Caspase inhibition in select olfactory neurons restores innate attraction behavior in aged Drosophila

Sensory and cognitive performance decline with age. Neural dysfunction caused by nerve death in senile dementia and neurodegenerative disease has been intensively studied; however, functional changes in neural circuits during the normal aging process are not well understood. Caspases are key regulators of cell death, a hallmark of age-related neurodegeneration. Using a genetic probe for caspase-3-like activity (DEVDase activity), we have mapped age-dependent neuronal changes in the adult brain throughout the lifespan of Drosophila. Spatio-temporally restricted caspase activation was observed in the antennal lobe and ellipsoid body, brain structures required for olfaction and visual place memory, respectively. We also found that caspase was activated in an age-dependent manner in specific subsets of Drosophila olfactory receptor neurons (ORNs), Or42b and Or92a neurons. These neurons are essential for mediating innate attraction to food-related odors. Furthermore, age-induced impairments of neural transmission and attraction behavior could be reversed by specific inhibition of caspase in these ORNs, indicating that caspase activation in Or42b and Or92a neurons is responsible for altering animal behavior during normal aging.This work was supported by grants from the Japan Society for the Promotion of Science and the Japan Ministry of Education, Culture, Sports, Science and Technology to TC and MMi, from the Uehara memorial foundation to TC, from NIH to JWW (DK092640), and from NIH to RLD (2R37 NS19904-30). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Age-Related Changes in Insulin-like Signaling Lead to Intermediate-Term Memory Impairment in Drosophila

Insulin and insulin-growth-factor-like signaling (IIS) plays important roles in the regulation of development, growth, metabolic homeostasis, and aging, as well as in brain functions such as learning and memory. The temporal-spatial role of IIS in learning and memory and its effect on age-dependent memory impairment remain unclear. Here, we report that intermediate-term memory (ITM), but not short-term memory (STM), in Drosophila aversive olfactory memory requires transient IIS during adulthood. The expression of Drosophila insulin-like peptide 3 (Dilp3) in insulin-producing cells and insulin receptor function in the fat body are essential for ITM. Although the expression of dilp3 decreases with aging, which is unique among dilp genes, the transient expression of dilp3 in aged flies enhances ITM. These findings indicate that ITM is systemically regulated by communication between insulin-producing cells and fat body and that age-dependent changes in IIS contribute to age-related memory impairment

Homeostatic Epithelial Renewal in the Gut Is Required for Dampening a Fatal Systemic Wound Response in Drosophila

Effective defense responses involve the entire organism. To maintain body homeostasis after tissue damage, a systemic wound response is induced in which the response of each tissue is tightly orchestrated to avoid incomplete recovery or an excessive, damaging response. Here, we provide evidence that in the systemic response to wounding, an apoptotic caspase pathway is activated downstream of reactive oxygen species in the midgut enterocytes (ECs), cells distant from the wound site, in Drosophila. We show that a caspase-pathway mutant has defects in homeostatic gut cell renewal and that inhibiting caspase activity in fly ECs results in the production of systemic lethal factors after wounding. Our results indicate that wounding remotely controls caspase activity in ECs, which activates the tissue stem cell regeneration pathway in the gut to dampen the dangerous systemic wound reaction

Genetic Evidence Linking Age-Dependent Attenuation of the 26S Proteasome with the Aging Process ▿ †

The intracellular accumulation of unfolded or misfolded proteins is believed to contribute to aging and age-related neurodegenerative diseases. However, the links between age-dependent proteotoxicity and cellular protein degradation systems remain poorly understood. Here, we show that 26S proteasome activity and abundance attenuate with age, which is associated with the impaired assembly of the 26S proteasome with the 19S regulatory particle (RP) and the 20S proteasome. In a genetic gain-of-function screen, we characterized Rpn11, which encodes a subunit of the 19S RP, as a suppressor of expanded polyglutamine-induced progressive neurodegeneration. Rpn11 overexpression suppressed the age-related reduction of the 26S proteasome activity, resulting in the extension of flies' life spans with suppression of the age-dependent accumulation of ubiquitinated proteins. On the other hand, the loss of function of Rpn11 caused an early onset of reduced 26S proteasome activity and a premature age-dependent accumulation of ubiquitinated proteins. It also caused a shorter life span and an enhanced neurodegenerative phenotype. Our results suggest that maintaining the 26S proteasome with age could extend the life span and suppress the age-related progression of neurodegenerative diseases

Caspase Inhibition in Select Olfactory Neurons Restores Innate Attraction Behavior in Aged <i>Drosophila</i>

<div><p>Sensory and cognitive performance decline with age. Neural dysfunction caused by nerve death in senile dementia and neurodegenerative disease has been intensively studied; however, functional changes in neural circuits during the normal aging process are not well understood. Caspases are key regulators of cell death, a hallmark of age-related neurodegeneration. Using a genetic probe for caspase-3-like activity (DEVDase activity), we have mapped age-dependent neuronal changes in the adult brain throughout the lifespan of <i>Drosophila</i>. Spatio-temporally restricted caspase activation was observed in the antennal lobe and ellipsoid body, brain structures required for olfaction and visual place memory, respectively. We also found that caspase was activated in an age-dependent manner in specific subsets of <i>Drosophila</i> olfactory receptor neurons (ORNs), Or42b and Or92a neurons. These neurons are essential for mediating innate attraction to food-related odors. Furthermore, age-induced impairments of neural transmission and attraction behavior could be reversed by specific inhibition of caspase in these ORNs, indicating that caspase activation in Or42b and Or92a neurons is responsible for altering animal behavior during normal aging.</p></div

DEVDase is activated in a subset of ORNs in an age-dependent manner.

