Metabolic ROS Signaling: To Immunity and Beyond.

Metabolism is a critical determinant of immune cell functionality. Immunometabolism, by definition, is a multidisciplinary area of immunology research that integrates the knowledge of energy transduction mechanisms and biochemical pathways. An important concept in the field is metabolic switch, a transition of immune cells upon activation to preferential utilization of select catabolic pathways for their energy needs. Mitochondria are not inert in this process and contribute to the metabolic adaptation by different mechanisms which include increasing ATP production to match dynamic bioenergetic demands and serving as a signaling platform. The latter involves generation of reactive oxygen species (ROS), one of the most intensively studied mitochondrial processes. While the role of mitochondrial ROS in the context of oxidative stress is well established, ROS signaling in immunity is an emerging and quickly changing field. In this review, we discuss ROS signaling and immunometabolism concepts from the standpoint of bioenergetics. We also provide a critical insight into the methodology for ROS assessment, outlining current challenges in the field. Finally, based on our analysis of the literature data, we hypothesize that regulatory ROS production, as opposed to oxidative stress, is controlled by mitochondrial biogenesis rather than metabolic switches.

Impaired brain creatine kinase activity in Huntington's disease.

BACKGROUND: Huntington's disease (HD) is associated with impaired energy metabolism in the brain. Creatine kinase (CK) catalyzes ATP-dependent phosphorylation of creatine (Cr) into phosphocreatine (PCr), thereby serving as readily available high-capacity spatial and temporal ATP buffering. OBJECTIVE: Substantial evidence supports a specific role of the Cr/PCr system in neurodegenerative diseases. In the brain, the Cr/PCr ATP-buffering system is established by a concerted operation of the brain-specific cytosolic enzyme BB-CK and ubiquitous mitochondrial uMt-CK. It is not yet established whether the activity of these CK isoenzymes is impaired in HD. METHODS: We measured PCr, Cr, ATP and ADP in brain extracts of 3 mouse models of HD - R6/2 mice, N171-82Q and HdhQ(111) mice - and the activity of CK in cytosolic and mitochondrial brain fractions from the same mice. RESULTS: The PCr was significantly increased in mouse HD brain extracts as compared to nontransgenic littermates. We also found an approximately 27% decrease in CK activity in both cytosolic and mitochondrial fractions of R6/2 and N171-82Q mice, and an approximately 25% decrease in the mitochondria from HdhQ(111) mice. Moreover, uMt-CK and BB-CK activities were approximately 63% lower in HD human brain samples as compared to nondiseased controls. CONCLUSION: Our findings lend strong support to the role of impaired energy metabolism in HD, and point out the potential importance of impairment of the CK-catalyzed ATP-buffering system in the etiology of HD.

A network of control mediated by regulator of calcium/calmodulin-dependent signaling.

Calmodulin (CaM) is a major effector for the intracellular actions of Ca2+ in nearly all cell types. We identified a CaM-binding protein, designated regulator of calmodulin signaling (RCS). G protein-coupled receptor (GPCR)-dependent activation of protein kinase A (PKA) led to phosphorylation of RCS at Ser55 and increased its binding to CaM. Phospho-RCS acted as a competitive inhibitor of CaM-dependent enzymes, including protein phosphatase 2B (PP2B, also called calcineurin). Increasing RCS phosphorylation blocked GPCR- and PP2B-mediated suppression of L-type Ca2+ currents in striatal neurons. Conversely, genetic deletion of RCS significantly increased this modulation. Through a molecular mechanism that amplifies GPCR- and PKA-mediated signaling and attenuates GPCR- and PP2B-mediated signaling, RCS synergistically increases the phosphorylation of key proteins whose phosphorylation is regulated by PKA and PP2B.

[Intracellular proteolysis: signals of selective protein degradation]. / Vnutrikletochnyi proteoluz. Signaly selektivnoi degradatsii belkov.

Selective proteolysis is one of the mechanisms for the maintenance of cell homeostasis via rapid degradation of defective polypeptides and certain short-lived regulatory proteins. In prokaryotic cells, high-molecular-mass oligomeric ATP-dependent proteases are responsible for selective protein degradation. In eukaryotes, most polypeptides are attacked by the multicatalytic 26S proteasome, and the degradation of the majority of substrates involves their preliminary modification with the protein ubiquitin. The proteins undergoing the selective proteolysis often contain specific degradation signals necessary for their recognition by the corresponding proteases.

[A test system based on the lux-regulon from Vibrio fischeri for studying the functional activity of mutant forms of Escherichia coli lon-proteinase]. / Test-sistema na osnove lux-regulona Vibrio fischeri pri issledovanii funktsional'noi aktivnosti mutantnykh form lon-proteinazy Escherichia coli.

