Kegg Pathway: Arginine and proline metabolism

Amino Acids. 2008 Jul 13;
Yin FG, Liu YL, Yin YL, Kong XF, Huang RL, Li TJ, Wu GY, Hou Y

Two experiments were conducted to evaluate the effects of dietary supplementation with Astragalus polysaccharide (APS) on growth performance, apparent ileal digestibilities (AID) of amino acids (AA), and their serum concentrations in early weaned piglets. In Exp. 1, 60 pigs were weaned at 21 days of age (BW 7.35 +/- 0.23 kg) and allocated to three treatments (20 pigs/treatment), representing supplementing 0.0% (control), 0.02% colistin (antibiotic), or 0.1% APS to a corn- and soybean meal-based diet. Average daily gain (ADG), average daily feed intake (ADFI), and feed/gain ratio (F/G) were measured weekly. Blood samples were obtained from five pigs selected randomly from each treatment for the measurement of serum free AA concentrations on days 7, 14, and 28. In Exp. 2, 12 pigs were weaned at 21 day of age (BW 7.64 +/- 0.71 kg), assigned to three treatment groups as in Exp. 1, and surgically fitted with a simple T-cannula at the terminal ileum. Ileal digesta samples were obtained for the measurement of AID of AA on days 7, 14 and 28. Dietary APS did not affect ADFI, but enhanced (P < 0.05) ADG by 11 and 4.4%, and improved F/G by 5.6 and 8.4%, respectively, compared with the control and antibiotic groups. Addition of APS to the diet increased AID and serum concentrations of most nutritionally essential and non-essential AA (including Arginine, proline, glutamate, lysine, methionine, tryptophan, and threonine) on days 14 and 28. Circulating levels of total AA were affected by the age of pigs and treatment x time interaction. Collectively, these findings indicate that APS may ameliorate the digestive and absorptive function and regulate AA metabolism to beneficially increase the entry of dietary AA into the systemic circulation, which provide a mechanism to explain the growth-promoting effect of APS in early weaned piglets.

J Nutr. 2008 Jul; 138(7): 1304-9
Zhan Z, Ou D, Piao X, Kim SW, Liu Y, Wang J

This study was conducted to evaluate the effects of dietary Arginine levels on microvascular development of the small intestine in early-weaned pigs. Twenty-four crossbred pigs (5.0 +/- 0.3 kg body weight) were individually housed and randomly allotted to 1 of 3 diets supplemented with 0, 0.7, and 1.2% L-Arginine (8 pigs per group). Pigs consumed the diets ad libitum for 10 d. We collected blood samples on d 3, 6, and 10. On d 10, 6 pigs from each group were randomly selected and killed for tissue sample collection. Compared with control pigs, dietary supplementation with 0.7% L-Arginine increased (P < 0.05) jejunal concentrations of nitrite and nitrate (stable oxidation products of nitric oxide), intestinal villus height, as well as plasma proline and Arginine concentrations on d 6 and 10. Dietary supplementation with 0.7% L-Arginine also increased (P < 0.05) immunoreactive expression of CD34 in duodenal submucosa, ileal mucosa and submucosa, and expression of vascular endothelial growth factor (VEGF) in duodenal submucosa, jejunal mucosa and submucosa, and ileal mucosa compared with the control and 1.2% L-Arginine supplementation. Dietary supplementation with 1.2% L-Arginine increased (P < 0.05) the concentration of jejunal endothelin-1 compared with the control pigs. Immunoexpression of VEGF in duodenal mucosa and plasma lysine concentrations on d 6 and 10 were lower (P < 0.05) in pigs supplemented with 1.2% L-Arginine than in unsupplemented pigs. Collectively, these findings indicate that the effects of L-Arginine on microvascular development are beneficial at lower levels but have adverse effects at higher intakes. Dietary supplementation with 0.7% L-Arginine may be a useful method to improve microvascular development in the small intestine of early-weaned pigs.

