Abnormal triaging of misfolded proteins by adult neuronal ceroid lipofuscinosis-associated DNAJC5/CSPα mutants causes lipofuscin accumulation.

Mutations in are associated with adult neuronal ceroid lipofuscinosis (ANCL), a dominant-inherited neurodegenerative disease featuring lysosome-derived autofluorescent torage materials (AFSMs) termed lipofuscin. Functionally, DNAJC5 has been implicated in chaperoning synaptic proteins and in misfolding-associated protein secretion (MAPS), but how DNAJC5 dysfunction causes lipofuscinosis and neurodegeneration is unclear. Here we report two functionally distinct but coupled chaperoning activities of DNAJC5, which jointly regulate lysosomal homeostasis: While endolysosome-associated DNAJC5 promotes ESCRT-dependent microautophagy, a fraction of perinuclear and non-lysosomal DNAJC5 mediates MAPS.

Mitochondrial Miro GTPases coordinate mitochondrial and peroxisomal dynamics.

Mitochondria and peroxisomes are highly dynamic, multifunctional organelles. Both perform key roles for cellular physiology and homoeostasis by mediating bioenergetics, biosynthesis, and/or signalling. To support cellular function, they must be properly distributed, of proper size, and be able to interact with other organelles.

A model of neuronal ceroid lipofuscinosis reveals a hypermorphic gain of function mechanism.

The autosomal dominant neuronal ceroid lipofuscinoses (NCL) is caused by mutations in the synaptic vesicle (SV) protein CSPα. We developed animal models of by expressing mutant human CSPα (hCSPα) in neurons. Similar to patients, mutations induced excessive oligomerization of hCSPα and premature lethality in a dose-dependent manner.

Cul4 ubiquitin ligase cofactor DCAF12 promotes neurotransmitter release and homeostatic plasticity.

We genetically characterized the synaptic role of the homologue of human DCAF12, a putative cofactor of Cullin4 (Cul4) ubiquitin ligase complexes. Deletion of DCAF12 impairs larval locomotion and arrests development. At larval neuromuscular junctions (NMJs), DCAF12 is expressed presynaptically in synaptic boutons, axons, and nuclei of motor neurons.

High Fidelity Cryopreservation and Recovery of Primary Rodent Cortical Neurons.

Cell cryopreservation improves reproducibility and enables flexibility in experimental design. Although conventional freezing methodologies have been used to preserve primary neurons, poor cell viability and reduced survival severely limited their utility. We screened several high-performance freezing media and found that CryoStor10 (CS10) provided superior cryoprotection to primary mouse embryonic cortical neurons compared to other commercially-available or traditional reagents, permitting the recovery of 68.

Post-transcriptional Inhibition of Hsc70-4/HSPA8 Expression Leads to Synaptic Vesicle Cycling Defects in Multiple Models of ALS.

Amyotrophic lateral sclerosis (ALS) is a synaptopathy accompanied by the presence of cytoplasmic aggregates containing TDP-43, an RNA-binding protein linked to ∼97% of ALS cases. Using a Drosophila model of ALS, we show that TDP-43 overexpression (OE) in motor neurons results in decreased expression of the Hsc70-4 chaperone at the neuromuscular junction (NMJ). Mechanistically, mutant TDP-43 sequesters hsc70-4 mRNA and impairs its translation.

Mitochondria on the Road to Power Axonal Regeneration.

In this issue of Neuron, Han et al. (2016) and Cartoni et al. (2016) define a critical role of mitochondrial transport for successful axon regeneration after injury and provide new insights into intrinsic mechanisms controlling neuronal regeneration capacity in worms and mice.

SIGNAL TRANSDUCTION. Membrane potential modulates plasma membrane phospholipid dynamics and K-Ras signaling.

Plasma membrane depolarization can trigger cell proliferation, but how membrane potential influences mitogenic signaling is uncertain. Here, we show that plasma membrane depolarization induces nanoscale reorganization of phosphatidylserine and phosphatidylinositol 4,5-bisphosphate but not other anionic phospholipids. K-Ras, which is targeted to the plasma membrane by electrostatic interactions with phosphatidylserine, in turn undergoes enhanced nanoclustering.

Miro's N-terminal GTPase domain is required for transport of mitochondria into axons and dendrites.

Mitochondria are dynamically transported in and out of neuronal processes to maintain neuronal excitability and synaptic function. In higher eukaryotes, the mitochondrial GTPase Miro binds Milton/TRAK adaptor proteins linking microtubule motors to mitochondria. Here we show that Drosophila Miro (dMiro), which has previously been shown to be required for kinesin-driven axonal transport, is also critically required for the dynein-driven distribution of mitochondria into dendrites.

TRPV1 channels: not so inactive on the ER.

In this issue of Neuron, Wong et al. (2014) report a remarkable evolutionarily conserved role for the Drosophila TRPV1 homolog Inactive controlling synaptic growth at larval neuromuscular junctions by facilitating Ca(2+) release from the endoplasmic reticulum.

PINK1-mediated phosphorylation of Miro inhibits synaptic growth and protects dopaminergic neurons in Drosophila.

Mutations in the mitochondrial Ser/Thr kinase PINK1 cause Parkinson's disease. One of the substrates of PINK1 is the outer mitochondrial membrane protein Miro, which regulates mitochondrial transport. In this study, we uncovered novel physiological functions of PINK1-mediated phosphorylation of Miro, using Drosophila as a model.

The Drosophila melanogaster phospholipid flippase dATP8B is required for odorant receptor function.

The olfactory systems of insects are fundamental to all aspects of their behaviour, and insect olfactory receptor neurons (ORNs) exhibit exquisite specificity and sensitivity to a wide range of environmental cues. In Drosophila melanogaster, ORN responses are determined by three different receptor families, the odorant (Or), ionotropic-like (IR) and gustatory (Gr) receptors. However, the precise mechanisms of signalling by these different receptor families are not fully understood.

