Endogenous ADP-Ribosylation in Brain: Initial Characterization of Substrate Proteins

Cholera and pertussis toxin-mediated ADP-ribosylation has been used extensively to study regulation of guanine nucleotide binding proteins (G proteins) in the nervous system, but much less is known about possible endogenous ADP-ribosylation of G proteins in brain. The present study demonstrates endogenous ADP-ribosylation, in the absence of cholera and pertussis toxins, of four predominate proteins in homogenates of rat cerebral cortex. These proteins showed apparent molecular masses of 20, 42, 45, and 50 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 42- and 45-kDa proteins comigrated precisely with the major cholera toxin-labeled bands. Furthermore, the endogenous ADP-ribosylated and cholera toxin-ADP-ribosylated bands yielded identical 32P-labeled peptide fragments by one-dimensional peptide mapping, indicating that they are probably the same proteins, presumably the alpha-subunits of Gs. In contrast, peptide maps of the 50-kDa protein, which migrated close to a 48-kDa cholera toxin-labeled band, demonstrated that this protein is distinct from the toxin-labeled band and from Gs alpha. Levels of endogenous ADP-ribosylation activity showed regional heterogeneity in brain, with a nearly threefold variation observed among the brain regions examined. Chronic administration (7 days) of corticosterone significantly increased overall levels of endogenous ADP-ribosylation, indicating that components of this system may be under hormonal control in vivo. Attempts to identify neurotransmitters or second messenger systems that regulate endogenous ADP-ribosylation activity in brain have so far been unsuccessful with one exception.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunochemical detection of guanine nucleotide binding proteins mono-ADP-ribosylated by bacterial toxins

Rabbits immunized with ADP-ribose chemically conjugated to carrier proteins developed antibodies reactive against guanine nucleotide binding proteins (G proteins) that had been mono-ADP-ribosylated by bacterial toxins. Antibody reactivity on immunoblots was strictly dependent on incubation of substrate proteins with both toxin and NAD and was quantitatively related to the extent of ADP-ribosylation. Gi, Go, and transducin (ADP-ribosylated by pertussis toxin) and elongation factor II (EF-II) (ADP-ribosylated by pseudomonas exotoxin) all reacted with ADP-ribose antibodies. ADP-ribose antibodies detected the ADP-ribosylation of an approximately 40-kilodalton (kDa) membrane protein related to Gi in intact human neutrophils incubated with pertussis toxin and the ADP-ribosylation of an approximately 90-kDa cytosolic protein, presumably EF-II, in intact HUT-102 cells incubated with pseudomonas exotoxin. ADP-ribose antibodies represent a novel tool for the identification and study of G proteins and other substrates for bacterial toxin ADP-ribosylation.     

Role of brefeldin A-dependent ADP-ribosylation in the control of intracellular membrane transport

The fungal toxin brefeldin A (BFA) dissociates coat proteins from Golgi membranes, causes the rapid disassembly of the Golgi complex and potently stimulates the ADP-ribosylation of two cytosolic proteins of 38 and 50 kDa. These proteins have been identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a novel guanine nucleotide binding protein (BARS-50), respectively. The role of ADP-ribosylation in mediating the effects of BFA on the structure and function of the Golgi complex was analyzed by several approaches including the use of selective pharmacological blockers of the reaction and the use of ADP-ribosylated cytosol and/or enriched preparations of the BFA-induced ADP-ribosylation substrates, GAPDH and BARS-50.A series of blockers of the BFA-dependent ADP-ribosylation reaction identified in our laboratory inhibited the effects of BFA on Golgi morphology and, with similar potency, the ADP-ribosylation of BARS-50 and GAPDH. In permeabilized RBL cells, the BFA-dependent disassembly of the Golgi complex required NAD+ and cytosol. Cytosol that had been previously ADP-ribosylated (namely, it contained ADP-ribosylated GAPDH and BARS-50), was instead sufficient to sustain the Golgi disassembly induced by BFA.Taken together, these results indicate that an ADP-ribosylation reaction is part of the mechanism of action of BFA and it might intervene in the control of the structure and function of the Golgi complex.     

