Biology subjects

Levitan, E.

Publications and source records attributed to Levitan, E..

5 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↗

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↗

bioRxiv2022

Release of large synaptic DCV proteins is triggered by Ca2+-independent Rugose-localized complexin phosphorylation

Neuronal dense-core vesicles (DCVs) contain neuropeptides and much larger proteins that affect synaptic growth and plasticity. Rather than using full collapse exocytosis that is common in endocrine cells, DCVs at a native intact synapse, the Drosophila neuromuscular junction, release their contents via fusion pores formed by kiss and run exocytosis. Here fluorogen activating protein (FAP) imaging reveals the permeability range of synaptic DCV fusion pores and then shows that this constraint is circumvented by cAMP-induced extra fusions with dilating pores that result in DCV emptying. These Ca2+-independent full fusions require PKA-R2, a PKA phosphorylation site on the fusion clamp protein complexin and the acute presynaptic function of Rugose/Neurobeachin, a PKA-R2 anchor implicated in learning and autism. Therefore, localized Ca2+-independent cAMP signaling opens dilating fusion pores to release large cargo proteins that cannot pass through the narrower fusion pores that normally dominate spontaneous and Ca2+-evoked synaptic protein release. Hence, two independent exocytosis triggers (Ca2+ and cAMP) vary the composition of released proteins at the synapse by differentially adjusting DCV fusion pores.

neuroscience↗

bioRxiv2018

Particulate Matter fractions and kitchen characteristics in Sri Lankan households using solid fuel and LPG

IntroductionUse of solid fuel for cooking is a major source of household air pollution in developing countries. Of the many pollutants emitted during solid fuel combustion, Particulate Matter (PM)is considered to be one of the most hazardous pollutants. We monitored PM fractions emitted during solid fuel and Liquefied Petroleum Gas(LPG) combustion in kitchens of Sri Lankan households.\n\nMethodsHouseholds of children in a longitudinal study in Ragama, Sri Lanka was the study population. At the age of 36 months of children, a sample of households were visited and different aerodynamic diameters of PM (PM1, PM2.5, PM10) were monitored during the main cooking session for 3 hours. Basic characteristics of kitchen (e.g., availability of chimney, functionality of chimney, etc.) were assessed by a questionnaire. Cooking energy, other sources of household air pollution, size of open spaces in the kitchen (e.g., windows), etc. were assessed at the time of PM monitoring.\n\nResultsQuestionnaire was administered for mothers in 426 households. Out of them, 245 (57.5%)and 116 (27.2%) households used LPG and wood as the primary cooking fuel respectively. During the cooking period, PM2.5 concentrations of households uses only wood fuel and cook inside the main housing building were 344.1 g/m3(Inter Quartile Range(IQR) = 173.2-878.0g/m3), 88.7 g/m3(54.8- 179.2 g/m3); 91.7 g/m3 (56.0- 184.9 g/m3) and 115.1 g/m3(83.4 - 247.9 g/m3) in kitchen, sleeping room, living room and immediate outdoor respectively. Immediate outdoor PM2.5 concentrations in wood burning households was higher among households not having chimney (n = 8)compare to those having a chimney (n = 8) (245.9g/m3 (IQR = 72.5 - 641.7g/m3)) VS. (105.7g/m3 (83.4- 195.8g/m3)).Fuel type and stove type, availability of a chimney and their functional status, ratio between open space and total space of kitchen, PM2.5 concentration at the non-cooking time (i.e., baseline PM2.5concentration) were the determinants of PM2.5 in wood using kitchens during cooking period.\n\nConclusionsPM concentrations were higher in kitchen and other microenvironments of the households use wood for cooking as compared to LPG use for cooking. Immediate outdoor PM concentration was higher than the sleeping and living room PM concentrations. Several factors determine the PM2.5concentrationsduring the cooking including the fuel type.

epidemiology↗