Venom chemistry of ants in the genusMonomorium

A comparative analysis of the venomous alkaloids produced by ant species in the subgenusMonomorium of the genusMonomorium has been undertaken. All species produce mixtures of unsymmetricaltrans-2,5-dialkylpyrrolidines, but the proportions of the constituents may vary considerably between species. All alkaloids contain both C6 and C9 side chains which are present as C9-saturated. C6-monounsaturated, and both C6-and C9-monounsaturated dialkylpyrrolidines. The structure of 2-(1-hex-5-enyl)-5-(1-non-8-enyl)pyrrolidine, a previously undescribed alkaloid, was proved by unambiguous synthesis after the location of the double bonds was established by the methoxymercuration-demercuration followed by mass spectrometry. The possible chemotaxonomic significance of the mixtures of venomous alkaloids produced by these species ofMonomorium is discussed.

Volatiles from mandibular glands of male beewolves (Hymenoptera: Sphecidae,Philanthus) and their possible roles

Observations of wasp behavior indicate that male beewolves,Philanthus basilaris andP. bicinctus apply a "marking pheromone" to the leaves and stems of plants within their territories. We now provide direct evidence for the presence of volatile chemicals in the paired mandibular glands of the males, provide preliminary identification of these volatiles, and show that all of the volatile chemicals in the mandibular glands are present on freshly marked plant surfaces but are absent from unmarked plants. Pyrazines, which have been reported in other species of aculeate wasps including the EuropeanPhilanthus triangulum, were not found inP. basilaris orP. bicinctus.

Novel 2-ethyl-5-alkylpyrrolidines in the venom of an australian ant of the genusMonomorium

Novel 2-ethyl-5-alkylpyrrolidines and their corresponding 1-pyrrolines have been identified as poison gland products from an unidentified Australian species ofMonomorium. The major alkaloids present in the venom of this ant aretrans-2-ethyl-5-undecylpyrrolidine andtrans-2-ethyl-5-(12-tridecen-1-yl)pyrrolidine. The position of the double bond in the latter was established from its dimethyl-disulfide adduct after the amine function had been protected, and the stereochemistry of the alkyl groups was determined by direct comparison with synthetic compounds. The corresponding 1-pyrrolines were also detected in varying amounts in this venom. The pyrrolidines and 1-pyrrolines possess considerable insecticidal activity when evaluated against termite workers. The alkaloidal venoms ofMonomorium appear to be an important factor contributing to the success of these small ants both as competitors and as predators.

Chemistry of venom alkaloids in the ant genusMegalomyrmex

Chemical analyses of three species in the Neotropical ant genusMegalomyrmex have identified this taxon as the third myrmicine genus to produce alkaloids as major venom products. Workers ofM. leoninus and workers and ergatoids ofM. goeldii produce one or more of fourtrans-2,5-dialkylpyrrolidines previously identified in other myrmicine genera.M. modestus, on the other hand, is distinctive in producing the novel alkaloid (5E,8E)-3-butyl-5-hexylpyrrolizidine (5d), whose structure was established using a micro-Hofmann degradation sequence. The relationship ofMegalomyrmex to other alkaloid-producing ant genera is discussed along with the possible chemotaxonomic significance of the analyzed species when viewed in terms of the recognized species groups in this genus.

Synthesis and structure-activity evaluation of isatin-β-thiosemicarbazones with improved selective activity toward multidrug-resistant cells expressing P-glycoprotein

