Following the fate of individual T cells throughout activation and clonal expansion. Signals from T cell receptor and CD28 differentially regulate the induction and duration of a proliferative response

A detailed understanding of the effects of costimulatory signals on primary T cell expansion has been limited by experimental approaches that measure the bulk response of a cell population, without distinguishing responses of individual cells. Here, we have labeled live T cells in vitro with a stable, fluorescent dye that segregates equally between daughter cells upon cell division, allowing the proliferative history of any T cell present or generated during a response to be monitored over time. This system permits simultaneous evaluation of T cell surface markers, allowing concomitant assessment of cellular activation and quantitative determination of T cell receptor (TCR) occupancy on individual cells. Through this approach, we find that TCR engagement primarily regulates the frequency of T cells that enter the proliferative pool, but has relatively little effect on the number of times these cells will ultimately divide. In contrast, CD28-costimulation regulates both the frequency of responding cells (particularly at sub-maximal levels of TCR engagement), and more prominently, the number of mitotic events that responding cells undergo. When CD28-stimulation is blocked, provision of IL-2 restores the frequency of responding cells and the normal pattern of mitotic progression, indicating that the other CD28-induced genes are not required for this effect. An unexpected finding was that even at maximal levels of TCR engagement and CD28-mediated costimulation, only 50-60% of the original T cells in culture can be induced to divide. The nondividing cells are heterogeneous for naive versus memory markers, suggesting a more complex relationship between expression of memory markers and the ability to be recruited into the dividing pool. From these studies, we conclude that a stringent checkpoint regulates the participation of activated T cells in clonal expansion, with TCR and CD28 signals having both overlapping and differential effects on the induction and maintenance of T cell responses.

High throughput protein fold identification by using experimental constraints derived from intramolecular cross-links and mass spectrometry

We have used intramolecular cross-linking, MS, and sequence threading to rapidly identify the fold of a model protein, bovine basic fibroblast growth factor (FGF)-2. Its tertiary structure was probed with a lysine-specific cross-linking agent, bis(sulfosuccinimidyl) suberate (BS(3)). Sites of cross-linking were determined by tryptic peptide mapping by using time-of-flight MS. Eighteen unique intramolecular lysine (Lys-Lys) cross-links were identified. The assignments for eight cross-linked peptides were confirmed by using post source decay MS. The interatomic distance constraints were all consistent with the tertiary structure of FGF-2. These relatively few constraints, in conjunction with threading, correctly identified FGF-2 as a member of the beta-trefoil fold family. To further demonstrate utility, we used the top-scoring homolog, IL-1beta, to build an FGF-2 homology model with a backbone error of 4.8 A (rms deviation). This method is fast, is general, uses small amounts of material, and is amenable to automation.

Identification and functional characterization of a second chain of the interleukin-10 receptor complex

Interleukin-10 (IL-10) is a pleiotropic cytokine which signals through a specific cell surface receptor complex. Only one chain, that for ligand binding (IL-10Ralpha or IL-10R1), was identified previously. We report here that, although human IL-10 binds to the human IL-10R1 chain expressed in hamster cells, it does not induce signal transduction. However, the co-expression of CRFB4, a transmembrane protein of previously unknown function belonging to the class II cytokine receptor family, together with the IL-10R1 chain renders hamster cells sensitive to IL-10. The IL-10:CRFB4 complex was detected by cross-linking to labeled IL-10. In addition, the IL-10R1 chain was able to be co-immunoprecipitated with anti-CRF antibody when peripheral blood mononuclear cells were treated with IL-10. These results demonstrate that the CRFB4 chain is part of the IL-10 receptor signaling complex. Thus, the CRFB4 chain, which we designate as the IL-10R2 or IL-10Rbeta chain, serves as an accessory chain essential for the active IL-10 receptor complex and to initiate IL-10-induced signal transduction events.

