The effects of dynein inhibition on the autophagic pathway in glioma cells

Impaired autophagic flux and dedifferentiation in podocytes lacking Asah1 gene: Role of lysosomal TRPML1 channel

Podocytopathy and associated nephrotic syndrome have been reported in a mouse strain (Asah1fl/fl/Podocre) with a podocyte-specific deletion of α subunit (the main catalytic subunit) of acid ceramidase (Ac). However, the pathogenesis of podocytopathy in these mice remains unclear. The present study tested whether Ac deficiency impairs autophagic flux in podocytes through blockade of transient receptor potential mucolipin 1 (TRPML1) channel as a potential pathogenic mechanism of podocytopathy in Asah1fl/fl/Podocre mice. We first demonstrated that impairment of autophagic flux occurred in podocytes lacking Asah1 gene, which was evidenced by autophagosome accumulation and reduced lysosome-autophagosome interaction. TRPML1 channel agonists recovered lysosome-autophagosome interaction and attenuated autophagosome accumulation in podocytes from Asah1fl/fl/Podocre mice, while TRPML1 channel inhibitors impaired autophagic flux in WT/WT podocytes and worsened autophagic deficiency in podocytes lacking Asah1 gene. The effects of TRPML1 channel agonist were blocked by dynein inhibitors, indicating a critical role of dynein activity in the control of lysosome movement due to TRPML1 channel-mediated Ca2+ release. It was also found that there is an enhanced phenotypic transition to dedifferentiation status in podocytes lacking Asah1 gene in vitro and in vivo. Such podocyte phenotypic transition was inhibited by TRPML1 channel agonists but enhanced by TRPML1 channel inhibitors. Moreover, we found that TRPML1 gene silencing induced autophagosome accumulation and dedifferentiation in podocytes. Based on these results, we conclude that Ac activity is essential for autophagic flux and maintenance of differentiated status of podocytes. Dysfunction or deficiency of Ac may impair autophagic flux and induce podocyte dedifferentiation, which may be an important pathogenic mechanism of podocytopathy and associated nephrotic syndrome.

The spectrum of neurodevelopmental, neuromuscular and neurodegenerative disorders due to defective autophagy

