Mutations in Pten-induced kinase 1 (PINK1) are linked to early-onset familial Parkinson's disease (FPD). PINK1 has previously been implicated in mitochondrial fission/fusion dynamics, quality control, and electron transport chain function. However, it is not clear how these processes are interconnected and whether they are sufficient to explain all aspects of PINK1 pathogenesis. Here we show that PINK1 also controls mitochondrial motility. In Drosophila, downregulation of dMiro or other components of the mitochondrial transport machinery rescued dPINK1 mutant phenotypes in the muscle and dopaminergic (DA) neurons, whereas dMiro overexpression alone caused DA neuron loss. dMiro protein level was increased in dPINK1 mutant but decreased in dPINK1 or dParkin overexpression conditions. In Drosophila larval motor neurons, overexpression of dPINK1 inhibited axonal mitochondria transport in both anterograde and retrograde directions, whereas dPINK1 knockdown promoted anterograde transport. In HeLa cells, overexpressed hPINK1 worked together with hParkin, another FPD gene, to regulate the ubiquitination and degradation of hMiro1 and hMiro2, apparently in a Ser-156 phosphorylation-independent manner. Also in HeLa cells, loss of hMiro promoted the perinuclear clustering of mitochondria and facilitated autophagy of damaged mitochondria, effects previously associated with activation of the PINK1/Parkin pathway. These newly identified functions of PINK1/Parkin and Miro in mitochondrial transport and mitophagy contribute to our understanding of the complex interplays in mitochondrial quality control that are critically involved in PD pathogenesis, and they may explain the peripheral neuropathy symptoms seen in some PD patients carrying particular PINK1 or Parkin mutations. Moreover, the different effects of loss of PINK1 function on Miro protein level in Drosophila and mouse cells may offer one explanation of the distinct phenotypic manifestations of PINK1 mutants in these two species.

Calcium (Ca) homeostasis is essential for neuronal function and survival. Altered Ca homeostasis has been consistently observed in neurological diseases. How Ca homeostasis is achieved in various cellular compartments of disease-relevant cell types is not well understood. Here we show in Parkinson's disease (PD) models that Ca transport from the endoplasmic reticulum (ER) to mitochondria through the ER-mitochondria contact site (ERMCS) critically regulates mitochondrial Ca (mito-Ca) homeostasis in dopaminergic (DA) neurons, and that the PD-associated PINK1 protein modulates this process. In mutant DA neurons, the ERMCS is strengthened and mito-Ca level is elevated, resulting in mitochondrial enlargement and neuronal death. Miro, a well-characterized component of the mitochondrial trafficking machinery, mediates the effects of PINK1 on mito-Ca and mitochondrial morphology, apparently in a transport-independent manner. Miro overexpression mimics loss-of-function effect, whereas inhibition of Miro or components of the ERMCS, or pharmacological modulation of ERMCS function, rescued mutant phenotypes. Mito-Ca homeostasis is also altered in the LRRK2-G2019S model of PD and the PAR-1/MARK model of neurodegeneration, and genetic or pharmacological restoration of mito-Ca level is beneficial in these models. Our results highlight the importance of mito-Ca homeostasis maintained by Miro and the ERMCS to mitochondrial physiology and neuronal integrity. Targeting this mito-Ca homeostasis pathway holds promise for a therapeutic strategy for neurodegenerative diseases.

This paper presents a novel run-time dynamic voltage scaling scheme for low-power real-time systems. It employs software feedback control of supply voltage, which is applicable to off-theshelf processors. It avoids interface problems from variable clock frequency. It provides efficient power reduction by fully exploiting slack time arising from workload variation. Using software analysis environment, the proposed scheme is shown to achieve 80~94% power reduction for typical real-time multimedia applications.