Development of tailor-made collagen-glycosaminoglycan matrices: EDC/NHS crosslinking, and ultrastructural aspects

The many biocharacteristics of glycosaminoglycans (GAGs) make them valuable molecules to be incorporated in collagenous biomaterials. To prepare tailor-made collagen-GAG matrices with a well-defined biodegradability and (bioavailable) GAG content, the crosslinking conditions have to be controlled. Additionally, the ultrastructural location of GAGs in engineered substrates should resemble that of the application site. Using chondroitin sulfate (CS) as a model GAG, these aspects were evaluated. The methodology was then applied for other GAGs. CS was covalently attached to collagen using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). A maximum of about 155 mg CS/g matrix could be immobilized. CS incorporation and bioavailability, as evaluated by interaction with specific antibodies and glycosidases, was dependent on the molar ratio EDC:carboxylic groups of CS. The denaturation temperature could be modulated from 61 to 85 degrees C. The general applicability of EDC/NHS for immobilizing GAGs was demonstrated with dermatan sulfate, heparin, and heparan sulfate. These matrices revealed comparable physico-chemical characteristics, biodegradabilities, and preserved bioavailable GAG moieties. At the ultrastructural level, GAGs appeared as discrete, electron-dense filaments, each filament representing a single GAG molecule. Distribution was independent of GAG type. They were observed throughout the matrix fibers and at the outer sites, and located, either parallel or orthogonally, at the periphery of individual collagen fibrils. Compositional and ultrastructural similarity between matrices and tissue structures like cartilage and basement membranes can be realized after attachment of specific GAG types. It is concluded that EDC/NHS is generally applicable for attachment of GAGs to collagen. Modulation of crosslinking conditions provides matrices with well-defined GAG contents, and biodegradabilities. Ultrastructural similarities between artificially engineered scaffolds and their possible application site may favor the use of specific collagen-GAG matrices in tissue engineering.

Pannexin1 channels contain a glycosylation site that targets the hexamer to the plasma membrane

Pannexins are newly discovered channel proteins expressed in many different tissues and abundantly in the vertebrate central nervous system. Based on membrane topology, folding and secondary structure prediction, pannexins are proposed to form gap junction-like structures. We show here that Pannexin1 forms a hexameric channel and reaches the cell surface but, unlike connexins, is N-glycosylated. Using site-directed mutagenesis we analyzed three putative N-linked glycosylation sites and examined the effects of each mutation on channel expression. We show for the first time that Pannexin1 is glycosylated at Asn-254 and that this residue is important for plasma membrane targeting. The glycosylation of Pannexin1 at its extracellular surface makes it unlikely that two oligomers could dock to form an intercellular channel. Ultrastructural analysis by electron microscopy confirmed that Pannexin1 junctional areas do not appear as canonical gap junctions. Rather, Pannexin1 channels are distributed throughout the plasma membrane. We propose that N-glycosylation of Pannexin1 could be a significant mechanism for regulating the trafficking of these membrane proteins to the cell surface in different tissues.

Two-step cross-linking method for identification of NF-kappaB gene network by chromatin immunoprecipitation

The chromatin immunoprecipitation (ChIP) assay has recently been exploited as a powerful and versatile technique for probing protein-DNA interactions within the chromatin environment. In this method, intact cells are fixed with a reversible DNA-protein cross-linking agent (formaldehyde), and associated DNA is enriched by immunoprecipitating a target DNA binding protein. The bound DNA in the immune complexes is then used to identify that specific DNA binding protein's endogenous genomic targets. Nuclear factor kappaB (NF-kappaB) is a highly inducible transcription factor that controls genetic networks important for pathogen- or cytokine-induced inflammation, immune response, and cellular survival. In our studies of the genetic network under control of the inducible NF-kappaB transcription factor, we found that the conventional ChIP technique using a single formaldehyde cross-linking step did not reproducibly cross-link it to DNA. As a result, we have developed a novel ChIP assay using a two-step cross-linking procedure, incorporating N-hydroxysuccinimide (NHS)-ester-mediated protein-protein cross-linking prior to conventional DNA-protein cross-linking. We demonstrate that this technique is highly efficient, cross-linking virtually all NF-kappaB/Rel A into covalent complexes, resulting in quantitative and robust identification of inducible NF-kappaB family binding to a variety of validated NF-kappaB-dependent genomic targets. To demonstrate the general utility of this two-step cross-linking procedure, we performed enhanced capture of cytokine-inducible signal transducer and activator of transcription-3 (STAT3) binding to one of its known target genes. Our method represents a significant improvement in the efficiency of ChIP analysis in the study of endogenous targets for rare transcription factors.

