No abstract

Swiss cheese (sws) mutant flies develop normally during larval life but show age-dependent neurodegeneration in the pupa and adult and have reduced life span. In late pupae, glial processes form abnormal, multilayered wrappings around neurons and axons. Degeneration first becomes evident in young flies as apoptosis in single scattered cells in the CNS, but later it becomes severe and widespread. In the adult, the number of glial wrappings increases with age. The sws gene is expressed in neurons in the brain cortex. The conceptual 1425 amino acid protein shows two domains with homology to the regulatory subunits of protein kinase A and to conceptual proteins of yet unknown function in yeast, worm, and human. Sequencing of two sws alleles shows amino acid substitutions in these two conserved domains. It is suggested that the novel SWS protein plays a role in a signaling mechanism between neurons and glia that regulates glial wrapping during development of the adult brain.

Neuronal Ca 2؉ signals can affect excitability and neural circuit formation. Ca 2؉ signals are modified by Ca 2؉ flux from intracellular stores as well as the extracellular milieu. However, the contribution of intracellular Ca 2؉ stores and their release to neuronal processes is poorly understood. Here, we show by neuron-specific siRNA depletion that activity of the recently identified store-operated channel encoded by dOrai and the endoplasmic reticulum Ca 2؉ store sensor encoded by dSTIM are necessary for normal flight and associated patterns of rhythmic firing of the flight motoneurons of Drosophila melanogaster. Also, dOrai overexpression in flightless mutants for the Drosophila inositol 1,4,5-trisphosphate receptor (InsP3R) can partially compensate for their loss of flight. Ca 2؉ measurements show that Orai gain-of-function contributes to the quanta of Ca 2؉ -release through mutant InsP3Rs and elevates store-operated Ca 2؉ entry in Drosophila neurons. Our data show that replenishment of intracellular store Ca 2؉ in neurons is required for Drosophila flight.calcium homeostasis ͉ flight patterns ͉ inositol 1,4,5-trisphosphate receptor ͉ sarco-endoplasmic reticulum-associated Ca 2ϩ ATPase ͉ STIM S everal aspects of neuronal function are regulated by ionic calcium (Ca 2ϩ ). Specific attributes of a Ca 2ϩ ''signature'' such as amplitude, duration, and frequency of the signal can determine the morphology of a neural circuit by affecting the outcome of cell migration, the direction taken by a growth-cone, dendritic development, and synaptogenesis (1). Ca 2ϩ signals also determine the nature and strength of neural connections in a circuit by specifying neurotransmitters and receptors (2). Most of these Ca 2ϩ signals have been attributed to the entry of extracellular Ca 2ϩ through voltage-operated channels or ionotropic receptors. However, other components of the ''Ca 2ϩ tool-kit'' coupled to Ca 2ϩ release from intracellular Ca 2ϩ stores are also present in neurons. These molecules include the store-operated Ca 2ϩ (SOC) channel, encoded by the Orai gene, identified recently in siRNA screens for molecules that reduce or abolish Ca 2ϩ influx from the extracellular milieu after intracellular Ca 2ϩ store depletion (3-5). Several reports have confirmed its identity as the pore forming subunit of the Ca 2ϩ -release activated Ca 2ϩ (CRAC) channel (6-8). Activation of this CRAC channel is mediated by the endoplasmic reticulum (ER) resident protein STIM (stromal interaction molecule), also identified in an RNAi screen for molecules that regulate SOC influx (9, 10). STIM senses the drop in ER Ca 2ϩ levels, and interacts with Orai by a mechanism which is only just being understood (11). Orai and STIM function in conjunction with the sarco-endoplasmic reticular Ca 2ϩ -ATPase pump (SERCA) to maintain ER store Ca 2ϩ and basal Ca 2ϩ . The importance of intracellular Ca 2ϩ homeostasis and SOC entry (E) in neural circuit formation and in neuronal function and physiology remains to be elucidated.Here, we report how Orai and STIM me...