Cancer multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters presents a significant unresolved clinical challenge. One strategy to resolve MDR is to develop compounds that selectively kill cells overexpressing the efflux transporter P-glycoprotein (MDR1, P-gp, ABCB1). We have previously reported structure-activity studies based around the lead compound NSC73306 (1, 1-isatin-4-(4'-methoxyphenyl)-3-thiosemicarbazone, 4.3-fold selective). Here we sought to extend this work on MDR1-selective analogues by establishing whether 1 showed "robust" activity against a range of cell lines expressing P-gp. We further aimed to synthesize and test analogues with varied substitution at the N4-position, and substitution around the N4-phenyl ring of isatin-β-thiosemicarbazones (IBTs), to identify compounds with increased MDR1-selectivity. Compound 1 demonstrated MDR1-selectivity against all P-gp-expressing cell lines examined. This selectivity was reversed by inhibitors of P-gp ATPase activity. Structural variation at the 4'-phenyl position of 1 yielded compounds of greater MDR1-selectivity. Two of these analogues, 1-isatin-4-(4'-nitrophenyl)-3-thiosemicarbazone (22, 8.3-fold selective) and 1-isatin-4-(4'-tert-butyl phenyl)-3-thiosemicarbazone (32, 14.8-fold selective), were selected for further testing and were found to retain the activity profile of 1. These compounds are the most active IBTs identified to date.

Natural Polyesters: Dufour's Gland Macrocyclic Lactones Form Brood Cell Laminesters in Colletes Bees

Bees in the genus Colletes make their brood cells in the ground and coat them with a highly resistant, waterproof, transparent membrane. This membrane is a polyester constructed mainly from 18-hydroxyoctadecanoic acid and 20-hydroxy-eicosanoic acid, which are stored as their corresponding lactones in the Dufour's gland of the bee. When lining the cells, the bee secretes its glandular content, and the membrane is apparently a product of polycondensation reaction of its contents. This appears to be the first report of a naturally occurring linear polyester. The term laminester (lamina approximately layer + ester) for this class of compounds is proposed.

Alkaloid from fire ant venom: identification and synthesis

An alkaloid, trans-2-methyl-6-n-undecylpiperidine (solenopsin A), has been isolated from the venom of the fire ant Solenopsis saevissima. The structure has been confirmed by an unambiguous synthesis.

Identification of compounds selectively killing multidrug-resistant cancer cells

There is a great need for the development of novel chemotherapeutic agents that overcome the emergence of multidrug resistance (MDR) in cancer. We catalogued the National Cancer Institute's DTP drug repository in search of compounds showing increased toxicity in MDR cells. By comparing the sensitivity of parental cell lines with MDR derivatives, we identified 22 compounds possessing MDR-selective activity. Analysis of structural congeners led to the identification of 15 additional drugs showing increased toxicity in Pgp-expressing cells. Analysis of MDR-selective compounds led to the formulation of structure activity relationships and pharmacophore models. This data mining coupled with experimental data points to a possible mechanism of action linked to metal chelation. Taken together, the discovery of the MDR-selective compound set shows the robustness of the developing field of MDR-targeting therapy as a new strategy for resolving Pgp-mediated MDR.

Synthesis, activity, and pharmacophore development for isatin-beta-thiosemicarbazones with selective activity toward multidrug-resistant cells

We have recently identified a new class of compounds that selectively kill cells that express P-glycoprotein (P-gp, MDR1), the ATPase efflux pump that confers multidrug resistance on cancer cells. Several isatin-beta-thiosemicarbazones from our initial study have been validated and a range of analogues synthesized and tested. A number demonstrated improved MDR1-selective activity over the lead, NSC73306 (1). Pharmacophores for cytotoxicity and MDR1 selectivity were generated to delineate the structural features required for activity. The MDR1-selective pharmacophore highlights the importance of aromatic/hydrophobic features at the N4 position of the thiosemicarbazone and the reliance on the isatin moiety as key bioisosteric contributors. Additionally, a quantitative structure-activity relationship (QSAR) model that yielded a cross-validated correlation coefficient of 0.85 effectively predicts the cytotoxicity of untested thiosemicarbazones. Together, the models serve as effective approaches for predicting structures with MDR1-selective activity and aid in directing the search for the mechanism of action of 1.

Detection of venous thromboembolism by proteomic serum biomarkers

Background

Available blood assays for venous thromboembolism (VTE) suffer from diminished specificity. Compared with single marker tests, such as D-dimer, a multi-marker strategy may improve diagnostic ability. We used direct mass spectrometry (MS) analysis of serum from patients with VTE to determine whether protein expression profiles would predict diagnosis.