Insulin stimulates long-chain fatty acid utilization by rat cardiac myocytes through cellular redistribution of FAT/CD36

The existence of an intracellular pool of fatty acid translocase (FAT/CD36), an 88-kDa membrane transporter for long-chain fatty acids (FAs), and the ability of insulin to induce translocation events prompted us to investigate the direct effects of insulin on cellular uptake of FA by the heart. Insulin (0.1 nmol/l and higher) increased FA uptake by isolated rat cardiac myocytes by 1.5-fold. This insulin-induced increase in FA uptake was completely blocked by phloretin, sulfo-N-succinimidylpalmitate (SSP), and wortmannin, indicating the involvement of FAT/CD36 and the dependence on phosphatidylinositol-3 (PI-3) kinase activation. Subcellular fractionation of insulin-stimulated cardiac myocytes demonstrated a 1.5-fold increase in sarcolemmal FAT/CD36 and a 62% decrease in intracellular FAT/CD36 with parallel changes in subcellular distribution of GLUT4. Induction of cellular contractions upon electrostimulation at 4 Hz enhanced cellular FA uptake 1.6-fold, independent of PI-3 kinase. The addition of insulin to 4 Hz-stimulated cells further stimulated FA uptake to 2.3-fold, indicating that there are at least two functionally independent intracellular FAT/CD36 pools, one recruited by insulin and the other mobilized by contractions. In conclusion, we have demonstrated a novel role of insulin in cardiac FA utilization. Malfunctioning of insulin-induced FAT/CD36 translocation may be involved in the development of type 2 diabetic cardiomyopathies.

Plasma membrane Ca2+ ATPase 4 is required for sperm motility and male fertility

Calcium and Ca(2+)-dependent signals play a crucial role in sperm motility and mammalian fertilization, but the molecules and mechanisms underlying these Ca(2+)-dependent pathways are incompletely understood. Here we show that homozygous male mice with a targeted gene deletion of isoform 4 of the plasma membrane calcium/calmodulin-dependent calcium ATPase (PMCA), which is highly enriched in the sperm tail, are infertile due to severely impaired sperm motility. Furthermore, the PMCA inhibitor 5-(and-6)-carboxyeosin diacetate succinimidyl ester reduced sperm motility in wild-type animals, thus mimicking the effects of PMCA4 deficiency on sperm motility and supporting the hypothesis of a pivotal role of the PMCA4 on the regulation of sperm function and intracellular Ca(2+) levels.

CD40 stimulation leads to effective therapy of CD40(-) tumors through induction of strong systemic cytotoxic T lymphocyte immunity

Adequate spontaneous activation of tumor-specific T lymphocytes in tumor-bearing hosts is rare, despite the expression of tumor antigens that are potentially highly immunogenic. For example, failure of the immune system to raise competent responses against established tumors expressing the human adenovirus E1A-antigen allows this tumor to grow in immunocompetent mice. We show that systemic in vivo administration of agonistic anti-CD40 antibodies into tumor-bearing mice results in tumor eradication mediated by CD8(+) T cells. Treatment resulted in a strong expansion and systemic accumulation of E1A-specific CTL and depended on CD40 expression on host cells, as the tumor was CD40(-), and therapy failed in CD40-deficient mice. Local intratumoral administration of anti-CD40 mAb is equally effective in licensing strong, systemic CTL immunity, resulting in the clearance of distant tumor nodules. Our data indicate that the immune response after cancer-host interactions can be directed toward competence, leading to the cure of established tumors merely by delivery of a CD40-dependent "license to kill" signal.

