Age-Related Unstructured Spike Patterns and Molecular Localization in Drosophila Circadian Neurons

Abstract

Aging decreases sleep quality by disrupting the molecular machinery that regulates the circadian rhythm. However, we do not fully understand the mechanism that underlies this process. In Drosophila, sleep quality is regulated by precisely timed patterns of spontaneous firing activity in posterior DN1 (DN1p) circadian clock neurons. How aging affects the physiological function of DN1p neurons is unknown. In this study, we found that aging altered functional parameters related to neural excitability and disrupted patterned spike sequences in DN1p neurons during nighttime. We also characterized age-associated changes in intrinsic membrane properties related to spike frequency adaptations and synaptic properties, which may account for the unstructured spike patterns in aged DN1p neurons. Because Slowpoke binding protein (SLOB) and the Na+/K+ ATPase β subunit (NaKβ) regulate clock-dependent spiking patterns in circadian networks, we compared the subcellular organization of these factors between young and aged DN1p neurons. Young DN1p neurons showed circadian cycling of HA-tagged SLOB and myc-tagged NaKβ targeting the plasma membrane, whereas aged DN1p neurons showed significantly disrupted subcellular localization patterns of both factors. The distribution of SLOB and NaKβ signals also showed greater variability in young vs. aged DN1p neurons, suggesting aging leads to a loss of actively formed heterogeneity for these factors. These findings showed that aging disrupts precisely structured molecular patterns that regulate structured neural activity in the circadian network, leading to age-associated declines in sleep quality. Thus, it is possible to speculate that a recovery of unstructured neural activity in aging clock neurons could help to rescue age-related poor sleep quality.

Age‐regulated cycling metabolites are relevant for behavior

“…With aging, PDF expression decreases in the s‐LNVs and their dorsal projections; and, overexpression of PDF in aged flies can rescue locomotor rhythm deficits (Vaccaro et al., 2017 ). Additionally, the daily remodeling of PDF + axon terminals is attenuated with age (Nguyen et al., 2022 ). Thus, aging impacts both G6PD and PDF + neurons, leading us to ask whether overexpression of G6PD in PDF + clock neurons impacts circadian rhythms of locomotor activity and sleep.…”

Research progress of drosophila biological clock genes involved in sleep regulation

“…After the heterodimers of clik and CYC proteins enter into the nucleus, they bind to the E. box element on period gene and timeless gene, activating the transcription, thereby regulating the per/tim feedback loop. At night, the PER-TIM protein heterodimer enters the nucleus and binds to the CLK-CYC protein heterodimer, inhibiting the role of the CLK-CYC heterodimer; by the time light appears (starting during the day), the PER-TIM protein heterodimer breaks down, and the CLK-CYC protein heterodimer reacts, continuing the feedback cycle the next day (second round) [6,9,10,16].…”