The possibility of application of the bioluminescence method (Lux-test) for studying in vivo functional activity of Escherichia coli protease Lon and its mutants was demonstrated. This assay is based on the capacity of protease Lon and its mutant forms for specific degradation of the LuxR protein, a positive transcriptional activator of the right operon luxICDABE from the marine bacterium Vibrio fischeri, and thus to affect the level of AB luciferase in the cells. A correlation between in vitro activity of the protease Lon mutants and the intensity of bioluminescence measured by the Lux-test was revealed.

The isolated proteolytic domain of Escherichia coli ATP-dependent protease Lon exhibits the peptidase activity.

Selective protein degradation is an energy-dependent process performed by high-molecular-weight proteases. The activity of proteolytic components of these enzymes is coupled to the ATPase activity of their regulatory subunits or domains. Here, we obtained the proteolytic domain of Escherichia coli protease Lon by cloning the corresponding fragment of the lon gene in pGEX-KG, expression of the hybrid protein, and isolation of the proteolytic domain after hydrolysis of the hybrid protein with thrombin. The isolated proteolytic domain exhibited almost no activity toward protein substrates (casein) but hydrolyzed peptide substrates (melittin), thereby confirming the importance of the ATPase component for protein hydrolysis. Protease Lon and its proteolytic domain differed in the efficiency and specificity of melittin hydrolysis.

A serine protease from the bovine duodenal mucosa, chymotrypsin-like duodenase.

Chymotrypsin-like duodenase (ChlD), a new protease from the bovine duodenum mucosa was isolated and purified. The enzyme molecule is a single chain (25 kDa); the native enzyme is a monomer with an isoelectric point > 10.0. ChlD displays the chymotrypsin-like activity and cleaves 4-nitroanilide substrates of chymotrypsin, chymases and cathepsin G. ChlD hydrolyzes its best substrate 2-N-succinylvalylprolylphenylalanine 4-nitroanilide with k(cat) of 2.8 s(-1) and catalytic efficiency k(cat)/Km of 2300 M(-1) s(-1). The enzyme is stable with a pH range of 3-10 and exhibits the maximum activity at pH 8-10. ChlD is irreversibly inhibited by diisopropylphosphofluoridate and phenylmethanesulfonyl fluoride, which is indicative of an active-site serine in this protease. Alpha-N-tosyl-L-phenylalanine chloromethane, a specific reagent for a catalytically active His, markedly inhibited ChlD. The enzyme activity was strongly inhibited by several natural inhibitors of serine proteases (from soybean, potato, Lima bean, kidney bean). The N-terminal sequence of the native ChlD (23 amino acids) shows high similarity, but not identity, to those of duodenase, granzymes, chymases and cathepsin G.

Mutations in the proteolytic domain of Escherichia coli protease Lon impair the ATPase activity of the enzyme.

Conserved residues of the proteolytic domain of Escherichia coli protease Lon, putative members of the classic catalytic triad (H665, H667, D676, and D743) were identified by comparison of amino acid sequences of Lon proteases. Mutant enzymes containing substitutions D676N, D743N, H665Y, and H667Y were obtained by site-directed mutagenesis. The mutant D743N retained the adenosine triphosphate (ATP)-dependent proteolytic activity, thereby indicating that D743 does not belong to the catalytic site. Simultaneously, the mutants D676N, H665Y, and H667Y lost the capacity for hydrolysis of protein substrates. The ATPase activity of these three mutants was decreased by more than an order of magnitude, which suggests a close spatial location of the ATPase and proteolytic active sites and their tight interaction in the process of protein degradation.

[Mechanism of action of the plant hormone jasmonate. 1. Jasomonate-interacting proteins that regulate transcription of the p. pinII potato gene]. / Mekhanizm deistviia rastitel'nogo gormona--zhasmonata. 1. Belki-reguliatory transkriptsii gena p. pinII kartofelia, vzaimodeistviushchie s zhasmonatom.

A fragment containing the regulatory region of the p. pinII gene was isolated from potato DNA by polymerase chain reaction. Interactions of this DNA region with jasmonate determines the transcriptional activation. The isolated DNA fragment was cloned into the pTE2pb plasmid, which was used for preparing an affinity sorbent. Using this sorbent, four proteins were isolated from the total protein capable of desorption at physiological concentration of jasmonate. These proteins are likely to be subunits of two transcription repressors, whereas jasmonate serves as an inducer. Three sequences of the regulatory regions (boxes G, I, and III) are binding sites for repressors; similar sequences were found in various plant genes activated by jasmonate.