The American Academy of Sleep Medicine (AASM) Sleep Apnea Definitions Task Force reviewed the current rules for scoring respiratory events in the 2007 AASM Manual for the Scoring and Sleep and Associated Events to determine if revision was indicated. The goals of the task force were (1) to clarify and simplify the current scoring rules, (2) to review evidence for new monitoring technologies relevant to the scoring rules, and (3) to strive for greater concordance between adult and pediatric rules. The task force reviewed the evidence cited by the AASM systematic review of the reliability and validity of scoring respiratory events published in 2007 and relevant studies that have appeared in the literature since that publication. Given the limitations of the published evidence, a consensus process was used to formulate the majority of the task force recommendations concerning revisions.The task force made recommendations concerning recommended and alternative sensors for the detection of apnea and hypopnea to be used during diagnostic and positive airway pressure (PAP) titration polysomnography. An alternative sensor is used if the recommended sensor fails or the signal is inaccurate. The PAP device flow signal is the recommended sensor for the detection of apnea, hypopnea, and respiratory effort related arousals (RERAs) during PAP titration studies. Appropriate filter settings for recording (display) of the nasal pressure signal to facilitate visualization of inspiratory flattening are also specified. The respiratory inductance plethysmography (RIP) signals to be used as alternative sensors for apnea and hypopnea detection are specified. The task force reached consensus on use of the same sensors for adult and pediatric patients except for the following: (1) the end-tidal PCO(2) signal can be used as an alternative sensor for apnea detection in children only, and (2) polyvinylidene fluoride (PVDF) belts can be used to monitor respiratory effort (thoracoabdominal belts) and as an alternative sensor for detection of apnea and hypopnea (PVDFsum) only in adults.The task force recommends the following changes to the 2007 respiratory scoring rules. Apnea in adults is scored when there is a drop in the peak signal excursion by ≥ 90% of pre-event baseline using an oronasal thermal sensor (diagnostic study), PAP device flow (titration study), or an alternative apnea sensor, for ≥ 10 seconds. Hypopnea in adults is scored when the peak signal excursions drop by ≥ 30% of pre-event baseline using nasal pressure (diagnostic study), PAP device flow (titration study), or an alternative sensor, for ≥ 10 seconds in association with either ≥ 3% arterial oxygen desaturation or an arousal. Scoring a hypopnea as either obstructive or central is now listed as optional, and the recommended scoring rules are presented. In children an apnea is scored when peak signal excursions drop by ≥ 90% of pre-event baseline using an oronasal thermal sensor (diagnostic study), PAP device flow (titration study), or an alternative sensor; and the event m...
BACE is a transmembrane protease with -secretase activity that cleaves the amyloid precursor protein (APP). After BACE cleavage, APP becomes a substrate for ␥-secretase, leading to release of amyloid- peptide (A), which accumulates in senile plaques in Alzheimer disease. APP and BACE are co-internalized from the cell surface to early endosomes. APP is also known to interact at the cell surface and be internalized by the low density lipoprotein receptor-related protein (LRP), a multifunctional endocytic and signaling receptor. Using a new fluorescence resonance energy transfer (FRET)-based assay of protein proximity, fluorescence lifetime imaging (FLIM), and co-immunoprecipitation we demonstrate that the light chain of LRP interacts with BACE on the cell surface in association with lipid rafts. Surprisingly, the BACE-LRP interaction leads to an increase in LRP C-terminal fragment, release of secreted LRP in the media and subsequent release of the LRP intracellular domain from the membrane. Taken together, these data suggest that there is a close interaction between BACE and LRP on the cell surface, and that LRP is a novel BACE substrate. BACE1 ( site of APP-cleaving enzyme) is a type I membrane-associated aspartyl protease that cleaves APP (1-4). Besides APP, the few BACE substrates that have been identified include the APP homologues APLP1 and -2 (5), P-selectin glycoprotein ligand-1 (PSGL-1), and a membrane-bound sialyltransferase (6). Post-translational processing of BACE involves N-glycosylation, removal of its prodomain by a furin-like protease, and further complex glycosylation (7-9). After glycosylation, BACE co-traffics with APP and is rapidly transported to the Golgi apparatus and distal secretory pathway (9). Measurable amounts of APP and BACE are present on the plasma membrane (10 -12) and in lipid rafts (12)(13)(14). BACE and APP are internalized from the cell surface to early endosomes and cycle between the cell membrane and endosomes (10,11,15).The low density lipoprotein receptor-related protein, LRP, is a type I integral membrane protein with a 515-kDa extracellular ␣-chain non-convalently bound to the 85 kDa membranespanning -chain. It is also found on the cell surface and cycles between the cell membrane and endosomes. Multiple intracellular adaptor and scaffolding proteins bind the LRP 100 amino acid cytoplasmic tail (16, 17); its four extracellular binding domains mediate endocytosis of a wide array of ligands, including several of potential importance for Alzheimer disease pathophysiology: APP, apolipoprotein E and ␣ 2 -macroglobulin (16 -18). The LRP ligand binding domains interact with KPIcontaining forms of APP. In addition, an interaction between the C-terminal domain of APP and LRP, mediated by the cytoplasmic adaptor protein Fe65, impacts APP internalization (18 -23). In addition to its role in endocytosis, LRP has an interesting pattern of proteolysis that parallels APP in some ways. Ectodomain shedding of LRP has been described (24) and proteolysis of LRP by matrix metalloproteas...
