the mechanisms of diseases associated with amino acid accumulation and offer potential avenues for the development of targeted therapeutic strategies.

Exploring the Mechanisms behind Non-aromatic Fluorescence with the Density Functional Tight Binding Method.

Recent experimental findings reveal nonconventional fluorescence emission in biological systems devoid of conjugated bonds or aromatic compounds, termed non-aromatic fluorescence (NAF). This phenomenon is exclusive to aggregated or solid states and remains absent in monomeric solutions. Previous studies focused on small model systems in vacuum show that the carbonyl stretching mode along with strong interaction of short hydrogen bonds (SHBs) remains the primary vibrational mode explaining NAF in these systems. In order to simulate larger model systems taking into account the effects of the surrounding environment, in this work we propose using the density functional tight-binding (DFTB) method in combination with non-adiabatic molecular dynamics (NAMD) and the mixed quantum/molecular mechanics (QM/MM) approach. We investigate the mechanism behind NAF in the crystal structure of l-pyroglutamine-ammonium, comparing it with the related nonfluorescent amino acid l-glutamine. Our results extend our previous findings to more realistic systems, demonstrating the efficiency and robustness of the proposed DFTB method in the context of NAMD in biological systems. Furthermore, due to its inherent low computational cost, this method allows for a better sampling of the nonradiative events at the conical intersection which is crucial for a complete understanding of this phenomenon. Beyond contributing to the ongoing exploration of NAF, this work paves the way for future application of this method in more complex biological systems such as amyloid aggregates, biomaterials, and non-aromatic proteins.

Chilean Market Protein Shakes Composition.

Understanding the nutritional content of protein supplements is crucial for optimal nutritional planning among athletes and other people. Distribution of macronutrients and aminograms in the main products available in the national Chilean market remains unknown. A descriptive cross-sectional study was conducted to identify the main protein supplements available in the Chilean market. Information on macronutrients and aminograms from the nutritional labels of each product was extracted. The analysis considered the content per portion and per 100 g. Cluster analysis models and graphical representations were explored. Eighty protein shakes were assessed in the Santiago de Chile market. The median protein dosage was 32 g (range from 25 to 52), and the median energy value stood at 390 kcal (range from 312 to 514). The median protein content per 100 g of product was found to be 75 g (range from 42.5 to 97.2). The combined median concentration of amino acids was 4749.75 mg. Among these, the essential amino acid L-Tryptophan exhibited the lowest concentration at 1591.50 mg, while the conditional amino acid L-Glutamine had the highest median concentration at 17,336 mg. There was a significant prevalence of animal-derived products, placing specific emphasis on protein supplements that feature elevated levels of the amino acids L-Glutamine and L-Leucine.

Outcomes of a complementary and alternative medicine based on vitamins, herbal products, and amino acid as a first line treatment in idiopathic overactive bladder syndrome in men and women without bladder outlet obstruction.

To evaluate the efficacy and tolerability of a complementary and alternative medicine (CAM) called Kubiker (Naturmed, Montegranaro, FM, Italy), consisting of vitamins (C and D), herbal products (cucurbita maxima, capsicum annum, polygonum cuspidatum), and amino acid L-Glutamine, as first line treatment of (OAB). According to institutional protocols, data on patients addressing to a tertiary referral centre for OAB symptoms were recorded. OAB was evaluated through validated questionnaires including ICIQ-SF, USS, and OAB-q-SF. Patients with previous antimuscarinic or β3 agonist treatment, neurological disease or pathologies which may mimic OAB, including infections, were excluded. Only unobstructed patients were considered and were given CAM twice daily for 12 weeks. After treatment, symptoms were re-evaluated repeating previous questionnaires and PGI-I was given to evaluate perceived improvement. A total of 41 patients were evaluated and 35 respected inclusion criteria and were enrolled. All subjects had a full compliance and adherence with CAM medication intake. The median patient's age was 65 (56-73). Male were 8 (22.9%) while females were 27 (77.1%). Median baseline OAB-q SF and ICIQ-SF scores were 18 (15-25) and 9 (6-13), respectively. After treatment, 85.7% patients had a clinical benefit, with a significant reduction of OAB symptoms, also according to USS (p < 0.01). The median OAB-q SF and ICIQ-SF scores were 10 (7-15) and 6 (0-8) (p < 0.01). CAM was successful with an improvement in subjective patient's satisfaction, with a median PGI-I score of 2 (1-3). Patients (men and women) who still had UUI after 3 months CAM medication were eight (22.8%), and among them, those who did not refer any therapeutic benefit were five (14.3%). According to our study, CAM may be useful medication for a first line treatment of uncomplicated idiopathic OAB cases, providing a nonnegligible effects on symptoms. However, further studies are mandatory to draw definitive conclusions.

