Biology subjects

Klose, M. K.

Publications and source records attributed to Klose, M. K..

7 recordsLinked to original sources

bioRxiv2026

Adult Clock Neuron Somatic Neuropeptide Release and Cytonemes Regulate Sleep

Drosophila s-LNv clock neurons promote nighttime sleep by releasing the neuropeptide sNPF to activate sNPF receptors (sNPF-Rs) on l-LNv clock neurons. Behavior is controlled by synaptic transmission, but s-LNv and l-LNv neurons are not connected directly by chemical synapses. To investigate the basis of sNPF/sNPF-R communication between LNv neurons, the spread of sNPF was imaged in the adult brain. We report the daily midmorning burst of sNPF released from s-LNv terminals does not reach l-LNv neurons or s-LNv somata. Instead, sNPF released by the s-LNv soma late at night in response to sleep-promoting IP3 signaling reaches l-LNv somata, but not their terminals. In addition to communication by neuropeptide diffusion, analysis of fly connectomes revealed that adult s-LNv and l-LNv neurons form non-synaptic direct contacts mediated by cytonemes. Remarkably, genetically perturbing LNv neuron cytonemes alters sleep latency, but not nighttime sleep, the target of somatic sNPF release, or circadian behavior, which depends on PDF neuropeptide released by LNv terminals. Therefore, three distinct aspects of adult rhythmic behavior are produced by terminals, the soma and cytonemes, with the latter possibly acting via contacts that are not currently annotated in the connectome.

neuroscience↗

bioRxiv2025

Circadian Capture of Dense-Core Vesicles Rhythmically Boosts Presynaptic Neuropeptide Content in a Clock Neuron

Neuropeptide release by Drosophila sLNv clock neurons controls circadian behaviors and sleep. Remarkably, neuropeptide content in sLNv terminals is rhythmic with late-night accumulation occurring while the axon arbor is expanding in preparation for midmorning synaptic exocytosis of neuropeptide-containing dense-core vesicles (DCVs). Past studies showed increased synaptic neuropeptide content can be produced by delivery of more neuropeptide to terminals or activity-dependent capture of circulating DCVs. To distinguish between these mechanisms, neuropeptide-containing DCVs were imaged in the living brain explant. First, post-exocytosis DCV axonal transport and synaptic neuropeptide accumulation following retrograde transport inhibition show that sLNv DCVs circulate. Furthermore, anterograde transport to terminals is constant throughout the day demonstrating there is no increase in DCV delivery. Rather, capture of circulating DCVs produces the daily boost in terminal neuropeptide content. Remarkably, this capture occurs before the daily increase in Ca2+ spike activity and is also independent of concurrent IP3 signaling and daily axon arbor expansion. Finally, a per clock gene mutation inhibits rhythmic DCV capture. Thus, rather than participating in axonal plasticity or responding to Ca2+ signaling, capture of circulating DCVs in sLNv presynapses is increased by the molecular clock in anticipation of activity-induced release hours later.

cell biology↗

bioRxiv2025

Tissue-specific modulation of NADH consumption as an anti-aging intervention in Drosophila

Aging is characterized by extensive metabolic dysregulation. Redox coenzyme nicotinamide adenine dinucleotide (NAD) can exist in oxidized (NAD+) or reduced (NADH) states, which together form a key NADH/NAD+ redox pair. Total levels of NAD decline with age in a tissue-specific manner, thereby playing a significant role in the aging process. Supplementation with NAD precursors boosts total cellular NAD levels and provides some therapeutic benefits in human clinical trials. However, supplementation studies cannot determine tissue-specific effects of an altered NADH/NAD+ ratio. Here, we created transgenic Drosophila expressing a genetically encoded xenotopic tool LbNOX to directly manipulate the cellular NADH/NAD+ ratio. We found that LbNOX expression in Drosophila impacts both NAD(H) and NADP(H) metabolites in a sex-specific manner. LbNOX rescues neuronal cell death induced by the expression of mutated alpha-B crystallin in the Drosophila eye, a widely used system to study reductive stress. Utilizing LbNOX, we demonstrate that targeting redox NAD metabolism in different tissues may have drastically different outcomes, as the expression of LbNOX solely in the muscle is much more effective for rescuing paraquat-induced oxidative stress compared to whole-body expression. Excitingly, we demonstrate that perturbing NAD(P) metabolism in non-neuronal tissues is sufficient to rejuvenate sleep profiles in aged flies to a youthful state. In summary, we used xenotopic tool LbNOX to identify tissues and metabolic processes which benefited the most from the modulation of the NAD metabolism thereby highlighting important aspects of rebalancing the NAD and NADP pools, all of which can be translated into novel designs of NAD-related human clinical trials. Significance statementTotal levels of NAD decline with age in a tissue-specific manner, thereby playing a significant role in the aging process. Supplementation with NAD precursors boosts organismal NAD levels but cannot determine tissue-specific effects of altered NAD metabolism. Here, we created transgenic Drosophila expressing a genetically encoded xenotopic tool, LbNOX, to directly manipulate NAD metabolism. We demonstrate that targeting NAD metabolism in just one tissue may be more effective than altering whole-body metabolism and can reverse some aging-related manifestations in a sex-specific manner. We anticipate that our work will define the tissues that benefit the most from targeting NAD metabolism and aid in designing better human clinical trials.