Summary Background An important goal of contemporary neuroscience research is to define the neural circuits and synaptic interactions that mediate behavior. In both mammals and Drosophila, the neuronal circuitry controlling circadian behavior has been the subject of intensive investigation, but roles for glial cells in the networks controlling rhythmic behavior have only begun to be defined in recent studies. Results Here, we show that conditional, glial-specific genetic manipulations affecting membrane (vesicle) trafficking, the membrane ionic gradient or calcium signaling lead to circadian arrhythmicity in adult behaving Drosophila. Correlated and reversible effects on a clock neuron peptide transmitter (PDF) and behavior demonstrate the capacity for glia-to-neuron signaling in the circadian circuitry. These studies also reveal the importance of a single type of glial cell – the astrocyte – and glial internal calcium stores in the regulation of circadian rhythms. Conclusions This is the first demonstration in any system that adult glial cells can physiologically modulate circadian neuronal circuitry and behavior. A role for astrocytes and glial calcium signaling in the regulation of Drosophila circadian rhythms emphasizes the conservation of cellular and molecular mechanisms that regulate behavior in mammals and insects.
Low density lipoprotein-related protein (LRP) is a transmembrane receptor, localized mainly in hepatocytes, fibroblasts, and neurons. It is implicated in diverse biological processes both as an endocytic receptor and as a signaling molecule. Recent reports show that LRP undergoes sequential proteolytic cleavage in the ectodomain and transmembrane domain. The latter cleavage, mediated by the Alzheimer-related ␥-secretase activity that also cleaves amyloid precursor protein (APP) and Notch, results in the release of the LRP cytoplasmic domain (LRPICD) fragment. This relatively small cytoplasmic fragment has several motifs by which LRP interacts with various intracellular adaptor and scaffold proteins. However, the function of this fragment is largely unknown. Here we show that the LRPICD is translocated to the nucleus, where it colocalizes in the nucleus with a transcription modulator, Tip60, which is known to interact with Fe65 and with the APP-derived intracellular domain. LRPICD dramatically inhibits APP-derived intracellular domain/Fe65 transactivation mediated by Tip60. LRPICD has a close interaction with Tip60 in the nucleus, as shown by a fluorescence resonance energy transfer assay. These observations suggest that LRPICD has a novel signaling function, negatively impacting transcriptional activity of the APP, Fe65, and Tip60 complex in the nucleus, and shed new light on the function of LRP in transcriptional modulation. LRP,1 a member of the low density lipoprotein (LDL) receptor family, is a type I integral membrane protein that has a very large extracellular domain and a relatively small cytoplasmic tail. Cleavage by furin (1, 2) produces the mature cell surface receptor, which consists of an 85-kDa membrane-bound carboxyl fragment and a noncovalently attached 515-kDa amino-terminal fragment. The 105-amino acid cytoplasmic domain interacts with intracellular adaptor and scaffold proteins. LRP is a multifunctional protein that interacts with and mediates endocytosis of a broad range of secreted proteins and cell surface molecules, such as plasminogen activators, plasminogen activator inhibitor-1, ␣ 2 -macroglobulin, amyloid precursor protein (APP), and apolipoprotein E (3-5).LRP has a complex set of interactions with APP. They interact both by virtue of an extracellular ligand-receptor interaction and via an interaction between the cytoplasmic tails of APP and LRP, mediated by the adaptor protein Fe65 (6 -11). Like APP, shedding of the extracellular domain of LRP from the cell surface by a metalloproteinase has been reported (12, 13). Furthermore, a recent report suggested that LRP undergoes a presenilin-dependent intramembranous proteolysis (14) in a manner analogous to Notch and APP. This cleavage releases a cytoplasmic fragment of LRP (LRPICD) from the membrane. However, the function of LRPICD is not yet known.In addition to its well characterized role as an endocytic receptor, recent data suggest that LRP (like other LDL receptor family members, VLDLR and ApoER2), could have essential signaling functi...
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