RANKL expression is related to the differentiation state of human osteoblasts

Human osteoblast phenotypes that support osteoclast differentiation and bone formation are not well characterized. Osteoblast differentiation markers were examined in relation to RANKL expression. RANKL expression was induced preferentially in immature cells. These results support an important link between diverse osteoblast functions. Cells of the osteoblast lineage support two apparently distinct functions: bone formation and promotion of osteoclast formation. The aim of this study was to examine the relationship between these phenotypes in human osteoblasts (NHBC), in terms of the pre-osteoblast marker, STRO-1, and the mature osteoblast marker, alkaline phosphatase (AP), and the expression of genes involved in osteoclast formation, RANKL and OPG. The osteotropic stimuli, 1alpha,25(OH)2vitamin D3 (vitD3) and dexamethasone, were found to have profound proliferative and phenotypic effects on NHBCs. VitD3 inhibited NHBC proliferation and increased the percentage of cells expressing STRO-1 over an extended culture period, implying that vitD3 promotes and maintains an immature osteogenic phenotype. Concomitantly, RANKL mRNA expression was upregulated and maintained in NHBC in response to vitD3. Dexamethasone progressively promoted the proliferation of AP-expressing cells, resulting in the overall maturation of the cultures. Dexamethasone had little effect on RANKL mRNA expression and downregulated OPG mRNA expression in a donor-dependent manner. Regression analysis showed that RANKL mRNA expression was associated negatively with the percentage of cells expressing AP (p < 0.01) in vitD3- and dexamethasone-treated NHBCs. In contrast, RANKL mRNA expression was associated positively with the percentage of STRO-1+ cells (p < 0.01). In NHBCs sorted by FACS based on STRO-1 expression (STRO-1bright and STRO-1dim populations), it was found that vitD3 upregulated the expression of RANKL mRNA preferentially in STRO-1bright cells. The results suggest that immature osteoblasts respond to osteotropic factors in a potentially pro-osteoclastogenic manner. Additionally, the dual roles of osteoblasts, in supporting osteoclastogenesis or forming bone, may be performed by the same lineage of cells at different stages of their maturation.

Nuclei of embryonic stem cells reprogram somatic cells

The restricted potential of a differentiated cell can be reverted back to a pluripotent state by cell fusion; totipotency can even be regained after somatic cell nuclear transfer. To identify factors involved in resetting the genetic program of a differentiated cell, we fused embryonic stem cells (ESCs) with neurosphere cells (NSCs). The fusion activated Oct4, a gene essential for pluripotency, in NSCs. To further identify whether cytoplasmic or nuclear factors are responsible for its reactivation, we fused either karyoplasts or cytoplasts of ESCs with NSCs. Our results show that ESC karyoplasts could induce Oct4 expression in the somatic genome, but cytoplasts lacked this ability. In addition, mitomycin C-treated ESCs, although incapable of DNA replication and cell division, could reprogram 5-azacytidine-treated NSCs. We therefore conclude that the Oct4 reprogramming capacity resides in the ESC karyoplast and that gene reactivation is independent of DNA replication and cell division.

Role of Erv29p in collecting soluble secretory proteins into ER-derived transport vesicles

Proteins are transported from the endoplasmic reticulum (ER) in vesicles formed by coat protein complex II (COPII). Soluble secretory proteins are thought to leave the ER in these vesicles by "bulk flow" or through recognition by hypothetical shuttling receptors. We found that Erv29p, a conserved transmembrane protein, was directly required for packaging glycosylated pro-alpha-factor (gpalphaf) into COPII vesicles in Saccharomyces cerevisiae. Further, an Erv29p-gpalphaf complex was isolated from ER-derived transport vesicles. In vivo, export of gpalphaf from the ER was saturable and depended on the expression level of Erv29p. These results indicate that membrane receptors can link soluble cargo proteins to the COPII coat.

Enhanced sarcolemmal FAT/CD36 content and triacylglycerol storage in cardiac myocytes from obese zucker rats

In obesity, the development of cardiomyopathy is associated with the accumulation of myocardial triacylglycerols (TAGs), possibly stemming from elevation of myocardial long-chain fatty acid (LCFA) uptake. Because LCFA uptake is regulated by insulin and contractions, we examined in cardiac myocytes from lean and obese Zucker rats the effects of insulin and the contraction-mimetic agent oligomycin on the initial rate of LCFA uptake, subcellular distribution of FAT/CD36, and LCFA metabolism. In cardiac myocytes from obese Zucker rats, under basal conditions, FAT/CD36 was relocated to the sarcolemma at the expense of intracellular stores. In addition, the LCFA uptake rate, LCFA esterification rate into TAGs, and the intracellular unesterified LCFA concentration each were significantly increased. All these metabolic processes were normalized by the FAT/CD36 inhibitor sulfo-N-succinimidyloleate, indicating its antidiabetic potential. In cardiac myocytes isolated from lean rats, in vitro administration of insulin induced the translocation of FAT/CD36 to the sarcolemma and stimulated initial rates of LCFA uptake and TAG esterification. In contrast, in myocytes from obese rats, insulin failed to alter the subcellular localization of FAT/CD36 and the rates of LCFA uptake and TAG esterification. In cardiac myocytes from lean and obese animals, oligomycin stimulated the initial rates of LCFA uptake and oxidation, although oligomycin only induced the translocation of FAT/CD36 to the sarcolemma in lean rats. The present results indicate that in cardiac myocytes from obese Zucker rats, a permanent relocation of FAT/CD36 to the sarcolemma is responsible for myocardial TAG accumulation. Furthermore, in vitro these cardiac myocytes, although sensitive to contraction-like stimulation, were completely insensitive to insulin, as the basal conditions in hyperinsulinemic, obese animals resemble the insulin-stimulated condition in lean littermates.