Methods and Results

We developed a direct MS and computational approach to the proteomic analysis of serum. Using this new method, we analyzed serum from inpatients undergoing radiographic evaluation for VTE. In a balanced cohort of 76 patients, a neural network-based prediction model was built using a training subset of the cohort to first identify proteomic patterns of VTE. The proteomic patterns were then validated in a separate group of patients within the cohort. The model yielded a sensitivity of 68% and specificity of 89%, which exceeded the specificity of D-dimer assay tested by latex agglutination, ELISA, and immunoturbimetric methods (sensitivity/specificity of 63.2%/60.5%, 97.4%/21.1%, 97.4%/15.8%, respectively). We validated differences in protein expression between patients with and without VTE using more traditional gel-based analysis of the same serum samples.

Conclusion

Protein expression analysis of serum using direct MS demonstrates potential diagnostic utility for VTE. This pilot study is the first such direct MS study to be applied to a cardiovascular disease. Differences in protein expression were identified and subsequently validated in a separate group of patients. The findings in this initial cohort can be evaluated in other independent cohorts, including patients with inflammatory conditions and chronic (but not acute) VTE, for the diagnosis of VTE.

Multisite phosphorylation of adipocyte and hepatocyte phosphodiesterase 3B

Phosphodiesterase 3B (PDE3B) is an important component of insulin and cAMP-dependent signalling pathways. In order to study phosphorylation of PDE3B, we have used an adenoviral system to express recombinant flag-tagged PDE3B in primary rat adipocytes and H4IIE hepatoma cells. Phosphorylation of PDE3B after treatment of cells with insulin, cAMP-increasing agents, or the phosphatase inhibitor, calyculin A was analyzed by two-dimensional tryptic phosphopeptide mapping and mass spectrometry. We found that PDE3B is multisite phosphorylated in adipocytes and H4IIE hepatoma cells in response to all these stimuli. Several sites were identified; serine (S)273, S296, S421, S424/5, S474 and S536 were phosphorylated in adipocyte as well as H4IIE hepatoma cells whereas S277 and S507 were phosphorylated in hepatoma cells only. Several of the sites were phosphorylated by insulin as well as cAMP-increasing hormones indicating integration of the two signalling pathways upstream of PDE3B, maybe at the level of protein kinase B.

Selective toxicity of NSC73306 in MDR1-positive cells as a new strategy to circumvent multidrug resistance in cancer

ATP-binding cassette (ABC) proteins include the best known mediators of resistance to anticancer drugs. In particular, ABCB1 [MDR1/P-glycoprotein (P-gp)] extrudes many types of drugs from cancer cells, thereby conferring resistance to those agents. Attempts to overcome P-gp-mediated drug resistance using specific inhibitors of P-gp has had limited success and has faced many therapeutic challenges. As an alternative approach to using P-gp inhibitors, we characterize a thiosemicarbazone derivative (NSC73306) identified in a generic screen as a compound that exploits, rather than suppresses, P-gp function to induce cytotoxicity. Cytotoxic activity of NSC73306 was evaluated in vitro using human epidermoid, ovarian, and colon cancer cell lines expressing various levels of P-gp. Our findings suggest that cells become hypersensitive to NSC73306 in proportion to the increased P-gp function and multidrug resistance (MDR). Abrogation of both sensitivity to NSC73306 and resistance to P-gp substrate anticancer agents occurred with specific inhibition of P-gp function using either a P-gp inhibitor (PSC833, XR9576) or RNA interference, suggesting that cytotoxicity was linked to MDR1 function, not to other, nonspecific factors arising during the generation of resistant or transfected cells. Molecular characterization of cells selected for resistance to NSC73306 revealed loss of P-gp expression and consequent loss of the MDR phenotype. Although hypersensitivity to NSC73306 required functional expression of P-gp, biochemical assays revealed no direct interaction between NSC73306 and P-gp. This article shows that NSC73306 kills cells with intrinsic or acquired P-gp-induced MDR and indirectly acts to eliminate resistance to MDR1 substrates.