Isolation and identification of novel ADP-ribosylated proteins from Streptomyces coelicolor A3(2)

An important role of protein ADP-ribosylation in bacterial morphogenesis has been proposed (J. Bacteriol. 178, 3785-3790; 178, 4935-4941). To clarify the detail of ADP-ribosylation, we identified a new kind of target protein for ADP-ribosylation in Streptomyces coelicolor A3(2) grown to the late growth phase. All four proteins (MalE, BldKB, a periplasmic protein for binding branched-chain amino-acids, and a periplasmic solute binding protein) were functionally similar and participated in the regulation of transport of metabolites or nutrients through the membrane. ADP-ribosylation was likely to occur on a cysteine residue, because the modification group was removed by mercuric chloride treatment. The modification site may be the site of lipoprotein modification necessary for protein export. This report is the first suggesting that certain proteins involved in membrane transport can be ADP-ribosylated.     

Demonstration and partial characterization of ADP-ribosylation in Pseudomonas maltophilia.

ADP-ribosylation of proteins occurs in many eukaryotes, and it is also the mechanism of action of a growing number of important bacterial toxins. To date, however, there is only one well-characterized ADP-ribosylation system where the ADP-ribosyltransferase and the substrate protein are both bacterial in origin, namely within the nitrogen-fixing bacterium Rhodospirillum rubrum. The present paper demonstrates the endogenous ADP-ribosylation of two proteins of Mr 32,000 and 20,000 within Pseudomonas maltophilia, a Gram-negative aerobe. The proteins have been partially purified: two apparently separate species of modified protein can be separated by ion-exchange chromatography and gel filtration (V0 and Mr 158,000 - Vi). The substrate protein(s) either has, or is co-eluted with, NAD+ glycohydrolase activity. The modification is mono-ADP-ribosyl in nature. The linkage between the acceptor amino acid and the ADP-ribose moiety is alkali-labile and stable to hydroxylamine, possibly indicating an S-glycosidic bond. The activity appears to be a true ADP-ribosylation reaction and not an NAD+ glycohydrolase activity followed by non-enzymic addition of ADP-ribose to protein. The results presented here indicate that ADP-ribosylation may have a wider significance within prokaryotic systems than previously thought.     

Isolation and Identification of Novel ADP-Ribosylated Proteins from Streptomyces coelicolor A3(2)

An important role of protein ADP-ribosylation in bacterial morphogenesis has been proposed (J. Bacteriol. 178, 3785-3790; 178, 4935-4941). To clarify the detail of ADP-ribosylation, we identified a new kind of target protein for ADP-ribosylation in Streptomyces coelicolor A3(2) grown to the late growth phase. All four proteins (MalE, BldKB, a periplasmic protein for binding branched-chain amino-acids, and a periplasmic solute binding protein) were functionally similar and participated in the regulation of transport of metabolites or nutrients through the membrane. ADP-ribosylation was likely to occur on a cysteine residue, because the modification group was removed by mercuric chloride treatment. The modification site may be the site of lipoprotein modification necessary for protein export. This report is the first suggesting that certain proteins involved in membrane transport can be ADP-ribosylated.     

Interaction of mastoparan with the low molecular mass GTP-binding proteins rho/rac

Mastoparan, which has been shown to active G proteins, inhibits the ADP-ribosylation of 20 kDa human platelet membrane proteins catalyzed by Clostridium botulinum exoenzyme C3 half-maximally and maximally (90%) at 20 and 100 microM concentrations, respectively. Inhibition of ADP-ribosylation was enhanced by GTP-gamma S. Mastoparan increased GTP hydrolysis by porcine brain rho protein and stimulated GTP binding in a concentration dependent manner. The data suggest that mastoparan not only interacts with heterotrimeric G proteins but also with low molecular mass GTP-binding proteins of the rho/rac family.     

Reversible ADP-ribosylation as a mechanism of enzyme regulation in procaryotes

Several cases of ADP-ribosylation of endogenous proteins in procaryotes have been discovered and investigated. The most thoroughly studied example is the reversible ADP-ribosylation of the dinitrogenase reductase from the photosynthetic bacteriumRhodospirillum rubrum and related bacteria. A dinitrogenase reductase ADP-ribosyltransferase (DRAT) and a dinitrogenase reductase ADP-ribose glycohydrolase (DRAG) fromR. rubrum have been isolated and characterized. The genes for these proteins have been isolated and sequences and show little similarity to the ADP-ribosylating toxins. Other targets for endogenous ADP-ribosylation by procaryotes include glutamine synthetase inR. rubrum andRhizobium meliloti and undefined proteins inStreptomyces griseus andPseudomonas maltophila.     

