Rosaria Arcone

Dual control of C-reactive protein gene expression by interleukin-1 and interleukin-6.

Human C‐reactive protein (CRP) is the major acute phase reactant during acute inflammation. The human CRP promoter is expressed in an inducible and cell‐specific manner when linked to the bacterial CAT gene and transfected into human hepatoma cell cultures. In this paper we analyze the effect of several recombinant cytokines or CRP promoter inducibility in human Hep3B cells. When cytokines are tested singly the major inducer of CRP‐CAT fusions is interleukin‐6 (IL‐6). Maximal CAT gene expression, however, is only achieved when both interleukin‐1 beta (IL‐1 beta) and IL‐6 are present. The response to the two cytokines is cooperative. Cooperativity is maintained when the CRP promoter is linked to a different coding region, that of the bacterial neomycin phosphotransferase II gene. With a series of 5′ and 3′ deletions we show the existence of two distinct and independent regions responsive to IL‐6 and located upstream to the TATA box. The IL‐1 effect is exerted at the level of downstream sequences that are probably important for optimal mRNA translatability or nuclear‐cytoplasmic transport. Inducibility is not influenced by the activation of protein kinases C or A and does not require new protein synthesis.

Constitutive and IL-6-induced nuclear factors that interact with the human C-reactive protein promoter

Transcription of the human C‐reactive protein (CRP) gene is induced by interleukin‐6 (IL‐6) during acute inflammation. Important information for inducible CRP expression is located within the 90 bases preceding the transcriptional start site. We show that the CRP promoter contains two adjacent binding sites (beta and alpha) that interact with at least two hepatocyte‐specific nuclear proteins, H‐APF‐1 and H‐APF‐2. Point mutations that abolish or reduce binding drastically affect the level of CRP gene expression. Binding to beta is identical when extracts from uninduced or IL‐6‐induced Hep3B cells are used. On the contrary, both quantitative and qualitative changes in the alpha binding can be detected with extracts from uninduced cells or from cells treated with IL‐6 or IL‐6 + cycloheximide. A synthetic promoter based on the multimerization of the beta‐binding domain, but not of the alpha‐domain, is highly inducible when transfected in hepatoma cells. These results are discussed in relation to the structure of the promoter region of other acute phase inducible genes.

Internal deletions of amino acids 29-42 of human interleukin-6 (IL-6) differentially affect bioactivity and folding.

Internal deletions of the human interleukin‐6 (IL‐6) cDNA have been generated in the region encoding residues 29 to 42. Mutant proteins were produced by in vitro transcription—translation or in Escherichia coli and tested for their biological activity using the hybridoma growth factor (HGF) assay or a transcriptional activation assay on human hepatoma cells. The folding of the mutants was also checked by immunoprecipitation with conformation‐specific monoclonal antibodies. The results show that only residues 29 to 34 are crucial for IL‐6 activity and that the first two amino acids are probably involved in the definition of the IL‐6 active site.

Design, Synthesis, and Evaluation of Donepezil-Like Compounds as AChE and BACE-1 Inhibitors

An ecofriendly synthetic pathway for the synthesis of donepezil precursors is described. Alternative energy sources were used for the total synthesis in order to improve yields, regioselectively, and rate of each synthetic step and to reduce the coproduction of waste at the same time. For all products, characterized by an improved structural rigidity respect to donepezil, the inhibitor activity on AChE, the selectivity vs BuChE, the side-activity on BACE-1, and the effect on SHSY-5Y neuroblastoma cells viability were tested. Two potential new lead compounds for a dual therapeutic strategy against Alzheimers disease were envisaged.

Synergistic Stimulation of Interleukin 6 Release and Gene Expression by Phorbol Esters and Interleukin 1β in Rat Cortical Astrocytes: Role of Protein Kinase C Activation and Blockade