Rational Design of Potent Inhibitors of a Metallohydrolase Using a Fragment-Based Approach.

Metallohydrolases form a large group of enzymes that have fundamental importance in a broad range of biological functions. Among them, the purple acid phosphatases (PAPs) have gained attention due to their crucial role in the acquisition and use of phosphate by plants and also as a promising target for novel treatments of bone-related disorders and cancer. To date, no crystal structure of a mammalian PAP with drug-like molecules bound near the active site is available. Herein, we used a fragment-based design approach using structures of a mammalian PAP in complex with the MaybridgeTM fragment CC063346, the amino acid L-glutamine and the buffer molecule HEPES, as well as various solvent molecules to guide the design of highly potent and efficient mammalian PAP inhibitors. These inhibitors have improved aqueous solubility when compared to the clinically most promising PAP inhibitors available to date. Furthermore, drug-like fragments bound in newly discovered binding sites mapped out additional scaffolds for further inhibitor discovery, as well as scaffolds for the design of inhibitors with novel modes of action.

Graphene oxide nanofilm and the addition of l-glutamine can promote development of embryonic muscle cells

BackgroundFormation of muscular pseudo-tissue depends on muscle precursor cells, the extracellular matrix (ECM)-mimicking structure and factors stimulating cell differentiation. These three things cooperate and can create a tissue-like structure, however, their interrelationships are relatively unknown. The objective was to study the interaction between surface properties, culture medium composition and heterogeneous cell culture. We would like to demonstrate that changing the surface properties by coating with graphene oxide nanofilm (nGO) can affect cell behaviour and especially their need for the key amino acid l-glutamine (L-Glu).ResultsChicken embryo muscle cells and their precursors, cultured in vitro, were used as the experimental model. The mesenchymal stem cell, collected from the hind limb of the chicken embryo at day 8 were divided into 4 groups; the control group and groups treated with nGO, L-Glu and nGO supplied with L-Glu (nGOxL-Glu). The roughness of the surface of the plastic plate covered with nGO was much lower than a standard plate. The test of nGO biocompatibility demonstrated that the cells were willing to settle on the nGO without any toxic effects. Moreover, nGO by increasing hydrophilicity and reducing roughness and presumably through chemical bonds available on the GO surface stimulated the colonisation of primary stromal cells that promote embryonic satellite cells. The viability significantly increased in cells cultured on nGOxL-Glu. Observations of cell morphology showed that the most mature state of myogenesis was characteristic for the group nGOxL-Glu. This result was confirmed by increasing the expression of MYF5 genes at mRNA and protein levels. nGO also increased the expression of MYF5 and also very strongly the expression of PAX7 at mRNA and protein levels. However, when analysing the expression of PAX7, a positive link was observed between the nGO surface and the addition of L-Glu.ConclusionsThe use of nGO and L-Glu supplement may improve myogenesis and also the myogenic potential of myocytes and their precursors by promoting the formation of satellite cells. Studies have, for the first time, demonstrated positive cooperation between surface properties nGO and L-Glu supplementation to the culture medium regarding the myogenic potential of cells involved in muscle formation.

Exploring the effect of amino acid and glucose on the biodegradation of pure Zn

To take insights into the participation of amino acid L-glutamine and glucose in the biodegradation of pure Zn, immersion tests and electrochemical approaches were conducted in designated electrolytes. It revealed that two organic components affected the Zn biodegradation distinctly and played significant parts in the formation of biodegradation products. In media buffered with Tris-HCl, solution pH was effectively adjusted while the involvement of organic components in the Zn biodegradation got noticeably altered. Moreover, with the introduction of two organic components, Tris-HCl buffered SBF may yield better replication of the in vivo biodegradation of zinc.