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SUMMARY Mitochondria play central roles in buffering intracellular Ca2+ transients. While basal mitochondrial Ca2+ (Ca2+mito) is needed to maintain organellar physiology, Ca2+mito overload can lead to cell death. How Ca2+mito homeostasis is regulated is not well understood. Here we show that Miro, a known component of the mitochondrial transport machinery, regulates Drosophila neural stem cell (NSC) development through Ca2+mito homeostasis control independent of its role in mitochondrial transport. Miro interacts with Ca2+ transporters at the ER-mitochondria contact site (ERMCS). Its inactivation causes Ca2+mito depletion and metabolic impairment, whereas its overexpression results in Ca2+mito overload, mitochondrial morphology change, and apoptotic response. Both conditions impaired NSC lineage progression. Ca2+mito homeostasis is influenced by Polo-mediated phosphorylation of a conserved residue in Miro, which positively regulates Miro localization to, and the integrity of, ERMCS. Our results elucidate a regulatory mechanism underlying Ca2+mito homeostasis and how its dysregulation may impact NSC metabolism/development and contribute to disease.

Axon extension and guidance require a coordinated assembly of F-actin and microtubules as well as regulated translation. The molecular basis of how the translation of mRNAs encoding guidance proteins could be closely tied to the pace of cytoskeletal assembly is poorly understood. Previous studies have shown that the F-actin-microtubule crosslinker Short stop (Shot) is required for motor and sensory axon extension in the Drosophila embryo. Here, we provide biochemical and genetic evidence that Shot functions with a novel translation inhibitor, Krasavietz (Kra, Exba), to steer longitudinally directed CNS axons away from the midline. Kra binds directly to the C-terminus of Shot, and this interaction is required for the activity of Shot to support midline axon repulsion. shot and kra mutations lead to weak robo-like phenotypes, and synergistically affect midline avoidance of CNS axons. We also show that shot and kra dominantly enhance the frequency of midline crossovers in embryos heterozygous for slit or robo, and that in kra mutant embryos, some Robo-positive axons ectopically cross the midline that normally expresses the repellent Slit. Finally, we demonstrate that Kra also interacts with the translation initiation factor eIF2␤ and inhibits translation in vitro. Together, these data suggest that Kra-mediated translational regulation plays important roles in midline axon repulsion and that Shot functions as a direct physical link between translational regulation and cytoskeleton reorganization.

In both mammalian and insect models of ethanol-induced behavior, low doses of ethanol stimulate locomotion. However, the mechanisms of the stimulant effects of ethanol on the CNS are mostly unknown. We have identified tao, encoding a serine-threonine kinase of the Ste20 family, as a gene necessary for ethanol-induced locomotor hyperactivity in Drosophila. Mutations in tao also affect behavioral responses to cocaine and nicotine, making flies resistant to the effects of both drugs. We show that tao function is required during the development of the adult nervous system and that tao mutations cause defects in the development of central brain structures, including the mushroom body. Silencing of a subset of mushroom body neurons is sufficient to reduce ethanol-induced hyperactivity, revealing the mushroom body as an important locus mediating the stimulant effects of ethanol. We also show that mutations in par-1 suppress both the mushroom body morphology and behavioral phenotypes of tao mutations and that the phosphorylation state of the microtubule-binding protein Tau can be altered by RNA interference knockdown of tao, suggesting that tao and par-1 act in a pathway to control microtubule dynamics during neural development.

The abnormal assembly of β-amyloid (Aβ) peptides into neurotoxic, β-sheet-rich amyloid aggregates is a major pathological hallmark of Alzheimer's disease (AD). Light-induced photosensitizing molecules can regulate Aβ amyloidogenesis. Multiple photochemical analyses using circular dichroism, atomic force microscopy, dot blot, and native gel electrophoresis verified that photoactivated meso-tetra(4-sulfonatophenyl)porphyrin (TPPS with M = 2H(+), Zn(2+), Cu(2+), Mn(2+)) successfully inhibits Aβ aggregation in vitro. Furthermore, Aβ toxicity was relieved in the photoexcited-TPPS-treated Drosophila AD model. TPPS suppresses neural cell death, synaptic toxicity, and behavioral defects in the Drosophila AD model under blue light illumination. Behavioral phenotypes, including larval locomotion defect and short lifespan caused by Aβ overexpression, were also rescued by blue light-excited TPPS.