Abstract: The involvement of protein kinase C and its interaction with interleukin 1β in the control of interleukin 6 release by cortical astrocytes was studied. The blockade of protein kinase C catalytic domain, by staurosporine, as well as the desensitization of protein kinase C by short‐term phorbol 12‐myristate 13‐acetate pretreatment, increased the basal release of interleukin 6 by rat cortical astrocytes, whereas calphostin C, an antagonist of phorbol ester binding on protein kinase C regulatory domain, did not affect the basal release of the cytokine. The activation of protein kinase C by phorbol 12‐myristate 13‐acetate enhanced concentration‐ and time‐dependently interleukin 6 release. This stimulatory action of phorbol 12‐myristate 13‐acetate was significantly reduced by staurosporine, by calphostin C, and by the desensitization of protein kinase C. Interleukin 1β increased interleukin 6 release in a concentration‐related manner. Protein kinase C inhibition, by staurosporine or desensitization, potentiated severalfold, whereas calphostin C reduced interleukin 1β stimulation of interleukin 6 release. The treatment of cortical astrocytes with both interleukin 1β (3 ng/ml) and phorbol 12‐myristate 13‐acetate (10 nM) caused a synergistic stimulation of interleukin 6 release and its gene expression, an effect that was not relieved by either 20 nM staurosporine or by calphostin C but was slightly affected by protein kinase C desensitization. In conclusion, our data show that in rat cortical astrocytes the basal release of interleukin 6 is under a tonic inhibition exerted by a protein kinase C isoform or isoforms sensitive to blockade by staurosporine and desensitization but insensitive to calphostin C. Interleukin 1β stimulated interleukin 6 secretion via a mechanism that is also negatively modulated by a protein kinase C isoform or isoforms sensitive to staurosporine and desensitization. Finally, we showed that interleukin 1β and phorbol 12‐myristate 13‐acetate synergistically stimulated interleukin 6 release and its gene expression, operating in a manner insensitive to protein kinase C blockers and slightly reduced by protein kinase C desensitization.

Internal deletions in human interleukin-6: structure-function analysis

By cDNA mutagenesis, we have constructed internal and C-terminal deletions (delta 21-51, delta 52-97, delta 97-104, delta 127-174, delta 97-184 and delta 134-184) in human interleukin-6 (hIL-6). All those deletion-carrying hIL-6 (delta hIL-6) proteins were then produced in Xenopus laevis oocytes and examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results show that, at least in frog oocytes, the first potential N-glycosylation site (Asn45) is utilized exclusively. The IL-6 conformation of these deletion-carrying proteins has been studied by immunoprecipitation with two kinds of monoclonal antibodies (mAbs): mAbs that show preference towards denatured hIL-6, or conformation-specific mAbs. The binding pattern of these two series of mAbs indicated that the IL-6 conformation has been largely destroyed for four of our delta-proteins. Proteins delta 21-51 and delta 127-174 have kept a part of the IL-6 tertiary structure since they are still recognized by some conformation-specific mAbs. All of these delta hIL-6 proteins were inactive in the IL-6 hybridoma growth factor (HGF) assay and unable to inhibit the HGF activity of the recombinant human wild-type IL-6 (wt hIL-6). Moreover, the oocyte-synthesized delta hIL-6 (delta 21-51, delta 127-174, delta 97-184, delta 134-184) did not bind to the IL-6 receptor. Finally, we have produced two proteins with aa 29-33 or 97-104 substituted by corresponding murine IL-6 (mIL-6) sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Research Article: The N‐Terminal Domain of 2′,3′‐Cyclic Nucleotide 3′‐Phosphodiesterase Harbors a GTP/ATP Binding Site

The interaction between 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase and guanine/adenine nucleotides was investigated. The binding of purine nucleotides to 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase was revealed by both direct and indirect methods. In fact, surface plasmon resonance experiments, triphosphatase activity measurements, and fluorescence experiments revealed that 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase binds purine nucleotide triphosphates with an affinity higher than that displayed for diphosphates; on the contrary, the affinity for both purine monophosphates and pyrimidine nucleotides was negligible. An interpretation of biological experimental data was achieved by a building of 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase N‐terminal molecular model. The structural elements responsible for nucleotide binding were identified and potential complexes between the N‐terminal domain of CNP‐ase and nucleotide were analyzed by docking simulations. Therefore, our findings suggest new functional and structural property of the N‐terminal domain of CNPase.

Thrombin mutants with altered enzymatic activity have an impaired mitogenic effect on mouse fibroblasts and are inefficient modulators of stellation of rat cortical astrocytes.