Primary dysfunction of autophagy due to Mendelian defects affecting core components of the autophagy machinery or closely related proteins have recently emerged as an important cause of genetic disease. This novel group of human disorders may present throughout life and comprises severe early-onset neurodevelopmental and more common adult-onset neurodegenerative disorders. Early-onset (or congenital) disorders of autophagy often share a recognizable "clinical signature," including variable combinations of neurological, neuromuscular and multisystem manifestations. Structural CNS abnormalities, cerebellar involvement, spasticity and peripheral nerve pathology are prominent neurological features, indicating a specific vulnerability of certain neuronal populations to autophagic disturbance. A typically biphasic disease course of late-onset neurodegeneration occurring on the background of a neurodevelopmental disorder further supports a role of autophagy in both neuronal development and maintenance. Additionally, an associated myopathy has been characterized in several conditions. The differential diagnosis comprises a wide range of other multisystem disorders, including mitochondrial, glycogen and lysosomal storage disorders, as well as ciliopathies, glycosylation and vesicular trafficking defects. The clinical overlap between the congenital disorders of autophagy and these conditions reflects the multiple roles of the proteins and/or emerging molecular connections between the pathways implicated and suggests an exciting area for future research. Therapy development for congenital disorders of autophagy is still in its infancy but may result in the identification of molecules that target autophagy more specifically than currently available compounds. The close connection with adult-onset neurodegenerative disorders highlights the relevance of research into rare early-onset neurodevelopmental conditions for much more common, age-related human diseases.Abbreviations: AC: anterior commissure; AD: Alzheimer disease; ALR: autophagic lysosomal reformation; ALS: amyotrophic lateral sclerosis; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; ASD: autism spectrum disorder; ATG: autophagy related; BIN1: bridging integrator 1; BPAN: beta-propeller protein associated neurodegeneration; CC: corpus callosum; CHMP2B: charged multivesicular body protein 2B; CHS: Chediak-Higashi syndrome; CMA: chaperone-mediated autophagy; CMT: Charcot-Marie-Tooth disease; CNM: centronuclear myopathy; CNS: central nervous system; DNM2: dynamin 2; DPR: dipeptide repeat protein; DVL3: disheveled segment polarity protein 3; EPG5: ectopic P-granules autophagy protein 5 homolog; ER: endoplasmic reticulum; ESCRT: homotypic fusion and protein sorting complex; FIG4: FIG4 phosphoinositide 5-phosphatase; FTD: frontotemporal dementia; GBA: glucocerebrosidase; GD: Gaucher disease; GRN: progranulin; GSD: glycogen storage disorder; HC: hippocampal commissure; HD: Huntington disease; HOPS: homotypic fusion and protein sorting complex; HSPP: hereditary spastic paraparesis; LAMP2A: lysosomal associated membrane protein 2A; MEAX: X-linked myopathy with excessive autophagy; mHTT: mutant huntingtin; MSS: Marinesco-Sjoegren syndrome; MTM1: myotubularin 1; MTOR: mechanistic target of rapamycin kinase; NBIA: neurodegeneration with brain iron accumulation; NCL: neuronal ceroid lipofuscinosis; NPC1: Niemann-Pick disease type 1; PD: Parkinson disease; PtdIns3P: phosphatidylinositol-3-phosphate; RAB3GAP1: RAB3 GTPase activating protein catalytic subunit 1; RAB3GAP2: RAB3 GTPase activating non-catalytic protein subunit 2; RB1: RB1-inducible coiled-coil protein 1; RHEB: ras homolog, mTORC1 binding; SCAR20: SNX14-related ataxia; SENDA: static encephalopathy of childhood with neurodegeneration in adulthood; SNX14: sorting nexin 14; SPG11: SPG11 vesicle trafficking associated, spatacsin; SQSTM1: sequestosome 1; TBC1D20: TBC1 domain family member 20; TECPR2: tectonin beta-propeller repeat containing 2; TSC1: TSC complex subunit 1; TSC2: TSC complex subunit 2; UBQLN2: ubiquilin 2; VCP: valosin-containing protein; VMA21: vacuolar ATPase assembly factor VMA21; WDFY3/ALFY: WD repeat and FYVE domain containing protein 3; WDR45: WD repeat domain 45; WDR47: WD repeat domain 47; WMS: Warburg Micro syndrome; XLMTM: X-linked myotubular myopathy; ZFYVE26: zinc finger FYVE-type containing 26.

Streptococcus lutetiensis Induces Autophagy via Oxidative Stress in Bovine Mammary Epithelial Cells

Streptococcus lutetiensis, an emerging pathogen causing bovine mastitis, has not been well characterized. We reported that S. lutetiensis was pathogenic both in vivo and in vitro and caused inflammatory reactions in the mammary gland. However, roles of autophagy and oxidative stress in the pathogenesis of S. lutetiensis-induced mastitis are unclear. In this study, an autophagy model of S. lutetiensis-infected bovine mammary epithelial cells (bMECs) was used to assess oxidative stress and autophagy flux. Expressions of Beclin1, light chain 3II, and Sequestosome 1/p62 were elevated in bMECs after S. lutetiensis infection. In addition, autophagosome and lysosome formation confirmed autophagy occurred. Based on LysoTracker Red and acridine orange, lysosome degradation was blocked, and lower expressions of lysosomal-associated membrane protein 2, cathepsins D, and cathepsins L confirmed lysosomal damage. Concurrently, the nuclear factor erythroid 2-related factor 2 (Nrf2), kelch-like ECH-associated protein 1 (Keap1), heme oxygenase 1 (HO1), and NAD (P)H: quinone oxidoreductase 1 (NQO1), and basilic proteins associated with the Nrf2/Keap1 signaling pathway, were detected. Decreased keap1 and increased Nrf2, HO1, NQO1, and reactive oxygen species (ROS) indicated increased oxidative stress. Treatment with N-Acetyl-L-cysteine (NAC), an ROS inhibitor, decreased both oxidative stress and autophagy. Therefore, we concluded that S. lutetiensis caused intracellular oxidative stress and autophagy in bMECs. In addition, crosstalk between autophagy and oxidative stress affected the autophagic flux and blocked downstream autophagy. The Nrf2-keap1-p62 pathway participated in this process, with ROS acting upstream of these effects, interfering with normal cell functions.

