DHX8 regulates degradation of RNA by RNautophagy.

RNautophagy is an intracellular degradation pathway in which RNA is directly taken up by lysosomes. The cytoplasmic regions of the lysosomal membrane proteins, LAMP2C and SIDT2, can interact with consecutive guanine sequences in RNA, mediating the uptake of RNA during RNautophagy. RNautophagy has also been implicated in the clearance of expanded CAG-repeat mRNA and RNA foci associated with polyQ disease.

Wipi3 is essential for alternative autophagy and its loss causes neurodegeneration.

Alternative autophagy is an Atg5/Atg7-independent type of autophagy that contributes to various physiological events. We here identify Wipi3 as a molecule essential for alternative autophagy, but which plays minor roles in canonical autophagy. Wipi3 binds to Golgi membranes and is required for the generation of isolation membranes.

Association Between Autophagy and Neurodegenerative Diseases.

Autophagy is a phylogenetically conserved mechanism that controls the degradation of subcellular constituents, including misfolded proteins, and damaged organelles. The progression of many neurodegenerative diseases is thought to be driven by the aggregation of misfolded proteins; therefore, autophagic activity is thought to affect disease severity to some extent. In some neurodegenerative diseases, the suppression of autophagic activity accelerates disease progression.

Regulatory Role of RNA Chaperone TDP-43 for RNA Misfolding and Repeat-Associated Translation in SCA31.

Microsatellite expansion disorders are pathologically characterized by RNA foci formation and repeat-associated non-AUG (RAN) translation. However, their underlying pathomechanisms and regulation of RAN translation remain unknown. We report that expression of expanded UGGAA (UGGAA) repeats, responsible for spinocerebellar ataxia type 31 (SCA31) in Drosophila, causes neurodegeneration accompanied by accumulation of UGGAA RNA foci and translation of repeat-associated pentapeptide repeat (PPR) proteins, consistent with observations in SCA31 patient brains.

Glucocerebrosidase deficiency accelerates the accumulation of proteinase K-resistant α-synuclein and aggravates neurodegeneration in a Drosophila model of Parkinson's disease.

Alpha-synuclein (αSyn) plays a central role in the pathogenesis of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Recent multicenter genetic studies have revealed that mutations in the glucocerebrosidase 1 (GBA1) gene, which are responsible for Gaucher's disease, are strong risk factors for PD and DLB. However, the mechanistic link between the functional loss of glucocerebrosidase (GCase) and the toxicity of αSyn in vivo is not fully understood.

Normalization of Overexpressed α-Synuclein Causing Parkinson's Disease By a Moderate Gene Silencing With RNA Interference.

The α-synuclein (SNCA) gene is a responsible gene for Parkinson's disease (PD); and not only nucleotide variations but also overexpression of SNCA appears to be involved in the pathogenesis of PD. A specific inhibition against mutant SNCA genes carrying nucleotide variations may be feasible by a specific silencing such as an allele-specific RNA interference (RNAi); however, there is no method for restoring the SNCA overexpression to a normal level. Here, we show that an atypical RNAi using small interfering RNAs (siRNAs) that confer a moderate level of gene silencing is capable of controlling overexpressed SNCA genes to return to a normal level; named "expression-control RNAi" (ExCont-RNAi).

Intercellular chaperone transmission via exosomes contributes to maintenance of protein homeostasis at the organismal level.

The heat shock response (HSR), a transcriptional response that up-regulates molecular chaperones upon heat shock, is necessary for cell survival in a stressful environment to maintain protein homeostasis (proteostasis). However, there is accumulating evidence that the HSR does not ubiquitously occur under stress conditions, but largely depends on the cell types. Despite such imbalanced HSR among different cells and tissues, molecular mechanisms by which multicellular organisms maintain their global proteostasis have remained poorly understood.

p62 plays a protective role in the autophagic degradation of polyglutamine protein oligomers in polyglutamine disease model flies.

Oligomer formation and accumulation of pathogenic proteins are key events in the pathomechanisms of many neurodegenerative diseases, such as Alzheimer disease, ALS, and the polyglutamine (polyQ) diseases. The autophagy-lysosome degradation system may have therapeutic potential against these diseases because it can degrade even large oligomers. Although p62/sequestosome 1 plays a physiological role in selective autophagy of ubiquitinated proteins, whether p62 recognizes and degrades pathogenic proteins in neurodegenerative diseases has remained unclear.

VPS35 dysfunction impairs lysosomal degradation of α-synuclein and exacerbates neurotoxicity in a Drosophila model of Parkinson's disease.