Biocompatibility and tissue regenerating capacity of crosslinked dermal sheep collagen

The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytotoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanate-crosslinked DSC (HDSC) seldom induced an increased infiltration of neutrophils or macrophages, as compared with normal wound healing; whereas new formation of collagen was observed. DSC crosslinked with glutaraldehyde (GDSC) followed by reaction with NaBH4 shortly after implantation showed an increased infiltration of neutrophils with a deviant morphology. Furthermore, a high incidence of calcification was observed, which may explain the minor ingrowth of giant cells and fibroblasts, and the poor formation of new rat collagen. Acyl azide-crosslinked DSC (AaDSC) first induced an increased infiltration of macrophages, and then of giant cells, both with high lipid formation. AaDSC degraded at least twice as slowly as HDSC and GDSC, finally leaving a matrix of newly formed rat collagen. Samples crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide (ENDSC) induced the same mild cellular reaction as HDSC; whereas, similar to AaDSC, the degradation rate was slow and an optimal rat collagen matrix was formed. Of the crosslinked DSC samples, ENDSC seems most promising for tissue regeneration.

Identification and characterization of the first class of potent bacterial acetyl-CoA carboxylase inhibitors with antibacterial activity

The multisubunit acetyl-CoA carboxylase, which catalyzes the first committed step in fatty acid biosynthesis, is broadly conserved among bacteria. Its rate-limiting role in formation of fatty acids makes this enzyme an attractive target for the design of novel broad-spectrum antibacterials. However, no potent inhibitors have been discovered so far. This report describes the identification and characterization of highly potent bacterial acetyl-CoA carboxylase inhibitors with antibacterial activity for the first time. We demonstrate that pseudopeptide pyrrolidine dione antibiotics such as moiramide B inhibit the Escherichia coli enzyme at nanomolar concentrations. Moiramide B targets the carboxyltransferase reaction of this enzyme with a competitive inhibition pattern versus malonyl-CoA (K(i) value = 5 nm). Inhibition at nanomolar concentrations of the pyrrolidine diones is also demonstrated using recombinantly expressed carboxyltransferases from other bacterial species (Staphylococcus aureus, Streptococcus pneumoniae, and Pseudomonas aeruginosa). We isolated pyrrolidine dione-resistant strains of E. coli, S. aureus, and Bacillus subtilis, which contain mutations within the carboxyltransferase subunits AccA or AccD. We demonstrate that such mutations confer resistance to pyrrolidine diones. Inhibition values (IC(50)) of >100 microm regarding an eukaryotic acetyl-CoA carboxylase from rat liver indicate high selectivity of pyrrolidine diones for the bacterial multisubunit enzyme. The natural product moiramide B and synthetic analogues show broad-spectrum antibacterial activity. The knowledge of the target and the availability of facile assays using carboxyltransferases from different pathogens will enable evaluation of the antibacterial potential of the pyrrolidine diones as a promising antibacterial compound class acting via a novel mode of action.

Dissociation of the complex of dystrophin and its associated proteins into several unique groups by n-octyl beta-D-glucoside

Dystrophin is purified as a complex with several proteins from the digitonin-solubilized muscle cell membrane. Most of dystrophin-associated proteins (DAPs) are assumed to form a large oligomeric transmembranous glycoprotein complex on the sarcolemma and link dystrophin with a basement membrane protein, laminin. In the present study, we found that the purified dystrophin-DAP complex was dissociated into several groups by n-octyl-beta-D-glucoside treatment. In particular, we found that the glycoprotein complex stated above was dissociated into two distinct groups: one composed of 156DAG and 43DAG (A3a) and the other composed of 50DAG, 35DAG and A3b. We confirmed by crosslinking and immunoaffinity chromatography that these two groups existed in a complexes. We thus concluded that the glycoprotein complex consists of these two subcomplexes. Furthermore, A3b and 43DAG, which had been formerly treated simply as the 43DAG doublets due to their similar electrophoretic mobilities in SDS/PAGE, were shown to be present in two different subcomplexes. Based on the analyses by two-dimensional gel electrophoresis, peptide mapping and immunoblotting, we concluded that A3b is a novel DAP different from 43DAG.

