All creatures great and small, including fruitflies, need sleep. Researchers have surmised that sleep – in any species -- is necessary for repairing proteins, consolidating memories, and removing wastes from cells. But, really, sleep is still a great mystery.

The timing of when we sleep versus are awake is controlled by cells in tune with circadian rhythms of light and dark. Most of the molecular components of that internal clock have been worked out. On the other hand, how much we sleep is regulated by another process called sleep homeostasis, however little is known about its molecular basis.

In a study published in eLIFE, Amita Sehgal, PhD, professor of Neuroscience at the Perelman School of Medicine, University of Pennsylvania, and colleagues, report a new protein involved in the homeostatic regulation of sleep in the fruitfly, Drosophila. Sehgal is also an investigator with the Howard Hughes Medical Institute (HHMI).

The researchers conducted a screen of mutant flies to identify short-sleeping individuals and found one, which they dubbed redeye. These mutants show a severe reduction in the amount of time they slumber, sleeping only half as long as normal flies. While the redeye mutants were able to fall asleep, they would wake again in only a few minutes.

The team found that the redeye gene encodes a subunit of the nicotinic acetylcholine receptor. This type of acetylcholine receptor consists of multiple protein subunits, which form an ion channel in the cell membrane, and, as the name implies, also binds to nicotine.  Although acetylcholine signaling -- and cigarette smoking -- typically promote wakefulness, the particular subunit studied in the eLIFE paper is required for sleep in Drosophila.

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