Structural Conservation of Mouse and Rat Zona Pellucida Glycoproteins. Probing the Native Rat Zona Pellucida Proteome by Mass Spectrometry

The mammalian zona pellucida is an egg extracellular matrix to which sperm bind. Mouse zonae are composed of three glycoproteins (ZP1, ZP2, and ZP3), while rat zonae contain four (ZP1, ZP2, ZP3, and ZP4/ZPB). Mouse sperm bind to zonae comprised solely of mouse ZP2 and ZP3. In this report, we show that rat sperm also bind to these zonae, indicating that ZP2 and ZP3 contain a "minimum structure(s)" to which rodent sperm can bind, and ZP1 and ZP4/ZPB are dispensable in these two rodents. These data are consistent with our mass spectrometric analysis of the native rat zona pellucida proteome (defined as the fraction of the total rat proteome to which the zonae glycoproteins contribute) demonstrating that the rat zonae glycoproteins share a high degree of conservation of structural features with respect to their mouse counterparts. The primary sequences of the rat zonae proteins have been deduced from cDNA. Each zona protein undergoes extensive co- and post-translational modification prior to its secretion and incorporation into an extracellular zona matrix. Each has a predicted N-terminal signal peptide that is cleaved off once protein translation begins and an anchoring C-terminal transmembrane domain from which the mature protein is released. Mass spectrometric analysis with a limited amount of native material allowed determination of the mature N-termini of rat ZP1 and ZP3, both of which are characterized by cyclization of glutamine to pyroglutamate; the N-terminus of ZP2 was identified by Edman degradation. The mature C-termini of ZP1 and ZP3 end two amino acids upstream of a conserved dibasic residue that is part of, but distinct from, the consensus furin cleavage sequence, while the C-terminus of ZP2 was not determined. Each zona protein contains a "zona domain" with eight conserved cysteine residues that is thought to play a role in the polymerization of the zona proteins into matrix filaments. Partial disulfide bond assignment indicates that the intramolecular disulfide patterns in rat ZP1, ZP2, and ZP3 are identical to those of their corresponding mouse counterparts. Last, nearly all potential N-glycosylation sites are occupied in the rat zonae glycoproteins (three of three for ZP1, six or seven of seven for ZP2, and four or five of six for ZP3). In comparison, potential O-glycosylation sites are numerous (59-83 Ser/Thr residues), but only two regions were observed to carry O-glycans in rat ZP3.

2-Methyl-(1Z,3E)-butadiene-1,3,4-tricarboxylic Acid, “Isoprenetricarboxylic Acid”

[reaction: see text] The synthesis of the title compound 7 from ethyl glyoxylate and dimethyl and diethyl beta-methylglutaconate is described along with its physical properties that suggest its inability to assume a cis-dienoid structure due to steric hindrance between the methyl and carboxyl groups.

Detection and characterization of the product of hydroethidine and intracellular superoxide by HPLC and limitations of fluorescence

Here we report the structural characterization of the product formed from the reaction between hydroethidine (HE) and superoxide (O(2)(.-)). By using mass spectral and NMR techniques, the chemical structure of this product was determined as 2-hydroxyethidium (2-OH-E(+)). By using an authentic standard, we developed an HPLC approach to detect and quantitate the reaction product of HE and O(2)(.-) formed in bovine aortic endothelial cells after treatment with menadione or antimycin A to induce intracellular reactive oxygen species. Concomitantly, we used a spin trap, 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO), to detect and identify the structure of reactive oxygen species formed. BMPO trapped the O(2)(.-) that formed extracellularly and was detected as the BMPO-OH adduct during use of the EPR technique. BMPO, being cell-permeable, inhibited the intracellular formation of 2-OH-E(+). However, the intracellular BMPO spin adduct was not detected. The definitive characterization of the reaction product of O(2)(.-) with HE described here forms the basis of an unambiguous assay for intracellular detection and quantitation of O(2)(.-). Analysis of the fluorescence characteristics of ethidium (E(+)) and 2-OH-E(+) strongly suggests that the currently available fluorescence methodology is not suitable for quantitating intracellular O(2)(.-). We conclude that the HPLC/fluorescence assay using HE as a probe is more suitable [corrected] for detecting intracellular O(2)(.-).