Crosstalk between autophagy inhibitors and endosome-related secretory pathways: a challenge for autophagy-based treatment of solid cancers

Autophagy is best known for its role in organelle and protein turnover, cell quality control, and metabolism. The autophagic machinery has, however, also adapted to enable protein trafficking and unconventional secretory pathways so that organelles (such as autophagosomes and multivesicular bodies) delivering cargo to lysosomes for degradation can change their mission from fusion with lysosomes to fusion with the plasma membrane, followed by secretion of the cargo from the cell. Some factors with key signalling functions do not enter the conventional secretory pathway but can be secreted in an autophagy-mediated manner.Positive clinical results of some autophagy inhibitors are encouraging. Nevertheless, it is becoming clear that autophagy inhibition, even within the same cancer type, can affect cancer progression differently. Even next-generation inhibitors of autophagy can have significant non-specific effects, such as impacts on endosome-related secretory pathways and secretion of extracellular vesicles (EVs). Many studies suggest that cancer cells release higher amounts of EVs compared to non-malignant cells, which makes the effect of autophagy inhibitors on EVs secretion highly important and attractive for anticancer therapy. In this review article, we discuss how different inhibitors of autophagy may influence the secretion of EVs and summarize the non-specific effects of autophagy inhibitors with a focus on endosome-related secretory pathways. Modulation of autophagy significantly impacts not only the quantity of EVs but also their content, which can have a deep impact on the resulting pro-tumourigenic or anticancer effect of autophagy inhibitors used in the antineoplastic treatment of solid cancers.

Study on the Prognostic Values of Dynactin Genes in Low-Grade Glioma

OBJECTIVE

This present study aims to investigate the potential prognostic values of dynactin genes (DCTN) for predicting the overall survival (OS) in low-grade glioma (LGG) patients.

METHODS

The DCTN mRNA expression data were downloaded from The Cancer Genome Atlas database containing 518 patients with LGG. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses for DCTN genes were performed by using Database for Annotation, Visualization, and Integrated Discovery platform, and their enrichment results were verified by using the Biological Networks Gene Ontology tool. Next, the correlations between DCTN genes and LGG were identified by Pearson correlation coefficient analysis. The OS was estimated by Kaplan-Meier survival analysis. The cBio Cancer Genomics Portal was used to analyze the mutations of DCTN genes and their effects on the prognosis of LGG. The correlation between the abundance of immune infiltration and tumor purity of DCTN genes were predicted by The Tumor Immune Estimation Resource.

RESULTS

Our research showed that the mRNA expression of DCTN4 in tumor tissues was much higher (P < 0.01) than that in normal tissues. Meanwhile, there was a certain correlation between the DCTN genes. Survival analysis showed that the high expression of DCTN1, DCTN3, DCTN4, DCTN6, and their co-expression were significantly correlated with favorable OS in LGG patients (P < 0.05). In DCTN2, a high mutation rate was observed. Further research showed that the genetic alteration in DCTN genes was related to a poor OS and progression-free survival of LGG patients. The expression of DCTN genes had a certain correlation with immune infiltrating cells.

CONCLUSION

Our study showed that the high expressions of DCTN1, DCTN3, DCTN4, and DCTN6 were associated with a favorable OS of LGG patients, indicating that these DCTN genes are potential biomarkers for evaluating the prognosis of LGG patients.

Staphylococcus aureus Avoids Autophagy Clearance of Bovine Mammary Epithelial Cells by Impairing Lysosomal Function

In dairy herds, mastitis caused by Staphylococcus aureus is difficult to completely cure on the account that S. aureus can invade bovine mammary epithelial cells (BMECs) and result in persistent infection in the mammary gland. Recent studies have demonstrated that autophagy can participate in cell homeostasis by eliminating intracellular microorganisms. The aim of the study was to investigate why S. aureus can evade autophagy clearance and survive in BMECs. The intracellular infection model was first constructed; then, the bacteria in autophagosome was detected by transmission electron microscopy. The autophagy flux induced by the S. aureus was also evaluated by immunoblot analysis and fluorescent labeling method for autophagy marker protein LC3. In addition, lysosomal alkalization and degradation ability were assessed using confocal microscopy. Results showed that, after infection, a double-layer membrane structure around the S. aureus was observed in BMECs, indicating that autophagy occurred. The change in autophagy marker protein and fluorescent labeling of autophagosome also confirmed autophagy. However, as time prolonged, the autophagy flux was markedly inhibited, leading to obvious autophagosome accumulation. At the same time, the lysosomal alkalization and degradation ability of BMECs were impaired. Collectively, these results indicated that S. aureus could escape autophagic degradation by inhibiting autophagy flux and damaging lysosomal function after invading BMECs.