Postepy Hig Med Dosw (Online). 2008; 62: 214-21
Mielczarek-Puta M, Chrzanowska A, Graboń W, Barańczyk-Kuźma A

Arginase (amidinohydrolase, EC 3.5.3.1) is known as the last enzyme in the urea cycle in the liver, but it is also present in extrahepatic tissues. Arginase hydrolyzes L-Arginine to L-ornithine and urea and its biochemical and physiological role varies depending on the organism and tissue. Besides its participation in ammonia detoxification, arginase is involved in the synthesis of polyamines, crucial for the proper course of many metabolic processes, proline, the main connective tissues protein, and glutamates, amino acids which take part in nitric metabolism, important in the nervous system and also a substrate for protein synthesis. The competition of arginase with nitric oxide synthase (NOS) for the common substrate L-Arginine indicates its participation in the regulation of nitric oxide (NO) synthesis. The physiological role of arginase and its common occurrence indicate its engagement in many pathologies. Due to its competition with NOS for Arginine and its participation in proline synthesis, arginase plays an important role in such diseases as cerebral stroke, trauma, inflammation, and depression, whereas its participation in polyamine synthesis indicates arginase's engagement in the development of neoplastic diseases in the human organism.

Postepy Hig Med Dosw (Online). 2008; 62: 206-13
Mielczarek-Puta M, Chrzanowska A, Barańczyk-Kuźma A

Arginase (amidinohydrolase, EC 3.5.3.1) is present in all living organisms, i.e. bacteria, yeasts, plants, invertebrates, and vertebrates. In ureolitic organisms, arginase expresses the highest activity in the liver, where it takes part in ammonia detoxifi cation. Arginase activity is much lower in extrahepatic tissues and its physiological function is still poorly understood; however, it seems to be involved in L-Arginine metabolism. Arginase is a homotrimer consisting of 20- to 40-kDa subunits acting at a pH of 10 and in the presence of manganese ions. proline, ornithine, and NG-hydroxy-L-Arginine, an intermediate in the biosynthesis of NO, are known as competitive arginase inhibitors. Two arginase isoenzymes, AI (the so-called "hepatic arginase") and AII ("extrahepatic arginase") are present in mammalian tissues. There are signifi cant differences between the isoenzymes regarding their subcellular localization, isoelectric point, substrate affinity, and immunological cross-reactivity. Arginase isoenzymes AI and AII have high substrate specifi city, but the affi nity to L-Arginine is higher for isoenzyme AI than AII. Both isoenzymes exist in most tissues and their expressions change depending on the functional state and metabosynlic requirements. Besides differences in the amino-acid content of the arginase isoforms within one or different species, they have highly conserved regions responsible for the structure and catalytic properties of arginase.

J Food Sci. 2008 May; 73(4): C249-55
Nam KA, You SG, Kim SM

The physicochemical properties of squid skin collagens and biological activity of their enzymatic hydrolysates were determined to produce more value-added materials. The amino acid compositions of the inner and outer squid skin collagens were similar, but distinct from that of bovine tendon collagen in respect to the higher levels of aspartic acid, Arginine, threonine, and serine, and of the lower levels of alanine, proline, and hydroxyproline. SDS-PAGE patterns suggested that squid skin collagen consisted of at least 2 different polypeptides (alpha1 and alpha2 chains) and their cross-linked chains. The molecular weights of alpha1 and alpha2 chains of bovine tendon collagens were higher than those of the corresponding alpha1 and alpha2 chains of squid skin collagens. The denaturation temperatures of inner and outer skin collagens were 27.1 and 27.3 degrees C, respectively, which were about 9 degrees C lower than that of bovine tendon collagen. Water holding capacities of inner and outer squid skin collagens were relatively similar, but were significantly greater than that of bovine tendon collagen. The maximum hydrolysis of squid skin collagens was obtained as follows: for outer skin collagen, enzyme concentration, 3.5%; hydrolysis time, 83 min; pH 7.0; hydrolysis temperature, 60 degrees C, whereas for inner skin collagen, enzyme concentration, 3.2%; hydrolysis time, 83 min; pH 7.0; hydrolysis temperature, 60 degrees C. The enzymatic hydrolysates of outer and inner skin collagens were separated by Sephacryl S-100 column, resulting in the production of 3 fractions (F1, F2, and F3). F3 fraction exhibited higher antioxidant, tyrosinase inhibitory, and antielastase activities than the other fractions.

