Coherent coupling of two quantum dots embedded in an Aharonov-Bohm interferometer

We define two laterally gated small quantum dots with less than 15 electrons in an Aharonov-Bohm geometry in which the coupling between the two dots can be changed. We measure Aharonov-Bohm oscillations for weakly coupled quantum dots. In an intermediate coupling regime we study molecular states of the double dot and extract the magnetic field dependence of the coherently coupled states.

Effects of the extracellular matrix on lumican expression in rat aortic smooth muscle cells in vitro

Lumican is a small leucine-rich proteoglycan (SLRP), which contributes to cell migration, proliferation, tissue hydration, and collagen fibrillogenesis. Whether lumican is localized in rat aortic smooth muscle cells (SMCs) and what its relationships might be to other extracellular matrix components have not yet been elucidated. In this study, using reverse transcription-polymerase chain reaction (RT-PCR), competitive RT-PCR, and western blot, lumican messenger ribonucleic acid (mRNA) was expressed in cultured rat aortic SMCs. SMCs cultured in serum-free medium showed four bands at 68, 62, 50, and 37 kD. The 68 and 62 kD bands corresponded to proteoglycan, the 50 kD band to glycoprotein, and the 37 kD band to the core protein form of lumican. The relationships of lumican to fibronectin and laminin were also investigated. The lumican mRNA level in SMCs cultured on fibronectin was highest at day 1, but it increased at day 3 in SMCs cultured on laminin. On the fibronectin or laminin-coated plates, SMCs expressed only the 68 and 62 kD bands, corresponding to proteoglycan. Pretreatment with anti-beta1 integrin receptor antibody revealed a decrease in the proteoglycan forms of lumican protein and an additional two bands at 50 and 37 kD, indicating glycoprotein and the core protein of lumican. These results show that lumican was synthesized in cultured rat aortic SMCs as proteoglycan, glycoprotein, and core protein. The extracellular matrix (ECM) affected lumican protein production and restricted the lumican protein form to proteoglycan via the beta1 integrin receptor in SMCs.

Gene therapy for head and neck cancer using vaccinia virus expressing IL-2 in a murine model, with evidence of immune suppression

We evaluated the efficiency of recombinant vaccinia virus expressing interleukin-2 (rvv-IL-2) as a tumor vaccine in an immunocompetent mouse model of head and neck squamous cell carcinoma (SCC VII/SF). Mice with five-day-old tumors in the floor of the mouth were treated with rvv-IL-2 by intratumoral injections. These treated mice survived longer (P <.03) than mice treated with control vaccines. Splenocytes, bone marrow, and lymph node cells from tumor-bearing mice responded poorly to concanavalin A stimulation, suggesting induction of immunosuppression. The rvv-IL-2 virus grew for 7 days in the tumor following intratumoral injection. We did not detect any virus particles in several normal organs following rvv-IL-2 injection. Comparison of expression levels of several potential immune inhibitory mediators between the tumors growing in mice and cultured tumor cells demonstrated higher expression of IL-10, GM-CSF, TGF-beta, and NO synthetase in tumors. These results suggested possible roles for these molecules in immunosuppression. We conclude that rvv-IL-2 has potential as a therapeutic vaccine for head and neck cancer and that it can be more effective provided the immunosuppression is reversed.

[Resection of gastric carcinoma with preserving of the spleen and pancreas and functional clearance lymph nodes of the spleen hillus and splenic artery]

OBJECTIVE

To study the practical effects of the preserved spleen and pancreas and functional, clearance of lymph nodes of the spleen hillus and splenic artery for gastric carcinoma.

METHODS

Spleen and pancreatic involvement was retrospectively reviewed in 439 cases of resectable carcinoma of the gastric cardia, gastric corpus and total stomach. During gastric operation, 2 ml methylene blue was injected into the subserosal space of the gastric cardia or corpus to observe the spreading of lymphatic flow of the stomach in 54 cases. The No10, No11 lymph node metastasis rates, postoperative complications and survival rates were observed in 63 case of gastric carcinoma that had received gastrectomy with preservation of the spleen and pancreas (PSP) and functional clearance of lymph nodes of the spleen hillus and splenic artery.