Odor Stimulation and Relation to Taste Stimuli in the Blind Cave Fish Astyanax fasciatus

The influence of odor stimulation with solutions of the amino acids L-glutamine and L-phenylalanine on the response of the cave fish Astyanax fasciatus (blind form) to the taste of agar pellets with L-glutamine and L-phenylalanine has been studied. It has been established that the odors used cause a food search behavior in fish, but do not affect the orosensory testing of the pellets. It is noted that the taste characteristics of both amino acids differ in the evaluation of the extraoral and oral taste systems, which indicates food selectivity in the blind cave fish, the food of which in its habitats is extremely monotonous. The attitude to the taste of amino acids is stable with a different smell background and a changing combination of odor and taste stimuli.

Automated radiosynthesis of 5-[11C]l-glutamine, an important tracer for glutamine utilization

IntroductionThe natural amino acid l-Glutamine (Gln) is essential for both cell growth and proliferation. In addition to glucose, cancer cells utilize Gln as a carbon source for ATP production, biosynthesis, and as a defense against reactive oxygen species. The utilization of [11C]Gln has been previously reported as a biomarker for tissues with an elevated demand for Gln, however, the previous reports for the preparation of [11C]Gln were found to be lacking several crucial aspects necessary for transition to human production. Namely, the presence of unreacted precursor and the use of non-commercialized, custom built, reaction platforms. Herein, we report the development and utilization of methodology for the automated production of [11C]Gln that meets institutional criteria for human use. MethodsThe preparation of [11C]Gln was carried out on the GE FX2N platform. Briefly, after trapping of [11C]HCN with a solution of CsHCO3 in DMF, the [11C]CsCN was reacted with a commercially available precursor. This intermediate was then purified by HPLC and deprotected/hydrolyzed under acidic conditions. Following pH adjustment, the product was filtered to give the desired [11C]Gln as a sterile injectable. The resulting product was then analyzed for quality assurance. ResultsAutomated production by this method reliably provides over 3.7 GBq (100 mCi) of [11C]Gln. The resulting final drug product was found to have a >99% radiochemical purity, <5% of D-Gln present, no detectable impurities, and the total preparation time was roughly 45 min from the end-of-bombardment. ConclusionsA fast, reliable and efficient automated radiosynthesis was developed using a commercially available module. Purifications used throughout allow for both a radiochemically and chemically pure final product solution of [11C]Gln.

Improvement of Soybean Agrobacterium-Mediated Transformation Efficiency by Adding Glutamine and Asparagine into the Culture Media.

As a genetically modified crop, transgenic soybean occupies the largest global scale with its food, nutritional, industrial, and pharmaceutical uses.Efficient transformation is a key factor for the improvement of genetically modified soybean. At present, the Agrobacterium-mediated method is primarily used for soybean transformation, but the efficiency of this method is still relatively low (below 5%) compared with rice (above 90%). In this study, we examined the influence of l-glutamine and/or l-asparagine on Agrobacterium-mediated transformation in soybean and explored the probable role in the process of Agrobacterium-mediated transformation. The results showed that when the amino acids l-glutamine and l-asparagine were added separately or together to the culture medium, the shoot induction frequency, elongation rate, and transformation frequency were improved. The combined effects of l-glutamine and l-asparagine were better than those of l-glutamine and l-asparagine alone. The 50 mg/L l-glutamine and 50 mg/L l-asparagine together can enhance the transformation frequency of soybean by attenuating the expression level of GmPRs (GmPR1, GmPR4, GmPR5, and GmPR10) and suppression of the plant defense response. The transgene was successfully transmitted to the T1 generation. This study will be useful in genetic engineering of soybean.