Pharmacological Tools to Modulate Autophagy in Neurodegenerative Diseases

Considerable evidences suggest a link between autophagy dysfunction, protein aggregation, and neurodegenerative diseases. Given that autophagy is a conserved intracellular housekeeping process, modulation of autophagy flux in various model organisms have highlighted its importance for maintaining proteostasis. In postmitotic cells such as neurons, compromised autophagy is sufficient to cause accumulation of ubiquitinated aggregates, neuronal dysfunction, degeneration, and loss of motor coordination-all hallmarks of neurodegenerative diseases. Reciprocally, enhanced autophagy flux augments cellular and organismal health, in addition to extending life span. These genetic studies not-withstanding a plethora of small molecule modulators of autophagy flux have been reported that alleviate disease symptoms in models of neurodegenerative diseases. This review summarizes the potential of such molecules to be, perhaps, one of the first autophagy drugs for treating these currently incurable diseases.

Links between autophagy and disorders of glycogen metabolism - Perspectives on pathogenesis and possible treatments

The glycogen storage diseases are a group of inherited metabolic disorders that are characterized by specific enzymatic defects involving the synthesis or degradation of glycogen. Each disorder presents with a set of symptoms that are due to the underlying enzyme deficiency and the particular tissues that are affected. Autophagy is a process by which cells degrade and recycle unneeded or damaged intracellular components such as lipids, glycogen, and damaged mitochondria. Recent studies showed that several of the glycogen storage disorders have abnormal autophagy which can disturb normal cellular metabolism and/or mitochondrial function. Here, we provide a clinical overview of the glycogen storage disorders, a brief description of autophagy, and the known links between specific glycogen storage disorders and autophagy.

Relationship between DYNLT1 and Beclin1 expression and the fertilising potential of human spermatozoa

This study aimed to evaluate dynein light chain type 1 (DYNLT1) mRNA expression in mature spermatozoa and to investigate its association with Beclin1 expression to help in understanding of pathogenesis of male infertility. It included 60 infertile men divided into idiopathic (n = 20), accessory gland inflammation (n = 20), and varicocele (n = 20) groups, and 20 healthy fertile men as a control group. Semen parameters were evaluated according to the 2010 World Health Organization criteria. Mature spermatozoa were isolated by Sil-select gradient. Relative quantification of DYNLT1 and Beclin1 mRNA expression in whole sperm pellet and mature spermatozoa was done using real-time PCR. Beclin1 protein was assessed in whole sperm pellet and mature spermatozoa by ELISA. Beclin1 mRNA and protein were significantly increased in spermatozoa from infertile patients of different aetiologies in comparison to healthy controls (p < .05). However, DYNLT1 mRNA expression was significantly decreased in infertile groups than controls (p < .05). Mature spermatozoa extracted from all studied subjects showed increased DYNLT1 mRNA and decreased Beclin1 mRNA and protein expression compared with the whole sample. It is concluded that decreased Beclin1 and increased DYNLT1 mRNA expression in mature spermatozoa may provide an insight into the biological processes that are activated or suppressed during sperm maturation.

