Activation of the chemotactic peptide receptor FPRL1 in monocytes phosphorylates the chemokine receptor CCR5 and attenuates cell responses to selected chemokines

FPRL1 is a seven-transmembrane (STM), G-protein coupled receptor which was originally identified as a low affinity receptor for the bacterial chemotactic formyl peptide and a high affinity receptor for the lipid metabolite lipoxin A4. We recently discovered that a number of peptides, including several synthetic domains of the HIV-1 envelope proteins and the serum amyloid A, use FPRL1 to induce migration and calcium mobilization in human monocytes and neutrophils. In this study, we report that a synthetic peptide domain of the V3 region of the HIV-1 envelope gp120, activates the FPRL1 receptor in monocytes and neutrophils. Furthermore, monocytes prestimulated with V3 peptide showed reduced response to several chemokines that use multiple cell receptors. This is associated with a rapid phosphorylation of the chemokine receptor CCR5 on the serine residues. Our study suggests that FPRL1, as a classical chemoattractant receptor, may play an important role in modulating monocyte activation in the presence of multiple stimuli.

Prototype neural semicircular canal prosthesis using patterned electrical stimulation

The design of a prototype semicircular canal prosthesis is presented along with preliminary results. This device measures angular velocity of the head (+/-500 degrees/s) using a piezoelectric vibrating gyroscope. With a digital filter this velocity is filtered to match the dynamic characteristics of the semicircular canals, which are the physiological rotation sensors of the vestibular system. This digitally filtered signal is used to modulate the pulse rate of electrical stimulation. The pulse rate is varied between 50 and 250 Hz via a sigmoidal lookup table relating pulse rate to angular velocity; the steady-state rate is 150 Hz. A current source utilizes these timing pulses to deliver charge balanced, cathodic-first, biphasic, current pulses to the nerves innervating the semicircular canal via platinum electrodes. Power is supplied via lithium batteries. dc/dc converters are used to generate regulated +/-5 V supplies from the batteries. All of the components are contained in a small, lightweight, Nylon box measuring roughly 43 mm x 31 mm x 25 mm, which can be mounted on the top of an animal's head. This device has been tested in guinea pigs having surgically implanted platinum electrodes, and the results show that the prosthesis can provide a rotational cue to the nervous system.

Biological reduction of uranium in groundwater and subsurface soil

Biological reduction of uranium is one of the techniques currently studied for in situ remediation of groundwater and subsurface soil. We investigated U(VI) reduction in groundwaters and soils of different origin to verify the presence of bacteria capable of U(VI) reduction. The groundwaters originated from mill tailings sites with U concentrations as high as 50 mg/l, and from other sites where uranium is not a contaminant, but was added in the laboratory to reach concentrations up to 11 mg/l. All waters contained nitrate and sulfate. After oxygen and nitrate reduction, U(VI) was reduced by sulfate-reducing bacteria, whose growth was stimulated by ethanol and trimetaphosphate. Uranium precipitated as hydrated uraninite (UO2 x xH2O). In the course of reduction of U(VI), Mn(IV) and Fe(III) from the soil were reduced as well. During uraninite precipitation a comparatively large mass of iron sulfides formed and served as a redox buffer. If the excess of iron sulfide is large enough, uraninite will not be oxidized by oxygenated groundwater. We show that bacteria capable of reducing U(VI) to U(IV) are ubiquitous in nature. The uranium reducers are primarily sulfate reducers and are stimulated by adding nutrients to the groundwater.

New mechanistic insights from structural studies of the oxygen-sensing domain of Bradyrhizobium japonicum FixL

The FixL heme domain serves as the dioxygen switch in the FixL/FixJ two-component system of Rhizobia. Recent structural studies of the Bradyrhizobium japonicum FixL heme domain (BjFixLH) have suggested an allosteric mechanism that is distinct from the classical hemoglobin model. To gain further insight into the FixL sensing mechanism, structures of BjFixLH bound to dioxygen, imidazole, and nitric oxide have been determined. These structures, particularly the structure of BjFixLH bound to its physiological ligand, dioxygen, have helped to address a number of important issues relevant to the BjFixLH sensing mechanism. On the basis of the oxy-BjFixLH structure, a conserved arginine is found to stabilize the dioxygen ligand in a mode reminiscent of the distal histidine in classical myoglobins and hemoglobins. The structure of BjFixLH bound to imidazole elucidates the structural requirements for accommodating sterically bulky ligands. Finally, the structure of BjFixLH bound to nitric oxide provides evidence for a structural intermediate in the heme-driven conformational change.

Utilization of two seven-transmembrane, G protein-coupled receptors, formyl peptide receptor-like 1 and formyl peptide receptor, by the synthetic hexapeptide WKYMVm for human phagocyte activation

Trp-Lys-Tyr-Val-D-Met (WKYMVm) is a synthetic leukocyte-activating peptide postulated to use seven-transmembrane, G protein-coupled receptor(s). In the study to characterize the receptor(s) for WKYMVm, we found that this peptide induced marked chemotaxis and calcium flux in human phagocytes. The signaling induced by WKYMVm in phagocytes was attenuated by high concentrations of the bacterial chemotactic peptide fMLP, suggesting that WKYMVm might use receptor(s) for fMLP. This hypothesis was tested by using cells over expressing genes encoding two seven-transmembrane receptors, formyl peptide receptor (FPR) and formyl peptide receptor-like 1 (FPRL1), which are with high and low affinity for fMLP, respectively. Both FPR- and FPRL1-expressing cells mobilized calcium in response to picomolar concentrations of WKYMVm. While FPRL1-expressing cells migrated to picomolar concentrations of WKYMVm, nanomolar concentrations of the peptide were required to induce migration of FPR-expressing cells. In contrast, fMLP elicited both calcium flux and chemotaxis only in FPR-expressing cells with an efficacy comparable with WKYMVm. Thus, WKYMVm uses both FPR and FPRL1 to stimulate phagocytes with a markedly higher efficacy for FPRL1. Our study suggests that FPR and FPRL1 in phagocytes react to a broad spectrum of agonists and WKYMVm as a remarkably potent agonist provides a valuable tool for studying leukocyte signaling via these receptors.

CART: from gene to function

CART was identified as a novel mRNA regulated by psychostimulant drugs. CART peptides appear to be neurotransmitters involved in a variety of functions such as feeding. The mouse gene has been characterized and localized to Chromosome 13. The processing of CART peptides is evident in Western blotting studies.

A new insight into the role of "old" chemotactic peptide receptors FPR and FPRL1: down-regulation of chemokine receptors CCR5 and CXCR4

N-formyl peptides, such as fMet-Leu-Phe (fMLP), are some of the first identified and most potent chemoattractants for phagocytic leukocytes. In addition to the bacterial peptide fMLP and the putative endogenously produced formylated peptides, we recently identified a number of other novel peptide agonists that selectively activate the prototype formyl peptide receptor (FPR) and/or its variant FPRL1. These agonists include several synthetic peptide domains derived from the envelope proteins of the human immunodeficiency virus type 1 (HIV-1) and intact human acute phase serum protein serum amyloid A. The activation of FPR and/or FPRL1 in monocytes by these agonists resulted in increased cell migration, calcium mobilisation and the heterologous down-regulation of the expression and function of chemokine receptors, notably CCR5 and CXCR4, two crucial fusion co-receptors for HIV-1. This down-regulation of CCR5 by FPR and FPRL1 agonists was associated with a rapid serine phosphorylation of CCR5. The desensitisation of CCR5 by FPR or FPRL1 agonists, not only inhibited its biological function induced by chemokine ligands, but also interfered with its capacity to act as a fusion co-receptor for monocyte tropic HIV-1. Thus, heterologous desensitisation by FPR and FPRL1 may play an important role in orchestrating the host innate immune responses which generate multiple chemotactic stimulants. Furthermore, the understanding of the structural and biochemical basis of FPR/FPRL1 activation may lead to the development of novel immunoregulatory and anti-HIV agents that emulate the process of heterologous desensitisation.

