Proinflammatory CD14+CD16+ monocytes are associated with subclinical atherosclerosis in renal transplant patients.

Atherosclerotic cardiovascular disease is a major cause of death in renal transplant (TX) recipients. Atherosclerotic lesions are characterized by monocytic infiltration. Circulating monocytes can be divided into functionally distinct subpopulations, among which CD14++CD16+ and CD14+CD16+ monocytes (summarized as CD16+ monocytes) are proinflammatory cells. We hypothesized that the frequency of circulating CD16+ monocytes is associated with subclinical atherosclerosis in TX patients. Monocyte subpopulations were quantified in 95 TX and 31 hemodialysis patients (HD). In TX patients, subclinical atherosclerosis was determined by carotid intima media thickness (IMT) measurement. TX patients had lower frequencies of CD16+ monocytes than HD patients. When stratifying by immunosuppressive treatment, patients on methylprednisolone (MP) therapy had fewer CD14+CD16+ monocytes than patients not receiving MP. CD14+CD16+ monocytes decrease very shortly after transplantation. CD14+CD16+ monocyte frequency correlated with IMT in TX recipients (r = 0.34, p < 0.001). This correlation was most pronounced among patients without MP treatment (r = 0.55, p = 0.02). In a multivariate regression analysis, the association of CD14+CD16+ monocytes with IMT was independent from traditional cardiovascular risk factors. The frequency of proinflammatory CD14+CD16+ monocytes is independently associated with subclinical atherosclerosis in transplant recipients. Further studies on the association between circulating leukocytes and atherosclerosis should take monocyte heterogeneity into account.

The R27080 glycoprotein is abundantly secreted from human cytomegalovirus-infected fibroblasts.

A 45 kDa glycoprotein was purified from the culture media of human cytomegalovirus (HCMV)-infected fibroblasts. N-terminal sequencing revealed that the protein, R27080, is the translation product of the R27080 open reading frame of HCMV. R27080 is highly glycosylated and contains no cysteine or methionine residues. Proteolytic cleavage of R27080 by a furin-like enzyme was analysed in transfected COS-7 cells. R27080 is the first identified viral protein secreted from HCMV-infected cells.

The periplasmic cyclodextrin binding protein CymE from Klebsiella oxytoca and its role in maltodextrin and cyclodextrin transport.

Klebsiella oxytoca M5a1 has the capacity to transport and to metabolize alpha-, beta- and gamma-cyclodextrins. Cyclodextrin transport is mediated by the products of the cymE, cymF, cymG, cymD, and cymA genes, which are functionally homologous to the malE, malF, malG, malK, and lamB gene products of Escherichia coli. CymE, which is the periplasmic binding protein, has been overproduced and purified. By substrate-induced fluorescence quenching, the binding of ligands was analyzed. CymE bound alpha-cyclodextrin, beta-cyclodextrin, and gamma-cyclodextrin, with dissociation constants (Kd) of 0.02, 0.14 and 0.30 microM, respectively, and linear maltoheptaose, with a Kd of 70 microM. In transport experiments, alpha-cyclodextrin was taken up by the cym system of K. oxytoca three to five times less efficiently than maltohexaose by the E. coli maltose system. Besides alpha-cyclodextrin, maltohexaose was also taken up by the K. oxytoca cym system, but because of the inability of maltodextrins to induce the cym system, growth of E. coli mal mutants on linear maltodextrin was not observed when the cells harbored only the cym uptake system. Strains which gained this capacity by mutation could easily be selected, however.

Expression and purification of correctly processed, active human TACE catalytic domain in Saccharomyces cerevisiae.

Human tumor necrosis factor-alpha (TNF alpha) converting enzyme (TACE) releases soluble TNF alpha from cells. It is a member of the adamalysin family of metalloproteases. A truncated form of TACE cDNA was expressed in Saccharomyces cerevisiae and purified to homogeneity in order to study TACE structure and function. Recombinant TACE was expressed as a preproprotein including the pro- and catalytic (PROCAT) domains fused to the yeast alpha-factor leader. A C-terminal immunoreactive FLAG peptide was added for Western blot detection and anti-FLAG antibody column purification. We constructed two glycosylation mutant PROCAT TACE isoforms to facilitate purification. A PROCAT isoform, mutated to eliminate two N-linked glycosylation sites, was buffer exchanged and purified to homogeneity by ion exchange chromatography and an anti-FLAG antibody affinity step. N-terminal sequence analysis showed that the mutant preproprotein was processed in yeast at the furin protease cleavage site and yielded an active catalytic domain which has TNF alpha peptide-specific protease activity. Mass spectrometry of the purified catalytic domain showed that removal of both N-linked sites results in a homogeneous sized polypeptide lacking further posttranslational modifications.