<p>(A) Percentages of aged brains (45-days-old) with cPAPR signals are shown. mCD8::PARP::Venus expression by various <i>Or-Gal4</i> drivers revealed that DEVDase is activated in a subset of ORNs in an age-dependent manner. Number on each column indicates the number of brains examined. (B, C) Representative images of aged fly brains expressing mCD8::PARP::Venus by <i>Or42b-Gal4</i> (B) or <i>Or85a-Gal4</i> (C). Note that cPARP signal was frequently observed in the axons of Or42b neurons (B) while it was rare in axons of Or85a neurons (C). cPARP signal, mCD8::PARP::Venus expression, and nc82 staining are shown in magenta, green, and blue, respectively. Broken lines indicate outlines of ALs. Scale bar: 75 µm. Genotypes: (A) Or42b: <i>Or42b-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or92a: <i>Or92b-Gal4/UAS-mCD8::PARP::Venus;UAS-mCD8::PARP::Venus/+</i>. Or35a: <i>Or35a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or47b: <i>Or47b-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or22a: <i>Or22a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or85a: <i>Or85a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or67d: <i>Or67d-Gal4, yw/+;;UAS-mCD8::PARP::Venus/+</i>. Or42a: <i>Or42a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or47a: <i>Or47aGal4/+;UAS-mCD8::PARP::Venus/TM2 or TM6B</i>. Or43b: <i>Or43b-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or69a: <i>Or69a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or9a: <i>Or9a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>. Or67a: <i>Or67aGal4/+;UAS-mCD8::PARP::Venus/+</i>. Or59b: <i>Or59b-Gal4, w/+;UAS-mCD8::PARP::Venus/+;UAS-mCD8::PARP::Venus/+</i>. Or67b: <i>Or67b-Gal4/UAS-mCD8::PARP::Venus</i>. Or98a: <i>Or98aGal4/+;UAS-mCD8::PARP::Venus/+</i>. Or10a: <i>Or10a-Gal4/+;UAS-mCD8::PARP::Venus/TM2 or TM6B</i>. (B) <i>Or42b-Gal4/+;UAS-mCD8::PARP::Venus/+.</i> (C) <i>Or85a-Gal4/+;UAS-mCD8::PARP::Venus/+</i>.</p

Spatio-temporal activation of DEVDase in adult <i>Drosophila</i> brains.

<p>(A) DEVDase activity detection with mCD8::PARP::Venus. Human anti-cPARP antibodies specifically recognize the N-terminal amino acid sequences of Venus that are generated by the cleavage of mCD8::PARP::Venus. (B) Percentages of brain samples with any cPARP signal at each time point are shown. “n” indicates the number of brains examined. (C, D) cPARP signals in young fly brains (1-day-old). A brain with cPARP signal near midline and the subesophageal ganglia (SOG) (C) and only near midline, without intense signals in the SOG (D). Circles of broken lines are antennal lobes (ALs). cPARP signal and mCD8::PARP::Venus expression are shown in magenta and green, respectively. Scale bar: 50 µm. (E) Schematic drawing of a <i>Drosophila</i> adult brain. The regions outlined by broken lines are ALs and SOGs. The ellipsoid body (EB) is located on the dorsal side of the AL. OL: optic lobe. (F) Graph indicating the percentage of young brains with cPARP signals. Genotypes: (B–D, F) <i>elav-Gal4;;UAS-mCD8::PARP::Venus.</i></p

Stereotyped DEVDase activation in the AL and EB structures of aged <i>Drosophila</i> brains.

<p>(A, B, D, E) Representative aged brains (45-days-old) bearing cPARP signals (DEVDase activity) in the dorso-medial side of the AL (A), the EB structure (B), the mushroom body (MB) (D) and the local interneuron (LN) of the AL (E). mCD8::PARP::Venus was expressed in most postmitotic neurons (<i>elav-Gal4;;UAS-mCD8::PARP::Venus</i>). Circles of broken lines are ALs. cPARP signal and mCD8::PARP::Venus expression are shown in magenta and green, respectively. Scale bar: 75 µm. (C) Percentages of brains with cPAPR signal in the EB and AL at each time point are shown. “n” indicates the number of brains examined. Genotypes: (A–E) <i>elav-Gal4;;UAS-mCD8::PARP::Venus.</i></p