A synthetic peptide derived from human immunodeficiency virus type 1 gp120 downregulates the expression and function of chemokine receptors CCR5 and CXCR4 in monocytes by activating the 7-transmembrane G-protein-coupled receptor FPRL1/LXA4R

Because envelope gp120 of various strains of human immunodeficiency virus type 1 (HIV-1) downregulates the expression and function of a variety of chemoattractant receptors through a process of heterologous desensitization, we investigated whether epitopes derived from gp120 could mimic the effect. A synthetic peptide domain, designated F peptide, corresponding to amino acid residues 414-434 in the V4-C4 region of gp120 of the HIV-1 Bru strain, potently reduced monocyte binding and chemotaxis response to macrophage inflammatory protein 1beta (MIP-1beta) and stromal cell-derived factor 1alpha (SDF-1alpha), chemokines that use the receptors CCR5 and CXCR4, respectively. Further study showed that F peptide by itself is an inducer of chemotaxis and calcium mobilization in human monocytes and neutrophils. In cross-desensitization experiments, among the numerous chemoattractants tested, only the bacterial chemotactic peptide fMLF, when used at high concentrations, partially attenuated calcium mobilization induced by F peptide in phagocytes, suggesting that this peptide domain might share a 7-transmembrane, G-protein-coupled receptor with fMLF. By using cells transfected with cDNAs encoding receptors that interact with fMLF, we found that F peptide uses an fMLF receptor variant, FPRL1, as a functional receptor. The activation of monocytes by F peptide resulted in downregulation of the cell surface expression of CCR5 and CXCR4 in a protein kinase C-dependent manner. These results demonstrate that activation of FPRL1 on human moncytes by a peptide domain derived from HIV-1 gp120 could lead to desensitization of cell response to other chemoattractants. This may explain, at least in part, the initial activation of innate immune responses in HIV-1-infected patients followed by immune suppression.

Crystal structure of the conserved core of the herpes simplex virus transcriptional regulatory protein VP16

On infection, the herpes simplex virus (HSV) virion protein VP16 (Vmw65; alphaTIF) forms a transcriptional regulatory complex-the VP16-induced complex-with two cellular proteins, HCF and Oct-1, on VP16-responsive cis-regulatory elements in HSV immediate-early promoters called TAATGARAT. Comparison of different HSV VP16 sequences reveals a conserved core region that is sufficient for VP16-induced complex formation. The crystal structure of the VP16 core has been determined at 2.1 A resolution. The results reveal a novel, seat-like protein structure. Together with the activity of mutant VP16 proteins, the structure of free VP16 suggests that it contains (1) a disordered carboxy-terminal region that associates with HCF, Oct-1, and DNA in the VP16-induced complex, and (2) a structured region involved in virion assembly and possessing a novel DNA-binding surface that differentiates among TAATGARAT VP16-response elements.

Inhibition of tyrosine kinase activation blocks the down-regulation of CXC chemokine receptor 4 by HIV-1 gp120 in CD4+ T cells

Because the binding of HIV-1 envelope to CD4 initiates a configurational change in glycoprotein 120 (gp120), enabling it to interact with fusion coreceptors, we investigated how this process interferes with the expression and function of CXC chemokine receptor 4 (CXCR4) in CD4+ T lymphocytes. A recombinant gp120 (MN), after preincubation with CD4+ T lymphocytes, significantly inhibited the binding and chemotaxis of the cells in response to the CXCR4 ligand stromal cell-derived factor-1alpha (SDF-1alpha), accompanied by a markedly reduced surface expression of CXCR4. gp120, but not SDF-1alpha, induced rapid tyrosine phosphorylation of src-like kinase p56lck in CD4+ T cells, whereas both gp120 and SDF-1alpha caused phosphorylation of the CXCR4. The tyrosine kinase inhibitor herbimycin A abolished the phosphorylation of p56lck and CXCR4 induced by gp120 in association with maintenance of normal expression of cell surface CXCR4 and a migratory response to SDF-1alpha. Thus, a CD4-associated signaling molecule(s) including p56lck is activated by gp120 and is required for the down-regulation of CXCR4.

Ku antigen-DNA conformation determines the activation of DNA-dependent protein kinase and DNA sequence-directed repression of mouse mammary tumor virus transcription

Mouse mammary tumor virus (MMTV) transcription is repressed by DNA-dependent protein kinase (DNA-PK) through a DNA sequence element, NRE1, in the viral long terminal repeat that is a sequence-specific DNA binding site for the Ku antigen subunit of the kinase. While Ku is an essential component of the active kinase, how the catalytic subunit of DNA-PK (DNA-PKcs) is regulated through its association with Ku is only beginning to be understood. We report that activation of DNA-PKcs and the repression of MMTV transcription from NRE1 are dependent upon Ku conformation, the manipulation of DNA structure by Ku, and the contact of Ku80 with DNA. Truncation of one copy of the overlapping direct repeat that comprises NRE1 abrogated the repression of MMTV transcription by Ku-DNA-PKcs. Remarkably, the truncated element was recognized by Ku-DNA-PKcs with affinity similar to that of the full-length element but was unable to promote the activation of DNA-PKcs. Analysis of Ku-DNA-PKcs interactions with DNA ends, double- and single-stranded forms of NRE1, and the truncated NRE1 element revealed striking differences in Ku conformation that differentially affected the recruitment of DNA-PKcs and the activation of kinase activity.

Structural basis for the design of antibiotics targeting peptide deformylase

While protein synthesis in bacteria begins with a formylated methionine, the formyl group of the nascent polypeptide is removed by peptide deformylase. Since eukaryotic protein synthesis does not involve formylation and deformylation at the N-terminus, there has been increasing interest in peptide deformylase as a potential target for antibacterial chemotherapy. Toward this end and to aid in the design of effective antibiotics targeting peptide deformylase, the structures of the protein-inhibitor complexes of both the cobalt and the zinc containing Escherichia coli peptide deformylase bound to the transition-state analogue, (S)-2-O-(H-phosphonoxy)-L-caproyl-L-leucyl-p-nitroanilide (PCLNA), have been determined. The proteins for both deformylase-inhibitor complexes show basically the same fold as for the native enzyme. The PCLNA inhibitor adopts an extended conformation and fits nicely into a hydrophobic cavity located near the metal site. On the basis of these structures, guidelines for the design of high-affinity deformylase inhibitors are suggested. As our results show that the protein residues which interact with the PCLNA inhibitor are conserved over a wide variety of species, we suggest that antibiotics targeting deformylase could have wide applicability.