RESULTS

Invasion of gastric cancer into the pancreas and spleen occurred in 5.7% (25/439) and 2.3% (10/439) respectively. Methylence blue was injected into the subserosal space of the stomach without diffusion into the spleen and pancreas. The No10, No11 lymph node metastasis rates of PSP, pancreas preservation (PR) and pancreas and spleen resection (PSR) were 17.5% (11/63), 19.1% (12/63); 20.8% (45/216), 25% (54/216); 20% (6/30), 23% (7/30), respectively (P > 0.05). The occurrence of postoperative complications and mortality was lower in patients with PSP than those with spleen and parts of pancreas resected, whereas the survival rate was higher in patients with PSP. The 5-year and 10-year survival rates of gastric carcinoma in stage II, III a were markedly improved in patients with PSP.

CONCLUSIONS

PSP for patients with gastric cancer is safe and functional resectable. The occurrence of postoperative complications is lower and the survival rates are higher in patients with PSP than those with spleen and part of pancreas resected. PSP is beneficial to those with gastric carcinoma in stage II, IIIa.

Transcriptional suppression of matrix metalloproteinase-9 gene expression by IFN-gamma and IFN-beta: critical role of STAT-1alpha

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that play crucial roles in proteolytic degradation of the extracellular matrix. Aberrant expression of the 92-kDa type IV collagenase (MMP-9) is implicated in the invasion and angiogenesis process of malignant tumors and in inflammatory diseases of the CNS. We investigated the effects of IFN-gamma and IFN-beta, cytokines used for treating some cancers and multiple sclerosis, on MMP-9 expression in human astroglioma and fibrosarcoma cell lines and primary astrocytes. Our results demonstrate that IFN-gamma and IFN-beta significantly inhibit MMP-9 enzymatic activity and protein expression that is induced by PMA and the cytokine TNF-alpha. The inhibitory effects of IFN-gamma and IFN-beta on MMP-9 expression correlate with decreased steady state MMP-9 mRNA levels and suppression of MMP-9 promoter activity. IFN-gamma- and IFN-beta-mediated inhibition of MMP-9 gene expression is dependent on the transcription factor STAT-1alpha, since IFN-gamma and IFN-beta fail to suppress MMP-9 expression in STAT-1alpha-deficient primary astrocytes and human fibrosarcoma cells. Reconstitution of human STAT-1alpha successfully restores the inhibitory effects of IFN-gamma and IFN-beta on MMP-9 gene expression. Thus, these data demonstrate the critical role of STAT-1alpha in IFN-gamma and IFN-beta suppression of MMP-9 gene expression.

Somatostatin suppresses endothelin-1-induced rat hepatic stellate cell contraction via somatostatin receptor subtype 1

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are considered therapeutic targets to decrease portal hypertension. To elucidate some of the hemodynamic effects of somatostatin (SST) on portal pressure, the presence and function of SST receptors (SSTRs) on HSCs were investigated.

METHODS

SSTR messenger RNA expression, and SSTR presence was investigated using reverse-transcription polymerase chain reaction, real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. The function of SSTRs was studied by examining the effects of SST and specific SSTR agonists on endothelin-1(ET-1)-induced HSC contraction.

RESULTS

Specific amplicons for SSTR subtypes 1, 2, and 3 were demonstrated in rat liver and in activated HSCs. The presence of SSTR subtypes 1, 2, and 3 was confirmed by Western blotting. With immunohistochemistry, a strong staining of HSCs was obtained for SSTR subtypes 1, 2, and 3 in CCl4-treated rats, but not in normal rat liver. Incubation of HSCs on collagen gels with buffer, 10(-8) mol/L SST, and 2 x 10(-8) mol/L ET-1 resulted in collagen surface area decreases of 5.5% +/- 3.3%, 6.8% +/- 4.4%, and 49.8% +/- 8.3%, respectively. Relative contraction of gels preincubated with 10(-8) mol/L SST followed by 2 x 10(-8) mol/L ET-1 or vice versa as compared with maximal contraction (100%) with 2 x 10(-8) mol/L ET-1 were 72.6% +/- 17.9% and 76.2% +/- 12.6%, respectively (P < 0.05). SSTR agonist 1, but not SSTR agonist 2 or 3, was able to counteract the contractile effect of ET-1. CONCLUSIONA: Activated rat HSCs bear SSTR subtypes 1, 2, and 3. SST causes significant partial inhibition of ET-1-induced contraction of activated HSCs, mainly by stimulation of SSTR subtype 1.