ADP-ribosylation of cyclophilin A by Pseudomonas aeruginosa exoenzyme S

The virulence of the opportunistic pathogen Pseudomonas aeruginosa (Pa) is in part mediated by the type III secretion (TTS) of bacterial proteins into eukaryotic hosts. Exoenzyme S (ExoS) is a bifunctional Pa TTS effector protein, with GTPase-activating (GAP) and ADP-ribosyltransferase (ADPRT) activities. Known cellular substrates of TTS-translocated ExoS (TTS-ExoS) ADPRT activity include proteins in the Ras superfamily and ERM family proteins. This study describes the ADP-ribosylation of a non-G-protein substrate of TTS-ExoS, cyclophilin A (CpA), a peptidyl-prolyl isomerase (PPIase). Four novel 17 kDa proteins (pI 6.5-6.8) were recognized in a proteomic screen of lysates of human epithelial cells that had been exposed to ExoS-producing Pa, but not an isogenic non-ExoS producing strain. The proteins were identified as isoforms of CpA using MALDI-TOF mass spectrometry and confirmed by Western blotting. Mutagenesis analysis identified arginine 55 and 69 of CpA as sites of ExoS ADP-ribosylation. Examination of the effect of ExoS ADP-ribosylation on CpA function found a moderate (19%) decrease in prolyl isomerization of a Xaa-Pro containing peptides. In comparison, GST-CpA co-immunoprecipitation studies found ExoS ADP-ribosylation of CpA to efficiently inhibit CpA binding to calcineurin/PP2B phosphatase. Our results support that ExoS ADP-ribosylates and affects the function of the cytosolic protein, CpA, with the predominant functional effect relating to interference of CpA-cellular protein interactions.     

Sirtuin chemical mechanisms

Sirtuins are ancient proteins widely distributed in all lifeforms of earth. These proteins are universally able to bind NAD⁺, and activate it to effect ADP-ribosylation of cellular nucleophiles. The most commonly observed sirtuin reaction is the ADP-ribosylation of acetyllysine, which leads to NAD⁺-dependent deacetylation. Other types of ADP-ribosylation have also been observed, including protein ADP-ribosylation, NAD⁺ solvolysis and ADP-ribosyltransfer to 5,6-dimethylbenzimidazole, a reaction involved in eubacterial cobalamin biosynthesis. This review broadly surveys the chemistries and chemical mechanisms of these enzymes.     

Effects of nucleotides on activity of a purified ADP-ribosyltransferase from turkey erythrocytes

A transferase purified from turkey erythrocytes catalyzed the NAD-dependent ADP-ribosylation of proteins in the supernatant, particulate, and detergent-solubilized fractions of bovine thymus as well as several purified proteins. Nucleoside triphosphates increased the rate of ADP-ribosylation of multiple soluble proteins from thymus and several purified proteins by about twofold. With lysozyme as substrate and 10 mm nucleotide, the order of effectiveness was ATP > ITP = GTP > CTP = UTP. Half-maximal stimulation of ADP-ribose incorporation into lysozyme was observed with 2.5 mm ATP. App(NH)p and inorganic tri- and tetrapolyphosphate were less effective than ATP; ADP, AMP, cAMP, and inorganic pyrophosphate were ineffective. Enhancement of transferase-catalyzed ADP-ribosylation by ATP was observed only at low (20–200 μm) NAD concentrations; with lysozyme as substrate, however, the effect of ATP was not due to prevention of NAD hydrolysis during the assay, nor was it due to an effect on ionic strength. The transferase catalyzed the ADP-ribosylation of several purified proteins and, depending on the protein substrate, ATP either increased, decreased, or did not alter the rate of ADP-ribosylation. It appears that ADP-ribosylation of cellular proteins by endogenous ADP-ribosyltransferases may be subject to regulation by nucleoside triphosphates.     

In vitro ADP-ribosylation of nuclear proteins in mouse tissues. Identification of an unusual group of acceptors in testis nuclei

1. Acceptor proteins for poly(ADP-ribose) have been identified in nuclei from mouse testis, liver, kidney and spleen. Purified nuclei were incubated in vitro with [14C]NAD, extracted sequentially with 5% HClO4 and 0.25 N-HCl and labelled proteins analysed on acetic acid/urea polyacrylamide gels pH 2.9. 2. Results show that: (a) in vitro there are significant differences between tissues in the extent of poly(ADP-ribosylation) of nuclear proteins; (b) in testis nuclei two tissue specific proteins are poly(ADP-ribosylated) to higher specific activity than histones; (c) there are significant differences between in vivo and in vitro studies on poly(ADP-ribosylation) of nuclear proteins in testis nuclei.     