Two distinct types of endothelin receptors are present on chick cardiac membranes

Competitive displacement experiments of 125I-endothelin (ET)-1, -2, or -3 binding to chick cardiac membranes were performed with unlabeled ET-1, -2, -3, and sarafotoxin S6b (STX) as competitors. 125I-ET-1 and -2 binding was competitively inhibited by increasing concentrations of these unlabeled peptides in the same order; i.e. ET-2 greater than or equal to ET-1 greater than ET-3 greater than STX. In contrast, the order of potency in displacing 125I-ET-3 binding was ET-3 greater than ET-2 greater than or equal to ET-1 greater than STX. Affinity labeling of the membranes by cross-linking with 125I-ET-1 and -2 via disuccinimidyl tartarate yielded one major specific band with an apparent Mr = 53,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography. On the other hand, affinity labeling with 125I-ET-3 showed that two major and one minor bands of Mr = 34,000, 46,000, and 53,000, respectively, were specifically labeled. These results indicate the presence of two distinct types of ET receptors, one of which has higher affinity for ET-1 and -2 than ET-3 and the other is conversely ET-3-preferring.

FAT/CD36-mediated long-chain fatty acid uptake in adipocytes requires plasma membrane rafts

We previously reported that lipid rafts are involved in long-chain fatty acid (LCFA) uptake in 3T3-L1 adipocytes. The present data show that LCFA uptake does not depend on caveolae endocytosis because expression of a dominant negative mutant of dynamin had no effect on uptake of [3H]oleic acid, whereas it effectively prevented endocytosis of cholera toxin. Isolation of detergent-resistant membranes (DRMs) from 3T3-L1 cell homogenates revealed that FAT/CD36 was expressed in both DRMs and detergent-soluble membranes (DSMs), whereas FATP1 and FATP4 were present only in DSMs but not DRMs. Disruption of lipid rafts by cyclodextrin and specific inhibition of FAT/CD36 by sulfo-N-succinimidyl oleate (SSO) significantly decreased uptake of [3H]oleic acid, but simultaneous treatment had no additional or synergistic effects, suggesting that both treatments target the same mechanism. Indeed, subcellular fractionation demonstrated that plasma membrane fatty acid translocase (FAT/CD36) is exclusively located in lipid rafts, whereas intracellular FAT/CD36 cofractionated with DSMs. Binding assays confirmed that [3H]SSO predominantly binds to FAT/CD36 within plasma membrane DRMs. In conclusion, our data strongly suggest that FAT/CD36 mediates raft-dependent LCFA uptake. Plasma membrane lipid rafts might control LCFA uptake by regulating surface availability of FAT/CD36.

Analysis of platelet adhesion with a radioactive chemical crosslinking reagent: interaction of thrombospondin with fibronectin and collagen

We have analyzed the interactions of platelets and platelet-secreted proteins with proteins bound to glass substrata. Using a newly developed radioactive crosslinking reagent, N-succinimidyl-3-[(2-nitro-4-azidophenyl)-2-aminoethyldithio] propionate, we observed crosslinking between thrombospondin released from the platelets and surface-bound fibronectin or collagen. The crosslinking was selective and specific, since thrombospondin showed little crosslinking to substratum-bound bovine serum albumin or ovalbumin, even though it bound to these surfaces. Furthermore, although albumin and fibrinogen released by platelets bound to fibronectin-coated substrata as well as did thrombospondin, these two proteins crosslinked at much lower levels than seen for thrombospondin. Interaction between fibronectin and thrombospondin was confirmed by affinity chromatography. These results suggest that thrombospondin and fibronectin may interact during platelet-substratum adhesion or during platelet-platelet aggregation, or both.