Ablation of tau causes an olfactory deficit in a murine model of Parkinson's disease

Parkinson's disease is diagnosed upon the presentation of motor symptoms, resulting from substantial degeneration of dopaminergic neurons in the midbrain. Prior to diagnosis, there is a lengthy prodromal stage in which non-motor symptoms, including olfactory deficits (hyposmia), develop. There is limited information about non-motor impairments and there is a need for directed research into these early pathogenic cellular pathways that precede extensive dopaminergic death in the midbrain. The protein tau has been identified as a genetic risk factor in the development of sporadic PD. Tau knockout mice have been reported as an age-dependent model of PD, and this study has demonstrated that they develop motor deficits at 15-months-old. We have shown that at 7-month-old tau knockout mice present with an overt hyposmic phenotype. This olfactory deficit correlates with an accumulation of α-synuclein, as well as autophagic impairment, in the olfactory bulb. This pathological feature becomes apparent in the striatum and substantia nigra of 15-month-old tau knockout mice, suggesting the potential for a spread of disease. Initial primary cell culture experiments have demonstrated that ablation of tau results in the release of α-synuclein enriched exosomes, providing a potential mechanism for disease spread. These alterations in α-synuclein level as well as a marked autophagy impairment in the tau knockout primary cells recapitulate results seen in the animal model. These data implicate a pathological role for tau in early Parkinson's disease.

Autophagy and neurodegeneration

Most neurodegenerative diseases that afflict humans are associated with the intracytoplasmic deposition of aggregate-prone proteins in neurons. Autophagy is a powerful process for removing such proteins. In this Review, we consider how certain neurodegenerative diseases may be associated with impaired autophagy and how this may affect pathology. We also discuss how autophagy induction may be a plausible therapeutic strategy for some conditions and review studies in various models that support this hypothesis. Finally, we briefly describe some of the signaling pathways that may be amenable to therapeutic targeting for these goals.

Acid sphingomyelinase-ceramide system in steatohepatitis: a novel target regulating multiple pathways

Steatohepatitis (SH) is an intermediate stage of fatty liver disease and is one of the most common causes of chronic liver disease worldwide that may progress to cirrhosis and liver cancer. SH encompasses alcoholic and non-alcoholic steatohepatitis, the latter being of particular concern as it is associated with obesity and insulin resistance and has become a major cause of liver transplantation. The molecular mechanisms governing the transition from steatosis to SH are not fully understood. Here we discuss emerging data indicating that the acid sphingomyelinase (ASMase), a specific mechanism of ceramide generation, is required for the activation of key pathways that regulate steatosis, fibrosis and lipotoxicity, including endoplasmic reticulum stress, autophagy and lysosomal membrane permeabilization. Moreover, ASMase modulates alterations of the methionine cycle and phosphatidylcholine homeostasis, two crucial events involved in SH that regulate methylation reactions, antioxidant defence and membrane integrity. These new findings suggest that targeting ASMase in combination with restoring methionine metabolism and phosphatidylcholine levels may be of utility in the treatment of SH.

Control of autophagy maturation by acid sphingomyelinase in mouse coronary arterial smooth muscle cells: protective role in atherosclerosis

Recent studies have indicated a protective role of autophagy in regulating vascular smooth muscle cells homeostasis in atherogenesis, but the mechanisms controlling autophagy, particularly autophagy maturation, are poorly understood. Here, we investigated whether acid sphingomyelinase (ASM)-regulated lysosome function is involved in autophagy maturation in coronary arterial smooth muscle cells (CASMCs) in the pathogenesis of atherosclerosis. In coronary arterial wall of ASM-deficient (Smpd1⁻/⁻) mice on Western diet, there were high expression levels of both LC3B, a robust marker of autophagosomes (APs), and p62, a selective autophagy substrate, compared with those in wild-type (Smpd1⁺/⁺) mice. By Western blotting and flow cytometry, atherogenic stimulation of Smpd1⁺/⁺ CASMCs with 7-ketocholesterol was found to significantly enhance LC3B expression and increase the content of both APs and autophagolysosomes (APLs). In Smpd1⁻/⁻ CASMCs, such 7-ketocholesterol-induced increases in LC3B and p62 expression and APs were further augmented, but APLs formation was abolished. Analysis of fluorescence resonance energy transfer between fluorescence-labeled LC3B and Lamp1 (lysosome marker) showed that 7-ketocholesterol markedly induced fusion of APs with lysosomes in Smpd1⁺/⁺ CASMCs, which was abolished in Smpd1⁻/⁻ CASMCs. Moreover, 7-ketocholesterol-induced expression of cell dedifferentiation marker vimentin and proliferation was enhanced in Smpd1⁻/⁻ CASMCs compared with those in Smpd1⁺/⁺ CASMCs. Lastly, overexpression of ASM further increased APLs formation in Smpd1⁺/⁺ CASMCs and restored APLs formation in Smpd1⁻/⁻ CASMCs indicating that increased ASM expression is highly correlated with enhanced APLs formation. Taken together, our data suggest that the control of lysosome trafficking and fusion by ASM is essential to a normal autophagic flux in CASMCs, which implicates that the deficiency of ASM-mediated regulation of autophagy maturation may result in imbalance of arterial smooth muscle cell homeostasis and thus serve as an important atherogenic mechanism in coronary arteries.