Modular construction of a tertiary RNA structure: the specificity domain of the Bacillus subtilis RNase P RNA

The structure of the specificity domain (S-domain) of the Bacillus subtilis RNase P RNA has been proposed to be composed of a core and a buttress module, analogous to the bipartite structure of the P4-P6 domain of the Tetrahymena group I ribozyme. The core module is the functional unit of the S-domain and contains the binding site for the T stem-loop of a tRNA. The buttress module provides structural stability to the core module and consists of a GA3 tetraloop and its receptor. To explicitly test the hypothesis that modular construction can describe the structure of the S-domain and is a useful RNA design strategy, we analyzed the equilibrium folding and substrate binding of three classes of S-domain mutants. Addition or deletion of a base pair in the helical linker region between the modules only modestly destabilizes the tertiary structure. tRNA binding selectivity is affected in one but not in two other mutants of this class. Elimination of the GA3 tetraloop-receptor interactions significantly destabilizes the core module and results in the loss of tRNA binding selectivity. Replacing the buttress module with that of a homologous RNase P RNA maintains the tRNA binding selectivity. Overall, we have observed that the linker regions between the two modules can tolerate moderate structural changes and that the buttress modules can be shuffled between homologous S-domains. These results suggest that it is feasible to design an RNA using a buttress module to stabilize a functional module.

An autosomal recessive polycystic kidney disease gene homolog is involved in intraflagellar transport in C. elegans ciliated sensory neurons

In this report, we show that the Caenorhabditis elegans gene osm-5 is homologous to the Chlamydomonas gene IFT88 and the mouse autosomal recessive polycystic kidney disease (ARPKD) gene, Tg737. The function of this ARPKD gene may be evolutionarily conserved: mutations result in defective ciliogenesis in worms [1], algae [2], and mice [2, 3]. Intraflagellar transport (IFT) is essential for the development and maintenance of motile and sensory cilia [4]. The biochemically isolated IFT particle from Chlamydomonas flagella is composed of 16 polypeptides in one of two Complexes (A and B) [5, 6] whose movement is powered by kinesin II (anterograde) and cytoplasmic dynein (retrograde) [7-9]. We demonstrate that OSM-5 (a Complex B polypeptide), DAF-10 and CHE-11 (two Complex A polypeptides), and CHE-2 [10], a previously uncategorized IFT polypeptide, all move at the same rate in C. elegans sensory cilia. In the absence of osm-5, the C. elegans autosomal dominant PKD (ADPKD) gene products [11] accumulate in stunted cilia, suggesting that abnormal or lack of cilia or defects in IFT may result in diseases such as polycystic kidney disease (PKD).

Comparative analysis and application of fluorescent protein-tagged connexins

In order to examine connexin transport, assembly, and turnover in living cells, we tagged green fluorescent protein or its color variants to several members of the connexin family of proteins. When green fluorescent protein was tagged to the carboxyl terminal end of connexin43 (Cx43-GFP), the resulting fusion protein was transported and assembled into functional gap junctions. However, when GFP was tagged to the amino terminal end of Cx43 (GFP-Cx43), this chimera was biosynthesized, transported to the plasma membrane, but failed to form gap junction channels that could transfer Lucifer yellow. Single cells that expressed Cx43-GFP were capable of transporting this fusion protein to the cell surface in the absence of cell-cell contact. Imaging of Cx43-yellow (Y)FP (Cx43-YFP) was quite efficient; however, the low quantum yield Cx43-BFP and the requirement for ultraviolet excitation made this chimera less suitable for time-lapse imaging. Cx43-cyan C(FP) (Cx43-CFP) was more suitable for imaging than Cx43-blue (B)FP and could be effectively separated from Cx43-YFP. The versatility of tagging GFP to the carboxyl terminal end of other members of the connexin family was established when Cx32-GFP and Cx26-YFP were found to assemble into gap junctions capable of transferring Lucifer yellow. Finally, we are examining the effectiveness of using a new red fluorescent protein (DsRed) fused to connexins in combination with Cx-GFP to simultaneously examine the kinetics, transport and turnover of two connexins. Together, our studies suggest that tagging fluorescent proteins to the carboxyl terminal end of connexins is an effective and valuable approach for studying the life cycle and dynamics of connexins in living cells.

Gastric rupture caused by acute gastric distention in non-neonatal children: clinical analysis of 3 cases

OBJECTIVE

To study gastric rupture, a progressive, rapid and high mortality condition, caused by acute gastric distention (GRAGD) and its appropriate diagnosis and treatment.