Characterization of the microheterogeneities of PIXY321, a genetically engineered granulocyte-macrophage colony-stimulating factor/interleukin-3 fusion protein expressed in yeast.

PIXY321, a human cytokine analog genetically engineered by the fusion of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), was expressed in yeast under the control of the alcohol dehydrogenase 2 (ADH2) promoter and the alpha-mating factor expression system. To provide the material necessary for the evaluation of PIXY321 in clinical trials, the production was scaled up to the 1200-1 scale and the PIXY321 molecule isolated by four successive steps of ion-exchange chromatography. Multiple heterogeneities, due to the presence of different patterns of glycosylation as well as multiple amino acid sequences at both N and C termini, were characterized on the purified molecule using complementary analytical techniques including electrophoresis, liquid chromatography and electrospray mass spectrometry. Four different N-terminal sequences were identified but simplified to a reproducible ratio of two sequences, the mature form and a form starting at Ala3, by adjustment of the process conditions. Molecules lacking 1-6 residues at the C-terminus were identified and their relative frequencies quantified. Amino acid modifications, such as three oxidized Met residues at positions 79, 141 and 187 and one deamidated Asn residue at position 176, were detected at low level. Microheterogeneities in glycosylation were characterized on four different sites, one located in the GM-CSF portion and three in the IL-3 portion of the molecule. The sites were shown to be differentially occupied and to carry 0-10 mannose residues according to their location in the sequence. Precise measurement of the heterogeneities at the molecular level were used to tune the process conditions and ensure reproducibility of the clinical product between lots.

Poxvirus genomes encode a secreted, soluble protein that preferentially inhibits beta chemokine activity yet lacks sequence homology to known chemokine receptors.

Poxvirus genomes encode several proteins which inhibit specific elements of the host immune response. We show the "35K" virulence gene in variola and cowpox viruses, whose vaccinia and Shope fibroma virus equivalents are strongly conserved in sequence, actually encodes a secreted soluble protein with high-affinity binding to virtually all known beta chemokines, but only weak or no affinity to the alpha and gamma classes. The viral protein completely inhibits the biological activity of monocyte chemotactic protein-1 (MCP-1) by competitive inhibition of chemokine binding to cellular receptors. As all beta chemokines are also shown to cross-compete with MCP1 binding to the viral protein, we conclude that this viral chemokine inhibitor (vCCI) not only interacts through a common binding site, but is likely a potent general inhibitor of beta chemokine activity. Unlike many poxvirus virulence genes to date, which are clearly altered forms of acquired cellular genes of the vertebrate immune system, this viral chemokine inhibitor (vCCI) shares no sequence homology with known proteins, including known cellular chemokine receptors, all of which are multiple membrane-spanning proteins. Thus, vCCI presumably has no cellular analogue and instead may be the product of unrelenting sequence variations which gave rise to a completely new protein with similar binding properties to native chemokine receptors. The proposed function of vCCI is inhibition of the proinflammatory (antiviral) activities of beta chemokines.

TRAIL-R2: a novel apoptosis-mediating receptor for TRAIL.

TRAIL is a member of the tumor necrosis factor (TNF) family of cytokines and induces apoptosis in a wide variety of cells. Based on homology searching of a private database, a receptor for TRAIL (DR4 or TRAIL-R1) was recently identified. Here we report the identification of a distinct receptor for TRAIL, TRAIL-R2, by ligand-based affinity purification and subsequent molecular cloning. TRAIL-R2 was purified independently as the only receptor for TRAIL detectable on the surface of two different human cell lines that undergo apoptosis upon stimulation with TRAIL. TRAIL-R2 contains two extracellular cysteine-rich repeats, typical for TNF receptor (TNFR) family members, and a cytoplasmic death domain. TRAIL binds to recombinant cell-surface-expressed TRAIL-R2, and TRAIL-induced apoptosis is inhibited by a TRAIL-R2-Fc fusion protein. TRAIL-R2 mRNA is widely expressed and the gene encoding TRAIL-R2 is located on human chromosome 8p22-21. Like TRAIL-R1, TRAIL-R2 engages a caspase-dependent apoptotic pathway but, in contrast to TRAIL-R1, TRAIL-R2 mediates apoptosis via the intracellular adaptor molecule FADD/MORT1. The existence of two distinct receptors for the same ligand suggests an unexpected complexity to TRAIL biology, reminiscent of dual receptors for TNF, the canonical member of this family.