Analysis and identification of ADP-ribosylated proteins of <Emphasis Type="Italic">Streptomyces coelicolor</Emphasis> M145

Mono-ADP-ribosylation is the enzymatic transfer of ADP-ribose from NAD⁺ to acceptor proteins catalyzed by ADP-ribosyltransferases. Using m-aminophenylboronate affinity chromatography, 2D-gel electrophoresis, in-gel digestion and MALDI-TOF analysis we have identified eight in vitro ADP-ribosylated proteins in Streptomyces coelicolor, which can be classified into three categories: (i) secreted proteins; (ii) metabolic enzymes using NAD⁺/NADH or NADP⁺/NADPH as coenzymes; and (iii) other proteins. The secreted proteins could be classified into two functional categories: SCO2008 and SC05477 encode members of the family of periplasmic extracellular solute-binding proteins, and SCO6108 and SC01968 are secreted hydrolases. Dehydrogenases are encoded by SC04824 and SC04771. The other targets are GlnA (glutamine synthetase I., SC02198) and SpaA (starvation-sensing protein encoded by SC07629). SCO2008 protein and GlnA had been identified as ADP-ribosylated proteins in previous studies. With these results we provided experimental support for a previous suggestion that ADP-ribosylation may regulate membrane transport and localization of periplasmic proteins. Since ADP-ribosylation results in inactivation of the target protein, ADP-ribosylation of dehydrogenases might modulate crucial primary metabolic pathways in Streptomyces. Several of the proteins identified here could provide a strong connection between protein ADP-ribosylation and the regulation of morphological differentiation in S. coelicolor.     

ADP-ribosylation of proteins in Bacillus subtilis and its possible importance in sporulation.

Endogenous ADP-ribosylation was detected in Bacillus subtilis, as determined in vitro with crude cellular extracts. The ADP-ribosylated protein profile changed during growth in sporulation medium, displaying a temporary appearance of two ADP-ribosylated proteins (36 and 58 kDa) shortly after the end of exponential growth. Mutants resistant to 3-methoxybenzamide, a known inhibitor of ADP-ribosyltransferase, were obtained, and a significant proportion (15%) were found to be defective in both sporulation and antibiotic production. These mutants failed to ADP-ribosylate the 36- and 58-kDa proteins. The parent strain also lost the ability to ADP-ribosylate these proteins when grown in the presence of 3-methoxybenzamide at a concentration at which sporulation but not cell growth was severely inhibited. Results from genetic transformations showed that the mutation conferring resistance to 3-methoxybenzamide, named brgA, was cotransformed with the altered phenotypes, i.e., defects in ADP-ribosylation and sporulation. spoOA and spoOF mutants displayed an ADP-ribosylation profile similar to that of the parent strain, but a spoOH mutant failed to ADP-ribosylate any proteins, including the 36- and 58-kDa proteins. The significance of protein ADP-ribosylation in sporulation was further indicated by the observation that ADP-ribosylation of the 36-kDa protein could be induced by treatment with decoyinine, an inhibitor of GMP-synthetase, and by amino acid limitation, both of which resulted in an immediate decrease in GTP pool size eventually leading to massive sporulation. We propose that a new sporulation gene, which presumably controls sporulation via ADP-ribosylation of certain functional proteins, exists.     

ADP-ribosylation of the bovine brain rho protein by botulinum toxin type C1

We have separated at least six GTP-binding proteins (G proteins) with Mr values between 20,000 and 25,000 from bovine brain crude membranes (Kikuchi, A., Yamashita, T., Kawata, M., Yamamoto, K., Ideda, K., Tanimoto, T., and Takai, Y. (1988) J. Biol. Chem. 263, 2897-2904). Three of these G proteins were copurified with the proteins ADP-ribosylated by botulinum toxin type C1. One G protein ADP-ribosylated by this toxin was identified to be the bovine brain rho protein (rho p20) which was purified to near homogeneity (Yamamoto, K., Kondo, J., Hishida, T., Teranishi, Y., and Takai, Y. (1988) J. Biol. Chem. 263, 9926-9932). rho p20 was ADP-ribosylated by botulinum toxin type C1 in time- and dose-dependent manners. About 0.4 mol of ADP-ribose was maximally incorporated into 1 mol of rho p20. The ADP-ribosylation of rho p20 was dependent on the presence of Mg2+. GTP enhanced the ADP-ribosylation in the presence of a low concentration (50 nM) of Mg2+ but not in the presence of a high concentration (0.5 mM) of Mg2+. The high concentration of Mg2+ fully stimulated the ADP-ribosylation even in the absence of GTP. The ADP-ribosylation of rho p20 did not affect its GTP gamma S-binding and GTPase activities. These results indicate that there are at least three G proteins ADP-ribosylated by botulinum toxin type C1 in bovine brain crude membranes and that one of them is rho p20. Two other G proteins have not yet been identified, but neither the c-ras protein, ADP-ribosylation factor for Gs, nor a G protein with a Mr of 24,000 was ADP-ribosylated by this toxin.     