METHODS

The etiology, pathology, clinical manifestations and experiences in 3 children with GRAGD were reviewed.

RESULTS

Case 1: After diagnosing GRAGD and stabilizing her shock with massive fluid replacement, gastrostomy was performed. Her postoperative course was uneventful because of fasting, suction, fluid infusion, correction of acidosis and supporting nutrition. Case 2: After diagnosing gastric distention which subsided with conservative therapy for 9 days, she suddenly had gastric rupture when she had not eaten for 6 days. She died of shock and had no chance for surgery. Case 3: The patient had sudden abdominal pain, distention and vomiting with severe shock for 4 days. Emergency surgery found gastric rupture and the method was the same as Case 1. The patient survived but has brain impairment. Case 1 and 3 showed multifocal transmural necrosis.

CONCLUSIONS

Symptoms like overeating, bulimia, changes in kind of food, X-ray showing large distended stomach and massive pneumoperitoneum were seen after gastric rupture and can help to diagnose this condition. Clinical course of gastric distention with toxic shock progresses rapidly, however subsequent gastric rupture exacerbates the shock and makes the treatment difficult treatment. It is extremely important that a laparotomy be performed at once after stabilizing shock with massive fluid replacement. Postoperative nutritional support and fluid replacement will increase survival. It is very important that when gastric distention disappears after conservative therapy, the doctor should assess carefully whether the gastric wall recovery is under way by using effective methods of examination.

Effects of extracellular matrix on phenotype modulation and MAPK transduction of rat aortic smooth muscle cells in vitro

The transition of arterial smooth muscle cells (SMCs) from a contractile to a synthetic phenotype may play an essential role in the formation of atherosclerotic and restenotic lesions. This process includes a prominent structural reorganization and allows cells to acquire the ability to migrate, proliferate, and secrete extracellular matrix components. According to Western blotting analysis and immunohistochemical and morphological observations, laminin not only retains SMCs in a contractile state but also possibly stimulates cells to transform a synthetic to a contractile phenotype at an early stage, mediated by P38 MAPK signal transduction. However, fibronectin promotes SMCs to transform from a contractile to a synthetic phenotype, mediated by the ERK MAPK signal pathway. The localization of smooth muscle alpha -actin, myosin heavy chain isoform SM2, and vimentin in explant-isolated rat SMCs was affected by a substrate of fibronectin and laminin and also by ERK MAP kinase inhibitor (PD098059) and P38 MAPK inhibitor (SB203580). Furthermore, vimentin may play a much more important role in differentiation than desmin in phenotype modulation in rat aortic smooth muscle cells.

[Down regulation of HER2/neu expression by adenovirus E1A and its anti-tumor activity]

OBJECTIVE

To study the growth inhibitory and chemo-sensitizing effects of adenovirus E1A gene on HER2/neu-overexpressing tumor cell lines.

METHODS

E1A was transfected in vitro and in vivo by adenovirus vector into HER2/neu overexpressing human mammary cancer cell lines MDA-MB-453 and SKBR3 and their growth was monitored. The chemo-sensitizing effect was examined by MTT assay.

RESULTS

E1A greatly inhibited growth of HER2/neu-overexpressing tumor and prolonged the survival time of tumor-bearing mice. Western blot and immunohistochemical analysis both showed suppression of p185 protein expression in E1A-transfected HER2/neu overexpressing cancer cell lines. E1A could sensitize HER2/neu-overexpressing human breast cancer cells to Taxotere by repressing HER2/neu expression.

CONCLUSION

Adenovirus E1A inhibits tumor growth and sensitizes tumor cells to chemotherapeutic agent via down regulation of HER2/neu expression.

Frequency of cytochrome P450 3A4 variant genotype in transplant population and lack of association with cyclosporin clearance

OBJECTIVE

Cytochrome P450 3A4 (CYP3A4) plays a vital role in the oxidative metabolism of many xenobiotics. Some recent reports have provided circumstantial evidence in support of an association between a genetic polymorphism (A-->G) in the 5'-flanking region (-290) of CYP3A4 and altered enzyme activity. We sought to determine whether genotyping patients for CYP3A4-G could assist with the dose optimisation of drugs metabolised by this system.

METHODS

Normal subjects and renal-transplant patients receiving cyclosporin for immune modulation were genotyped for the CYP3A4-G variant. A surrogate for cyclosporin clearance was estimated from the ratio of the cyclosporin dose, normalised for body weight and the corresponding trough concentration. The association between genotype and clearance was examined in patients who received twice-daily doses of cyclosporin and who were not on concurrent medication known to modify CYP3A4 function.