Mutations in vacuolar protein sorting 35 (VPS35) have been linked to familial Parkinson's disease (PD). VPS35, a component of the retromer, mediates the retrograde transport of cargo from the endosome to the trans-Golgi network. Here we showed that retromer depletion increases the lysosomal turnover of the mannose 6-phosphate receptor, thereby affecting the trafficking of cathepsin D (CTSD), a lysosome protease involved in α-synuclein (αSYN) degradation.

Identification of ter94, Drosophila VCP, as a strong modulator of motor neuron degeneration induced by knockdown of Caz, Drosophila FUS.

In humans, mutations in the fused in sarcoma (FUS) gene have been identified in sporadic and familial forms of amyotrophic lateral sclerosis (ALS). Cabeza (Caz) is the Drosophila ortholog of human FUS. Previously, we established Drosophila models of ALS harboring Caz-knockdown.

Knockdown of the Drosophila fused in sarcoma (FUS) homologue causes deficient locomotive behavior and shortening of motoneuron terminal branches.

Mutations in the fused in sarcoma/translated in liposarcoma gene (FUS/TLS, FUS) have been identified in sporadic and familial forms of amyotrophic lateral sclerosis (ALS). FUS is an RNA-binding protein that is normally localized in the nucleus, but is mislocalized to the cytoplasm in ALS, and comprises cytoplasmic inclusions in ALS-affected areas. However, it is still unknown whether the neurodegeneration that occurs in ALS is caused by the loss of FUS nuclear function, or by the gain of toxic function due to cytoplasmic FUS aggregation.

α-Synuclein Transgenic Drosophila As a Model of Parkinson's Disease and Related Synucleinopathies.

α-Synuclein (α-Syn) is a major component of protein inclusions known as Lewy bodies, which are hallmarks of synucleinopathies such as Parkinson's disease (PD). The α-Syn gene is one of the familial PD-causing genes and is also associated with an increased risk of sporadic PD. Numerous studies using α-Syn expressing transgenic animals have indicated that α-Syn plays a critical role in the common pathogenesis of synucleinopathies.

Induction of molecular chaperones as a therapeutic strategy for the polyglutamine diseases.

Protein misfolding and aggregation in the brain have been implicated as a common molecular pathogenesis of various neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and the polyglutamine (polyQ) diseases. The polyQ diseases are a group of nine hereditary neurodegenerative diseases, including Huntington's disease (HD) and various types of spinocerebellar ataxia (SCA), which are caused by abnormal expansions of the polyQ stretch (> 35-40 repeats) in unrelated disease-causative proteins. The expanded polyQ stretch is thought to trigger misfolding of these proteins, leading to their aggregation and accumulation as inclusion bodies in affected neurons, eventually resulting in neurodegeneration.

Surface plasmon resonance characterization of specific binding of polyglutamine aggregation inhibitors to the expanded polyglutamine stretch.

Proteins with an abnormally expanded polyglutamine (polyQ) stretch are prone to change their conformations, leading to their aggregation, and cause inherited neurodegenerative diseases called the polyQ diseases. Although screening for polyQ aggregation inhibitors has been extensively performed, many common false-positive hits have been identified so far. In this study, we employed surface plasmon resonance (SPR) to characterize the binding specificities and affinities of polyQ aggregation inhibitors to the expanded polyQ stretch.

Residual laminin-binding activity and enhanced dystroglycan glycosylation by LARGE in novel model mice to dystroglycanopathy.

Hypoglycosylation and reduced laminin-binding activity of alpha-dystroglycan are common characteristics of dystroglycanopathy, which is a group of congenital and limb-girdle muscular dystrophies. Fukuyama-type congenital muscular dystrophy (FCMD), caused by a mutation in the fukutin gene, is a severe form of dystroglycanopathy. A retrotransposal insertion in fukutin is seen in almost all cases of FCMD.

ER stress is the initial response to polyglutamine toxicity in PC12 cells.

Persistent endoplasmic reticulum (ER) stress and impairment of the ubiquitin-proteasome system (UPS) cause neuronal cell death. However, the relationship between these two phenomena remains controversial. In our current study, we have utilized an expanded polyglutamine fusion protein (polyQ81) expression system in PC12 cells to further examine the involvement of ER stress and UPS impairment in cell death.

Heat shock transcription factor 1-activating compounds suppress polyglutamine-induced neurodegeneration through induction of multiple molecular chaperones.