Raman spectroscopy under high pressures and DFT calculations of the amino acid l-glutamine

l-glutamine crystal was obtained by the slow evaporation method and its crystallographic structure was verified by X-ray diffraction experiments and the Rietveld method. The vibrational modes of l-glutamine were investigated through Raman spectroscopy and the normal modes were obtained using the Density Functional Theory with the B3LYP functional and set of bases 6-31G++(d, p). With such approach, it was possible to make a theoretical-experimental comparison of the results obtained and to furnish a more precise assignment of the normal modes. The crystal was submitted to high pressure conditions and the Raman spectra between 3055 and 40 cm−1 were recorded for pressures up to 6.1 GPa in a diamond anvil cell. This study allowed us to understand that the crystal undergoes a reversible structural phase transition around 4.0 GPa, characterized mainly by spectral changes in the region of the external modes.

Adsorption of essential minerals on l-glutamine functionalized zigzag graphene nanoribbon-A first principles DFT study

The current work focuses on the covalent chemical functionalization of zigzag graphene nanoribbon (ZGNR(6,0)) with the naturally occurring nonessential amino acid l-glutamine (C5H10N2O3) named as, g-ZGNR. The five major essential minerals required for a human body are sodium (Na), potassium (K), calcium (Ca), phosphorous (P) and magnesium (Mg). The changes in the physical and chemical properties of g-ZGNR upon adsorption of these minerals have been investigated. The mineral adsorbed systems are named as gX-ZGNR, in which X=Na/K/Ca/P/Mg respectively. All the calculations were framed out in the premises of the first principles density functional theory using the local density approximation (LDA) and double zeta polarized basis set. The lowest exchange correlation functional, higher partial charges and Gibb’s free energy of solvation have been obtained for gCa-ZGNR to validate it as an effective nanocarrier to be used for targeted drug delivery application.

Physiological regulation of the heat shock response by glutamine: implications for chronic low-grade inflammatory diseases in age-related conditions

AbstractAging is an intricate process modulated by different molecular and cellular events, such as genome instability, epigenetic and transcriptional changes, molecular damage, cell death and senescence, inflammation, and metabolic dysfunction. Particularly, protein quality control (chaperone systems) tends to be negatively affected by aging, thus leading to cellular senescence in metabolic tissues and, as a consequence, to the increasing dissemination of inflammation throughout the body. The heat shock (HS) response and its associated expression of the 70 kDa family of heat shock proteins (HSP70), which are anti-inflammatory molecular chaperones, are found to be markedly decreased during muscle inactivity and aging, while evidence supports the loss of HSP70 as a key mechanism which may drive muscle atrophy, contractile dysfunction, and reduced regenerative capacity. In addition, abnormal stress response is linked with higher incidence of neurodegenerative diseases as well as low-grade inflammatory diseases that are associated with physical inactivity and obesity. Therefore, strategies to increase or, at least, to maintain the levels of HSP70, and its accompanying HS response to stress, are key to reduce biological cell dysfunctions that occur in aging. In this sense, physical exercise is of note as it is the most powerful inducer of the HS response, comparable only to heat stress and fever-like conditions. On the other hand, the amino acidl-glutamine, whose production within the skeletal muscle and liberation into the blood stream is dependent on muscle activity, is a potentializer of HSP70 expression and HS response, particularly via its entering in hexosamine biosynthetic pathway (HBP). Herein, we discuss the collaborative role of glutamine (and its donors/precursors) and physical exercise (mostly responsible for glutamine release into the circulation) as potential tools to increase HSP70 expression and the HS response in the elderly.

Glutamine up-regulates MAPK phosphatase-1 induction via activation of Ca2+→ ERK cascade pathway

The non-essential amino acid L-glutamine (Gln) displays potent anti-inflammatory activity by deactivating p38 mitogen activating protein kinase and cytosolic phospholipase A2 via induction of MAPK phosphatase-1 (MKP-1) in an extracellular signal-regulated kinase (ERK)-dependent way. In this study, the mechanism of Gln-mediated ERK-dependency in MKP-1 induction was investigated. Gln increased ERK phosphorylation and activity, and phosphorylations of Ras, c-Raf, and MEK, located in the upstream pathway of ERK, in response to lipopolysaccharidein vitro and in vivo. Gln-induced dose-dependent transient increases in intracellular calcium ([Ca2+]i) in MHS macrophage cells. Ionomycin increased [Ca2+]i and activation of Ras → ERK pathway, and MKP-1 induction, in the presence, but not in the absence, of LPS. The Gln-induced pathways involving Ca2+→ MKP-1 induction were abrogated by a calcium blocker. Besides Gln, other amino acids including L-phenylalanine and l-cysteine (Cys) also induced Ca2+ response, activation of Ras → ERK, and MKP-1 induction, albeit to a lesser degree. Gln and Cys were comparable in suppression against 2, 4-dinitrofluorobenzene-induced contact dermatitis. Gln-mediated, but not Cys-mediated, suppression was abolished by MKP-1 small interfering RNA. These data indicate that Gln induces MKP-1 by activating Ca2+→ ERK pathway, which plays a key role in suppression of inflammatory reactions.