RESULTS

The allelic frequencies of the CYP3A4-G variant were estimated to be 2.6% and 3% in transplant patients and normal subjects, respectively. The median cyclosporin pseudo-clearance of transplant patients with wild-type CYP3A4 was 0.90 l/h/kg (range: 0.35-3.8 l/h/kg; n = 86), whereas the corresponding value for the five patients heterozygotic for the CYP3A4-G variant was 0.71 l/h/kg (range 0.35-0.91 l/h/kg). The distribution of the pseudo-clearance according to genotype was not found to be significant according to a Fisher's exact test (P = 0.15).

CONCLUSION

Genotyping for the CYP3A4-G polymorphism is unlikely to assist cyclosporin dose selection in transplant patients.

[Terminal differentiation of human acute promyelocytic leukemia (APL) cells induced by Tanshinone II A in primary culture]

The aim of this study was to investigate whether Tanshinone II A (Tan II A) can induce human acute promyelocytic leukemia (APL) cells to differentiate or not in primary culture. The APL cells from 5 cases were cultured respectively with Tan II A at the concentration of 0.5 microgram/ml for 7 days in vitro. The differentiations of these leukemia cells were observed cytomorphologically and examined by nitroblue tetrazolium (NBT) test. The cell DNA cycle and membrane cluster differentiation (CD) antigens (CD33, CD11b) were analyzed by flow cytometry. The results showed that 82.5% +/- 4.8% of APL cells were induced into morphologically and functionally differentiated cells. The cell growth curve showed that the growth of APL cells was inhibited. The degree of differentiation and growth inhibition induced by Tan II A was not different from that by ATRA (P > 0.05). Flow cytometry analysis showed that Tan II A arrested APL cells in G0/G1 phase and inhibited cellular DNA synthesis. This study demonstrates that Tan II A can induce differentiation of APL cells in vitro, and hence it is worthy of further studies for clinical use.

Hirudin display on the surface of bacteriophage M13

Hirudin was fused to the N terminus of M13 minor protein gp3 (197-406) through a linker GGGS by inserting both the hirudin gene and the gp8 signal sequence into the modified phagemid vector pCANTAB 5V to construct pCANTAB 5G8-Hir. The expressed fusion protein was directed by gp8 signal peptide into the periplasm and assembled to the phage particle to form the hirudin-phage. The fusion protein and fusion phage were detected with biotin-thrombin by Western blotting analysis. Antithrombin activity analysis confirmed that the hirudin portion in the fusion protein and fusion phage bear similar native conformation. The successful display of hirudin on the surface of M13 phage laid a sound foundation for the further study on directed evolution of antithrombotic proteins with altered properties.

[Significance and expression of insulin-like growth factor II and its receptor in hepatocellular carcinogenesis]

OBJECTIVE

To provide information on the potential role of insulin-like growth factor II (IGF-II) and insulin-like growth factor II receptor (IGF-IIR) during different liver diseases and hepatocarcinogenesis.

METHODS

Southern hybridization was used to detect HBV DNA integration in various kinds of liver tissues, and DNA-RNA in situ hybridization to observe and analyze the mRNA of IGF-II and IGF-II receptor in chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC).

RESULTS

The expression of IGF-II and IGF-II receptor mRNA was observed not only in HCC, but also in chronic hepatitis and cirrhosis. An increasing gradient of IGF-II and IGF-IIR Mrna expression was in turn from chronic hepatitis (33. 3%), HCC (66.7%) to cirrhosis (72.0%). Strongly positive expression was found in liver cell dysplasia, regenerative nodules and poorly differentiated HCC cells.

CONCLUSION

IGF-II and its receptor might play an important role in the development of HCC.

Synergetic effect of dialyzer membrane and lipopolysaccharide on peripheral blood mononuclear cell cytokine production in uremic patients

OBJECTIVE

To investigate the effect of lipopolysaccharide(LPS) and dialyzer membrane on cytokine gene expression and protein production in uremic patients on continuous ambulatory peritoneal dialysis (CAPD) and regular hemodialysis(HD).

METHODS

Interleukin-1 beta (IL-1 beta) and interleukin-1 receptor antagonist (IL-1Ra) produced by cultured peripheral blood mononuclear cells (PBMC) after exposure to cuprammonium (Cup) membrane, polysulfone (PS) membranes or endotoxin were detected using enzyme-linked immunoabsorbent assay. mRNA expression was determined simultaneously by in situ hybridization.

