Loss of DmGluRA exacerbates age-related sleep disruption and reduces lifespan

Genetic and Pharmacological Inhibition of Metabotropic Glutamate Receptor Signalling Extends Lifespan in Drosophila

Invertebrate models have been instrumental in advancing our understanding of the molecular mechanisms of ageing. The isolation of single gene mutations that both extend lifespan and improve age-related health have identified potential targets for therapeutic intervention to alleviate age-related morbidity. Here, we find that genetic loss of function of the G protein-coupled metabotropic glutamate receptor (DmGluRA) in Drosophila extends the lifespan of female flies. This longevity phenotype was accompanied by lower basal levels of oxidative stress and improved stress tolerance, and differences in early-life behavioural markers. Gene expression changes in DmGluRA mutants identified reduced ribosome biogenesis, a hallmark of longevity, as a key process altered in these animals. We further show that the pro-longevity effects of reduced DmGluRA signalling are dependent on the fly homologue of Fragile X Mental Retardation Protein (FMRP), an important regulator of ribosomal protein translation. Importantly, we can recapitulate lifespan extension using a specific pharmacological inhibitor of mGluR activity. Hence, our study identifies metabotropic glutamate receptors as potential targets for age-related therapeutics.

The Glutamate-gated Chloride Channel Facilitates Sleep by Enhancing the Excitability of Two Pairs of Neurons in the Ventral Nerve Cord of Drosophila

Sleep, an essential and evolutionarily conserved behavior, is regulated by numerous neurotransmitter systems. In mammals, glutamate serves as the wake-promoting signaling agent, whereas in Drosophila, it functions as the sleep-promoting signal. However, the precise molecular and cellular mechanisms through which glutamate promotes sleep remain elusive. Our study reveals that disruption of glutamate signaling significantly diminishes nocturnal sleep, and a neural cell-specific knockdown of the glutamate-gated chloride channel (GluClα) markedly reduces nocturnal sleep. We identified two pairs of neurons in the ventral nerve cord (VNC) that receive glutamate signaling input, and the GluClα derived from these neurons is crucial for sleep promotion. Furthermore, we demonstrated that GluClα mediates the glutamate-gated inhibitory input to these VNC neurons, thereby promoting sleep. Our findings elucidate that GluClα enhances nocturnal sleep by mediating the glutamate-gated inhibitory input to two pairs of VNC neurons, providing insights into the mechanism of sleep promotion in Drosophila.

Enhanced memory despite severe sleep loss in Drosophila insomniac mutants

Sleep is crucial for cognitive functions and life span across species. While sleep homeostasis and cognitive processes are linked through cellular and synaptic plasticity, the signaling pathways connecting them remain unclear. Here, we show that Drosophila insomniac (inc) short sleep mutants, which lack an adaptor protein for the autism-associated Cullin-3 ubiquitin ligase, exhibited enhanced Pavlovian aversive olfactory learning and memory, unlike other sleep mutants with normal or reduced memory. Through a genetic modifier screen, we found that a mild reduction of Protein Kinase A (PKA) signaling specifically rescued the sleep and longevity phenotypes of inc mutants. However, this reduction further increased their excessive memory and mushroom body overgrowth. Since inc mutants displayed higher PKA signaling, we propose that inc loss-of-function suppresses sleep via increased PKA activity, which also constrains the excessive memory of inc mutants. Our data identify a signaling cascade for balancing sleep and memory functions, and provide a plausible explanation for the sleep phenotypes of inc mutants, suggesting that memory hyperfunction can provoke sleep deficits.

Small-molecule screening in aged Drosophila identifies mGluR as a regulator of age-related sleep impairment

As a normal physiological phenomenon, aging has a significant impact on sleep. Aging leads to sleep impairment, including sleep loss, fragmented sleep, and a lower arousal threshold, leading to various diseases. Because sleep regulates memory consolidation, age-dependent sleep impairment also affects memory. However, the mechanisms underlying age-related sleep dysregulation and its impact on memory remain unclear. Using male and female Drosophila as a model, which possesses sleep characteristics similar to those of mammals and exhibits age-dependent sleep impairment, we performed small-molecule screening to identify novel regulators of age-dependent decline in sleep. The screening identified 3,3'-difluorobenzaldazine (DFB), a positive allosteric modulator of the metabotropic glutamate receptor (mGluR) 5, as a novel sleep-promoting compound in aged flies. We found that mutant flies of mGluR, a single mGluR gene in Drosophila, and decreased mGluR expression had significant impairment in sleep and memory due to olfactory conditioning. The decreased sleep phenotype in the mGluR mutants was not promoted by DFB, suggesting that the effects of DFB on age-dependent sleep impairment are dependent on mGluR. Although aging decreases the expression of mGluR and the binding scaffold proteins Homer and Shank, the transient overexpression of mGluR in neurons improves sleep in both young and aged flies. Overall, these findings indicate that age-dependent decreased expression or function of mGluR impairs sleep and memory in flies, which could lead to age-related sleep and memory impairment.

A brain-wide form of presynaptic active zone plasticity orchestrates resilience to brain aging in Drosophila

The brain as a central regulator of stress integration determines what is threatening, stores memories, and regulates physiological adaptations across the aging trajectory. While sleep homeostasis seems to be linked to brain resilience, how age-associated changes intersect to adapt brain resilience to life history remains enigmatic. We here provide evidence that a brain-wide form of presynaptic active zone plasticity ("PreScale"), characterized by increases of active zone scaffold proteins and synaptic vesicle release factors, integrates resilience by coupling sleep, longevity, and memory during early aging of Drosophila. PreScale increased over the brain until mid-age, to then decreased again, and promoted the age-typical adaption of sleep patterns as well as extended longevity, while at the same time it reduced the ability of forming new memories. Genetic induction of PreScale also mimicked early aging-associated adaption of sleep patterns and the neuronal activity/excitability of sleep control neurons. Spermidine supplementation, previously shown to suppress early aging-associated PreScale, also attenuated the age-typical sleep pattern changes. Pharmacological induction of sleep for 2 days in mid-age flies also reset PreScale, restored memory formation, and rejuvenated sleep patterns. Our data suggest that early along the aging trajectory, PreScale acts as an acute, brain-wide form of presynaptic plasticity to steer trade-offs between longevity, sleep, and memory formation in a still plastic phase of early brain aging.

G protein-coupled receptors that influence lifespan of human and animal models

Humanity has always sought to live longer and for this, multiple strategies have been tried with varying results. In this sense, G protein-coupled receptors (GPCRs) may be a good option to try to prolong our life while maintaining good health since they have a substantial participation in a wide variety of processes of human pathophysiology and are one of the main therapeutic targets. In this way, we present the analysis of a series of GPCRs whose activity has been shown to affect the lifespan of animal and human models, and in which we put a special interest in describing the molecular mechanisms involved. Our compilation of data revealed that the mechanisms most involved in the role of GPCRs in lifespan are those that mimic dietary restriction, those related to insulin signaling and the AMPK and TOR pathways, and those that alter oxidative homeostasis and severe and/or chronic inflammation. We also discuss the possibility of using agonist or antagonist drugs, depending on the beneficial or harmful effects of each GPCR, in order to prolong people's lifespan and healthspan.