Methods Enzymol. 2008; 440: 221-30
Kepka-Lenhart D, Ash DE, Morris SM

Of all Arginine catabolic enzymes, the arginases and nitric oxide (NO) synthases are the ones that are of greatest interest to many investigators. Mammalian arginases catalyze the hydrolysis of Arginine to ornithine and urea and are composed of two distinct isozymes: arginase I, located within the cytosol, and arginase II, located within mitochondria. The arginases not only can inhibit NO synthesis by reducing Arginine availability, but also can promote the synthesis of polyamines or proline via production of the common precursor ornithine. Because of their inducibility in many cell types and to their potential impact on multiple biochemical pathways in health and disease, there is growing interest in assays of arginase activity. Although arginase activity may be determined by either spectrophotometric or radiochemical assays, radiochemical assays afford greater sensitivity and do not require correction for any ornithine or urea that may be present in the samples. Part of the arginase assay protocol described in this chapter also can be used for radiochemical assays of enzymes that catalyze decarboxylation reactions. No activity assay currently available is capable of distinguishing the arginase isozymes.

BMC Plant Biol. 2008; 8: 40
Funck D, Stadelhofer B, Koch W

BACKGROUND: Like many other plant species, Arabidopsis uses Arginine (Arg) as a storage and transport form of nitrogen, and proline (Pro) as a compatible solute in the defence against abiotic stresses causing water deprivation. Arg catabolism produces ornithine (Orn) inside mitochondria, which was discussed controversially as a precursor for Pro biosynthesis, alternative to glutamate (Glu). RESULTS: We show here that ornithine-delta-aminotransferase (deltaOAT, At5g46180), the enzyme converting Orn to pyrroline-5-carboxylate (P5C), is localised in mitochondria and is essential for Arg catabolism. Wildtype plants could readily catabolise supplied Arg and Orn and were able to use these amino acids as the only nitrogen source. Deletion mutants of deltaOAT, however, accumulated urea cycle intermediates when fed with Arg or Orn and were not able to utilize nitrogen provided as Arg or Orn. Utilisation of urea and stress induced Pro accumulation were not affected in T-DNA insertion mutants with a complete loss of deltaOAT expression. CONCLUSION: Our findings indicate that deltaOAT feeds P5C exclusively into the catabolic branch of Pro metabolism, which yields Glu as an end product. Conversion of Orn to Glu is an essential route for recovery of nitrogen stored or transported as Arg. Pro biosynthesis occurs predominantly or exclusively via the Glu pathway in Arabidopsis and does not depend on Glu produced by Arg and Orn catabolism.