Method for isolating tight-binding inhibitors of rat lens aldose reductase

Numerous animal studies indicate that aldose reductase inhibitors (ARIs) are beneficial for the prevention or amelioration of diabetic complications such as neuropathy, nephropathy and the ocular complications of cataract, retinopathy and keratopathy. To aid in the identification of novel potent ARIs, we have previously developed a screening method that is based on the formation of a non-covalent ternary tight-binding enzyme-inhibitor-nucleotide (AR-ARI-NADPH) complex that can be isolated using YM-10 filter units. Here, we report a modification of this method that permits us to rapidly identify tight binding ARIs that are isolated by denaturation from AR-ARI-NADPH complexes that are free of possible contamination resulting from the reaction of methanol with the YM-10 filter units. For the development of this procedure, nine structurally diverse ARIs were mixed with purified recombinant rat lens aldose reductase (RLAR) bound with NADPH to form tight-binding RLAR-ARI-NADPH complexes. These complexes were purified by high pressure Sephadex 75 size exclusion chromatography using ammonium acetate buffer and the formation of each complex was confirmed by electrospray ionisation mass spectrometry (ESI-MS). Each of the complexes was then denatured with methanol, rechromatographed on the size exclusion column, and the identity of the bound ARIs was confirmed by ESI-MS. The apparent ARI binding with aldose reductase to form a tight binding ARI complex appeared proportional to their IC50 values. This procedure allows for the rapid identification of tight binding ARIs with apparent IC50s<0.1 microm.

Regulation of ASAP1 by phospholipids is dependent on the interface between the PH and Arf GAP domains

ASAP1 is an Arf GAP with a PH domain immediately N-terminal to the catalytic Arf GAP domain. PH domains are thought to regulate enzymes by binding to specific phosphoinositide lipids in membranes, thereby recruiting the enzyme to a site of action. Here, we have examined the functional relationship between the PH and Arf GAP domains. We found that GAP activity requires the cognate PH domain of ASAP1, leading us to hypothesize that the Arf GAP and PH domains directly interact to form the substrate binding site. This hypothesis was supported by the combined results of protection and hydrodynamic studies. We then examined the role of the PH domain in the regulation of Arf GAP activity. The results of saturation kinetics, limited proteolysis, FRET and fluorescence spectrometry support a model in which regulation of the GAP activity of ASAP1 involves a conformational change coincident with recruitment to a membrane surface, and a second conformational change following the specific binding of phosphatidylinositol 4,5-bisphosphate.

Mass Spectrometry Analysis of Recombinant Human ZP3 Expressed in Glycosylation-Deficient CHO Cells

The zona pellucida is an extracellular matrix that mediates taxon-specific fertilization in which human sperm will not bind to mouse eggs. The mouse zona pellucida is composed of three glycoproteins (ZP1, ZP2, ZP3). The primary structure of each has been deduced from the cDNA nucleic acid sequence, and each has been analyzed by mass spectrometry. However, determination of the secondary structure and processing of the human zona proteins have been hampered by the paucity of biological material. To investigate if taxon-specific sperm-egg recognition was ascribable to structural differences in a zona protein required for matrix formation, recombinant human ZP3 was expressed in CHO-Lec3.2.8.1 cells and compared to mouse ZP3. With nearly complete coverage, LC-QTOF mass spectrometry was used to determine the cleavage of an N-terminal signal peptide (amino acids 1-22) and the release of secreted ZP3 from a C-terminal transmembrane domain (amino acids 379-424). The resultant N-terminal glutamine was cyclized to pyroglutamate (pyrGln(23)), and several C-terminal peptides were detected, including one ending at Asn(350). The disulfide bond linkages of eight cysteine residues in the conserved zona domain were ascertained (Cys(46)/Cys(140), Cys(78)/Cys(99), Cys(217)/Cys(282), Cys(239)/Cys(300)), but the precise linkage of two additional disulfide bonds was indeterminate due to clustering of the remaining four cysteine residues (Cys(319), Cys(321), Cys(322), Cys(327)). Three of the four potential N-linked oligosaccharide binding sites (Asn(125), Asn(147), Asn(272)) were occupied, and clusters of O-glycans were observed within two regions, amino acids 156-173 and 260-281. Taken together, these data indicate that human and mouse ZP3 proteins are quite similar, and alternative explanations of taxon-specific sperm binding warrant exploration.