Many neurodegenerative diseases including Alzheimer, Parkinson, and polyglutamine (polyQ) diseases are thought to be caused by protein misfolding. The polyQ diseases, including Huntington disease and spinocerebellar ataxias (SCAs), are caused by abnormal expansions of the polyQ stretch in disease-causing proteins, which trigger misfolding of these proteins, resulting in their deposition as inclusion bodies in affected neurons. Although genetic expression of molecular chaperones has been shown to suppress polyQ protein misfolding and neurodegeneration, toward developing a therapy, it is ideal to induce endogenous molecular chaperones by chemical administration.

Delivery of the aggregate inhibitor peptide QBP1 into the mouse brain using PTDs and its therapeutic effect on polyglutamine disease mice.

The polyglutamine (polyQ) diseases are neurodegenerative diseases caused by proteins with an abnormally expanded polyQ stretch, which triggers abnormal aggregation of these proteins in the brain. We previously showed that the polyQ-binding peptide QBP1 inhibits polyQ aggregation, and further that administration of QBP1 fused with a protein transduction domain (PTD) suppresses polyQ-induced neurodegeneration in Drosophila. As the next step towards developing a therapy using QBP1, we investigated the delivery of PTD-QBP1 to the mouse brain upon its administration.

Detection of polyglutamine protein oligomers in cells by fluorescence correlation spectroscopy.

Abnormal aggregation of misfolded proteins and their deposition as inclusion bodies in the brain have been implicated as a common molecular pathogenesis of neurodegenerative diseases including Alzheimer, Parkinson, and the polyglutamine (poly(Q)) diseases, which are collectively called the conformational diseases. The poly(Q) diseases, including Huntington disease and various types of spinocerebellar ataxia, are caused by abnormal expansions of the poly(Q) stretch within disease-causing proteins, which triggers the disease-causing proteins to aggregate into insoluble beta-sheet-rich amyloid fibrils. Although oligomeric structures formed in vitro are believed to be more toxic than mature amyloid fibrils in these diseases, the existence of oligomers in vivo has remained controversial.

[Therapeutic strategies for the polyglutamine diseases].

The polyglutamine diseases are a group of nine inherited neurodegenerative diseases including Huntington disease, spinocerebellar ataxia type 1, 2, 3, 6, 7 and 17, dentatorubral pallidoluysian atrophy, and spinobulbar muscular atrophy, which are caused by an abnormal expansion of the CAG repeat encoding a polyglutamine stretch in each unrelated disease-causing gene. In the pathogenesis of the polyglutamine diseases, expansion of the polyglutamine stretch causes misfolding and conformational alterations of the disease-causing proteins, leading to pathogenic protein-protein interactions including aggregate formation, and subsequently resulting in their deposition as inclusion bodies in affected neurons. Expression of these expanded polyglutamine proteins has been reported to impair protein degradation, transcriptional regulation, axonal transport, mitochondrial function, etc.

A toxic monomeric conformer of the polyglutamine protein.

Polyglutamine (polyQ) diseases are classified as conformational neurodegenerative diseases, like Alzheimer and Parkinson diseases, and they are caused by proteins with an abnormally expanded polyQ stretch. However, conformational changes of the expanded polyQ protein and the toxic conformers formed during aggregation have remained poorly understood despite their important role in pathogenesis. Here we show that a beta-sheet conformational transition of the expanded polyQ protein monomer precedes its assembly into beta-sheet-rich amyloid-like fibrils.

Protein transduction domain-mediated delivery of QBP1 suppresses polyglutamine-induced neurodegeneration in vivo.

Many neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and the polyglutamine (polyQ) diseases share common features including abnormal aggregation of misfolded proteins and their deposition as inclusion bodies in the brain. The polyQ diseases are caused by abnormal expansion of a polyQ stretch in each disease-causing protein, which triggers these proteins to form aggregates. We previously showed that genetic expression of the aggregate inhibitor peptide polyQ binding peptide 1 (QBP1) suppresses polyQ-induced neurodegeneration in Drosophila.

Molecular interaction between fukutin and POMGnT1 in the glycosylation pathway of alpha-dystroglycan.

The recent identification of mutations in genes encoding demonstrated or putative glycosyltransferases has revealed a novel mechanism for congenital muscular dystrophy. Hypoglycosylated alpha-dystroglycan (alpha-DG) is commonly seen in Fukuyama-type congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), Walker-Warburg syndrome (WWS), and Large(myd) mice. POMGnT1 and POMTs, the gene products responsible for MEB and WWS, respectively, synthesize unique O-mannose sugar chains on alpha-DG.