Cell Cycle. 2008 Apr; 7(7): 848-52
Hu W, Feng Z, Atwal GS, Levine AJ

The roles of the p53 protein in tumor suppression have been firmly established. However, the functions of this protein under normal conditions or in the absence of stress, if any, have remained a mystery. In humans, some alleles containing a functional single nucleotide polymorphism in the p53 gene and its negative regulator, the Mdm2 gene, are under positive selection over evolutionary time frames, suggesting that the p53 pathway might have important functions that are optimized and selected for by evolutionary or reproductive pressures. Indeed, a recent study demonstrated a new function for the p53 protein in the regulation of maternal reproduction in mice, through transcriptional regulation of leukemia inhibitory factor (LIF), a novel p53 target gene. Sufficient uterine LIF levels are essential for the implantation of blastocysts or early embryos into the uterus. p53 deficient (p53(-/-)) female mice have a reduced pregnancy rate and litter size, due to impaired implantation resulting from decreased uterine LIF levels. Administration of LIF to pregnant p53(-/-) mice restored maternal reproduction by improving implantation. An association has been reported between women carrying the p53 codon 72 polymorphism (a proline to Arginine change) with recurrent implantation failure, suggesting a similar function for p53 in humans. These findings of a new function for the p53 protein in reproduction may help to explain the observed evolutionary selection of some alleles of the p53 and Mdm2 genes. This may also be an excellent example of antagonistic pleiotrophy.

Eur J Pharmacol. 2008 May 13; 585(2-3): 375-84
Maarsingh H, Zaagsma J, Meurs H

Allergic asthma is a chronic disease characterized by early and late asthmatic reactions, airway hyperresponsiveness, airway inflammation and airway remodelling. Changes in l-Arginine homeostasis may contribute to all these features of asthma by decreased nitric oxide (NO) production and increased formation of peroxynitrite, polyamines and l-proline. Intracellular l-Arginine levels are regulated by at least three distinct mechanisms: (i) cellular uptake by cationic amino acid (CAT) transporters, (ii) metabolism by NO-synthase (NOS) and arginase, and (iii) recycling from l-citrulline. Ex vivo studies using animal models of allergic asthma have indicated that attenuated l-Arginine bioavailability to NOS causes deficiency of bronchodilating NO and increased production of procontractile peroxynitrite, which importantly contribute to allergen-induced airway hyperresponsiveness after the early and late asthmatic reaction, respectively. Decreased cellular uptake of l-Arginine, due to (eosinophil-derived) polycations inhibiting CATs, as well as increased consumption by increased arginase activity are major causes of substrate limitation to NOS. Increasing substrate availability to NOS by administration of l-Arginine, l-citrulline, the polycation scavenger heparin, or an arginase inhibitor alleviates allergen-induced airway hyperresponsiveness by restoring the production of bronchodilating NO. In addition, reduced l-Arginine levels may contribute to the airway inflammation associated with the development of airway hyperresponsiveness, which similarly may involve decreased NO synthesis and increased peroxynitrite formation. Increased arginase activity could also contribute to airway remodelling and persistent airway hyperresponsiveness in chronic asthma via increased synthesis of l-ornithine, the precursor of polyamines and l-proline. Drugs that increase the bioavailability of l-Arginine in the airways - particularly arginase inhibitors - may have therapeutic potential in allergic asthma.

FEBS J. 2008 May; 275(9): 2185-99
Lee VH, Healy T, Fonseca BD, Hayashi A, Proud CG

Mammalian target of rapamycin complex 1 (mTORC1) phosphorylates proteins such as eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and the S6 kinases. These substrates contain short sequences, termed TOR signalling (TOS) motifs, which interact with the mTORC1 component raptor. Phosphorylation of 4E-BP1 requires an additional feature, termed the RAIP motif (Arg-Ala-Ile-Pro). We have analysed the interaction of 4E-BP1 with raptor and the amino acid residues required for functional RAIP and TOS motifs, as assessed by raptor binding and the phosphorylation of 4E-BP1 in human cells. Binding of 4E-BP1 to raptor strongly depends on an intact TOS motif, but the RAIP motif and additional C-terminal features of 4E-BP1 also contribute to this interaction. Mutational analysis of 4E-BP1 reveals that isoleucine is a key feature of the RAIP motif, that proline is also very important and that there is greater tolerance for substitution of the first two residues. Within the TOS motif, the first position (phenylalanine in the known motifs) is most critical, whereas a wider range of residues function in other positions (although an uncharged aliphatic residue is preferred at position three). These data provide important information on the structural requirements for efficient signalling downstream of mTORC1.