Mitochondrial long chain fatty acid oxidation, fatty acid translocase/CD36 content and carnitine palmitoyltransferase I activity in human skeletal muscle during aerobic exercise

Mitochondrial fatty acid transport is a rate-limiting step in long chain fatty acid (LCFA) oxidation. In rat skeletal muscle, the transport of LCFA at the level of mitochondria is regulated by carnitine palmitoyltransferase I (CPTI) activity and the content of malonyl-CoA (M-CoA); however, this relationship is not consistently observed in humans. Recently, fatty acid translocase (FAT)/CD36 was identified on mitochondria isolated from rat and human skeletal muscle and found to be involved in LCFA oxidation. The present study investigated the effects of exercise (120 min of cycling at approximately 60% V(O2peak)) on CPTI palmitoyl-CoA and M-CoA kinetics, and on the presence and functional significance of FAT/CD36 on skeletal muscle mitochondria. Whole body fat oxidation rates progressively increased during exercise (P < 0.05), and concomitantly M-CoA inhibition of CPTI was progressively attenuated. Compared to rest, 120 min of cycling reduced (P < 0.05) the inhibition of 0.7, 2, 5 and 10 microM M-CoA by 16%, 21%, 30% and 34%, respectively. Whole body fat oxidation and palmitate oxidation rates in isolated mitochondria progressively increased (P < 0.05) during exercise, and were positively correlated (r = 0.78). Mitochondrial FAT/CD36 protein increased by 63% (P < 0.05) during exercise and was significantly (P < 0.05) correlated with mitochondrial palmitate oxidation rates at all time points (r= 0.41). However, the strongest (P < 0.05) correlation was observed following 120 min of cycling (r = 0.63). Importantly, the addition of sulfo-N-succimidyloleate, a specific inhibitor of FAT/CD36, reduced mitochondrial palmitate oxidation to approximately 20%, indicating FAT/CD36 is functionally significant with respect to LCFA oxidation. We hypothesize that exercise-induced increases in fatty acid oxidation occur as a result of an increased ability to transport LCFA into mitochondria. We further suggest that decreased CPTI M-CoA sensitivity and increased mitochondrial FAT/CD36 protein are both important for increasing whole body fatty acid oxidation during prolonged exercise.

Novel spirosuccinimides with incorporated isoindolone and benzisothiazole 1,1-dioxide moieties as aldose reductase inhibitors and antihyperglycemic agents

Compounds from two novel series of spirosuccinimides were prepared. Analogs of series 2 possessed a spiro-fused isoindolone moiety while those of series 3 contained a spiro-fused benzisothiazole S,S-dioxide group. These compounds were evaluated as aldose reductase inhibitors (ARI) in vitro by their ability to inhibit glyceraldehyde reduction using a partially purified bovine lens aldose reductase preparation and in vivo as inhibitors of galactitol accumulation in the lens, sciatic nerve, and diaphragm of galactose-fed rats. Many members from the isoindolone series 2, particularly those containing an isoindolone N-methyl moiety, showed good in vitro and in vivo potency. The most potent member, the 6-chloro analog 32, was resolved, and aldose reductase activity was found to reside almost exclusively in the (+)-enantiomer. Compound 32 was approximately equipotent in the sciatic nerve of the galactose-fed rat to other cyclic imide ARI's of similar in vitro activity, namely sorbinil and ADN-138 and also to tolrestat, an acetic acid-based ARI (ED50's 4-8 mg/kg). Compounds from both series, 2 and 3, were also found to lower plasma glucose levels of genetically obese db/db and ob/ob mice with potency similar to that of ciglitazone. However, members from these series failed to lower insulin levels of the ob/ob mouse at the doses tested.

Mapping of the protein import machinery in the mitochondrial outer membrane by crosslinking of translocation intermediates

Mitochondria contain a complex machinery for the import of nuclear-encoded proteins. Receptor proteins exposed on the outer membrane surface are required for the specific binding of precursor proteins to mitochondria, either by binding of cytosolic signal recognition factors or by direct recognition of the precursor polypeptides. Subsequently, the precursors are inserted into the outer membrane at the general insertion site GIP (general insertion protein). Here we report the analysis of receptors and GIP by crosslinking of translocation intermediates and by coimmunoprecipitation. Surface-accumulated precursors were crosslinked to the receptors MOM19 and MOM72, suggesting a direct interaction of preproteins with surface receptors. We identified three novel mitochondrial outer membrane proteins, MOM7, MOM8, and MOM30 that, together with the previously identified MOM38, seem to form the GIP site and are present in the mitochondrial receptor complex.