NADH enzyme-dependent fluorescence recovery after photobleaching (ED-FRAP): applications to enzyme and mitochondrial reaction kinetics, in vitro

NADH enzyme-dependent fluorescence recovery after photobleaching (ED-FRAP) was evaluated for studying enzyme kinetics in vitro and in isolated mitochondria. Mass, optical, and nuclear magnetic resonance spectroscopy data were consistent with the UV NADH photolysis reaction being NADH --> NAD* + H+ + e-. The overall net reaction was O2 + 2NADH + 2H+ --> 2NAD+ + 2H2O, or in the presence of other competing electron acceptors such as cytochrome c, NADH + 2Cyt(ox) --> NAD+ + H+ + 2Cyt(red). Solution pH could differentiate between these free-radical scavenging pathways. These net reactions represent the photooxidation of NADH to NAD+. Kinetic models and acquisition schemes were developed, varying [NADH] and [NAD] by altering NADH photolysis levels, for extracting kinetic parameters. UV irradiation levels used did not damage mitochondrial function or enzymatic activity. In mitochondria, [NADH] is a high affinity product inhibitor that significantly reduced the NADH regeneration rate. Matrix NADH regeneration only slightly exceeded the net rate of NADH consumption, suggesting that the NADH regeneration process is far from equilibrium. Evaluation of NADH regeneration in active mitochondria, in comparison to rotenone-treated preparations, revealed other regulatory elements in addition to matrix [NADH] and [NAD] that have yet to be fully characterized. These studies demonstrate that the rapid UV photolysis of NADH to NAD is an effective tool in evaluating the steady-state kinetic properties of enzyme systems. Initial data support the notion that the NADH regeneration process is far from equilibrium in mitochondria and is potentially controlled by NADH levels as well as several other matrix factors.

Divinyl Sulfone as a Postdigestion Modifier for Enhancing the a1 Ion in MS/MS and Postsource Decay: Potential Applications in Proteomics

Divinyl sulfone reacts at pH 8-9 with the alpha-amino groups of N-terminal residues, proline, the epsilon-amino groups of lysine, and the histidine side chains of peptides. This reaction leads to great enhancement of the abundance of the normally weak or missing "a(1)" fragment ion in MS/MS analysis defining the N-terminal residue of a peptide in a digest. This provides "one-step Edman-like" information that, together with a fairly accurately determined mass, often enables one to correctly identify a protein or family of proteins. The applicability of this procedure in proteomics was demonstrated with several peptides and tryptic digests of protein mixtures by LC-MS/MS experiments using a QTOF and MALDI-PSD analyses. Advantages of this approach are its simple chemistry, retention of charge multiplicity, and possibly, shortening of database search time. Used with other MS/MS data, it provides higher confidence in the scores and identification of a protein found in peptide mass fingerprinting. Moreover, this approach has an advantage in "de novo" sequencing due to its ability to decipher the first amino acid of a peptide whose information is normally unavailable in MS/MS spectra.