A seven-transmembrane, G protein-coupled receptor, FPRL1, mediates the chemotactic activity of serum amyloid A for human phagocytic cells

We have previously reported (Badolato, R., J.M. Wang, W.J. Murphy, A. R. Lloyd, D.F. Michiel, L.L. Bausserman, D.J. Kelvin, and J.J. Oppenheim. 1994. J. Exp. Med. 180:203; Xu, L., R. Badolato, W.J. Murphy, D.L. Longo, M. Anver, S. Hale, J.J. Oppenheim, and J.M. Wang. 1995. J. Immunol. 155:1184.) that the acute phase protein serum amyloid A (SAA) is a potent chemoattractant for human leukocytes in vitro and mouse phagocytes in vivo. To identify the signaling mechanisms, we evaluated patterns of cross-desensitization between SAA and other leukocyte chemoattractants. We found that the chemotactic bacterial peptide, N-formyl- methionyl-leucyl-phenylalanine (fMLP), was able to specifically attenuate Ca2+ mobilization in human phagocytes induced by SAA, but only at very high concentrations, suggesting that SAA uses a low affinity fMLP receptor. Here we demonstrate that SAA selectively induced Ca2+ mobilization and migration of HEK cells expressing FPRL1, a human seven-transmembrane domain phagocyte receptor with low affinity for fMLP, and high affinity for lipoxin A4. Furthermore, radiolabeled SAA specifically bound to human phagocytes and FPRL1-transfected 293 cells. In contrast, SAA was not a ligand or agonist for FPR, the high affinity fMLP receptor. Thus, SAA is the first chemotactic ligand identified for FPRL1. Our results suggest that FPRL1 mediates phagocyte migration in response to SAA.

Structure of a biological oxygen sensor: a new mechanism for heme-driven signal transduction

The FixL proteins are biological oxygen sensors that restrict the expression of specific genes to hypoxic conditions. FixL's oxygen-detecting domain is a heme binding region that controls the activity of an attached histidine kinase. The FixL switch is regulated by binding of oxygen and other strong-field ligands. In the absence of bound ligand, the heme domain permits kinase activity. In the presence of bound ligand, this domain turns off kinase activity. Comparison of the structures of two forms of the Bradyrhizobium japonicum FixL heme domain, one in the "on" state without bound ligand and one in the "off" state with bound cyanide, reveals a mechanism of regulation by a heme that is distinct from the classical hemoglobin models. The close structural resemblance of the FixL heme domain to the photoactive yellow protein confirms the existence of a PAS structural motif but reveals the presence of an alternative regulatory gateway.

Expression of different isoforms of TGF-beta and the latent TGF-beta binding protein (LTBP) by rat Kupffer cells

BACKGROUND/AIMS

Kupffer cells (liver resident macrophages) make an important contribution to the perpetuation of liver diseases by synthesis and secretion of TGF-beta. In some cell types TGF-beta, is expressed as a large latent complex containing the latent TGF-beta binding protein (LTBP) in addition to the N-terminal TGF-beta precursor (latency associated peptide). This study aimed to identify LTBP expression in rat Kupffer cells.

METHODS

Cells were isolated from rat liver by collagenase-pronase reperfusion, purified and cultured under standard conditions. TGF-beta and LTBP expression were characterized using alkaline phosphatase-anti-alkaline phosphatase immunostainings, reverse transcription-polymerase chain reaction and immunoprecipitation of metabolically labeled proteins.

RESULTS

Immunostainings of Kupffer cells with anti-sera against LTBP-1 (ab 39) and LTBP-2 indicated the expression of both LTBP isoforms in addition to the expression of latency associated peptide and TGF-beta. Transcripts of three LTBP isoforms (LTBP-1,-2,-3) and TGF-beta isoforms (TGF-beta-1,-2,-3) were detectable by reverse transcription-polymerase chain reaction. The LTBP-1D splice variant missing a part of the proteinase sensitive hinge region which has recently been described in hepatic stellate cells is expressed in Kupffer cells, too. Metabolic labeling of Kupffer cells with [35S]-Met/Cys followed by immunoprecipitation of the conditioned media using antisera against LTBP-1 and LTBP-2 indicated the secretion of high molecular mass TGF-beta complexes containing LTBP proteins of 230 and 170 kDa (LTBP-1) or 230 kDa (LTBP-2).

CONCLUSION

The results show that Kupffer cells partly synthesize and release TGF-beta as large latent complexes. This requires the extracellular activation of TGF-beta as a prerequisite for receptor binding and cellular signaling.

[Determination of the valence of iron by the conventional XRF spectrometer]

FeKbeta emission spectra and parameters of mixtures are studied by conventional XRF spectrometer and PEAKFIT programs. The true spectra profile and it's parameters are obtained by profile resolving method. Integral area ratios are also calculated. The relations of these parameters and the valences of the iron are found. Fe3O4 sample and the iron ore which has different valences are quantified.

Chemokines and their role in tumor growth and metastasis

Chemokines are a superfamily of pro-inflammatory polypeptide cytokines that selectively attract and activate different cell types. Many patho-physiological conditions require the participation of chemokines, including inflammation, infection, tissue injury, allergy, cardiovascular diseases, as well as malignant tumors. Chemokines activate cells through their binding to shared or unique cell surface receptors which belong to the seven-transmembrane, G-protein-coupled Rhodopsin superfamily. The role of chemokines in malignant tumors is complex: while some chemokines may enhance innate or specific host immunity against tumor implantation, others may favor tumor growth and metastasis by promoting tumor cell proliferation, migration or neovascularization in tumor tissue. In this review, the authors summarize some of the recent advances in chemokine research and emphasis is made on the effect of chemokines in tumor growth and metastasis.

Crystal structures of acutolysin A, a three-disulfide hemorrhagic zinc metalloproteinase from the snake venom of Agkistrodon acutus

Acutolysin A alias AaHI, a 22 kDa hemorrhagic toxin isolated from the snake venom of Agkistrodon acutus, is a member of the adamalysin subfamily of the metzincin family and is a snake venom zinc metalloproteinase possessing only one catalytic domain. Acutolysin A was found to have a high-activity and a low-activity under weakly alkaline and acidic conditions, respectively. With the adamalysin II structure as the initial trial-and-error model, the crystal structures were solved to the final crystallographic R-factors of 0. 168 and 0.171, against the diffraction data of crystals grown under pH 5.0 and pH 7.5 conditions to 1.9 A and 1.95 A resolution, respectively. One zinc ion, binding in the active-site, one structural calcium ion and some water molecules were localized in both of the structures. The catalytic zinc ion is coordinated in a tetrahedral manner with one catalytic water molecule anchoring to an intermediate glutamic acid residue (Glu143) and three imidazole Nepsilon2 atoms of His142, His146 and His152 in the highly conserved sequence H142E143XXH146XXGXXH152. There are two new disulfide bridges (Cys157-Cys181 and Cys159-Cys164) in acutolysin A in addition to the highly conserved disulfide bridge Cys117-Cys197. The calcium ion occurs on the molecular surface. The superposition showed that there was no significant conformational changes between the two structures except for a few slight changes of some flexible residue side-chains on the molecular surface, terminal residues and the active-site cleft. The average contact distance between the catalytic water molecule and oxygen atoms of the Glu143 carboxylate group in the weakly alkaline structure was also found to be closer than that in the weakly acidic structure. By comparing the available structural information of the members of the adamalysin subfamily, it seems that, when lowering the pH value, the polarization capability of the Glu143 carboxylate group to the catalytic water molecule become weaker, which might be the structural reason why the snake venom metalloproteinases are inactive or have a low activity under acidic conditions.