Ammonium ions improve the survival of glutamine-starved hybridoma cells.

BackgroundAs a consequence of a reprogrammed metabolism, cancer cells are dependent on the amino acid l-glutamine for their survival, a phenomenon that currently forms the basis for the generation of new, cancer-specific therapies. In this paper, we report on the role which ammonium ions, a product of glutaminolysis, play on the survival of l-glutamine-deprived Sp2/0-Ag14 mouse hybridoma cells.ResultsThe supplementation of l-glutamine-starved Sp2/0-Ag14 cell cultures with either ammonium acetate or ammonium chloride resulted in a significant increase in viability. This effect did not depend on the ability of cells to synthesize l-glutamine, and was not affected by the co-supplementation with α-ketoglutarate. When we examined the effect of ammonium acetate and ammonium chloride on the induction of apoptosis by glutamine deprivation, we found that ammonium salts did not prevent caspase-3 activation or cytochrome c leakage, indicating that they did not act by modulating core apoptotic processes. However, both ammonium acetate and ammonium chloride caused a significant reduction in the number of l-glutamine-starved cells exhibiting apoptotic nuclear fragmentation and/or condensation.ConclusionAll together, our results show that ammonium ions promote the survival of l-glutamine-deprived Sp2/0-Ag14 cells and modulate late-apoptotic events. These findings highlight the complexity of the modulation of cell survival by l-glutamine, and suggest that targeting survival-signaling pathways modulated by ammonium ions should be examined as a potential anti-cancer strategy.

Drug−Amino Acid Interactions in Aqueous Medium: Volumetric, Compressibility, and Viscometric Studies

Density (ρ), speed of sound (u), and viscosity (η) measurements of amino acids l-glutamine and l-histidine in aqueous solutions of metformin hydrochloride (an antidiabetic drug) (0.01, 0.07, and 0.13 mol·kg–1) were carried out in the concentration range (0.02–0.20 mol·kg–1) at 293.15, 298.15, 303.15, 308.15, and 313.15 K. The experimental data has been meticulously used to enumerate various parameters which assist to procure valuable information regarding the presence of different kinds of intermolecular interactions present in the ternary (metformin hydrochloride + water + amino acids) system. The results were interpreted in terms of various metformin hydrochloride–amino acid intermolecular interactions through a cosphere overlap model. The ion–ion interactions are the key players in ternary system and these interactions are of higher order in the case of histidine as compared to glutamine. Also application of transition state theory has been made to calculate the thermodynamic activation parameters for ...

Intermolecular interactions of l-glutamine and l-histidine in aqueous solutions of metformin hydrochloride: Thermo-acoustic and optical properties

The speed of sound (u)in conjunction with density (ρ) and viscosity (η) for amino acids l-glutamine and l-histidine in aqueous solutions of metformin hydrochloride (an anti-diabetic drug) (0.01, 0.07, and 0.13mol·kg−1) have been measured in the concentration range (0.02–0.20mol·kg−1) at (293.15, 298.15, 303.15, 308.15, and 313.15) K. In order to account for the consequences of drug–amino acid interactions, various acoustical parameters such as intermolecular free length (Lf), relative association (RA), specific acoustic impedance (Z), and molar sound number ([U]) have been evaluated from density and speed of sound data. Combined with viscosity values, the speed of sound data have been used to estimate parameters like relaxation time (τ), internal pressure (πi), molar cohesive energy (MCE)and free volume (Vf). The results of acoustical studies are substantiated with UV–Vis studies for ternary system (water+drug+amino acid). The different kinds of intermolecular interactions existing between different components of the mixture are found to be responsible for the varying trends in aforesaid different acoustic parameters.

