Lysosomal enzyme activity during aging in Drosophila melanogaster

What do we mean by "aging"? Questions and perspectives revealed by studies in Drosophila

What is the nature of aging, and how best can we study it? Here, using a series of questions that highlight differing perspectives about the nature of aging, we ask how data from Drosophila melanogaster at the organismal, tissue, cellular, and molecular levels shed light on the complex interactions among the phenotypes associated with aging. Should aging be viewed as an individual's increasing probability of mortality over time or as a progression of physiological states? Are all age-correlated changes in physiology detrimental to vigor or are some compensatory changes that maintain vigor? Why do different age-correlated functions seem to change at different rates in a single individual as it ages? Should aging be considered as a single, integrated process across the scales of biological resolution, from organismal to molecular, or must we consider each level of biological scale as a separate, distinct entity? Viewing aging from these differing perspectives yields distinct but complementary interpretations about the properties and mechanisms of aging and may offer a path through the complexities related to understanding the nature of aging.

Age-related endolysosome dysfunction in the rat urothelium

Lysosomal dysfunction is associated with a number of age-related pathologies that affect all organ systems. While much research has focused on neurodegenerative diseases and aging-induced changes in neurons, much less is known about the impact that aging has on lower urinary tract function. Our studies explored age-dependent changes in the content of endo-lysosomal organelles (i.e., multivesicular bodies, lysosomes, and the product of their fusion, endolysosomes) and age-induced effects on lysosomal degradation in the urothelium, the epithelial tissue that lines the inner surface of the bladder, ureters, and renal pelvis. When examined by transmission electron microscopy, the urothelium from young adult rats (~3 months), mature adult rats (~12 months), and aged rats (~26 months old) demonstrated a progressive age-related accumulation of aberrantly large endolysosomes (up to 7μm in diameter) that contained undigested content, likely indicating impaired degradation. Stereological analysis confirmed that aged endolysosomes occupied approximately 300% more volume than their younger counterparts while no age-related change was observed in multivesicular bodies or lysosomes. Consistent with diminished endolysosomal degradation, we observed that cathepsin B activity was significantly decreased in aged versus young urothelial cell lysates as well as in live cells. Further, the endolysosomal pH of aged urothelium was higher than that of young adult (pH 6.0 vs pH 4.6). Our results indicate that there is a progressive decline in urothelial endolysosomal function during aging. How this contributes to bladder dysfunction in the elderly is discussed.

Structure-function relationships of acid ribonucleases: lysosomal, vacuolar, and periplasmic enzymes

It is surprising that only relatively recently has attention been directed to the characterization of the properties of acid ribonucleases (RNases), leading to some understanding of their biochemistry and their functional roles. The present review summarizes current progress in this field under the following general topics: (1) the wide distribution of acid RNases in organisms from viruses to animals; (2) recent findings concerning their primary and three-dimensional structure; (3) the structure-function relationship of acid RNases, with a fungal RNase from Rhizopus niveus as a model enzyme; (4) the unique localization of acid RNases in the periplasm of bacteria, vacuoles in plants, and lysosomes of animals and protozoa; and (5) the diversity of physiological roles, depending on the organism, such as self-incompatibility factors and defense proteins in some plants, the surface protein of an animal virus related to pathogenicity, and possible relationship to human cancer.

Decline in synthesis of elongation factor one (EF-1) precedes the decreased synthesis of total protein in aging Drosophila melanogaster

The decrease in the rate of protein synthesis in aging adult Drosophila melanogaster was found previously to be due, to a great extent, to a drop in the rate of peptide chain elongation, and principally to lowered activity of elongation factor one (EF-1). This decrease does not appear to be caused by appearance of an inhibitor of peptide chain elongation. Instead, the synthesis of EF-1 declines markedly early in adult life. This decrease is followed by lowered activity of EF-1 and by a drop in the synthesis of most of the cellular proteins.

Decreased rates of protein synthesis by cell-free preparations from different organs of aging mice

Protein synthetic activity was determined in postmitochondrial preparations from heart, brain, kidney, liver and skeletal muscle of 5-26-month-old female C57B1/6J mice. An age-dependent decrease in the rate of protein synthesis was exhibited by all preparations except heart muscle. A 65% decrease in translational rate was found in liver, with the greatest decrease appearing after 21 months. Translation in the brain preparation declined little during the first 20 months, but dropped 33% between 20 and 26 months. The kidney preparation decreased 30% during the first 16 months and 70% by the end of 26 months of age. Skeletal muscle showed an overall decrease of 85% in translation rate. In contrast, heart muscle decreased no more than 10% over the life-span of the mice. From these results, it appears that aging has a differential effect on protein synthesis in different kinds of cells.

Influence of procaine HCl on larval development, adult lifespan and acid phosphatase activity in Musca domestica L

By treating larvae of Musca domestica L. with 4 x 10(-4%) procaine HCl we could shorten larval development, decrease larval mortality and increase number of adult offspring. A high concentration of procaine HCl (0.4%) caused a prolongation of the larval development, a lower pupal weight and a decreased number of adult offspring, which are, in our opinion, indications of a toxic effect. The effects of procaine HCl on ageing and acid phosphatase activity are not so clear. The distribution of subpopulations in a population and the correlation with acid phosphatase activity during adult lifespan are discussed.

Progressive reduction in protein synthesis during involution and aging of the mouse thymus

Total proteolytic activity and protein synthesis were measured in cell-free extracts of the thymus during its involution in 1-30-week-old C57Bl/6J mice, and in 10-, 12-, 14-, and 24-month-old adult mice of the same strain. The mean specific activity of the proteolytic enzymes exhibited no significant change during involution or throughout the mean life-span of the animals. In contrast, the rate of protein synthesis decreased rapidly during involution, and continued to decrease at a slower rate during aging of the mice.

Effects of age on the post-initiation stages of protein synthesis

The peptide chain elongation stage of protein synthesis in Drosophila melanogaster was found to decrease markedly with age. The decrease paralleled the age-related decrease in overall protein synthesis. In contrast, the termination stage showed little decrease until the organisms were very old. Of the three reactions that comprise peptide chain elongation, the binding of aminoacyl-tRNA to ribosomes decreased greatly with age, and the decrease paralleled that of peptide chain elongation and of overall protein synthesis. The peptidyl transfer reaction decreased moderately, and the translocation reaction exhibited no measurable decrease with age. Thus, decreased binding of aminoacyl-tRNA to ribosomes appeared to be a major contributor to the age-related decreases in peptide chain elongation and overall protein synthesis.