Aging is associated with loss of quality control in protein turnover. The ubiquitin-proteasome pathway is critical to this quality control process as it degrades mutated and damaged proteins. We identified a unique aging-dependent mechanism that contributes to proteasome dysfunction in Drosophila melanogaster. Our studies are the first to show that the major proteasome form in old (43-47 days old) female and male flies is the weakly active 20S core particle, while in younger (1-32 days old) flies highly active 26S proteasomes are preponderant. Old (43-47 days) flies of both genders also exhibit a decline (approximately 50%) in ATP levels, which is relevant to 26S proteasomes, as their assembly is ATP-dependent. The steep declines in 26S proteasome and ATP levels were observed at an age (43-47 days) when the flies exhibited a marked drop in locomotor performance, attesting that these are "old age" events. Remarkably, treatment with a proteasome inhibitor increases ubiquitinated protein levels and shortens the life span of old but not young flies. In conclusion, our data reveal a previously unknown mechanism that perturbs proteasome activity in "old-age" female and male Drosophila most likely depriving them of the ability to effectively cope with proteotoxic damages caused by environmental and/or genetic factors.

The Drosophila fushi tarazu (ftz) upstream element is an enhancer-like element that is required for the correct expression of fez in developing embryos and that directs transcription from a minimal promoter in a ftz-like seven-striped pattern. Using a deletion analysis, we have identified several independent c/s-regulatory elements in the upstream element. A distal enhancer directs fusion gene expression in seven stripes primarily in the mesoderm. A more complex proximal enhancer contains a mesodermally active element and a second element with which it interacts to generate seven stripes in the ectoderm. Striped expression directed by each enhancer is ftz-dependent, and each contains binding sites for purified ftz homeo domain. We suggest that ftz protein acts in combination with germ layer-restricted transcription factors directly and positively to regulate the transcription of its own gene. The development of a complex organism from a fertilized egg requires the differential expression of genetic information in a temporally and spatially restricted fashion. This differential expression is frequently regulated at the level of transcription initiation (for reviews, see Maniatis et al. 1987;Mitchell and Tjian 1989). In such cases, cis-acting DNA sequences mediate interactions between trans-acting protein factors and RNA polymerase II or the "general transcription machinery" to activate transcription. Promoter elements, located close to the transcription start site, are required for efficient initiation and positioning of the start site, whereas upstream regulatory elements or enhancers act to increase the rate of transcription from a given promoter. Enhancers are characterized by their abilities to (1) stimulate transcription over large and varying distances, (2) act in an orientation-independent fashion, and (3) stimulate transcription of heterologous promoters (Serfling et al. 1985). For both viral and cellular genes, discrete cisacting regulatory elements have been identified that direct transcription in a cell type-restricted fashion. Although some cell type-specific enhancers have been studied in detail (Atchison 1988), only a small number have been examined in their native cellular environments in transgenic animals (Posakony et al. 1985;Garabedian et al. 1986;Hammer et al. 1987; Pinkert et al. 1987; Johnson et al. 1989;Logan et al. 1989). Much of what we know about enhancer function comes from studies of viral model systems. Analysis of the wellcharacterized viral SV40 enhancers suggests that the basic building blocks of enhancers are short "enhansons" that correspond to the binding sites for transacting factors (Ondek et al. 1988}. Different enhancer motifs may be active in different cell types, suggesting that the availability of cell type-specific transcription factors may control the specificity of enhancer activation {Schirm et al. 1987). Given the complexity of promoter and enhancer elements, it is possible to construct a scenario in which transcriptional specificity is determined by the combinatoria...

SummaryIn all cells, protein degradation is a constant, ongoing process that is critical for cell survival and repair. The ubiquitin/proteasome pathway (UPP) is the major proteolytic pathway that degrades intracellular proteins in a regulated manner. It plays critical roles in many cellular processes and diseases. Disruption of the UPP is particularly relevant to pathophysiological conditions that provoke the accumulation of aberrant proteins, such as in aging as well as in a variety of neurodegenerative disorders including Alzheimer's and Parkinson's diseases. For unknown reasons, most of these neurodegenerative disorders that include familial and sporadic cases exhibit a late onset. It is possible that these neurodegenerative conditions exhibit a late onset because proteasome activity decreases with aging. Aging-dependent impairment in proteolysis mediated by the proteasome may have profound ramifications for cell viability. It can lead to the accumulation of modified, potentially toxic proteins in cells and can cause cell injury or premature cell death by apoptosis or necrosis. While it is accepted that aging affects UPP function, the question is why does aging cause a decline in regulated protein degradation by the UPP? Herein, we review some of the properties of the UPP and mechanisms mediating its age-dependent impairment. We also discuss the relevance of these findings leading to a model that proposes that UPP dysfunction may be one of the milestones of aging.

The immune response of the CNS is a defense mechanism activated upon injury to initiate repair mechanisms while chronic over-activation of the CNS immune system (termed neuroinflammation) may exacerbate injury. The latter is implicated in a variety of neurological and neurodegenerative disorders such as Alzheimer and Parkinson diseases, amyotrophic lateral sclerosis, multiple sclerosis, traumatic brain injury, HIV dementia, and prion diseases. Cyclooxygenases (COX-1 and COX-2), which are key enzymes in the conversion of arachidonic acid into bioactive prostanoids, play a central role in the inflammatory cascade. J2 prostaglandins are endogenous toxic products of cyclooxygenases, and because their levels are significantly increased upon brain injury, they are actively involved in neuronal dysfunction induced by pro-inflammatory stimuli. In this review, we highlight the mechanisms by which J2 prostaglandins (1) exert their actions, (2) potentially contribute to the transition from acute to chronic inflammation and to the spreading of neuropathology, (3) disturb the ubiquitin-proteasome pathway and mitochondrial function, and (4) contribute to neurodegenerative disorders such as Alzheimer and Parkinson diseases, and amyotrophic lateral sclerosis, as well as stroke, traumatic brain injury (TBI), and demyelination in Krabbe disease. We conclude by discussing the therapeutic potential of targeting the J2 prostaglandin pathway to prevent/delay neurodegeneration associated with neuroinflammation. In this context, we suggest a shift from the traditional view that cyclooxygenases are the most appropriate targets to treat neuroinflammation, to the notion that J2 prostaglandin pathways and other neurotoxic prostaglandins downstream from cyclooxygenases, would offer significant benefits as more effective therapeutic targets to treat chronic neurodegenerative diseases, while minimizing adverse side effects.