RESULTS

In the absence of endotoxin, a small amount of IL-1 beta and IL-1 Ra was produced by PBMC harvested from HD and CAPD patients after incubation with Cup or PS during subsequent 24-hour culture. For healthy controls, IL-1 beta was barely detectable just above the detection limit. Although no differences could be found in protein synthesis between Cup and PS, in situ hybridization showed that Cup induced markedly higher level mRNA coding for IL-1 beta and IL-1Ra. In contrast, when subsequently stimulated with endotoxin, PBMC incubated with Cup could produce significantly larger amount of IL-1 beta and IL-1Ra compared with either unstimulated cells or post-incubation PBMC with PS. LPS-stimulated PBMC in healthy subjects produced similar amount of IL-1 beta and markedly lower IL-1Ra as compared with uremic patients on HD and CAPD.

CONCLUSIONS

Two steps are required in healthy control for IL-1 beta and IL-1Ra production: induction of mRNA transcription by membrane contact, followed by LPS-induced translation, while in uremic patients on HD or CAPD bioincompatibility-membrane and LPS have a synergetic effect on IL-1 beta and IL-1Ra production. There exists an unbalance between IL-1 beta and its specific inhibitor in maintenance dialysis patients.

Complete genome sequence of Neisseria meningitidis serogroup B strain MC58

The 2,272,351-base pair genome of Neisseria meningitidis strain MC58 (serogroup B), a causative agent of meningitis and septicemia, contains 2158 predicted coding regions, 1158 (53.7%) of which were assigned a biological role. Three major islands of horizontal DNA transfer were identified; two of these contain genes encoding proteins involved in pathogenicity, and the third island contains coding sequences only for hypothetical proteins. Insights into the commensal and virulence behavior of N. meningitidis can be gleaned from the genome, in which sequences for structural proteins of the pilus are clustered and several coding regions unique to serogroup B capsular polysaccharide synthesis can be identified. Finally, N. meningitidis contains more genes that undergo phase variation than any pathogen studied to date, a mechanism that controls their expression and contributes to the evasion of the host immune system.

Alpha-galactose based neoglycopeptides. Inhibition of verotoxin binding to globotriosylceramide

Solution and solid phase strategies for the synthesis of alpha-galactose based neoglycopeptide derivatives 2-13 were developed. Neoglycopeptides generated were tested for the inhibition of verotoxin binding to globotriosylceramide (Gb3) using ELISA. Among all of the compounds tested, only the lipid derivatives of neoglycopeptides, 11, 12 and 13 were found to be inhibitors, IC50 = 2.0 mM (11b and 12c) and 0.2 mM (11c and 13c). All of the inhibitors (11b, 11c, 12c and 13c) have a similar branching of the two alpha-galactosyl units at the N-terminal glycine residue of a short peptide and a lipid moiety attached at the C-terminal site. Both of these factors seem to be crucial for the inhibition. It is interesting to note that the inhibitors have only a portion of the natural trisaccharide ligand. The secondary groups either may contribute in sub-site oriented interactions with the protein receptors or may mimic the internal sugar units of the cell-surface ligand, Gb3.

The transcription factors Sp1, Sp3, and AP-2 are required for constitutive matrix metalloproteinase-2 gene expression in astroglioma cells

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that contribute to pathological conditions associated with angiogenesis and tumor invasion. MMP-2 is highly expressed in human astroglioma cells, and contributes to the invasiveness of these cells. The human MMP-2 promoter contains potential cis-acting regulatory elements including cAMP response element-binding protein, AP-1, AP-2, PEA3, C/EBP, and Sp1. Deletion and site-directed mutagenesis analysis of the MMP-2 promoter demonstrates that the Sp1 site at -91 to -84 base pairs and the AP-2 site at -61 to -53 base pairs are critical for constitutive activity of this gene in invasive astroglioma cell lines. Electrophoretic gel shift analysis demonstrates binding of specific DNA-protein complexes to the Sp1 and AP-2 sites: Sp1 and Sp3 bind to the Sp1 site, while the AP-2 transcription factor binds the AP-2 element. Co-transfection expression experiments in Drosophilia SL2 cells lacking endogenous Sp factors demonstrate that Sp1 and Sp3 function as activators of the MMP-2 promoter and synergize for enhanced MMP-2 activation. Overexpression of AP-2 in AP-2-deficient HepG2 cells enhances MMP-2 promoter activation. These findings document the functional importance of Sp1, Sp3, and AP-2 in regulating constitutive expression of MMP-2. Delineation of MMP-2 regulation may have implications for development of new therapeutic strategies to arrest glioma invasion.