HIV-1 envelope gp120 inhibits the monocyte response to chemokines through CD4 signal-dependent chemokine receptor down-regulation

Since HIV-1 infection results in severe immunosuppression, and the envelope protein gp120 has been reported to interact with some of the chemokine receptors on human T lymphocytes, we postulated that gp120 may also affect monocyte activation by a variety of chemokines. This study shows that human peripheral blood monocytes when preincubated with gp120 either purified from laboratory-adapted strains or as recombinant proteins exhibited markedly reduced binding, calcium mobilization, and chemotactic response to chemokines. The gp-120-pretreated monocytes also showed a decreased response to FMLP. This broad inhibition of monocyte activation by chemoattractants required interaction of gp120 with CD4, since the effect of gp120 was only observed in CD4+ monocytes and in HEK 293 cells only if cotransfected with both chemokine receptors and an intact CD4, but not a CD4 lacking its cytoplasmic domain. Anti-CD4 mAbs mimicked the effect of gp120, and both anti-CD4 Ab and gp120 caused internalization of CXCR4 in HEK 293 cells provided they also expressed CD4. Staurosporine blocked the inhibitory effect of gp120 on monocytes, suggesting that cellular signaling was required for gp120 to inhibit the response of CD4+ cells to chemoattractants. Our study demonstrates a broad suppressive effect of gp120 on monocyte activation by chemoattractants through the down-regulation of cell surface receptors. Thus, gp120 may be used by HIV-1 to disarm the monocyte response to inflammatory stimulation.

[Preliminary report of xenogenic bone graft for sixty-five cases]

From January 1984 to November 1997, the boiling xenogenic bone (porcine and bovine bone) was applied in 65 patients. The xenogenic bone was used to promote bone healing in 24 cases, intramedullary bone graft in 37 and osteomyelitis in 4. All of the patients were followed up for 2 to 35 months. The results showed that in five cases there was infection after operation, and all other the wounds had primary healing. The xenogenic bone seemed to induce rejection in vivo. In the sevious cases immunosuppressive treatment was often needed. The volume of the bone grafted and the extent of the periosteum being stripped seemed to be important whether xenogenic bone graft would be successful or. There were lots of problem needed investigation.

HIV-1 envelope gp41 is a potent inhibitor of chemoattractant receptor expression and function in monocytes

HIV-1 uses CD4 and chemokine receptors as cofactors for cellular entry. The viral envelope transmembrane protein gp41 is thought to participate in viral fusion with CD4(+) cells. We investigated whether gp41 interacts with chemokine receptors on human monocytes by testing its effect on the capacity of cells to respond to chemokine stimulation. Monocytes preincubated with gp41 of the MN strain showed markedly reduced binding, calcium mobilization, and chemotaxis in response to a variety of chemokines as well as to the bacterial peptide fMLP. This generalized inhibition of monocyte activation by chemoattractants required the presence of CD4, since the effect of gp41 was only observed in CD4(+) monocytes and in HEK293 cells cotransfected with chemokine receptors and an intact CD4, but not a CD4 lacking its cytoplasmic domain. Confocal microscopy showed that gp41 caused internalization of CXCR4 in HEK293 cells provided they were also cotransfected with intact CD4. In addition, pretreatment of monocytes with protein kinase C inhibitors partially reversed the inhibitory effect of gp41. Thus, gp41, which had not previously been implicated as interacting with HIV-1 fusion cofactors, downregulates chemoattractant receptors on monocytes by a CD4-dependent pathway.

Chemokines, receptors, and their role in cardiovascular pathology

A superfamily of leukocyte chemotactic proteins, known as chemokines, has been identified during the past decade. Chemokines selectively attract and activate different leukocyte subpopulations and are key mediators of a variety of patho-physiological states, including hematopoiesis, inflammation, infection, allergy, atheroslerosis, reperfusion injury, as well as malignant tumors. Chemokines bind and activate a number of specific or promiscuous, G-protein-coupled seven-transmembrane receptors. Some of these receptors are utilized by human immuno-deficiency virus type 1 as essential fusion co-factors. Further understanding of the role of chemokines and their receptors in host defense will help develop means by which the beneficial versus detrimental effects of these molecules can be balanced.

GABAergic modulation of ventral pallidal dopamine release studied by in vivo microdialysis in the freely moving rat

The mesopallidal dopamine system, which originates from the ventral tegmental area and projects to the ventral pallidum (VP), has been recently shown to play an important role in self-stimulation reward and cocaine reward. VP also receives a GABAergic projection from nucleus accumbens (NAS). The aim of the present study was to examine the involvement of this GABAergic projection in the modulation of VP dopamine release. Both the GABAA antagonist picrotoxin (2-200 microM) and the GABAB antagonist phaclofen (20-2,000 microM), perfused locally, dose-responsively increased VP extracellular dopamine 2-2.5-fold. Cocaine (10 microM) produced a 6.5-fold increase of VP dopamine. Neither picrotoxin (200 microM), phaclofen (2,000 microM), nor GABA (20-2,000 microM) altered the response of VP dopamine to locally applied cocaine. GBR 12909 (0.5 microM), a selective dopamine uptake blocker, induced a 3.5-fold increase of VP dopamine. The increase of VP dopamine in response to GBR 12909 was further augmented to 8.5-fold of baseline when picrotoxin (200 microM) was added to the perfusate. The data from the present study demonstrate that the GABAergic NAS-VP projection can modulate ventral pallidal dopamine release. However, the effect of GABA on the mesopallidal dopamine system's response to locally applied cocaine may be complicated by actions of cocaine other than dopamine uptake inhibition.

Transformation-dependent susceptibility of rat hepatic stellate cells to apoptosis induced by soluble Fas ligand

Cytokine-driven activation of hepatic stellate cells (HSC) in tissue injury and inflammation is a key pathogenetic event in liver fibrogenesis leading to an expanded pool of matrix producing myofibroblasts (MFB) which represent the transformed counterpart of HSC. We hypothesize that expansion of the pool of MFB might also be accomplished by modulation of apoptosis, which plays an opposite and complementary role to mitosis in the cellular homeostasis. We characterized the susceptibility of HSC in primary culture and of MFB in secondary culture to apoptosis induced by the soluble Fas ligand (sFasL) and related the effects to the expression levels of Fas (APO-1/CD95) and some major proapoptotic and contra-apoptotic protooncogenes. MFB showed a dose-dependent apoptotic reaction upon exposure to sFasL as evidenced by a strong increase of nucleosomal DNA fragments, loss of cellular DNA, positive TUNEL reaction, and annexin staining. The effect was found only if protein synthesis (cycloheximide) or RNA synthesis (actinomycin D) were arrested. HSC maintained for various times in primary culture were completely resistant to sFasL in combination with cycloheximide, but in late primary cultures (day 7 onward) an increasing susceptibility to sFasL-mediated apoptosis was developed. By semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR) analysis and alkaline phosphatase-anti-alkaline phosphatase staining Fas receptor was identified both in HSC and MFB at comparable expression levels. The expression of the contra-apoptotic protooncogenes bcl-2 and bcl-xl was found to be much stronger in early HSC than in late HSC and MFB as shown by ribonuclease protection assay. The expression of bcl-2 was additionally confirmed by semiquantitative RT-PCR and immunoblotting. Proapoptotic bax was found in comparable quantities at the RNA level in HSC and MFB but at the protein level MFB showed increased bax expression. It is concluded that transformation of HSC to MFB is paralleled by an increasing sensitivity to sFasL-mediated apoptosis, which might be related to a strong decrease of bcl-2 and bcl-xl expression, leading to a preponderance of proapoptotic gene expression in MFB. Modulation of apoptotic susceptibility of transforming HSC could be an important complementary pathway in the pathogenesis of fibrosis.