A metalloproteinase disintegrin that releases tumour-necrosis factor-alpha from cells.

Mammalian cells proteolytically release (shed) the extracellular domains of many cell-surface proteins. Modification of the cell surface in this way can alter the cell's responsiveness to its environment and release potent soluble regulatory factors. The release of soluble tumour-necrosis factor-alpha (TNF-alpha) from its membrane-bound precursor is one of the most intensively studied shedding events because this inflammatory cytokine is so physiologically important. The inhibition of TNF-alpha release (and many other shedding phenomena) by hydroxamic acid-based inhibitors indicates that one or more metalloproteinases is involved. We have now purified and cloned a metalloproteinase that specifically cleaves precursor TNF-alpha. Inactivation of the gene in mouse cells caused a marked decrease in soluble TNF-alpha production. This enzyme (called the TNF-alpha-converting enzyme, or TACE) is a new member of the family of mammalian adamalysins (or ADAMs), for which no physiological catalytic function has previously been identified. Our results should facilitate the development of therapeutically useful inhibitors of TNF-alpha release, and they indicate that an important function of adamalysins may be to shed cell-surface proteins.

Relaxed specificity of matrix metalloproteinases (MMPS) and TIMP insensitivity of tumor necrosis factor-alpha (TNF-alpha) production suggest the major TNF-alpha converting enzyme is not an MMP.

Tumor necrosis factor-alpha is released from cells by a proteolytic cleavage. Previous work suggested that a specific, non-matrix metalloproteinase carries out this cleavage, but matrix metalloproteinases have also been implicated. In this paper, we report that none of the matrix metalloproteinases tested cleaved peptide substrates as specifically as the non-matrix metalloproteinase. A matrix metalloproteinase did process tumor necrosis factor-alpha extracted from COS cells, but neither tissue inhibitor of metalloproteinases-1 nor -2 blocked tumor necrosis factor-alpha processing by human monocytes. Moreover, tissue inhibitor of metalloproteinases-1 had at most a partial effect on the in vivo release of the cytokine in mice. We conclude that a non-matrix metalloproteinase is the major physiological tumor necrosis factor-alpha convertase.

T1/ST2 signaling establishes it as a member of an expanding interleukin-1 receptor family.

Through data base searches, we have discovered new proteins that share homology with the signaling domain of the type I interleukin-1 receptor (IL-1RI): human "randomly sequenced cDNA 786" (rsc786), murine MyD88, and two partial Drosophila open reading frames, MstProx and STSDm2245. Comparisons between these new proteins and known IL-1RI homologous proteins such as Toll, 18-Wheeler, and T1/ST2 revealed six clusters of amino acid similarity. We tested the hypothesis that sequence similarity between the signaling domain of IL-1RI and the three mammalian family members might indicate functional similarity. Chimeric IL-1RI receptors expressing the putative signaling domains of T1/ST2, MyD88, and rsc786 were assayed by three separate IL-1 responsive assays, NF-kappaB, phosphorylation of an epidermal growth factor receptor peptide, and an interleukin 8 promoter-controlled reporter construct, for their ability to transduce an IL-1-stimulated signal. All three assays were positive in response to the T1/ST2 chimera, while the MyD88 and rsc786 chimeras failed to respond. These data indicate that the sequence homology between IL-1RI and T1/ST2 indicates a functional homology as well.

Direct evidence of a heterotrimeric complex of human interleukin-4 with its receptors.

The mode of binding of interleukin-4 (IL-4) to its two known receptors, specific receptor IL-4R and a shared receptor gamma c, was investigated using gel filtration and gel electrophoresis. A ternary complex between IL-4 and the soluble domains of the two receptors was shown to exist in solution. The association constant between gamma c and the stable complex of IL-4/sIL-4R is in the millimolar range, making the ternary complex a feasible target for crystallization studies.

Ethanol inhibits some of the early effects of epidermal growth factor in vivo.