KEY MESSAGES

Acid sphingomyelinase (ASM) controls autophagy maturation in smooth muscle cells. ASM maintains smooth muscle cell homeostasis and its contractile phenotype. ASM plays a protective role in smooth muscle dysfunction and atherosclerosis.

MTOR-independent, autophagic enhancer trehalose prolongs motor neuron survival and ameliorates the autophagic flux defect in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder caused by selective motor neuron degeneration. Abnormal protein aggregation and impaired protein degradation pathways may contribute to the disease pathogenesis. Although it has been reported that autophagy is altered in patients and animal model of ALS, little is known about the role of autophagy in motor neuron degeneration in this disease. Our previous study shows that rapamycin, an MTOR-dependent autophagic activator, accelerates disease progression in the SOD1(G93A) mouse model of ALS. In the present report, we have assessed the role of the MTOR-independent autophagic pathway in ALS by determining the effect of the MTOR-independent autophagic inducer trehalose on disease onset and progression, and on motor neuron degeneration in SOD1(G93A) mice. We have found that trehalose significantly delays disease onset prolongs life span, and reduces motor neuron loss in the spinal cord of SOD1(G93A) mice. Most importantly, we have documented that trehalose decreases SOD1 and SQSTM1/p62 aggregation, reduces ubiquitinated protein accumulation, and improves autophagic flux in the motor neurons of SOD1(G93A) mice. Moreover, we have demonstrated that trehalose can reduce skeletal muscle denervation, protect mitochondria, and inhibit the proapoptotic pathway in SOD1(G93A) mice. Collectively, our study indicated that the MTOR-independent autophagic inducer trehalose is neuroprotective in the ALS model and autophagosome-lysosome fusion is a possible therapeutic target for the treatment of ALS.

Regulation of autophagic flux by dynein-mediated autophagosomes trafficking in mouse coronary arterial myocytes

Autophagic flux is an important process during autophagy maturation in coronary arterial myocytes (CAMs). Here, we defined the role and molecular mechanism of the motor protein dynein in the regulation of autophagic flux in CAMs. In mouse CAMs, dynein protein is abundantly expressed. Pharmacological or genetic inhibition of dynein activity dramatically enhanced 7-ketocholesterol (7-Ket)-induced expression of the autophagic marker LC3B and increased the cellular levels of p62, a selective substrate for autophagy. Inhibition of dynein activity increased 7-Ket-induced formation of autophagosomes (APs), but reduced the number of autophagolysosomes (APLs) in CAMs. Furthermore, 7-Ket increased the fusion of APs with lysosomes and the velocity of APs movement in mouse CAMs, which was abolished when the dynein activity in these cells was inhibited. Interestingly, 7-Ket increased lysosomal Ca(2+) release and stimulated dynein ATPase activity, both of which were abolished by NAADP antagonists, NED-19 and PPADS. Taken together, our data suggest that NAADP-mediated Ca(2+) release plays a crucial role in regulating dynein activity, which mediates APs trafficking and fusion with lysosomes to form APLs thus regulating autophagic flux in CAMs under atherogenic stimulation.

