title: SLEEPLESS is a bifunctional regulator of excitability and cholinergic synaptic transmission.
abstract: BACKGROUND
  Although sleep is conserved throughout evolution, the molecular basis of its control is still largely a mystery. We previously showed that the quiver/sleepless (qvr/sss) gene encodes a membrane-tethered protein that is required for normal sleep in Drosophila. SLEEPLESS (SSS) protein functions, at least in part, by upregulating the levels and open probability of Shaker (Sh) potassium channels to suppress neuronal excitability and enable sleep. Consistent with this proposed mechanism, loss-of-function mutations in Sh phenocopy qvr/sss-null mutants. However, sleep is more genetically modifiable in Sh than in qvr/sss mutants, suggesting that SSS may regulate additional molecules to influence sleep.
  
  
  RESULTS
  Here we show that SSS also antagonizes nicotinic acetylcholine receptors (nAChRs) to reduce synaptic transmission and promote sleep. Mimicking this antagonism with the nAChR inhibitor mecamylamine or by RNAi knockdown of specific nAChR subunits is sufficient to restore sleep to qvr/sss mutants. Regulation of nAChR activity by SSS occurs posttranscriptionally, since the levels of nAChR mRNAs are unchanged in qvr/sss mutants. Regulation of nAChR activity by SSS may in fact be direct, since SSS forms a stable complex with and antagonizes nAChR function in transfected cells. Intriguingly, lynx1, a mammalian homolog of SSS, can partially restore normal sleep to qvr/sss mutants, and lynx1 can form stable complexes with Shaker-type channels and nAChRs.
  
  
  CONCLUSIONS
  Together, our data point to an evolutionarily conserved, bifunctional role for SSS and its homologs in controlling excitability and synaptic transmission in fundamental processes of the nervous system such as sleep.
authors.affiliation: Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA.
authors.forename: Meilin
authors.initials: M
authors.lastname: Wu
authors.affiliation: Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093-0636, USA.
authors.forename: James E
authors.initials: JE
authors.lastname: Robinson
authors.affiliation: Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093-0636, USA; Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA 92093-0636, USA; Center for Chronobiology, University of California, San Diego, La Jolla, CA 92093-0636, USA. Electronic address: wjoiner@ucsd.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Joiner
mesh_terms: D000818:Animals; D059329:Cholinergic Neurons / Q000502:physiology*; D029721:Drosophila Proteins / Q000502:physiology*; D004331:Drosophila melanogaster; D055785:Gene Knockdown Techniques; D008565:Membrane Proteins / Q000502:physiology*; D024521:Mushroom Bodies / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology; D051637:Shaker Superfamily of Potassium Channels / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; D008565:Membrane Proteins; C530371:Qvr protein, Drosophila; D011978:Receptors, Nicotinic; D051637:Shaker Superfamily of Potassium Channels