Analysis of the expression pattern of the latent transforming growth factor beta binding protein isoforms in normal and diseased human liver reveals a new splice variant missing the proteinase-sensitive hinge region

Latent transforming growth factor beta binding protein (LTBP), a component of the extracellular matrix (ECM) of various tissues, is important for the secretion of TGF-beta and, furthermore, for the storage of TGF-beta in ECM. The proteolytic cleavage of LTBP is assumed to be the prerequisite for the activation of TGF-beta. We investigated the mRNA expression pattern of the three LTBP isoforms (LTBP-1, -2, -3) and the protein distribution of the components of the large latent TGF-beta complex, namely LTBP-1 and -2, latency-associated protein (LAP), and TGF-beta, in human liver using reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemical alkaline phosphatase anti-alkaline phosphatase (APAAP) staining. Parts of explanted livers diagnosed as hepatitis B, hepatitis C, primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC) and normal liver tissue were examined. LTBP transcripts were detected in the same manner in all liver specimens. Interestingly, we found a new splice variant of LTBP-1 (LTBP-1D), in which the sequence coding for the proteinase-sensitive hinge region is deleted. The corresponding parts of the human LTBP-2 and LTBP-3 cDNA coding for the hinge region were sequenced and show neither similar proteinase cleavage sites nor deleted cDNA sequences. The proposed proteinase cleavage site of mouse LTBP-3 seems not to be conserved in the human LTBP-3 gene. By immunohistochemistry, LTBP-1, -2, and LAP were detectable in normal and diseased livers and showed a different staining pattern for both LTBP isoforms. By contrast, TGF-beta showed a spotted staining pattern in diseased livers only, predominantly in the area of parenchymal cells that are close to fibrotic tissue. This strongly suggests the release of active TGF-beta from preexisting latent complexes. The LTBP-1D splice variant, which is probably less sensitive against proteolytic degradation and therefore may protect TGF-beta from activation, may have importance for modulating the biological activity of TGF-beta in normal and diseased liver.

[A new approach to correction method for matrix effect in X-ray fluorescence spectroscopy analysis]

With the help of fundamental parameter program developed by the authors, the matrix effect of multicomponent complex sample and the composition of each element's X-ray fluorescence intensity are calculated. A new mathematical model for correcting multicomponent matrix effect is deduced theoretically. This model provides a new method to calculate influence coefficients alpha and beta. The correction model and the influence coefficients introduced by this paper have clear and definite physical meaning, which give satisfactory result when utilized in analyzing stainless steel sample. The paper also indicates that the effect of tertiary fluorescence can not be neglected in some cases. From the result of comparison experiments, we draw a conclusion that the tertiary fluorescence effect must be considered while analyzing Cr in a steel sample with high concentration of Ni.

Activation of the Src/p21ras/Erk pathway by progesterone receptor via cross-talk with estrogen receptor

The molecular mechanisms by which ovarian hormones stimulate growth of breast tumors are unclear. It has been reported previously that estrogens activate the signal-transducing Src/p21(ras)/Erk pathway in human breast cancer cells via an interaction of estrogen receptor (ER) with c-Src. We now show that progestins stimulate human breast cancer T47D cell proliferation and induce a similar rapid and transient activation of the pathway which, surprisingly, is blocked not only by anti-progestins but also by anti-estrogens. In Cos-7 cells transfected with the B isoform of progesterone receptor (PRB), progestin activation of the MAP kinase pathway depends on co-transfection of ER. A transcriptionally inactive PRB mutant also activates the signaling pathway, demonstrating that this activity is independent of transcriptional effects. PRB does not interact with c-Src but associates via the N-terminal 168 amino acids with ER. This association is required for the signaling pathway activation by progestins. We propose that ER transmits to the Src/p21(ras)/Erk pathway signals received from the agonist-activated PRB. These findings reveal a hitherto unrecognized cross-talk between ovarian hormones which could be crucial for their growth-promoting effects on cancer cells.

Purification and identification of chemokines potentially involved in kidney-specific metastasis by a murine lymphoma variant: induction of migration and NFkappaB activation

The ESb-MP cell line is the subclone of a highly malignant variant of murine methylcholanthrene-induced T lymphoma, ESb. When injected in vivo, ESb-MP cells metastasize to the kidney with high frequency, whereas a non-adherent variant, ESb cells, rarely form metastatic foci in the kidney. Our previous results showed that ESb-MP, but not ESb, cells were able to migrate in response to murine kidney-conditioned media (KCM). In an effort to characterize the tumor cell chemoattractant(s) produced by kidney cells, we found that the murine kidney mesangial cell line MES-13 released more chemotactic activity for ESb-MP cells than present in KCM. A major heparin-binding chemotactic activity was purified to homogeneity by sequential fast-performance liquid chromatography and reversed phase high-performance liquid chromatography. Amino acid sequencing of the formic acid-digested active fractions revealed that the purified protein was identical to murine MCP-1(JE) and its activity was neutralized by an anti-MCP-1(JE) antibody. Another chemokine, RANTES, was also purified from MES-13 cell supernatant. The chemotactic activity contained in the MES-13 cell supernatant and in murine KCM was neutralized in part by a combination of anti-MCP-1(JE) and anti-RANTES antibodies. We further examined the differences in the ESb-MP and ESb cells. Binding studies using a variety of radio-iodinated chemokines showed that although both ESb-MP and ESb cells expressed substantial levels of high-affinity binding sites for CC chemokines, only ESb-MP cells migrated in response to CC chemokines and these cells constitutively expressed higher levels of beta2 integrin adhesion protein CD11b than their parental ESb cells. CC chemokines also activated NFkappaB in ESb-MP but not in ESb cells. Our results indicate that CC chemokines selectively chemoattract and activate ESb-MP cells. Thus, locally produced chemokines, MCP-1(JE) and RANTES in particular, may contribute to the preferential metastasis of ESb-MP cells to the kidneys.

Monocyte chemotactic protein-2 activates CCR5 and blocks CD4/CCR5-mediated HIV-1 entry/replication

Human immunodeficiency virus, type I (HIV-1) cell-type tropism is dictated by chemokine receptor usage: T-cell line tropic viruses use CXCR4, whereas monocyte tropic viruses primarily use CCR5 as fusion coreceptors. CC chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and RANTES (regulated on activation normal T cell expressed and secreted) inhibit CD4/CCR5-mediated HIV-1 cell fusion. MCP-2 is also a member of the CC chemokine subfamily and has the capacity to interact with at least two receptors including CCR-1 and CCR2B. In an effort to further characterize the binding properties of MCP-2 on leukocytes, we observed that MCP-2, but not MCP-1, effectively competed with MIP-1beta for binding to monocytes, suggesting that MCP-2 may interact with CCR5. As predicted, MCP-2 competitively inhibited MIP-1beta binding to HEK293 cells stably transfected with CCR5 (CCR5/293 cells). MCP-2 also bound to and induced chemotaxis of CCR5/293 cells with a potency comparable with that of MIP-1beta. Confocal microscopy indicates that MCP-2 caused remarkable and dose-dependent internalization of CCR5 in CCR5/293 cells. Furthermore, MCP-2 inhibited the entry/replication of HIV-1ADA in CCR5/293 cells coexpressing CD4. These results indicated that MCP-2 uses CCR5 as one of its functional receptors and is an additional potent natural inhibitor of HIV-1.