Eur J Pharmacol. 2008 Apr 28; 584(2-3): 368-75
Chen SX, Song T, Zhou SH, Liu YH, Wu SJ, Liu LY

To explore detrimental effects of advanced oxidation protein products-bovine serum albumin (BSA) on endothelial function and compare the favorable effects of angiotensin-converting enzyme (ACE) inhibitors: captopril and enalapril. Male Sprague-Dawley rats were randomly divided into groups: control, advanced oxidation protein products-BSA, captopril (10, 20 mg/kg/day), enalapril (15 mg/kg/day), and N(G)-nitro-l-Arginine methyl ester (l-NAME, 300 mg/kg/day) plus captopril (20 mg/kg/day) groups. All animals were given advanced oxidation protein products-BSA (100 mg/kg/day, i.v.) except for control group (iv. equal volume of PBS). Rats in other groups were received different drugs intragastrically after advanced oxidation protein products-BSA administration. Endothelium-dependent relaxation of thoracic aorta was assayed. Content of nitrite/nitrate (NO), malondialdehyde (MDA), activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and of ACE in Sera, as well as renal function index including blood urea nitrogen and creatinine were measured. After 30 days, the endothelium-dependent relaxation of blood vessels in received advanced oxidation protein products-BSA rats was significantly impaired compared with control rats. The impairment was accompanied by decreases of serum NO, activity of GSH-Px and SOD. Administration of captopril and enalapril not only decreased damage of endothelium-dependent relaxation, but also reverse the changes of MDA levels, NO content and activity of SOD. The protective effect of captopril was abolished by L-NAME. Blood urea nitrogen and creatinine had no significant differences between various groups. ACE activities were decreased in high captopril and enalapril groups, but did not significantly change in other groups. The results suggested that captopril and enalapril have similar effects on endothelial dysfunction induced by advanced oxidation protein products-BSA, which indicated that protective effects of captopril are not related to sulfhydryl group.

Pediatrics. 2008 Apr; 121(4): e920-6
Scholl-Bürgi S, Haberlandt E, Heinz-Erian P, Deisenhammer F, Albrecht U, Sigl SB, Rauchenzauner M, Ulmer H, Karall D

OBJECTIVE: The purpose of this work was to investigate the influence of age, gender, and antiepileptic therapy on amino acid cerebrospinal fluid/plasma ratios in children. PATIENTS AND METHODS: Concentrations of 17 amino acids measured by ion-exchange chromatography with ninhydrin detection in plasma and cerebrospinal fluid from 68 patients with neurologic diseases were used to calculate their cerebrospinal fluid/plasma ratios (70 measurements; 28 female patients [29 punctures] and 40 male patients [41 punctures]). Age dependence and the effects of gender and antiepileptic medication on amino acid cerebrospinal fluid/plasma ratios were investigated by linear multiple regression analysis, and nonstandardized predicted mean values for 2 age groups were calculated (cutoff: 3 years old). RESULTS: The cerebrospinal fluid/plasma ratios ranged between 0.02 for glycine and 0.93 for glutamine. Age had a significant influence on cerebrospinal fluid/plasma ratios for valine, isoleucine, leucine, and tyrosine, with higher ratios in younger children. Gender had a significant influence only on the glutamine cerebrospinal fluid/plasma ratio (female patients had lower ratios). Cerebrospinal fluid/plasma ratios of glutamine and tyrosine were significantly elevated by valproate therapy and those of serine, asparagine, glutamine, valine, methionine, and phenylalanine by phenobarbital therapy. No significant influence of age, gender, and antiepileptic drugs was detectable on cerebrospinal fluid/plasma ratios of threonine, proline, glycine, alanine, histidine, ornithine, lysine, and Arginine. CONCLUSIONS: Cerebrospinal fluid/plasma ratios, especially for essential neutral amino acids and for serine, asparagine, and glutamine were influenced to different degrees by age, gender, and antiepileptic therapy.