Charles River male Wistar rats (200-300 g) were meal fed for 9-10 days, injected with either saline, epidermal growth factor (EGF), ethanol, or ethanol combined with EGF and their livers were freeze clamped 5 min after intraperitoneal injection of EGF. Metabolites were measured and the redox state and phosphorylation potential were calculated. Epidermal growth factor alone elevated hepatic content of glucose 1-P, glucose 6-P, fructose 6-P, and 3-phosphoglycerate 1.2-1.3-fold when compared to saline treatment. Ethanol alone decreased hepatic content of 3-phosphoglycerate and phosphoenolpyruvate 3.2-3.7-fold below saline-treated levels. Ethanol, in combination with EGF, decreased hepatic values for 3-phosphoglycerate and phosphoenolpyruvate 2.0-2.3-fold from saline treatment but elevated the content of phosphoenolpyruvate 1.6-fold over ethanol treatment alone. Epidermal growth factor inhibited pyruvate kinase activity 1.3-fold when compared to saline controls but ethanol in the presence of EGF facilitated the recovery of activity of this enzyme.

Epidermal growth factor binding in the presence of ethanol.

Epidermal growth factor (EGF) is a mitogen which has been shown to stimulate maxillo-facial growth and DNA synthesis. Ethanol has been reported to inhibit cell regeneration in vivo and in vitro and to produce diminished maxillo-facial development in fetal alcohol syndrome. Recent findings from this laboratory have elucidated rapid metabolic changes in the hepatic content of some of the glycolytic intermediates resulting from injection of EGF, ethanol or EGF combined with ethanol in vivo. An immediate effect of EGF in vivo is to increase hepatic tissue content of 3-phosphoglycerate and phosphoenolpyruvate 1.2-1.3 fold when compared to saline treatment. Ethanol however causes a marked fall in the hepatic content of 3-phosphoglycerate and phosphoenolpyruvate 3.2-3.7 fold below saline treated levels. Ethanol in combination with EGF decreases hepatic values for 3-phosphoglycerate and phosphoenolpyruvate 2.0-2.3 fold from saline treated, but elevates the content of phosphoenolpyruvate 1.6 fold over ethanol treatment alone. Such metabolite changes occurring with ethanol treatment have been attributed alternately to redox shifts or to membrane perturbations. We wished to determine whether dimunition of 3-phosphoglycerate and or phosphoenolpyruvate below certain levels perhaps critically necessary for normal mitogenic action of EGF was due in this case to ethanol effects of binding of EGF to the cell membrane.

Alterations in brain lipid composition of mice made physically dependent to ethanol.

The ability of chronic ethanol treatment to alter CNS membrane lipids was tested. Adult C57/BL6 mice were given a liquid diet containing ethanol for eight days. This regimen produced strong physical dependence as judged by withdrawal seizures, tremors and concomitant hypothermia. Analyses were performed on cholesterol, total phospholipid content and total phospholipid acyl composition of myelin, crude (P2), light and heavy synaptosomes as well as synaptosomal plasma membranes. Chronic ethanol treatment had no effect on total phospholipid levels nor phospholipid acyl composition in any of the above subcellular fractions. In ethanol dependent mice, significant increases in cholesterol content and cholesterol/phospholipid ratios were observed in synaptosomal plasma membranes.

Effects of ethanol diets on cholesterol content and phospholipid acyl composition of rat hepatocytes.

Chronic treatment of adult male rats with ethanol liquid diets resulted in alterations in phospholipid and cholesterol contents as well as the acyl composition of phosphatidylethanolamine (PE), phosphatidylinositol (PI)-phosphatidylserine (PS) mixture, and phosphatidylcholine (PC) of isolated hepatocytes. The influence of ethanol on these lipids was largely dependent on the proportion of dietary fat. Phospholipid and total cholesterol contents were elevated 23 and 27%, respectively, by ethanol when offered in a low-fat diet (5% corn oil). Only the percentage of arachidonic acid from PI-PS was significantly reduced in the low-fat ethanol group. Exposure to a high-fat (34% corn oil) diet in the presence of ethanol for 4-5 weeks resulted in a significant decrease in arachidonate/linoleate ratios of hepatic PE, PS-PI and PC, while total phospholipid content remained constant. In the high-fat, ethanol-treated group, hepatic cholesterol content was increased 2-fold. These results suggest that the level of dietary fat plays an important role in determining the effects of chronic ethanol consumption on hepatic cholesterol content and phospholipid acyl composition.