synthetic biology↗

bioRxiv2023

Activity-dependent capture of neuropeptide vesicles prepares clock neuron synapses for daily release

Drosophila sLNv clock neurons release the co-packaged neuropeptides PDF and sNPF to regulate circadian behaviors (e.g., morning anticipation) and nighttime sleep1-3. Previous studies of membrane potential and cytoplasmic Ca2+ at the soma suggested that sLNv neuron activity peaks at night4,5, but exocytosis of neuropeptide-containing dense-core vesicles (DCVs) at their terminals peaks hours later at midmorning6. To resolve the basis of the timing mismatch between somatic physiology and terminal exocytosis, recently developed probes were used to measure daily rhythms in sLNv neuron synaptic Ca2+ and sNPF release. Remarkably, at midmorning after soma Ca2+ has dropped, both Ca2+ spiking and clock-dependent native neuropeptide release peak in the distal terminals of the protocerebrum. Furthermore, Ca2+ in the soma and terminals differ in dependence on Ca2+ influx. Finally, synaptic DCV exocytosis requires Ca2+ spike activity at terminals that is not evident at the soma. These results lead to two striking conclusions. First, soma Ca2+ recording, which is the focus of many circuit studies, is not indicative of presynaptic Ca2+ and neuropeptide release in distal sLNv terminals. Second, daily clock- and activity-dependent sLNv terminal neuropeptide release occurs [~]9-18 hours in advance of known sLNv neuropeptide effects on nighttime sleep and morning behavior.

neuroscience↗

bioRxiv2021

Sleep promoting neurons remodel their response properties to calibrate sleep drive with environmental demands.

Falling asleep at the wrong time can place an individual at risk of immediate physical harm. However, not sleeping degrades cognition and adaptive behavior. To understand how animals match sleep need with environmental demands, we used live-brain imaging to examine the physiological response properties of the Drosophila sleep homeostat (dFB) following interventions that modify sleep (sleep deprivation, starvation, time-restricted feeding, memory consolidation). We report that dFB neurons can distinguish between different types of waking and can change their physiological response-properties accordingly. That is, dFB neurons are not simply passive components of a hard-wired circuit. Rather, the dFB neurons themselves can determine their response to the activity from upstream circuits. Finally, we show that the dFB appears to contain a memory trace of prior exposure to metabolic challenges induced by starvation or time-restricted feeding. Together these data highlight that the sleep homeostat is plastic and suggests an underlying mechanism.

neuroscience↗

bioRxiv2020

Independently Regulated Multi-compartment Neuropeptide Release from a Clock Neuron Controls Circadian Behavior

Neuropeptides control rhythmic behaviors, but the timing and location of their release within circuits is unknown. Here imaging in the brain shows that synaptic neuropeptide release by Drosophila clock neurons is diurnal, peaking at times of day that were not anticipated by prior electrical and Ca2+ data. Furthermore, hours before peak synaptic neuropeptide release, neuropeptide release occurs at the soma, a neuronal compartment that has not been implicated in peptidergic transmission. The timing disparity between release at the soma and terminals results from independent and compartmentalized mechanisms for daily rhythmic release: consistent with conventional electrical activity-triggered synaptic transmission, terminals require Ca2+ influx, while somatic neuropeptide release is triggered by the biochemical signal IP3. Upon disrupting the somatic mechanism, the rhythm of terminal release and locomotor activity period are unaffected, but the number of flies with rhythmic behavior and sleep-wake balance are reduced. These results support the conclusion that somatic neuropeptide release controls specific features of clock neuron dependent behaviors. Thus, compartment specific mechanisms within individual clock neurons produce temporally and spatially partitioned neuropeptide release to expand the peptidergic connectome underlying daily rhythmic behaviors. Significance StatementIt is believed that electrical activity simultaneously stimulates widespread release sites in single neurons to elicit neuropeptide dependent behaviors. However, optically detecting neuropeptide release in the intact brain shows that clock neurons release neuropeptides from different sites at different times of the day. This is possible because one neuronal compartment, the soma, uses biochemical signaling instead of electrical activity to evoke release. Disrupting somatic release affects specific features of circadian locomotor activity and sleep. Thus, neuropeptide release is elicited by independent triggers from distinct parts of clock neurons to engage different regions of behavior regulating circuitry. This strategy for expanding the connectome may be used for other neuropeptide dependent behaviors, such as feeding and pain perception.

neuroscience↗

bioRxiv2019

Sleep-drive reprograms clock neuronal identity through CREB-binding protein induced PDFR expression

Neuronal circuits can be re-modeled by Hebbian plasticity, synaptic scaling and, under some circumstances, activity-dependent respecification of cell-surface receptors. Although the impact of sleep on Hebbian plasticity and synaptic scaling are well studied, sleeps role in receptor respecification remains unclear. We demonstrate that high sleep-pressure quickly reprograms the Drosophila wake-promoting large-ventrolateral clock-neurons to express the Pigment Dispersing Factor receptor. The addition of this signaling input into the circuit is associated with increased waking and early mating success. The respecification of Pigment Dispersing Factor receptor in both young and adult large ventrolateral neurons requires two dopamine receptors and activation of the transcriptional regulator nejire (CREB-binding protein). These data identify receptor-respecification as an important mechanism to sculpt circuit function to match sleep levels with demand.

cell biology↗