J Immunol. 2008 Mar 15; 180(6): 3969-79
Moesta AK, Norman PJ, Yawata M, Yawata N, Gleimer M, Parham P

Interactions between HLA-C ligands and inhibitory killer cell Ig-like receptors (KIR) control the development and response of human NK cells. This regulatory mechanism is usually described by mutually exclusive interactions of KIR2DL1 with C2 having lysine 80, and KIR2DL2/3 with C1 having asparagine 80. Consistent with this simple rule, we found from functional analysis and binding assays to 93 HLA-A, HLA-B, and HLA-C isoforms that KIR2DL1*003 bound all C2, and only C2, allotypes. The allotypically related KIR2DL2*001 and KIR2DL3*001 interacted with all C1, but they violated the simple rule through interactions with several C2 allotypes, notably Cw*0501 and Cw*0202, and two HLA-B allotypes (B*4601 and B*7301) that share polymorphisms with HLA-C. Although the specificities of the "cross-reactions" were similar for KIR2DL2*001 and KIR2DL3*001, they were stronger for KIR2DL2*001, as were the reactions with C1. Mutagenesis explored the avidity difference between KIR2DL2*001 and KIR2DL3*001. Recombinant mutants mapped the difference to the Ig-like domains, where site-directed mutagenesis showed that the combination, but not the individual substitutions, of Arginine for proline 16 in D1 and cysteine for Arginine 148 in D2 made KIR2DL2*001 a stronger receptor than KIR2DL3*001. Neither residue 16 or 148 is part of, or near to, the ligand-binding site. Instead, their juxtaposition near the flexible hinge between D1 and D2 suggests that their polymorphisms affect the ligand-binding site by changing the hinge angle and the relative orientation of the two domains. This study demonstrates how allelic polymorphism at sites distal to the ligand-binding site of KIR2DL2/3 has diversified this receptor's interactions with HLA-C.

Helicobacter. 2008 Apr; 13(2): 103-11
Gao XX, Ge HM, Zheng WF, Tan RX

BACKGROUND: Helicobacter pylori, the human pathogenic gram-negative microaerophilic bacterium, causes chronic gastric infection in more than half of the human population regardless of race. The infection of microbe is not yet controllable to pose a substantial public health impact and a growing social burden. The management of H. pylori infection primarily necessitates accurate and timely diagnosis at case level, on-demand supervision of pathologic progression, and reliable evaluation of the impact of pharmacologic interventions on the patients' population. METHODS: The characterization of H. pylori infection on gerbils model was performed by metabolic profiling, employing 1H NMR spectroscopy compounding multivariate pattern recognition strategies. In the same manner, urine samples were individually collected from 10 gerbils infected with H. pylori GS13, and from 10 uninfected control animals equally accessible to feed and water. RESULTS: The resultant metabolic profiles indicate that H. pylori infection disturbs carbohydrate metabolism to elevate the levels of alpha- and beta-glucose, and cis-aconitate (a TCA cycle intermediate). In addition to the energy metabolism alteration, the colonization of H. pylori in gerbil stomach generates a remarkable deviation of amino acid metabolism as indicated by depletion of taurine and Arginine, and elevation of proline and glutamine in the animal urine. Moreover, the H. pylori infection modifies the gut microbiota as highlighted by a range of microbial-related metabolites such as indoxyl sulfate and hippurate. CONCLUSIONS: These findings demonstrate that the (1)H NMR-based urine metabolic profiling is a promising technique capable of providing an accurate, noninvasive, and rapid diagnosis of H. pylori infection.