Isoforms and splice variant of transforming growth factor beta-binding protein in rat hepatic stellate cells

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are one important source for transforming growth factor beta (TGF-beta). They produce TGF-beta in a latent form associated with latency-associated peptide and latent TGF-beta-binding protein (LTBP). This study was designed to investigate, on RNA and protein levels, which isoforms of LTBP and TGF-beta are expressed in HSCs and myofibroblasts.

METHODS

HSCs isolated from rat liver were analyzed for LTBP and TGF-beta at various times of culture during transdifferentiation into myofibroblasts using immunocytochemical staining, metabolic labeling and immunoprecipitation, reverse-transcription polymerase chain reaction (RT-PCR), and sequencing.

RESULTS

Alkaline phosphatase-anti-alkaline phosphatase staining and fluorescence immunostainings indicated the expression of all three components of the large latent TGF-beta complex in HSCs and myofibroblasts. Transcripts of three TGF-beta and LTBP isoforms were detected by RT-PCR and confirmed by sequence analyses. A new LTBP-1 splice form was found lacking part of the hinge region with a potential proteinase cleavage site. Metabolic labeling followed by immunoprecipitation with LTBP antiserum confirmed the synthesis and secretion of various LTBP-related proteins.

CONCLUSIONS

The existence of different LTBP isoforms and splice variants in HSCs and myofibroblasts suggests multiple functions of the LTBP family in rat liver, which might not be restricted to the maintenance of TGF-beta latency.

Production of neutrons from interactions of GCR-like particles

In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.

Crystal structure of the Escherichia coli peptide deformylase

Protein synthesis in bacteria involves the formylation and deformylation of the N-terminal methionine. As eukaryotic organisms differ in their protein biosynthetic mechanisms, peptide deformylase, the bacterial enzyme responsible for deformylation, represents a potential target for antibiotic studies. Here we report the crystallization and 2.9 A X-ray structure solution of the zinc containing Escherichia coli peptide deformylase. While the primary sequence, tertiary structure, and use of coordinated cysteine suggest that E. coli deformylase belongs to a new subfamily of metalloproteases, the environment around the metal appears to have strong geometric similarity to the active sites of the thermolysin family. This suggests a possible similarity in their hydrolytic mechanisms. Another important issue is the origin of the enzyme's specificity for N-formylated over N-acetylated substrates. Based on the structure, the specificity appears to result from hydrogen-bonding interactions which orient the substrate for cleavage, and steric factors which physically limit the size of the N-terminal carbonyl group.

Chemically synthesized SDF-1alpha analogue, N33A, is a potent chemotactic agent for CXCR4/Fusin/LESTR-expressing human leukocytes

Stromal cell-derived factor (SDF) 1 is a potent chemoattractant for leukocytes through activation of the receptor CXCR4/Fusin/LESTR, which is a fusion co-factor for the entry of T lymphocytotropic human immunodeficiency virus type 1 (HIV-1). This CXCR4-mediated HIV-1 fusion can be inhibited by SDF-1. Because of its importance in the study of immunity and AIDS, large scale production of SDF-1 is desirable. In addition to recombinant technology, chemical synthesis provides means by which biologically active proteins can be produced not only in large quantity but also with a variety of designed modifications. In this study, we investigated the binding and function of an SDF-1alpha analogue, N33A, synthesized by a newly developed native chemical ligation approach. Radioiodinated N33A showed high affinity binding to human monocytes, T lymphocytes, as well as neutrophils, and competed equally well with native recombinant SDF-1alpha for binding sites on leukocytes. N33A also showed equally potent chemoattractant activity as native recombinant SDF-1alpha for human leukocytes. Further study with CXCR4/Fusin/LESTR transfected HEK 293 cells showed that N33A binds and induces directional migration of these cells in vitro. These results demonstrate that the chemically synthesized SDF-1alpha analogue, N33A, which can be produced rapidly in large quantity, possesses the same capacity as native SDF-1alpha to activate CXCR4-expressing cells and will provide a valuable agent for research on the host immune response and AIDS.

Isolation of human and mouse HMG2a cDNAs: evidence for an HMG2a-specific 3' untranslated region

We have isolated cDNAs of the human gene for high mobility group protein HMG2a, using the method of direct cDNA selection. The gene maps to chromosome band Xq28, and is located within 40 kb from marker DXS1684, at a distance of 5.4 Mb from the telomere. The deduced human HMG2a protein sequence has a length of 199 amino acids and is 97% identical to the sequence of chicken HMG2a. The 3' untranslated regions of the HMG2a gene in both species are highly homologous (87% identical nucleotides), and are even more conserved than the coding sequences (84% identical nucleotides). In addition, a partial cDNA sequence of the putative HMG2a gene from mouse was identified. The 3' untranslated regions from human and mouse are 90% identical. We conclude that the 3' untranslated sequences have been under strong selective pressure during evolution. Whereas expression of the chicken HMG2a gene has previously been demonstrated in liver of newly hatched chicken, the human HMG2a gene is transcribed mainly in placenta.

Point mutation in the ligand-binding domain of the progesterone receptor generates a transdominant negative phenotype

A short conserved alpha-helix in the carboxyl-terminal activation function of the ligand-binding domain of steroid hormone receptors, called AF2, is important for ligand-dependent transactivation of inducible genes. We have generated two AF2 mutants of the B isoform of human progesterone receptor (PRB): a point mutant, PRBE911A, and a short deletion, PRB delta907-913R. The two mutants are expressed at levels comparable to the wild type receptor in transfected cells. The PRBE911A mutant showed similar hormone- and DNA- binding affinities as the wild type receptor, whereas the PRB delta907-913R mutant was defective in hormone and DNA binding. Both mutants were inactive when transiently transfected in CV-1 cells, which do not express endogenous PR. However, the point mutant, but not the deletion mutant, inhibited transactivation by cotransfected wild type PRB in a hormone-dependent fashion. The activity of endogenous PR in T47D cells or of endogenous glucocorticoid receptor in HeLa cells was also inhibited by the PRBE911A, but not by the deletion mutant. The point mutant was less active when introduced into an N-terminal truncated form of PR, where it gave rise to proteins that formed homodimers with poor affinity for DNA, but were able to form heterodimers with PRB. The negative dominant phenotype of the PRBE911A mutant likely originates from competition with wild type receptors for binding to DNA and will be useful for mechanistic studies of receptor function.