Mutation of a conserved hydrophobic patch prevents incorporation of ZP3 into the zona pellucida surrounding mouse eggs

Three glycoproteins (ZP1, ZP2, and ZP3) are synthesized in growing mouse oocytes and secreted to form an extracellular zona pellucida that mediates sperm binding and fertilization. Each has a signal peptide to direct it into a secretory pathway, a "zona" domain implicated in matrix polymerization and a transmembrane domain from which the ectodomain must be released. Using confocal microscopy and enhanced green fluorescent protein (EGFP), the intracellular trafficking of ZP3 was observed in growing mouse oocytes. Replacement of the zona domain with EGFP did not prevent secretion of ZP3, suggesting the presence of trafficking signals and a cleavage site in the carboxyl terminus. Analysis of linker-scanning mutations of a ZP3-EGFP fusion protein in transient assays and in transgenic mice identified an eight-amino-acid hydrophobic region required for secretion and incorporation into the zona pellucida. The hydrophobic patch is conserved among mouse zona proteins and lies between a potential proprotein convertase (furin) cleavage site and the transmembrane domain. The cleavage site that releases the ectodomain from the transmembrane domain was defined by mass spectrometry of native zonae pellucidae and lies N-terminal to a proprotein convertase site that is distinct from the hydrophobic patch.

Roles of TRP14, a thioredoxin-related protein in tumor necrosis factor-alpha signaling pathways

The possible roles of a 14-kDa human thioredoxin (Trx)-related protein (TRP14) in TNF-alpha signaling were studied in comparison with those of Trx1 by RNA interference in HeLa cells. Depletion of TRP14 augmented the TNF-alpha-induced phosphorylation and degradation of I kappa B alpha as well as the consequent activation of NF-kappa B to a greater extent than did Trx1 depletion. Deficiency of TRP14 or Trx1 enhanced TNF-alpha-induced activation of caspases and subsequent apoptosis by a similar extent. The TNF-alpha-induced activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs), however, was promoted by depletion of TRP14 but not by that of Trx1. Unlike Trx1, TRP14 neither associated with nor inhibited the kinase activity of apoptosis signal-regulating kinase-1 (ASK1), an upstream activator of JNK and p38. In combination with the results in the accompanying paper that TRP14 did not reduce the known substrates of Trx1, these results suggest that TRP14 modulates TNF-alpha signaling pathways, provably by interacting with proteins distinct from the targets of Trx1. In an effort to identify target proteins of TRP14, a mutant of TRP14, in which the active site cysteine (Cys(46)) was substituted with serine, was shown to form a disulfide-linked complex with LC8 cytoplasmic dynein light chain. The complex was detected in HeLa cells treated with H(2)O(2) or TNF-alpha but not in untreated cells, suggesting that LC8 cytoplasmic dynein light chain is a possible substrate of TRP14.

Structural characterization of native mouse zona pellucida proteins using mass spectrometry

The zona pellucida is an extracellular matrix consisting of three glycoproteins that surrounds mammalian eggs and mediates fertilization. The primary structures of mouse ZP1, ZP2, and ZP3 have been deduced from cDNA. Each has a predicted signal peptide and a transmembrane domain from which an ectodomain must be released. All three zona proteins undergo extensive co- and post-translational modifications important for secretion and assembly of the zona matrix. In this report, native zonae pellucidae were isolated and structural features of individual zona proteins within the mixture were determined by high resolution electrospray mass spectrometry. Complete coverage of the primary structure of native ZP3, 96% of ZP2, and 56% of ZP1, the least abundant zona protein, was obtained. Partial disulfide bond assignments were made for each zona protein, and the size of the processed, native protein was determined. The N termini of ZP1 and ZP3, but not ZP2, were blocked by cyclization of glutamine to pyroglutamate. The C termini of ZP1, ZP2, and ZP3 lie upstream of a dibasic motif, which is part of, but distinct from, a proprotein convertase cleavage site. The zona proteins are highly glycosylated and 4/4 potential N-linkage sites on ZP1, 6/6 on ZP2, and 5/6 on ZP3 are occupied. Potential O-linked carbohydrate sites are more ubiquitous, but less utilized.

