RESUMO
Genetic factors strongly contribute to the pathogenesis of sporadic Alzheimer's disease (AD). Nevertheless, genome-wide association studies only yielded single nucleotide polymorphism loci of moderate importance. In contrast, microsatellite repeats are functionally less characterized structures within our genomes. Previous work has shown that endothelin-converting enzyme-1 (ECE-1) is able to reduce amyloid ß content. Here we demonstrate that a CpG-CA repeat within the human ECE-1c promoter is highly polymorphic, harbors transcriptional start sites, is able to recruit the transcription factors poly(ADP-ribose) polymerase-1 and splicing factor proline and glutamine-rich, and is functional regarding haplotype-specific promoter activity. Furthermore, genotyping of 403 AD patients and 444 controls for CpG-CA repeat length indicated shifted allelic frequency distributions. Sequencing of 245 haplotype clones demonstrated that the overall CpG-CA repeat composition of AD patients and controls is distinct. Finally, we show that human and chimpanzee [CpG](m)-[CA](n) ECE-1c promoter repeats are genetically and functionally distinct. Our data indicate that a short genomic repeat structure constitutes a novel core promoter element, coincides with human evolution, and contributes to the pathogenesis of AD.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Ácido Aspártico Endopeptidases/genética , Evolução Biológica , Metaloendopeptidases/genética , Repetições de Microssatélites/genética , Regiões Promotoras Genéticas/genética , Transcrição Gênica/genética , Animais , Western Blotting , Doenças Cardiovasculares/genética , Doenças Cardiovasculares/fisiopatologia , Cromatografia em Gel , DNA/genética , DNA/isolamento & purificação , Ensaio de Desvio de Mobilidade Eletroforética , Enzimas Conversoras de Endotelina , Genótipo , Humanos , Ensaios de Proteção de Nucleases , Pan troglodytes , Poli(ADP-Ribose) Polimerase-1 , Poli(ADP-Ribose) Polimerases/genética , RNA/genética , RNA/isolamento & purificação , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Angiotensin II type 2 (AT(2)) receptors can be regarded as an endogenous repair system, because the AT(2) receptor is upregulated in tissue damage and mediates tissue protection. A potential therapeutic use of this system has only recently come within reach through synthesis of the first selective, orally active, nonpeptide AT(2) receptor agonist, compound 21 (C21; dissociation constant for AT(2) receptor: 0.4 nM; dissociation constant for angiotensin II type 1 receptor: >10,000 nM). This study tested AT(2) receptor stimulation with C21 as a potential future therapeutic approach for the inhibition of proinflammatory cytokines and of nuclear factor kappaB. C21 dose-dependently (1 nM to 1 micromol/L) reduced tumor necrosis factor-alpha-induced interleukin 6 levels in primary human and murine dermal fibroblasts. AT(2) receptor specificity was controlled for by inhibition with the AT(2) receptor antagonist PD123319 and by the absence of effects in AT(2) receptor-deficient cells. AT(2) receptor-coupled signaling leading to reduced interleukin 6 levels involved inhibition of nuclear factor kappaB, activation of protein phosphatases, and synthesis of epoxyeicosatrienoic acid. Inhibition of interleukin 6 promoter activity by C21 was comparable in strength to inhibition by hydrocortisone. C21 also reduced monocyte chemoattractant protein 1 and tumor necrosis factor-alpha in vitro and in bleomycin-induced toxic cutaneous inflammation in vivo. This study is the first to show the anti-inflammatory effects of direct AT(2) receptor stimulation in vitro and in vivo by the orally active, nonpeptide AT(2) receptor agonist C21. These data suggest that pharmacological AT(2) receptor stimulation may be an orally applicable future therapeutic approach in pathological settings requiring the reduction of interleukin 6 or inhibition of nuclear factor kappaB.
Assuntos
Ácido 8,11,14-Eicosatrienoico/metabolismo , Inflamação/metabolismo , NF-kappa B/metabolismo , Receptor Tipo 2 de Angiotensina/agonistas , Receptor Tipo 2 de Angiotensina/metabolismo , Animais , Núcleo Celular/metabolismo , Células Cultivadas , Quimiocina CCL2/genética , Quimiocina CCL2/metabolismo , Relação Dose-Resposta a Droga , Ensaio de Imunoadsorção Enzimática , Feminino , Fibroblastos/citologia , Humanos , Interleucina-6/genética , Interleucina-6/metabolismo , Camundongos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Sulfonamidas/farmacologia , Tiofenos/farmacologia , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
The renin-angiotensin system (RAS) plays a crucial role in cardiovascular and neuronal (patho-)physiology. The angiotensin AT2 receptor (AT2R) seems to counteract the proinflammatory, prohypertrophic and profibrotic actions of the AT1 receptor. Recently, we identified a novel protein, termed "AT2R binding protein" (ATBP/ATIP) which seems essential for AT2R-mediated growth inhibition. Poly(ADP-ribose) polymerase-1 (PARP-1) can act as a nuclear integrator of angiotensin II-mediated cell signalling, and has been implicated in the pathogenesis of cardiovascular and neuronal disease. In this study, promoters of human AT2R and ATIP1 were cloned and two transcriptional start sites in the ATIP1 promoter were identified whereas only one was detected in the AT2R promoter. Promoter assays indicated that the exon 1-intron 1 region of AT2R is necessary and sufficient for AT2R promoter activity. Inverse cloning experiments indicated that this regulatory region is a promoter but not an enhancer element implicating (a) further start site(s) in this region. Consistently, the exon 1-intron 1 region of AT2R was shown to tether the basal transcriptional machinery. Overexpression, pharmacological inhibition and ablation of PARP demonstrated that PARP-1 activates the ATIP1 gene but represses the AT2R on promoter and mRNA levels in vitro, and in brain tissue in vivo. Additional experiments indicated that AT2R activation does not modulate PARP-1 transcript levels but increases AT2R promoter activity, thereby creating a positive feedback mechanism. Our results demonstrate that PARP-1 acts as novel node within the RAS network based on its ability to regulate downstream targets such as AT2R and its adapter protein ATBP.
Assuntos
Regulação da Expressão Gênica , Poli(ADP-Ribose) Polimerases/fisiologia , Receptor Tipo 2 de Angiotensina/genética , Linhagem Celular Tumoral , Humanos , Proteínas de Membrana Transportadoras , RNA Mensageiro , Transcrição GênicaRESUMO
Cap-independent internal initiation of translation occurs on a number of viral and cellular mRNAs and is directed by internal ribosome entry site (IRES) elements. Rhopalosiphum padi virus (RhPV) is a member of the Dicistroviridae. These viruses have single-stranded, positive-sense RNA genomes that contain two open reading frames, both preceded by IRES elements. Previously, the activity of the RhPV 5' UTR IRES has been demonstrated in mammalian, Drosophila and wheat germ in vitro translation systems. It is now shown that this IRES also functions within Spodoptera frugiperda (Sf21) cells which are widely used in the baculovirus expression system, and in a novel Sf21 cell-based lysate system. Inclusion of the RhPV IRES in a dicistronic reporter mRNA transcript increased translation of the second cistron 23-fold within Sf21 cells. In contrast, the encephalomyocarditis virus IRES was inactive in both systems. The RhPV IRES therefore has the potential to be utilized in insect cell expression systems.