CD36 Mediated Fatty Acid-Induced Podocyte Apoptosis via Oxidative Stress

Background

Hyperlipidemia-induced apoptosis mediated by fatty acid translocase CD36 is associated with increased uptake of ox-LDL or fatty acid in macrophages, hepatocytes and proximal tubular epithelial cells, leading to atherosclerosis, liver damage and fibrosis in obese patients, and diabetic nephropathy (DN), respectively. However, the specific role of CD36 in podocyte apoptosis in DN with hyperlipidemia remains poorly investigated.

Methods

The expression of CD36 was measured in paraffin-embedded kidney tissue samples (Ctr = 18, DN = 20) by immunohistochemistry and immunofluorescence staining. We cultured conditionally immortalized mouse podocytes (MPC5) and treated cells with palmitic acid, and measured CD36 expression by real-time PCR, Western blot analysis and immunofluorescence; lipid uptake by Oil red O staining and BODIPY staining; apoptosis by flow cytometry assay, TUNEL assay and Western blot analysis; and ROS production by DCFH-DA fluorescence staining. All statistical analyses were performed using SPSS 21.0 statistical software.

Results

CD36 expression was increased in kidney tissue from DN patients with hyperlipidemia. Palmitic acid upregulated CD36 expression and promoted its translocation from cytoplasm to plasma membrane in podocytes. Furthermore, palmitic acid increased lipid uptake, ROS production and apoptosis in podocytes, Sulfo-N-succinimidyloleate (SSO), the specific inhibitor of the fatty acid binding site on CD36, decreased palmitic acid-induced fatty acid accumulation, ROS production, and apoptosis in podocytes. Antioxidant 4-hydroxy-2,2,6,6- tetramethylpiperidine -1-oxyl (tempol) inhibited the overproduction of ROS and apoptosis in podocytes induced by palmitic acid.

Conclusions

CD36 mediated fatty acid-induced podocyte apoptosis via oxidative stress might participate in the process of DN.

Detection of the nueroleptic properties of clozapine, sulpiride and thioridazine

The cataleptic and antistereotypic abilities of clozapine, sulpiride and thioridazine were determined in the rat and compared with the responses of typical neuroleptic agents, haloperidol, fluphenazine and pimozide. Haloperidol and fluphenazine caused a dose-dependent cataleptic state which attained maximum intensity: the effects of pimozide were also dose-dependent but, although the catalepsy was marked, maximum intensity was not attained. In contrast, thioridazine, clozapine and sulpiride each caused a very weak, but definite, cataleptic response although a dose-dependency could not be demonstrated. Pretreatment of animals with alpha-methylparatyrosine was shown to significantly potentiate the cataleptic actions of haloperidol, fluphenazine, pimozide, thioridazine and sulpiride but failed to modify the action of clozapine, Threshold cataleptic doses of all agents markedly synergised in the production of catalepsy with threshold doses of the cholinergic drug RS86. Similarly, all "neuroleptic" agents tested were shown to reduce the intensity of the stereotyped behaviour induced by amphetamine, apomorphine and nomifensine in a dose-dependent manner but only haloperidol, fluphenazine and pimozide were shown to be capable of 100% inhibition. The antistereotypic abilities of haloperidol, fluphenazine and pimozide were most marked against amphetamine, but this was not a consistent observation for thioridazine, clozapine and sulpiride. Threshold, or even subthreshold, doses of both the typical and atypical neuroleptic agents combined with threshold doses of RS86 markedly synergised in the antagonism of the stereotypic actions of amphetamine, apomorphine and nomifensine.

Local expression of B7-H1 promotes organ-specific autoimmunity and transplant rejection

A number of studies have suggested B7-H1, a B7 family member, inhibits T cell responses. Therefore, its expression on nonlymphoid tissues has been proposed to prevent T cell-mediated tissue destruction. To test this hypothesis, we generated transgenic mice that expressed B7-H1 on pancreatic islet beta cells. Surprisingly, we observed accelerated rejection of transplanted allogeneic B7-H1-expressing islet beta cells. Furthermore, transgenic B7-H1 expression broke immune tolerance, as some of the mice spontaneously developed T cell-dependent autoimmune diabetes. In addition, B7-H1 expression increased CD8+ T cell proliferation and promoted autoimmunity induction in a T cell adoptive transfer model of diabetes. Consistent with these findings, B7-H1.Ig fusion protein augmented naive T cell priming both in vitro and in vivo. Our results demonstrate that B7-H1 can provide positive costimulation for naive T cells to promote allograft rejection and autoimmune disease pathogenesis.