Expression, purification, mass spectrometry, crystallization and multiwavelength anomalous diffraction of selenomethionyl PvuII DNA methyltransferase (cytosine-N4-specific)

The type II DNA-methyltransferase (cytosine N4-specific) M.PvuII was overexpressed in Escherichia coli, starting from the internal translation initiator at Met14. Selenomethionine was efficiently incorporated into this short form of M.PvuII by a strain prototrophic for methionine. Both native and selenomethionyl M.PvuII were purified to apparent homogeneity by a two-column chromatography procedure. The yield of purified protein was approximately 1.8 mg/g bacterial paste. Mass spectrometry analysis of selenomethionyl M.PvuII revealed three major forms that probably differ in the degree of selenomethionine incorporation and the extent of selenomethionine oxidation. Amino acid sequencing and mass spectrometry analysis of selenomethionine-containing peptides suggests that Met30, Met51, and Met261 were only partially replaced by selenomethionine. Furthermore, amino acid 261 may be preferentially oxidized in both native and selenomethionyl form. Selenomethionyl and native M.PvuII were crystallized separately as binary complexes of the methyl donor S-adenosyl-L-methionine in the monoclinic space group P2(1). Two complexes were present per asymmetric unit. Six out of nine selenium positions (per molecule), including the three that were found to be partially substituted, were identified crystallographically.

Isolation and characterization of a gene from the DiGeorge chromosomal region homologous to the mouse Tbx1 gene

DiGeorge syndrome, velocardiofacial syndrome, conotruncal anomaly face syndrome, and isolated and familial forms of conotruncal cardiac defects have been associated with deletions of chromosomal region 22q11.2. This report describes the identification, cloning, and characterization of the human TBX1 gene, which maps to the center of the DiGeorge chromosomal region. Further, we have extended the mouse cDNA sequence to permit comparisons between human and mouse Tbx1. TBX1 is a member of a phylogenetically conserved family of genes that share a common DNA-binding domain, the T-box. T-box genes are transcription factors involved in the regulation of developmental processes. There is 98% amino acid identity between human and mouse TBX1 proteins overall, and within the T-box domain, the proteins are identical except for two amino acids. Expression of human TBX1 in adult and fetal tissues, as determined by Northern blot analysis, is similar to that found in the mouse. Additionally, using 3 'RACE, we obtained a differentially spliced message in adult skeletal muscle. Mouse Tbx1 has been previously shown to be expressed during early embryogenesis in the pharyngeal arches, pouches, and otic vesicle. Later in development, expression is seen in the vertebral column and tooth bud. Thus, human TBX1 is a candidate for some of the features seen in the 22q11 deletion syndrome.

Structure of pvu II DNA-(cytosine N4) methyltransferase, an example of domain permutation and protein fold assignment

We have determined the structure of Pvu II methyltransferase (M. Pvu II) complexed with S -adenosyl-L-methionine (AdoMet) by multiwavelength anomalous diffraction, using a crystal of the selenomethionine-substituted protein. M. Pvu II catalyzes transfer of the methyl group from AdoMet to the exocyclic amino (N4) nitrogen of the central cytosine in its recognition sequence 5'-CAGCTG-3'. The protein is dominated by an open alpha/beta-sheet structure with a prominent V-shaped cleft: AdoMet and catalytic amino acids are located at the bottom of this cleft. The size and the basic nature of the cleft are consistent with duplex DNA binding. The target (methylatable) cytosine, if flipped out of the double helical DNA as seen for DNA methyltransferases that generate 5-methylcytosine, would fit into the concave active site next to the AdoMet. This M. Pvu IIalpha/beta-sheet structure is very similar to those of M. Hha I (a cytosine C5 methyltransferase) and M. Taq I (an adenine N6 methyltransferase), consistent with a model predicting that DNA methyltransferases share a common structural fold while having the major functional regions permuted into three distinct linear orders. The main feature of the common fold is a seven-stranded beta-sheet (6 7 5 4 1 2 3) formed by five parallel beta-strands and an antiparallel beta-hairpin. The beta-sheet is flanked by six parallel alpha-helices, three on each side. The AdoMet binding site is located at the C-terminal ends of strands beta1 and beta2 and the active site is at the C-terminal ends of strands beta4 and beta5 and the N-terminal end of strand beta7. The AdoMet-protein interactions are almost identical among M. Pvu II, M. Hha I and M. Taq I, as well as in an RNA methyltransferase and at least one small molecule methyltransferase. The structural similarity among the active sites of M. Pvu II, M. Taq I and M. Hha I reveals that catalytic amino acids essential for cytosine N4 and adenine N6 methylation coincide spatially with those for cytosine C5 methylation, suggesting a mechanism for amino methylation.

Dissociation of locomotor and conditioned place preference responses following manipulation of GABA-A and AMPA receptors in ventral pallidum

1. This study examined the roles of GABAergic and glutamatergic neurotransmission in ventral pallidum (VP) in conditioned place preference and locomotor activity. 2. Picrotoxin (0.1 microgram), a GABA antagonist, and (+/-)alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA; 0.14 microgram), a non-NMDA glutamatergic agonist, were injected bilaterally into VP through implanted cannulae. 3. Both drugs produced a robust increase in locomotion, but neither produced conditioned place preference. 4. These results suggest a dissociation of locomotor activity and reward at the level of ventral pallidum. In addition, it was argued that the GABAergic projection from nucleus accumbens to ventral pallidum may not be involved in the processing of reward initiated from dopaminergic activation in nucleus accumbens.

Differential expression of binding sites for chemokine RANTES on human T lymphocytes

The C-C chemokine RANTES, a T lymphocyte chemoattractant, is considered an important mediator of inflammation, allergy, and host defense against HIV-1 infection. In this study, we investigated the modulation of binding of RANTES to T lymphocytes. Human peripheral blood CD3+ T cells, when freshly isolated from buffy-coat blood, expressed a considerable number of high-affinity binding sites for RANTES. These cells also showed significant chemotactic migration in response to RANTES in vitro. After 6-15 h incubation at 37 degrees C, the binding of RANTES, but not of macrophage inflammatory protein-1 alpha (MIP-1 alpha) or of monocyte chemotactic protein-3 (MCP-3), consistently increased. Scatchard analyses indicated that the number of binding sites for RANTES increased about threefold by 15 h without any change in the affinity. The increase in RANTES binding was no longer detected by 24 h. This increase in the specific binding was mainly attributable to CD4+ T cells and was not associated with increased chemotactic activity of these cells in response to RANTES. Incubation with anti-CD3 antibody for 15 h markedly reduced the binding capability of T cells for RANTES and was associated with decreased chemotactic activity. On the other hand, when T cells were incubated with interleukin-2 (IL-2) for 1 week, the specific binding for all three C-C chemokines, RANTES, MIP-1 alpha, and MCP-3 was markedly increased in comparison to cells cultured in the absence of IL-2. These results suggest that the expression of binding sites on T cells for RANTES is differentially modulated, indicating the existence of novel receptors for RANTES that do not bind MIP-1 alpha.