Recombinant vaccinia virus expressing cytokine GM-CSF as tumor vaccine

The efficacy of a recombinant vaccinia virus (rvv-GM-CSF) expressing the granulocyte macrophage colony stimulating factor (GM-CSF) as tumor vaccine was evaluated in the murine B16-F10 melanoma model. The vaccine was prepared by infection of irradiated tumor cells with rvv-GM-CSF. Control vaccine was B-16 cells infected with a recombinant vaccinia virus expressing Escherichia coli beta-galactosidase (rvv-lacZ). Pre-vaccination of naive C57BL/6 mice later inoculated with tumor cells and treatment of mice bearing tumors with GM-CSF vaccine inhibited tumor development and prolonged survival. Lung metastasis of B-16 was also inhibited by treatment with GM-CSF vaccine. The vaccine effects appeared to be tumor cell specific. The efficacy of the vaccine was comparable to a retroviral vaccine (MFG-muGM-CSF) in this system. The vaccine was also effective when rvv-GM-CSF was directly injected into the tumor. These data suggest that this vaccine approach has potential for use in cancer treatment, especially for patients with easily accessible tumors.

Substitution of the sixth axial ligand of Rhodobacter capsulatus cytochrome c1 heme yields novel cytochrome c1 variants with unusual properties

The cytochrome (cyt) c1 heme of the ubihydroquinone:cytochrome c oxidoreductase (bc1 complex) is covalently attached to two cysteine residues of the cyt c1 polypeptide chain via two thioether bonds, and the fifth and sixth axial ligands of its iron atom are histidine (H) and methionine (M), respectively. The latter residue is M183 in Rhodobacter capsulatus cyt c1, and previous mutagenesis studies revealed its critical role for the physicochemical properties of cyt c1 [Gray, K. A., Davidson, E., and Daldal, F. (1992) Biochemistry 31, 11864-11873]. In the homologous chloroplast b6f complex, the sixth axial ligand is provided by the amino group of the amino terminal tyrosine residue. To further pursue our investigation on the role played by the sixth axial ligand in heme-protein interactions, novel cyt c1 variants with histidine-lysine (K) and histidine-histidine axial coordination were sought. Using a R. capsulatus genetic system, the cyt c1 mutants M183K and M183H were constructed by site-directed mutagenesis, and chromatophore membranes as well as purified bc1 complexes obtained from these mutants were characterized in detail. The studies revealed that these mutants incorporated the heme group into the mature cyt c1 polypeptides, but yielded nonfunctional bc1 complexes with unusual spectroscopic and thermodynamic properties, including shifted optical absorption maxima (lambdamax) and decreased redox midpoint potential values (Em7). The availability and future detailed studies of these stable cyt c1 mutants should contribute to our understanding of how different factors influence the physicochemical and folding properties of membrane-bound c-type cytochromes in general.

Structural basis of procaspase-9 recruitment by the apoptotic protease-activating factor 1

Caspase-9-mediated apoptosis (programmed cell death) plays a central role in the development and homeostasis of all multicellular organisms. Mature caspase-9 is derived from its procaspase precursor as a result of recruitment by the activating factor Apaf-1. The crystal structures of the caspase-recruitment domain of Apaf-1 by itself and in complex with the prodomain of procaspase-9 have been determined at 1.6 and 2.5 A resolution, respectively. These structures and other evidence reveal that each molecule of Apaf-1 interacts with a molecule of procaspase-9 through two highly charged and complementary surfaces formed by non-conserved residues; these surfaces determine recognition specificity through networks of intermolecular hydrogen bonds and van der Waals interactions. Mutation of the important interface residues in procaspase-9 or Apaf-1 prevents or reduces activation of procaspase-9 in a cell-free system. Wild-type, but not mutant, prodomains of caspase-9 completely inhibit catalytic processing of procaspase-9. Furthermore, analysis of homologues from Caenorhabditis elegans indicates that recruitment of CED-3 by CED-4 is probably mediated by the same set of conserved structural motifs, with a corresponding change in the specificity-determining residues.