Inhibition of MCL-1 by obatoclax sensitizes Sp2/0-Ag14 hybridoma cells to glutamine deprivation-induced apoptosis.

For several cancer cell types, the lack of an adequate supply of the amino acidl-glutamine (Gln) triggers apoptosis, a phenomenon termed Gln addiction. In this report, we examined the role of the anti-apoptotic proteins of the B-cell lymphoma 2 (BCL-2) protein family in the survival of Sp2/0-Ag14 (Sp2/0) mouse hybridoma cells, a cell line that undergoes apoptosis within minutes of Gln deprivation. Western blot analysis revealed that myeloid cell leukaemia 1 (MCL-1) was expressed at much higher levels than BCL-2, B-cell lymphoma extra-large and BCL-2-like protein 2 making it the prominent pro-survival BCL-2 family member in this hybridoma. Gln deprivation triggered a progressive decrease in MCL-1 protein levels, which coincided with the decrease in Sp2/0 cell survival. Moreover, Sp2/0 cells were much more sensitive to the broad Bcl-2 homology domain-3 (BH3) mimetic obatoclax (which targets MCL-1) than to the more selective drug ABT-737 (which does not target MCL-1). Finally, we show that obatoclax sensitizes Sp2/0 cells to apoptosis following Gln starvation. All together, the data presented here reveal that modulation of the pro-survival protein MCL-1 is an important step in the sequence of events leading to the initiation of apoptosis in Gln-starved Sp2/0 cells. Cancer cells require an adequate supply ofl-glutamine for their survival. Using a mouse hybridoma cell line that is exquisitely sensitive to glutamine starvation, we show that the levels of the pro-survival BCL-2 family protein MCL-1 decrease upon glutamine starvation in a manner that correlates with the loss of cell viability. Moreover, inhibiting MCL-1 with the drug obatoclax sensitizes hybridoma cells to glutamine starvation. Thus, in some cancer cells, glutamine starvation triggers the inactivation of pro-survival proteins. Our data suggest that the combined inhibition of glutamine biosynthesis pathways and BCL-2 proteins may prove effective against some cancers.

Mechanism of glutamine inhibition of cytosolic phospholipase a2 (cPLA2 ): Evidence of physical interaction between glutamine-Induced mitogen-activated protein kinase phosphatase-1 and cPLA2.

Non-essential amino acid L-glutamine (Gln) possesses anti-inflammatory activity via deactivating cytosolic phospholipase A2 (cPLA2 ). We showed previously that Gln deactivated cPLA2 indirectly via dephosphorylating p38 mitogen-activated protein kinase (MAPK), the major kinase for cPLA2 phosphorylation, through inducing MAPK phosphatase-1 (MKP-1). In this study, we investigated the precise mechanism underlying Gln deactivation of cPLA2 . In lipopolysaccharide (LPS)-treated mice, Gln injection resulted in dephosphorylation of phosphorylated cPLA2 (p-cPLA2 ), which coincided with rapid Gln induction of MKP-1. MKP-1 small interfering RNA (siRNA) abrogated the ability of Gln to induce MKP-1 as well as the dephosphorylation of cPLA2 . Co-immunoprecipitation and in-situ proximity ligation assay revealed a physical interaction between MKP-1 and p-cPLA2 . In a murine model of allergic asthma, we also demonstrated the physical interaction between MKP-1 and p-cPLA2 . Furthermore, Gln suppressed various allergic asthma phenotypes, such as neutrophil and eosinophil recruitments into the airway, airway levels of T helper type 2 (Th2) cytokines [interleukin (IL)-4, IL-5 and IL-13], airway hyperresponsiveness, mucin production and metabolites (leukotriene B4 and platelet-activating factor) through inhibiting cPLA2 in a MKP-1-dependent manner. These data suggest that MKP-1 uses cPLA2 , in addition to p38, as a substrate, which further potentiates the anti-inflammatory action of Gln.