Chin-Sang, I. | bioRxiv Science

bioRxiv2026

Characterization of NPR-14 in the Regulation of Sleep-Like Behaviour in Caenorhabditis elegans

Sleep-like quiescence is an evolutionarily conserved state essential for physiological homeostasis; however, its dysregulation can lead to sleep disorders such as narcolepsy, which can be caused by abnormal neuropeptide signaling. In Caenorhabditis elegans, the G-protein-coupled receptor NPR-14 belongs to the orexin/allatotropin receptor family and has been proposed as a homolog of mammalian orexin receptors. Using npr-14 loss-of-function (lf) mutants, we demonstrate that NPR-14 promotes arousal and inhibits sleep-like quiescence. npr-14(lf) mutants exhibit prolonged quiescence, reduced locomotion, impaired sensory responses, and metabolic defects including elevated fat accumulation and decreased feeding and egg-laying. NPR-14 is expressed in ASH and ASI sensory neurons and in GABAergic DD, VD, and VC motor neurons, positioning it to modulate both sensory-motor integration and motor output directly. Genetic epistasis analysis revealed that NPR-14 functions upstream of EGL-4/protein kinase G (PKG): egl-4 loss-of-function suppressed the enhanced quiescence of npr-14 mutants, while egl-4 gain-of-function phenotypes were not enhanced by loss of npr-14. Caffeine treatment partially suppressed npr-14 mutant quiescence, suggesting convergence with adenosine-sensitive arousal pathways. These findings establish NPR-14 as a wake-promoting GPCR that inhibits EGL-4/PKG signalling to regulate quiescence and arousal. The NPR-14-EGL-4 axis suggests functional parallels to arousal regulation in other systems.

genetics↗

bioRxiv2018

A functional study of all 40 C. elegans insulin-like peptides

The human genome encodes ten insulin-like genes, whereas the C. elegans genome remarkably encodes forty insulin-like genes. The roles of insulin/insulin-like peptide ligands (INS) in C. elegans are not well understood. The functional redundancy of the forty INS genes makes it challenging to address their functions by using knock out strategies. Here, we individually overexpressed each of the forty ins genes pan-neuronally, and monitored multiple phenotypes including: L1 arrest life span, neuroblast divisions under L1 arrest, dauer formation and fat accumulation, as readouts to characterize the functions of each INS in vivo. Of the 40 INS peptides, we found functions for 35 INS peptides and functionally categorized each as agonists, antagonists or of pleiotropic function. In particular, we found that 9 of 16 agonistic INS peptides shortened L1 arrest life span and promoted neuroblast divisions during L1 arrest. Our study revealed that a subset of {beta}-class INS peptides that contain a distinct F peptide sequence are agonists. Our work is the first to categorize the structures of INS peptides and relate these structures to the functions of all forty INS peptides in vivo. Our findings will promote the study of insulin function on development, metabolism, and aging-related diseases.\n\nAuthor SummaryInsulin and insulin-like growth factors are found in all animals and regulate many physiological and developmental processes. The human genome has 10 insulin-like peptides including the well characterized insulin hormone. The nematode C. elegans has 40 insulin-like (INS) peptide genes. All 40 INS peptides have been knocked out but no single INS gene knock out resembles the loss of the C. elegans insulin receptor suggesting that the other INS peptides can compensate when one INS is lost. We have used a genetic approach to overexpress each of the 40 INS peptides in C. elegans and have identified in vivo function for 35 of the 40 INS peptides. Like the human insulin and IGF-1, C. elegans INS peptides are derived from a precursor protein and we have shown that INS peptides with an associated peptide called the F peptide are strong activators of the C. elegans insulin-like receptor. We also identified several INS peptides that inhibit the insulin-like receptor and these inhibitory INS peptides may have therapeutic potential.

genetics↗