A new detection method for arginine-specific ADP-ribosylation of protein -- a combinational use of anti-ADP-ribosylarginine antibody and ADP-ribosylarginine hydrolase

Arginine-specific ADP-ribosylation is one of the posttranslational modifications of proteins by transferring one ADP-ribose moiety of NAD to arginine residues of target proteins. This modification, catalyzed by ADP-ribosyltransferase (Art), is reversed by ADP-ribosylarginine hydrolase (AAH).

In this study, we describe a new method combining an anti-ADP-ribosylarginine antibody (ADP-R-Arg Ab) and AAH for detection of the target protein of ADP-ribosylation. We have raised ADP-R-Arg Ab with ADP-ribosylated histone and examined the reactivity of the antibody with proteins treated by Art and/or AAH, as well as in situ ADP-ribosylation system with mouse T cells. Our results indicate that the detection of ADP-ribosylated protein with ADP-R-Arg Ab and AAH is a useful tool to explore the target proteins of ADP-ribosylation. We applied the method to search endogenously ADP-ribosylated protein in the rat, and detected possible target proteins in the skeletal muscle, which has high Art activity.     

Identification of enzymatic activities which process protein bound mono(ADP-ribose)

Enzymatic activities have been identified in extracts of cultured mouse cells which catalyze the removal of intact mono(ADP-ribosyl) residues linked to proteins at arginine. Activities that sequentially remove AMP and ribose 5-phosphate have also been identified. These results suggest that mono(ADP-ribosylation) of proteins is a reversible post translational modification.     

ADP-ribosylation of proteins in nuclei and mitochondria from tissues rats of various age exposed gamma-radiation

Constitutive and gamma-induced ADP-ribosylation of nuclei and mitochondrial proteins in 2- and 29-month-old rats was studied. ADP-ribosylation was determined by binding of [3H]-adenin with the proteins after incubation of cellular organells in reaction mixture supplemented with [adenin-2,8-3H]-NAD. It was detected that the level of total protein ADP-ribosylation in the nuclei is 4.5-6.2 times higher than in the mitochondria. By inhibition of poly(ADP-ribose) polymerase (PARP) with 3-aminobenzamidine and treatment of ADP-ribosylated proteins with phosphodiesterase I, it was demonstrated that about 90% of [3H]-adenin bound by proteins in the nuclei and 70% in the mitochondria was the result of PARP activity. The level of total ADP-ribosylation of nuclear and mitochondrial proteins in the tissues of old rats was reliably lower than in young animals. This reduction of ADP-ribosylation in old animals is the result of the lower activity of PARP, not of mono(ADP-ribosyl) transferase (MART). The level of ADP-ribosylation of proteins in the nuclei of brain and spleen cells of 2-month-old rats irradiated with of 5 and 10 Gy was by 49-109% higher than in the control. At the same doses of radiation, the level of ADP-ribosylation of nuclear proteins in brain and spleen of old rats increased only by 29-65% compared to the control. Unlike cell nuclei, the radiation-induced activation of ADP-ribosylation in mitochondria was less expressed: the level of ADP-ribosylation increased by 34-37% in young rats and by 11-27% in old animals. This increased binding of ADP-ribose residues by the proteins of nuclei and mitochondria from tissues of gamma-irradiated rats is exceptionally conditioned by activation of poly(ADP-ribosyl)ation because the level of mono(ADP-ribosyl)ation remains constant. The results of this study enable the suggestion that poly(ADP-ribosyl)ation also occurs in the mitochondria of brain and spleen cells of the gamma-irradiated rats, though less pronounced than in cell the cell nuclei of these tissues. Thus, one of the probable causes of the less efficient repair of radiation-induced DNA damage in old organisms is a decline of both constitutive and induced poly(ADP-ribosyl)ation of proteins in cell nucleus and mitochondria.