Memory, synapse stability, and β-adducin.

In this issue of Neuron, two studies by Pielage et al. and Bednarek and Caroni suggest that the cytoskeleton regulator β-Adducin provides an activity-dependent switch controlling synapse disassembly and assembly at the Drosophila neuromuscular junction (NMJ) and the mouse hippocampus. In mice, the β-Adducin switch is required for the improvement of learning and memory induced by enriched environments.

Cysteine-string protein's neuroprotective role.

Cysteine-string protein (CSP), a member of the DnaJ/Hsp40 family of cochaperones, is critical for maintaining neurotransmitter release and preventing neurodegeneration. CSP likely forms a chaperone complex on synaptic vesicles together with the 70-kDa heat shock cognate (Hsc70) and the small glutamine-rich tetratricopeptide repeat (TPR)-containing protein (SGT) that may control or protect the assembly and activity of SNARE proteins and various other protein substrates. Here, the author summarizes studies that elucidated CSP's neuroprotective role.

Presynaptic mitochondria in functionally different motor neurons exhibit similar affinities for Ca2+ but exert little influence as Ca2+ buffers at nerve firing rates in situ.

Mitochondria accumulate within nerve terminals and support synaptic function, most notably through ATP production. They can also sequester Ca(2+) during nerve stimulation, but it is unknown whether this limits presynaptic Ca(2+) levels at physiological nerve firing rates. Similarly, it is unclear whether mitochondrial Ca(2+) sequestration differs between functionally different nerve terminals.

Ferrying wingless across the synaptic cleft.

Secreted Wnt morphogens mediate cell-cell communication, but the mechanism of Wnt transfer between cells is unknown. Korkut et al. (2009) report that the transmembrane protein Evi is a versatile carrier that guides Wingless to presynaptic terminals of motor neurons and then escorts it across the synaptic cleft.

Mitochondrial transport dynamics in axons and dendrites.

Mitochondrial dynamics and transport have emerged as key factors in the regulation of neuronal differentiation and survival. Mitochondria are dynamically transported in and out of axons and dendrites to maintain neuronal and synaptic function. Transport proceeds through a controlled series of plus- and minus-end directed movements along microtubule tracks (MTs) that are often interrupted by short stops.

Genetic modifiers of dFMR1 encode RNA granule components in Drosophila.

Mechanisms of neuronal mRNA localization and translation are of considerable biological interest. Spatially regulated mRNA translation contributes to cell-fate decisions and axon guidance during development, as well as to long-term synaptic plasticity in adulthood. The Fragile-X Mental Retardation protein (FMRP/dFMR1) is one of the best-studied neuronal translational control molecules and here we describe the identification and early characterization of proteins likely to function in the dFMR1 pathway.

Drosophila Miro is required for both anterograde and retrograde axonal mitochondrial transport.

Microtubule-based transport of mitochondria into dendrites and axons is vital for sustaining neuronal function. Transport along microtubule tracks proceeds in a series of plus and minus end-directed movements that are facilitated by kinesin and dynein motors. How the opposing movements are controlled to achieve effective transport over large distances remains unclear.

Effects of imaging conditions on mitochondrial transport and length in larval motor axons of Drosophila.

The distribution of mitochondria is sensitive to physiological stresses and changes in metabolic demands. Consequently, it is important to carefully define the conditions facilitating live imaging of mitochondrial transport in dissected animal preparations. In this study, we examined Schneider's and the haemolymph-like solutions HL3 and HL6 for their suitability to image mitochondrial transport in motor axons of dissected Drosophila melanogaster larvae.

Synaptic homeostasis on the fast track.

Synaptic homeostasis is a phenomenon that prevents the nervous system from descending into chaos. In this issue of Neuron, Frank et al. overturn the notion that synaptic homeostasis at Drosophila NMJs is a slow developmental process.

Morphological and functional effects of altered cysteine string protein at the Drosophila larval neuromuscular junction.

The synaptic vesicle-associated cysteine string protein (CSP) is critical for neurotransmitter release at the neuromuscular junction (NMJ) of Drosophila, where the approximately 4% of mutant flies lacking CSP that survive to adulthood exhibit spastic jumping and shaking, temperature-sensitive paralysis, and premature death. Previously, it has been shown that CSP is also required for nerve terminal growth and the prevention of neurodegeneration in Drosophila and mice. At larval csp null mutant NMJs of Drosophila, intracellular recordings from the muscle showed that evoked release is significantly reduced at room temperature.

The GTPase dMiro is required for axonal transport of mitochondria to Drosophila synapses.

We have identified EMS-induced mutations in Drosophila Miro (dMiro), an atypical mitochondrial GTPase that is orthologous to human Miro (hMiro). Mutant dmiro animals exhibit defects in locomotion and die prematurely. Mitochondria in dmiro mutant muscles and neurons are abnormally distributed.

The multiple functions of cysteine-string protein analyzed at Drosophila nerve terminals.

The synaptic vesicle-associated cysteine-string protein (CSP) is important for synaptic transmission. Previous studies revealed multiple defects at neuromuscular junctions (NMJs) of csp null-mutant Drosophila, but whether these defects are independent of each other or mechanistically linked through J domain mediated-interactions with heat-shock cognate protein 70 (Hsc70) has not been established. To resolve this issue, we genetically dissected the individual functions of CSP by an in vivo structure/function analysis.

Endophilin and synaptojanin hook up to promote synaptic vesicle endocytosis.

Clathrin-mediated endocytosis of synaptic vesicles requires molecular rearrangements of proteins as well as lipids. In this issue of Neuron, Schuske et al. and Verstreken et al.