Pallidin function in Drosophila surface glia regulates sleep and is dependent on amino acid availability.

The Pallidin protein is a central subunit of a multimeric complex called biogenesis of lysosome-related organelles complex 1 (BLOC1) that regulates specific endosomal functions and has been linked to schizophrenia. We show here that downregulation of Pallidin and other members of BLOC1 in the surface glia, the Drosophila equivalent of the blood-brain barrier, reduces and delays nighttime sleep in a circadian-clock-dependent manner. In agreement with BLOC1 involvement in amino acid transport, downregulation of the large neutral amino acid transporter 1 (LAT1)-like transporters JhI-21 and mnd, as well as of TOR (target of rapamycin) amino acid signaling, phenocopy Pallidin knockdown. Furthermore, supplementing food with leucine normalizes the sleep/wake phenotypes of Pallidin downregulation, and we identify a role for Pallidin in the subcellular trafficking of JhI-21. Finally, we provide evidence that Pallidin in surface glia is required for GABAergic neuronal activity. These data identify a BLOC1 function linking essential amino acid availability and GABAergic sleep/wake regulation.

Early brain metabolic disturbances associated with delayed cerebral ischemia in patients with severe subarachnoid hemorrhage.

Delayed cerebral ischemia (DCI) is a devastating complication of aneurysmal subarachnoid hemorrhage (ASAH) causing brain infarction and disability. Cerebral microdialysis (CMD) monitoring is a focal technique that may detect DCI-related neurochemical changes as an advance warning. We conducted retrospective analyses from 44 poor-grade ASAH patients and analyzed glucose, lactate, pyruvate, and glutamate concentrations in control patients without DCI (n = 19), and in patients with DCI whose CMD probe was located within (n = 17) or outside (n = 8) a new infarct. When monitored from within a lesion, DCI was preceded by a decrease in glucose and a surge in glutamate, accompanied by increases in lactate/pyruvate and lactate/glucose ratios whereas these parameters remained stable in control patients. When CMD monitoring was performed outside the lesion, the glutamate surge was absent, but glucose and L/G ratio were still significantly altered. Overall, glucose and L/G ratio were significant biomarkers of DCI (se96.0, spe73.7-68.4). Glucose and L/G predicted DCI 67 h before CT detection of a new infarct. The pathogenesis of DCI therefore induces early metabolic disturbances that can be detected by CMD as an advance warning. Glucose and L/G could provide a trigger for initiating further examination or therapy, earlier than when guided by other monitoring techniques.

LAT1-like transporters regulate dopaminergic transmission and sleep in Drosophila.

Amino acid transporters are involved in functions reportedly linked to the sleep/wake cycle: neurotransmitter synthesis and recycling, the regulation of synaptic strength, protein synthesis, and energy metabolism. In addition, the existence of bidirectional relationships among extracellular content, transport systems, and sleep/wake states is receiving emerging support. Nevertheless, the connection between amino acid transport and sleep/wake regulation remains elusive. To address this question, we used Drosophila melanogaster and investigated the role of LAT1 (large neutral amino acid transporter 1) transporters. We show that the two Drosophila LAT1-like transporters: Juvenile hormone Inducible-21 and minidiscs (Mnd) are required in dopaminergic neurons for sleep/wake regulation. Down-regulating either gene in dopaminergic neurons resulted in higher daily sleep and longer sleep bout duration during the night, suggesting a defect in dopaminergic transmission. Since LAT1 transporters can mediate in mammals the uptake of L-DOPA, a precursor of dopamine, we assessed amino acid transport efficiency by L-DOPA feeding. We find that downregulation of JhI-21, but not Mnd, reduced the sensitivity to L-DOPA as measured by sleep loss. JhI-21 downregulation also attenuated the sleep loss induced by continuous activation of dopaminergic neurons. Since LAT1 transporters are known to regulate target of rapamycin (TOR) signaling, we investigated the role of this amino acid sensing pathway in dopaminergic neurons. Consistently, we report that TOR activity in dopaminergic neurons modulates sleep/wake states. Altogether, this study provides evidence that LAT1-mediated amino acid transport in dopaminergic neurons is playing a significant role in sleep/wake regulation and is providing several entry points to elucidate the role of nutrients such as amino acids in sleep/wake regulation.