Plant Physiol. 2008 Apr; 146(4): 2008-19
Jubault M, Hamon C, Gravot A, Lariagon C, Delourme R, Bouchereau A, Manzanares-Dauleux MJ

The hypertrophy and hyperplasia of infected roots into clubs are the intrinsic characteristics of clubroot, one of the economically most important diseases in Brassica crops worldwide. Polyamines, Arginine (Arg)-derived metabolites, have long been recognized as cell proliferation and differentiation regulators in plants and consequently are suitable candidates for potential gall development factors. Furthermore, Arg catabolism, through arginase, which is strongly connected to polyamine metabolism, would play an important role in response to wound trauma and pathogen infection. In this study, we exploited the Arabidopsis (Arabidopsis thaliana)-Plasmodiophora brassicae pathosystem to investigate the involvement of polyamine metabolism and Arg catabolism in host responses to the pathogen infection and in partial clubroot resistance mechanisms. We demonstrated at the transcriptional, enzymatic, and metabolic levels that polyamine metabolism and Arg catabolism are induced during the later stages of disease in compatible Arabidopsis-P. brassicae interactions. However, susceptible and partially resistant plants showed strikingly different Arg metabolism signatures. Susceptible plants were characterized by a transient agmatine production, a massive induction of arginase, and a strong accumulation of proline. The potential functions of this marked activation of the arginase pathway in the P. brassicae pathogenicity strategy are discussed. Partially resistant plants showed a continuous agmatine production and a weaker arginase pathway activity than the susceptible genotype. Results suggest that the symptom severity was strongly associated to the differential regulation of root polyamine metabolism and Arg catabolism. Further work using arginase transgenic plants will provide insight into the physiological function of the arginase pathway in partial clubroot resistance.

Mikrobiologiia. 2007 Nov-Dec; 76(6): 752-8
Riazanova LP, Smirnov AV, Kulakovskaia TV, Kulaev IS

Brevibacteria able to decrease phosphate concentration in the medium are of interest for the study of the role of bacteria in the phosphorus cycle and for development of biotechnology of phosphate removal from waste. Brevibacterium casei, Brevibacterium linens, and Brevibacterium epidermidis grown in media with initial phosphorus concentrations of 1-11 mM were shown to decrease its concentration by 90%. The composition of the incubation medium required for B. casei to carry out this process was established. This process occurs in the absence of glucose but requires the presence of Mg2+, NH4+, and alpha-ketoglutarate. The latter two components may be replaced by amino acids metabolized to NH4+ and alpha-ketoglutarate: histidine, Arginine, glutamine, proline, or glutamic acid. No formation of insoluble phosphate salts was observed when the media were incubated under the same conditions with heat-inactivated cells or without cells at pH 7-8.5.

J Biol Chem. 2008 Apr 18; 283(16): 10485-92
Cooper SK, Pandhare J, Donald SP, Phang JM

proline and hydroxyproline are metabolized by distinct pathways. proline is important for protein synthesis, as a source of glutamate, Arginine, and tricarboxylic acid cycle intermediates, and for participating in a metabolic cycle that shuttles redox equivalents between mitochondria and cytosol. Hydroxyproline, in contrast, is not reutilized for protein synthesis. The first steps in the degradation of proline and hydroxyproline are catalyzed by proline oxidase (POX) and hydroxyproline oxidase (OH-POX), respectively. Because it is well documented that POX is induced by p53 and plays a role in apoptosis, we considered whether OH-POX also participates in the response to cytotoxic stress. In LoVo and RKO cells, which respond to adriamycin with a p53-mediated induction of POX and generation of reactive oxygen species, we found that adriamycin also induced OH-POX gene expression and markedly increased OH-POX catalytic activity, and this increase in activity was not observed in the cell lines HT29 and HCT15, which do not have a functional p53. We also observed an increase in reactive oxygen species generation and activation of caspase-9 with adriamycin in a hydroxyproline-dependent manner. Therefore, we hypothesize that OH-POX plays a role analogous to POX in growth regulation, ROS generation, and activation of the apoptotic cascade.