Inhibition of cytoplasmic streaming by cytochalasin D is superior to paraformaldehyde fixation for measuring FRET between fluorescent protein-tagged Golgi components

Protein-protein interaction at the organelle level can be analyzed by using tagged proteins and assessing Förster resonance energy transfer (FRET) between fluorescent donor and acceptor proteins. Such studies are able to uncover partners in the regulation of proteins and enzymes. However, any organelle movement is an issue for live FRET microscopy, as the observed organelle must not change position during measurement. One of the mobile organelles in plants is the Golgi apparatus following cytoplasmic streaming. It is involved in the decoration of proteins and processing of complex glycan structures for the cell wall. Understanding of these processes is still limited, but evidence is emerging that protein-protein interaction plays a key role in the function of this organelle. In the past, mobile organelles were usually immobilized with paraformaldehyde (PFA) for FRET-based interaction studies. Here, we show that the actin inhibitor Cytochalasin D (CytD) is superior to PFA for immobilization of Golgi stacks in plant cells. Two glycosyltransferases known to interact were tagged with cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP), respectively, coexpressed in Nicotiana benthamiana leaves and analyzed using confocal microscopy and spectral imaging. Fixation with PFA leads to reduced emission intensity when compared to CytD treatment. Furthermore, the calculated FRET efficiency was significantly higher with CytD than with PFA. The documented improvements are beneficial for all methods measuring FRET, where immobilization of the investigated molecules is necessary. It can be expected that FRET measurement in organelles of animal cells will also benefit from the use of inhibitors acting on the cytoskeleton.

Autophagy and Its Comprehensive Impact on ALS

Autophagy is a degradative modality that involves intracellular elimination of proteins and organelles by lysosomes. It is a conservative process and plays a crucial role in cell growth and development, and keeping cellular homeostasis especially under stress-induced situations. Recently, increasing evidence suggests that autophagic alternations may contribute to amyotrophic lateral sclerosis (ALS) as one of initial factors. LC3-II and p62 are found increased in spinal cord of both ALS patients and experimental models, indicating overwhelming autophagic level. But the aggregation of ALS-associated proteins, including SOD1 and TDP-43 suggest possible insufficiency of autophagy induction. Besides, augment autophagic level through genetic pathway or rapamycin leads to paradoxical results in different neurodegenerative diseases models. So, it remains controversial about autophagic effects on ALS progress. In this review, we will depict a comprehensive role that autophagy plays in ALS and focus on the influence of impaired autophagic flux and excessive autophagic vacuoles (AVs) that may aggregate ALS development. And we will discuss the potential therapeutic targets through modulating autophagic level to treat this disease.

Autophagy dysregulation in amyotrophic lateral sclerosis

Autophagy is an intracellular lysosomal degradation process, which plays an important role in cell growth and development, and keeping cellular homeostasis in all eukaryotes. Autophagy has multiple physiological functions, including protein degradation, organelle turnover and response to stress. Emerging evidences support the notion that dysregulation of autophagy might be critical for pathogenesis of amyotrophic lateral sclerosis (ALS). The autophagy dysregulation in motor neurons of ALS may occur in different steps of the autophagic process. Recent studies have shown that two ALS associated proteins, TDP-43 and superoxide dismutase 1 (SOD1), are involved in the abnormal autophagy regulation. Furthermore, it is reported that several genetic mutations in ALS disturb the autophagic process in the motor neurons. This review will provide new evidence of autophagy dysregulation as a critical pathogenic process leading to ALS, and will discuss the prospect of future therapeutic targets using autophagic regulation to treat this disease.

TDP-43 and FUS/TLS: cellular functions and implications for neurodegeneration

TDP-43 (transactive response binding protein of 43 kDa) and FUS (fused in sarcoma) comprise the neuropathological protein aggregates of distinct subtypes of the neurodegenerative diseases frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Moreover, the genes encoding TDP-43 and FUS are linked to these diseases. Both TDP-43 and FUS contain RNA binding motifs, and specific targets are being identified. Potential actions of TDP-43 and FUS include transcriptional regulation, mRNA processing and micro RNA biogenesis. These activities are probably modulated by interacting proteins in cell type specific manners as well as distinctly within the nucleus and cytosol, as both proteins shuttle between these compartments. In this minireview the specific functions of TDP-43 and FUS are described and discussed in the context of how TDP-43 and FUS may contribute to the pathogenesis of frontotemporal lobar degeneration and amyotrophic lateral sclerosis.

