Sleep-promoting molecule found in flies
Even the humble fruit fly needs sleep. Toda et al. screened ∼12,000 fruit fly lines and identified a single sleep-promoting molecule encoded by a gene they named nemuri (Japanese for “sleep,” abbreviated nur) (see the Perspective by Oikonomou and Prober). NEMURI (or NUR) is an antimicrobial peptide secreted from neurons that also promotes sleep. Overexpression of NUR helps flies survive a bacterial infection, and increased sleep helps in fighting infection; thus, NUR mediates a two-pronged strategy. Secretion of NUR also appears to underlie the sleepiness observed in sleep-deprived flies.
Abstract
Sleep remains a major mystery of biology. In particular, little is known about the mechanisms that account for the drive to sleep. In an unbiased screen of more than 12,000 Drosophila lines, we identified a single gene, nemuri, that induces sleep. The NEMURI protein is an antimicrobial peptide that can be secreted ectopically to drive prolonged sleep (with resistance to arousal) and to promote survival after infection. Loss of nemuri increased arousability during daily sleep and attenuated the acute increase in sleep induced by sleep deprivation or bacterial infection. Conditions that increase sleep drive induced expression of nemuri in a small number of fly brain neurons and targeted it to the sleep-promoting, dorsal fan-shaped body. We propose that NEMURI is a bona fide sleep homeostasis factor that is particularly important under conditions of high sleep need; because these conditions include sickness, our findings provide a link between sleep and immune function.
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