The prion diseases are neurodegenerative conditions, transmissible by inoculation, and in some cases inherited as an autosomal dominant disorder. They include Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. The prion consists principally of a post-translationally modified form of a host-encoded glycoprotein (PrPC), designated PrPSc (ref. 1); the normal cellular function of PrPC is, however, unknown. Although PrP is highly conserved among mammals and widely expressed in early embryogenesis, mice homozygous for disrupted PrP genes appear developmentally and behaviourally normal. PrP is a protein anchored to the neuronal surface by glycosylphosphatidylinositol, suggesting a role in cell signalling or adhesion. Here we report that hippocampal slices from PrP null mice have weakened GABAA (gamma-aminobutyric acid type A) receptor-mediated fast inhibition and impaired long-term potentiation. This impaired synaptic inhibition may be involved in the epileptiform activity seen in Creutzfeldt-Jakob disease and we argue that loss of function of PrPC may contribute to the early synaptic loss and neuronal degeneration seen in these diseases.

Sleep is an essential process conserved from flies to humans. The importance of sleep is underscored by its tight homeostatic control. Here, through a forward-genetic screen, we identify a novel gene, sleepless, required for sleep in Drosophila. sleepless encodes a brain-enriched, glycosylphosphatidylinositol-anchored protein. Loss of SLEEPLESS protein causes an extreme (>80%) reduction in sleep. Furthermore, a moderate reduction in SLEEPLESS protein has minimal effects on baseline sleep, but markedly reduces recovery sleep following sleep deprivation. Genetic and molecular analyses reveal that quiver, a mutation that impairs Shaker-dependent K + current, is an allele of sleepless. Consistent with this finding, Shaker protein level is reduced in sleepless mutants. We propose that SLEEPLESS is a signaling molecule that connects sleep drive to lowered membrane excitability.Insufficient and poor quality sleep is an increasing problem in industrialized nations. Chronic sleep problems diminish quality of life, reduce workplace productivity, and contribute to fatal accidents (1). Although the biological needs fulfilled by sleep are unclear (2), they are likely to be important because sleep is conserved from flies to humans (3-7), and prolonged sleep deprivation can lead to lethality (8-10). Identifying mechanisms that control sleep may lead to novel approaches for improving sleep quality.Sleep is regulated by two main processes: circadian and homeostatic (11,12). The circadian clock regulates the timing of sleep, whereas the homeostatic mechanism controls sleep need. Homeostatic pressure to sleep increases with time spent awake and decreases with time spent asleep. Homeostatic control is thought to influence sleep under normal (baseline) conditions as well as recovery (rebound) sleep following deprivation. However, the molecular mechanisms underlying homeostatic regulation of sleep remain unclear.A powerful approach to unraveling a poorly understood biological process is to conduct unbiased genetic screens to identify novel molecules required for that process. The Drosophila model for sleep is well-suited for such an approach, which proved invaluable for elucidation of the molecular basis of the circadian clock. Although several Drosophila genes have been implicated in sleep regulation (for example, 13-15), only one of these, the gene encoding the Shaker (Sh) K + channel, was isolated as a result of a genetic screen (16). A mutation in this gene causes one of the shortest-sleeping phenotypes known, validating the use of screens and suggesting that control of membrane excitability is a critical requirement for # This manuscript has been accepted for publication in Science. This version has not undergone final editing. Please refer to the complete version of record at http://www.sciencemag.org/. Their manuscript may not be reproduced or used in any manner that does not fall within the fair use provisions of the

Sleep is a whole–organism phenomenon accompanied by global changes in neural activity. We previously identified SLEEPLESS (SSS) as a novel glycosylphosphatidyl–inositol–anchored protein required for sleep in Drosophila. Here, we demonstrate a critical role for SSS in regulating the sleep–modulating potassium channel, Shaker. SSS and Shaker exhibit similar expression patterns in the brain and specifically affect each other’s expression levels. sss mutants exhibit altered Shaker localization, reduced Shaker current density, and slower Shaker current kinetics. Transgenic expression of sss in sss mutants rescues defects in Shaker expression and activity cell–autonomously and also suggests that SSS functions in wake–promoting, cholinergic neurons. Importantly, in heterologous cells, SSS accelerates kinetics of Shaker currents and can be co–immunoprecipitated with Shaker, suggesting that SSS interacts with Shaker and modulates its activity. SSS is predicted to belong to the Ly–6/neurotoxin superfamily, suggesting a novel mechanism for regulation of neuronal excitability by endogenous toxin–like molecules.

We present a map at 21 Å resolution of clathrin assembled into cages with the endocytic adaptor complex, AP-2. The map was obtained by cryo-electron microscopy and single-particle reconstruction. It reveals details of the packing of entire clathrin molecules as they interact to form a cage with two nested polyhedral layers. The proximal domains of each triskelion leg depart from a cage vertex in a skewed orientation, forming a slightly twisted bundle with three other leg domains. Thus, each triskelion contributes to two connecting edges of the polyhedral cage. The clathrin heavy chains continue inwards under the vertices with local 3-fold symmetry, the terminal domains contributing to 'hook-like' features which form an intermediate network making possible contacts with the surface presented by the inner adaptor shell. A node of density projecting inwards from the vertex may correspond to the C-termini of clathrin heavy chains which form a protrusion on free triskelions at the vertex. The inter-subunit interactions visible in this map provide a structural basis for considering the assembly of clathrin coats on a membrane and show the contacts which will need to be disrupted during disassembly.