ALS genetic modifiers that increase survival of SOD1 mice and are suitable for therapeutic development

Amyotrophic lateral sclerosis (ALS) is a frequently fatal motor neuron disease without any cure. To find molecular therapeutic targets, several studies crossed transgenic ALS murine models with animals transgenic for some ALS target genes. We aimed to revise the new discoveries and new works in this field. We selected the 10 most promising genes, according to their capability when down-regulated or up-regulated in ALS animal models, for increasing life span and mitigating disease progression: XBP-1, NogoA and NogoB, dynein, heavy and medium neurofilament, NOX1 and NOX2, MLC-mIGF-1, NSE-VEGF, and MMP-9. Interestingly, some crucial modifier genes have been described as being involved in common pathways, the most significant of which are inflammation and cytoskeletal activities. The endoplasmic reticulum also seems to play an important role in ALS pathogenesis, as it is involved in different selected gene pathways. In addition, these genes have evident links to each other, introducing the hypothesis of a single unknown, common pathway involving all of these identified genes and others to be discovered.

Microtubule and kinesin/dynein-dependent, bi-directional transport of autolysosomes in neurites of PC12 cells

Autophagy, a major degradative pathway of the lysosomal system, has been implicated in various neurodegenerative diseases. During autophagic process, organelles and proteins are encapsulated in double-membrane vacuoles called autophagosomes, which finally fuse with lysosomes to form autolysosomes where incorporated materials are degraded. Despite extensive investigations in identifying the molecular components that participate in autophagy, little is known about routes and dynamics of autophagosomes/autolysosomes in the neurites of live cells. Hence, in the present study, we aim to investigate the biophysical characteristics of neuritic transport of autolysosomes in PC12 cells. Our study demonstrated that monomeric red fluorescence protein-light chain 3 (mRFP-LC3)-labeled autolysosomes were motile and moved along PC12 neurites in both anterograde and retrograde directions with a bias towards the nucleus during starvation. By using image processing, quantitative analysis was made to show the dynamic biophysical characteristics of these vesicles. The average velocity of anterograde and retrograde transport was 0.33±0.04μm/s and 0.39±0.05μm/s, respectively. Disruption of microtubules by nocodazole completely abolished their movements, suggesting the neuritic transport of autolysosomes depends on microtubules. The directional transport of autolysosomes was also affected by blockage of motor protein activity. Altogether, our study documents many aspects of the highly dynamic movement of autolysosome in PC12 neurites. Autolysosomes transported in a bi-directional manner along microtubules by dynein and kinesin motor proteins. These findings provide valuable insight into understanding the mechanism and control of autophagy in neurites under physiological and pathological conditions.

Autophagy protects against aminochrome-induced cell death in substantia nigra-derived cell line

Aminochrome, the precursor of neuromelanin, has been proposed to be involved in the neurodegeneration neuromelanin-containing dopaminergic neurons in Parkinson's disease. We aimed to study the mechanism of aminochrome-dependent cell death in a cell line derived from rat substantia nigra. We found that aminochrome (50μM), in the presence of NAD(P)H-quinone oxidoreductase, EC 1.6.99.2 (DT)-diaphorase inhibitor dicoumarol (DIC) (100μM), induces significant cell death (62 ± 3%; p < 0.01), increase in caspase-3 activation (p < 0.001), release of cytochrome C, disruption of mitochondrial membrane potential (p < 0.01), damage of mitochondrial DNA, damage of mitochondria determined with transmission electron microscopy, a dramatic morphological change characterized as cell shrinkage, and significant increase in number of autophagic vacuoles. To determine the role of autophagy on aminochrome-induced cell death, we incubated the cells in the presence of vinblastine and rapamycin. Interestingly, 10μM vinblastine induces a 5.9-fold (p < 0.001) and twofold (p < 0.01) significant increase in cell death when the cells were incubated with 30μM aminochrome in the absence and presence of DIC, respectively, whereas 10μM rapamycin preincubated 24 h before addition of 50μM aminochrome in the absence and the presence of 100μM DIC induces a significant decrease (p < 0.001) in cell death. In conclusion, autophagy seems to be an important protective mechanism against two different aminochrome-induced cell deaths that initially showed apoptotic features. The cell death induced by aminochrome when DT-diaphorase is inhibited requires activation of mitochondrial pathway, whereas the cell death induced by aminochrome alone requires inhibition of autophagy-dependent degrading of damaged organelles and recycling through lysosomes.