Prog Neuropsychopharmacol Biol Psychiatry. 2008 Apr 1; 32(3): 870-5
Wang LH, Chen JY, Liou YJ, Wang YC, Lai IC, Liao DL, Chen CH

Abnormal dopamine signal transduction is implicated in the pathophysiology of schizophrenia. A recent study showed that prostate apoptosis response 4 protein (Par-4) interacts with dopamine D2 receptor and plays an important role in dopamine signaling. Par-4 knockout mice showed depression-like behavior, suggesting that Par-4 gene may be associated with mental disorders in human. The study was aimed to determine whether the PRKC, apoptosis, WT1, regulator gene (PAWR) that encodes the human homolog of Par-4 protein is a susceptibility gene for schizophrenia. We systematically screened for mutations at the 5' untranslated region (5'UTR) and all the exonic regions of the PAWR gene in a sample of Han Chinese schizophrenic patients from Taiwan. We identified two missense single nucleotide polymorphisms (SNPs) that are in strong linkage in our sample (D'=0.98), i.e. P78R at exon 2 and I199M at exon 3, respectively. SNP- and haplotype-based analysis showed that these two variants are associated with schizophrenia; there is an overrepresentation of RR homozygotes of P78R (OR=2.00, 95% CI=1.05-3.83) and MM homozygotes of I199M (OR=1.81, 95% CI=0.95-3.54) in schizophrenic patients as compared to control subjects. When subjects were divided by gender, the association is specifically with female patients (OR=2.94 for RR and OR=2.7 for MM), but not with male patients. Our results indicate that the PAWR gene is associated with schizophrenia in our population, and this study provides genetic evidence to support the dopamine hypothesis of schizophrenia.

N Engl J Med. 2008 Feb 14; 358(7): 709-15
Teles MG, Bianco SD, Brito VN, Trarbach EB, Kuohung W, Xu S, Seminara SB, Mendonca BB, Kaiser UB, Latronico AC

Gonadotropin-dependent, or central, precocious puberty is caused by early maturation of the hypothalamic-pituitary-gonadal axis. In girls, this condition is most often idiopathic. Recently, a G protein-coupled receptor, GPR54, and its ligand, kisspeptin, were described as an excitatory neuroregulator system for the secretion of gonadotropin-releasing hormone (GnRH). In this study, we have identified an autosomal dominant GPR54 mutation--the substitution of proline for Arginine at codon 386 (Arg386Pro)--in an adopted girl with idiopathic central precocious puberty (whose biologic family was not available for genetic studies). In vitro studies have shown that this mutation leads to prolonged activation of intracellular signaling pathways in response to kisspeptin. The Arg386Pro mutant appears to be associated with central precocious puberty.

J Gen Virol. 2008 Mar; 89(Pt 3): 676-86
Tamm K, Merits A, Sarand I

The cytotoxicity of Semliki Forest virus (SFV) infection is caused partly by the non-structural protein nsP2, an essential component of the SFV replicase complex. Due to the presence of a nuclear localization signal (NLS), nsP2 also localizes in the nucleus of infected cells. The present study analysed recombinant SFV replicons and genomes with various deletions or substitutions in the NLS, or with a proline-to-glycine mutation at position 718 of nsP2 (P718G). Deletion of one or two Arginine residues from the NLS or substitution of two of the Arginines with aspartic acid resulted in a virus with a temperature-sensitive phenotype, and substitution of all three Arginines was lethal. Thus, most of the introduced mutations severely affected nsP2 functioning in viral replication; in addition, they inhibited the ability of SFV to induce translational shut-off and kill infected cells. SFV replicons with a P718G mutation or replacement of the NLS residues (648)RRR(650) with RDD were found to be the least cytotoxic. Corresponding replicons expressed non-structural proteins at normal levels, but had severely reduced genomic RNA synthesis and were virtually unable to replicate and transcribe co-electroporated helper RNA. The non-cytotoxic phenotype was maintained in SFV full-length genomes harbouring the corresponding mutations; however, during a single cycle of cell culture, these were converted to a cytotoxic phenotype, probably due to the accumulation of compensatory mutations.