Summary: Scientists investigating the tiny roundworm Caenorhabditis elegans have identified an unexpected mechanism in which a single chemical signal both initiates sleep and terminates it. The neuropeptide FLP-11 binds to the receptor DMSR-1 on distinct neurons to silence wake-promoting cells or to self-inhibit the sleep neuron, functioning like a biological on-off switch for sleep.
This dual action not only controls when sleep begins but also helps determine how long it lasts. The discovery sheds light on fundamental sleep-regulating pathways and could guide future research into human sleep disorders such as insomnia and narcolepsy.
Key Facts:
- Single molecule, dual role: The neuropeptide FLP-11 both promotes and limits sleep in C. elegans by acting on different target neurons.
- Essential receptor: The G protein–coupled receptor DMSR-1 mediates FLP-11’s effects and is required for normal sleep behavior in the worm.
- Broader relevance: While studied in nematodes, this mechanism points to conserved principles of sleep regulation that may extend to other animals, including humans.
Source: TUD
People spend about a third of their lives asleep, yet many molecular details of how brains switch between sleep and wakefulness remain unclear.
A research team led by Prof. Henrik Bringmann at the Biotechnology Center (BIOTEC) of TU Dresden has revealed a new piece of this puzzle. Their work shows how one neurochemical functions as a compact switch that both triggers sleep and later stops it, balancing sleep onset and duration.
The findings, published in the journal Current Biology, relied on experiments in the model organism C. elegans. With its simple nervous system and a single sleep-active neuron, the worm provides a clear system for mapping molecular sleep pathways that are difficult to disentangle in more complex brains.
“Falling asleep is essential, but waking up is equally important,” says Prof. Bringmann, who directed the study. “Sleep-active neurons are known to control these transitions, but the downstream molecular steps that effect sleep onset and termination have been much harder to pin down.”
Unlike humans, which use many sleep-regulating neurons, C. elegans relies primarily on one sleep-active neuron called RIS. That simplicity enabled the team to trace how signals released from RIS control both sleep initiation and its cessation through specific molecular interactions.
Understanding these basic mechanisms matters because sleep disturbances such as insomnia and narcolepsy profoundly affect quality of life. Discovering conserved molecular functions in simple animals can point to targets for future research in human sleep biology.
One Molecule, Two Jobs
The researchers centered their investigation on the neuropeptide FLP-11. When the sleep-active RIS neuron becomes active, it secretes FLP-11. These neuropeptides act like signaling molecules that convey instructions to other neurons.
Using genetic screens and targeted manipulations, the team identified the receptor DMSR-1 as the primary mediator of FLP-11’s effects. Worms lacking DMSR-1 showed markedly reduced sleep, indicating the receptor’s essential role.
Crucially, DMSR-1 is expressed in multiple neuron types and produces different outcomes depending on its location. In cholinergic neurons that promote wakefulness, FLP-11 binding to DMSR-1 inhibits those wake-promoting cells, helping the animal enter sleep. Conversely, DMSR-1 is also present in the RIS neuron itself, where its activation reduces RIS activity and thereby terminates sleep.
“We discovered that FLP-11 acts on DMSR-1 in two distinct neuron classes,” explains Lorenzo Rossi, a PhD student who performed many of the experiments. “On one hand, it shuts down wake-promoting neurons to induce sleep; on the other, it provides negative feedback within the sleep neuron to stop sleep, effectively limiting sleep duration.”
This arrangement creates an efficient, compact system: a single neuropeptide triggers sleep and then self-limits its duration by acting on different cellular targets. The mechanism couples sleep onset with a built-in stop signal, avoiding excessively long sleep episodes.
A Universal Principle?
“Sleep episodes in C. elegans are brief—about 20 minutes—but many molecular players in sleep are conserved across species,” says Prof. Bringmann. “We cannot yet say whether an identical switch exists in humans, but the principle of a neuropeptide that both induces and self-inhibits sleep offers a promising lead for broader investigations of sleep regulation.”
About this sleep and neuroscience research news
Author: Magdalena Gonciarz
Source: TUD
Contact: Magdalena Gonciarz – TUD
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The neuropeptide FLP-11 induces and self-inhibits sleep through the receptor DMSR-1 in Caenorhabditis elegans” by Henrik Bringmann et al. Current Biology
Abstract
The neuropeptide FLP-11 induces and self-inhibits sleep through the receptor DMSR-1 in Caenorhabditis elegans
Sleep is triggered by activation of sleep-active neurons, which release neurotransmitters such as GABA and conserved RFamide neuropeptides to control sleep onset and wakefulness. How signals from sleep-active neurons both induce sleep and determine its duration has remained unclear. In C. elegans, the single sleep-active RIS neuron is essential for sleep and exerts its effects by releasing FLP-11.
This study identifies the G protein–coupled receptor DMSR-1 as the receptor that mediates FLP-11’s actions. Cell-specific knockdowns show that dmsr-1 promotes sleep through action in downstream cholinergic neurons; pharmacological data indicate that reducing cholinergic signaling is required for sleep. Expression of DMSR-1 in cholinergic neurons is necessary for core sleep functions, including protective gene expression and survival. In contrast, dmsr-1 in RIS provides negative feedback that limits RIS calcium activation and shortens sleep, thereby reducing protective gene expression and survival when active in RIS.
Together, these results show that DMSR-1 links sleep induction with a built-in sleep-stop signal. RFamide neuropeptide–GPCR signaling could underlie similar dual control mechanisms in other species, and self-inhibition of sleep-active neurons may be a conserved strategy to limit sleep duration.