Monocyte chemotactic protein-2 (MCP-2) uses CCR1 and CCR2B as its functional receptors

Monocyte chemotactic protein (MCP)-2 is a member of the C-C chemokine subfamily, which shares more than 60% sequence homology with MCP-1 and MCP-3 and about 30% homology with macrophage inflammatory protein (MIP)-1alpha, regulated on activation of normal T cell expressed (RANTES), and MIP-1beta. Despite this considerable sequence homology to other C-C chemokines, MCP-2 appears to have unique functional properties in comparison with other C-C chemokines such as MCP-1 and MCP-3. Although evidence obtained from studies on leukocytes suggested that MCP-2 may share the receptors with these C-C chemokines, the actual functional receptors for MCP-2 have not yet been identified. In this study, by using radioiodinated MCP-2, we identified high affinity binding sites for MCP-2 on human peripheral blood monocytes. The MCP-2 binding was competed for by MCP-1 and MCP-3, but less well by MIP-1alpha or RANTES. In experiments using cells transfected with C-C chemokine receptors, 125I-MCP-2 bound to human embryonic kidney 293 cells transfected with CCR1 or CCR2B, known to also bind MIP-1alpha/RANTES and MCP-1, respectively, but both shared by MCP-3. The binding of 125I-MCP-2 to these receptor-transfected cells was displaced completely by chemokines that bind to these receptors. Both CCR1- and CCR2B-transfected 293 cells showed significant migration in response to MCP-2, in addition to responding to other specific chemokines. These results clearly demonstrate that MCP-2, unlike MCP-1, uses both CCR1 as well as CCR2B as its functional receptors, and this accounts for the unique activities of MCP-2.

6-Hydroxydopamine lesion of ventral pallidum blocks acquisition of place preference conditioning to cocaine

In parallel with nucleus accumbens (NAS), ventral pallidum (VP) also receives a dopaminergic projection from the ventral tegmental area (VTA). The present study examined the involvement of this mesopallidal dopaminergic system in the action of cocaine. In the first experiment, the effect of cocaine injections on VP dopamine was examined by microdialysis. Intraperitoneal (i.p.) injections of cocaine 5-20 mg/kg dose-dependently increased the extracellular dopamine level in VP 2.5-4.5-fold. In addition, intra-VP perfusion of 20 microM cocaine induced a 12-fold increase of dopamine locally. The second experiment examined the role of VP dopamine in cocaine-induced conditioned place preference (CPP) and locomotor activation. Rats received bilateral intra-VP injections of 3-4 microg 6-OHDA or ascorbic acid vehicle in 0.5 microl volume. Tissue assays indicated that the 6-OHDA-lesioned rats had significantly lowered dopamine concentration in VP, but not in NAS or striatum. As a group, 6-OHDA lesions blocked the development of CPP to 5 mg/kg cocaine but not to 10 mg/kg cocaine. However, rats with more than 60% depletion in VP dopamine did not develop CPP to cocaine at either dose. Preference for the cocaine-paired side correlated significantly with dopamine concentration in VP, but not in NAS or striatum. It was concluded that VP dopamine may play a critical role in the initial rewarding effect of cocaine. 6-OHDA lesions also blocked locomotor activation induced by 5 mg/kg cocaine but had no effect on 10 mg/kg cocaine-induced locomotion. Dopamine concentration in VP did not correlate with the locomotor activation response to cocaine at either dose. These findings further establish the involvement of the mesopallidal dopaminergic system in the action of cocaine.

Disruption of the clathrin heavy chain-like gene (CLTCL) associated with features of DGS/VCFS: a balanced (21;22)(p12;q11) translocation

The smallest region of deletion overlap in the patients we have studied defines a DIGeorge syndrome/velocardiofacial syndrome (DGS/VCFS) minimal critical region (MDGCR) of approximately 250 kb within 22q11. A de novo constitutional balanced translocation has been identified within the MDGCR. The patient has some features which have been reported in individuals with DGS/VCFS, including: facial dysmorphia, mental retardation, long slender digits and genital anomalies. We have cloned the breakpoint of his translocation and shown that it interrupts the clathrin heavy chain-like gene (CLTCL) within the MDGCR. The breakpoint of the translocation partner is in a repeated region telomeric to the rDNA cluster on chromosome 21p. Therefore, it is unlikely that the patient's findings are caused by interruption of sequences on 21p. The chromosome 22 breakpoint disrupts the 3' coding region of the CLTCL gene and leads to a truncated transcript, strongly suggesting a role for this gene in the features found in this patient. Further, the patient's partial DGS/VCFS phenotype suggests that additional features of DGS/VCFS may be attributed to other genes in the MDGCR. Thus, haploinsufficiency for more than one gene in the MDGCR may be etiologic for DGS/VCFS.

Purification, characterization and conformational analysis of a haemorrhagin from the venom of Agkistrodon acutus

AaHIV, a medium-sized toxin with a mol. wt of 44,000, a pI of 5.0 and a low cysteine content, was isolated from the venom of Agkistrodon acutus by ion-exchange and gel filtration chromatography. It had haemorrhagic, lethal and caseinolytic activities, the last of which was inhibited by EDTA, Zn(CH3COO)2 or CuSO4. The circular dichroism spectrum at pH 7.0 showed two negative bands at 210 nm and 219 nm, corresponding to secondary structure contents of 18.2% alpha-helix, 31.0% beta-sheet, 17.2% beta-turn and 33.6% random-coil. The effect of various pH values or the addition of EDTA or Zn(CH3COO)2 on the circular dichroism spectrum was also investigated.

Structural and mutational analysis of a conserved gene (DGSI) from the minimal DiGeorge syndrome critical region

The majority of patients with DiGeorge syndrome (DGS), velocardiofacial syndrome (VCFS), conotruncal anomaly face syndrome (CTAFS) and some individuals with familial or sporadic conotruncal cardiac defects have hemizygous deletions of chromosome 22. Most patients with these disorders share a common large deletion, spanning > 1.5 Mb within 22q11.21-q11.23. Recently, the smallest region of deletion overlap has been narrowed to a 250 kb area, the minimal DGS critical region (MDGCR), which includes the locus D22S75 (N25). We have isolated and characterized a novel, highly conserved gene, DGSI, within the MDGCR. DGSI has 10 exons and nine introns encompassing 1702 bp of cDNA sequence and 11 kb of genomic DNA. The encoded protein has 476 amino acids with a predicted mol. wt of 52.6 kDa. The intron-exon boundaries have been analyzed and conform to the consensus GT/AG motif. The corresponding murine Dgsi has been isolated and localized to proximal mouse chromosome 16. The mouse gene contains the same number of exons and introns, and the predicted protein has 479 amino acids with 93.2% identity to that of the human DGSI gene. By database searching, both genes have significant homology to a Caenorhabditis elegans hypothetical protein, F42H10.7. Further, mutation analysis has been performed in 16 patients, who have no detectable 22q11.2 deletion and some of the characteristic clinical features of DGS/VCFS. We have detected eight sequence variants in DGSI. These occurred in the 5'-untranslated region, the coding region and the intronic regions adjacent to the intron-exon boundaries of the gene. Seven of the eight variants were also present in normal controls or unaffected family members, suggesting they may not be of etiologic significance.

A region of mouse chromosome 16 is syntenic to the DiGeorge, velocardiofacial syndrome minimal critical region

DGS and VCFS, haploinsufficiencies characterized by multiple craniofacial and cardiac abnormalities, are associated with a microdeletion of chromosome 22q11.2. Here we document synteny between a 150-kb region on mouse chromosome 16 and the most commonly deleted portion of 22q11.2. Seven genes, all of which are transcribed in the early mouse embryo, have been identified. Of particular interest are two serine/threonine kinase genes and a novel goosecoid-like homeobox gene (Gscl). Comparative sequence analysis of a 38-kb segment reveals similarities in gene content, order, exon composition, and transcriptional direction. Therefore, if deletion of these genes results in DGS/VCFS in humans, then haploinsufficiencies involving this region of chromosome 16 should recapitulate the developmental field defects characteristic of this syndrome.