Specific regulation of the adaptor protein complex AP-3 by the Arf GAP AGAP1

Arf1 regulates membrane trafficking at several membrane sites by interacting with at least seven different vesicle coat proteins. Here, we test the hypothesis that Arf1-dependent coats are independently regulated by specific interaction with Arf GAPs. We find that the Arf GAP AGAP1 directly associates with and colocalizes with AP-3, a coat protein complex involved in trafficking in the endosomal-lysosomal system. Binding is mediated by the PH domain of AGAP1 and the delta and sigma3 subunits of AP-3. Overexpression of AGAP1 changes the cellular distribution of AP-3, and reduced expression of AGAP1 renders AP-3 resistant to brefeldin A. AGAP1 overexpression does not affect the distribution of other coat proteins, and AP-3 distribution is not affected by overexpression of other Arf GAPs. Cells overexpressing AGAP1 also exhibit increased LAMP1 trafficking via the plasma membrane. Taken together, these results support the hypothesis that AGAP1 directly and specifically regulates AP-3-dependent trafficking.

Reversible oxidative modification as a mechanism for regulating retroviral protease dimerization and activation

Human immunodeficiency virus protease activity can be regulated by reversible oxidation of a sulfur-containing amino acid at the dimer interface. We show here that oxidation of this amino acid in human immunodeficiency virus type 1 protease prevents dimer formation. Moreover, we show that human T-cell leukemia virus type 1 protease can be similarly regulated through reversible glutathionylation of its two conserved cysteine residues. Based on the known three-dimensional structures and multiple sequence alignments of retroviral proteases, it is predicted that the majority of retroviral proteases have sulfur-containing amino acids at the dimer interface. The regulation of protease activity by the modification of a sulfur-containing amino acid at the dimer interface may be a conserved mechanism among the majority of retroviruses.

Attachment of neutrals during tandem mass spectrometry of sulfonic acid dyes and intermediates in an ion trap

Several positional isomers of 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione mono- and disulfonic acids prepared as reference materials for development of analytical methods involved in FDA certification of D&C Yellow No. 10 (Quinoline Yellow) were found consistently to show [MH + 14](+) ions when their electrospray- or atmospheric pressure chemical ionization-prepared MH(+) ions were subjected to collisional activation. The source of these ions was found to be the methanol used as solvent in these procedures which combined with their [MH - H(2)O](+) ions under chemical ionization conditions. The reaction was found to be sensitive to their isomeric and chemical structures and other examples of this process are reviewed.

Oxidative modifications of kynostatin-272, a potent human immunodeficiency virus type 1 protease inhibitor: potential mechanism for altered activity in monocytes/macrophages

Previous studies have indicated that human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs) are less active at blocking viral replication in HIV-1 infected peripheral blood monocytes/macrophages (M/M) than in HIV-1-infected T cells. We explored the hypothesis that oxidative modification and/or metabolism of the PIs in M/M might account for this reduced potency. We first tested the susceptibility of several PIs (kynostatin-272 [KNI-272], saquinavir, indinavir, ritonavir, or JE-2147) to oxidation after exposure to hydrogen peroxide (H(2)O(2)): only KNI-272 was highly susceptible to oxidation. Treatment of KNI-272 with low millimolar concentrations of H(2)O(2) resulted in mono-oxidation of the sulfur in the S-methyl cysteine (methioalanine) moiety, as determined by reversed-phase high-performance liquid chromatography and mass spectrometry (RP-HPLC/MS). Higher concentrations of H(2)O(2) led to an additional oxidation of the sulfur in the thioproline moiety of KNI-272. None of the PIs were metabolized or oxidized when added to T cells and cultured for up to 12 days. However, when KNI-272 was added to M/M, the concentration of the original KNI-272 steadily decreased with a corresponding increase in the production of three KNI-272 metabolites as identified by RP-HPLC/MS. The structures of these metabolites were different from those produced by H(2)O(2) treatment. The two major products of M/M metabolism of KNI-272 were identified as isomeric forms of KNI-272 oxidized solely on the thioproline ring. Both metabolites had reduced capacities to inhibit HIV-1 protease activity when tested in a standard HIV-1 protease assay. These studies demonstrate that antiviral compounds can be susceptible to oxidative modification in M/M and that this can affect their antiviral potency.