We produced recombinant human thrombin mutants to investigate the correlation between the thrombin enzyme and mitogenic activity. Single amino acid substitutions were introduced in the catalytic triad (H43N, D99N, S205A, S205T), in the oxy-anion binding site (G203A) and in the anion binding exosite-1 region (R73E). Proteins were produced as prethrombin-2 mutants secreted in the culture medium of DXB11-derived cell lines. All mutants were activated by ecarin to the corresponding thrombin mutants; the enzymatic activity was assayed on a chromogenic substrate and on the procoagulant substrate fibrinogen. Mutations S205A and G203A completely abolished the enzyme activity. Mutations H43N, D99N and S205T dramatically impaired the enzyme activity toward both substrates. The R73E mutation dissociated the amidolytic activity and the clotting activity of the protein. The ability of thrombin mutants to induce proliferation was investigated in NIH3T3 mouse fibroblasts and rat cortical astrocytes. The ability of the thrombin mutants to revert astrocyte stellation was also studied. The mitogenic activity and the effect on the astrocyte stellation of the thrombin mutants correlated with their enzymatic activity. Furthermore the receptor occupancy by the inactive S205A mutant prevented the thrombin effects providing strong evidence that a proteolytically activated receptor is involved in cellular responses to thrombin.

Protease Nexin-1 affects the migration and invasion of C6 glioma cells through the regulation of urokinase Plasminogen Activator and Matrix Metalloproteinase-9/2.

Protease Nexin-1 (PN-1) or Serpine2 is a physiological regulator of extracellular proteases as thrombin and urokinase (uPA) in the brain. Besides, PN-1 is also implicated in some human cancers and further identified as a substrate for Matrix Metalloproteinase (MMP)-9, a key enzyme in tumor invasiveness. Our aim was to study the role of PN-1 in the migration and invasive potential of glioma cells, using the rat C6 glioma cell line as stable clones transfected with pAVU6+27 vector expressing PN-1 short-hairpin RNA. We find that PN-1 knockdown enhanced the in vitro migration and invasiveness of C6 cells which also showed a strong gelatinolytic activity by in situ zymography. PN-1 silencing did not alter prothrombin whereas increased uPA, MMP-9 and MMP-2 expression levels and gelatinolytic activity in a conditioned medium from stable C6 cells. Selective inhibitors for MMP-9 (Inhibitor I), MMP-2 (Inhibitor III) or exogenous recombinant PN-1 added to the culture medium of C6 silenced cells restored either the migration and invasive ability or gelatinolytic activity thus validating the specificity of PN-1 silencing strategy. Phosphorylation levels of extracellular signal-related kinases (Erk1/2 and p38 MAPK) involved in MMP-9 and MMP-2 signaling were increased in PN-1 silenced cells. This study shows that PN-1 affects glioma cell migration and invasiveness through the regulation of uPA and MMP-9/2 expression levels which contribute to the degradation of extracellular matrix during tumor invasion.

Stage-specific gene expression in early differentiating oligodendrocytes

The screening of a differential library from precursor and differentiated oligodendrocytes, obtained through the representational difference analysis (RDA) technique, has generated a number of cDNA recombinants corresponding to mRNA coding for known and unknown proteins: (1) mRNA coding for proteins involved in protein synthesis, (2) mRNA coding for proteins involved in the organization of the cytoskeleton, and (3) mRNA coding for proteins of unknown function. The expression profile of the mRNA was studied by Northern blot hybridization to the poly‐A+ mRNA from primary rat progenitor and differentiated oligodendrocytes. In most cases, hybridization to the precursor was higher than hybridization to the differentiated mRNA, supporting the validity of the differential screening. Hybridization of the cDNA to rat cerebral hemisphere and brain stem poly‐A+ mRNA, isolated from 1‐ to 90‐day‐old rats, confirms the results obtained with the mRNA from differentiating oligodendrocytes. The intensity of the hybridization bands decreases as differentiation proceeds. The pattern of expression observed in oligodendrocytes is different from that found in the brain only in the case of the nexin‐1 mRNA, the level of which remains essentially constant throughout differentiation both in the brain stem and in the cerebral hemispheres, in agreement with the published data. In contrast, the intensity of hybridization to the oligodendrocyte mRNA is dramatically lower in the differentiated cells compared with the progenitor oligodendrocyte cells. Some of the recombinant cDNA represent mRNA sequences present at high frequency distribution in the cells, while others belong to the rare sequences group. Six recombinants code for proteins of the ribosomal family, suggesting that of approximately 70 known ribosomal proteins, only a few are upregulated during oligodendrocyte differentiation. The third category of open reading frame (ORF) is represented by rare messengers coding for proteins of unknown functions and includes six clones: RDA 279, 11, 95, 96, 254, and 288. GLIA 39:114–123, 2002.