Defects In Autophagic Flux Research Articles

Retinal cells derived from patients with DRAM2-dependent CORD21 dystrophy exhibit key lysosomal enzyme deficiency and lysosomal content accumulation

Biallelic mutations in DRAM2 lead to an autosomal recessive cone-rod dystrophy known as CORD21, which typically presents between the third and sixth decades of life. Although DRAM2 localizes to the lysosomes of photoreceptor and retinal pigment epithelium (RPE) cells, its specific role in retinal degeneration has not been fully elucidated. In this study, we generated and characterized retinal organoids (ROs) and RPE cells from induced pluripotent stem cells (iPSCs) derived from two CORD21 patients. Our investigation revealed that CORD21-ROs and RPE cells exhibit abnormalities in lipid metabolism, defects in autophagic flux, accumulation of aberrant lysosomal content, and reduced lysosomal enzyme activity. We identified potential interactions of DRAM2 with vesicular trafficking proteins, suggesting its involvement in this cellular process. These findings collectively suggest that DRAM2 plays a crucial role in maintaining the integrity of photoreceptors and RPE cells by regulating lysosomal function, autophagy, and potentially vesicular trafficking.

Protective effect of saffron carotenoids against amyloid beta-induced neurotoxicity in differentiated PC12 cells via the unfolded protein response and autophagy.

The preventive effect of saffron against Alzheimer's disease (AD) has been reported. Herein, we studied the effect of Cro and Crt, saffron carotenoids, on the cellular model of AD. The MTT assay, flow cytometry, and elevated p-JNK, p-Bcl-2, and c-PARP indicated the AβOs-induced apoptosis in differentiated PC12 cells. Then, the protective effects of Cro/Crt on dPC12 cells against AβOs were investigated in preventive and therapeutic modalities. Starvation was used as a positive control. RT-PCR and Western blot results revealed the reduced eIF2α phosphorylation and increased spliced-XBP1, Beclin1, LC3II, and p62, which indicate the AβOs-induced autophagic flux defect, autophagosome accumulation, and apoptosis. Cro and Crt inhibited the JNK-Bcl-2-Beclin1 pathway. They altered Beclin1 and LC3II and decreased p62 expressions, leading cells to survival. Cro and Crt altered the autophagic flux by different mechanisms. So, Cro increased the rate of autophagosome degradation more than Crt, while Crt increased the rate of autophagosome formation more than Cro. The application of 4μ8C and chloroquine as the inhibitors of XBP1 and autophagy, respectively, confirmed these results. So, augmentation of the survival branches of UPR and autophagy is involved and may serve as an effective strategy to prevent the progression of AβOs toxicity.

APOL1 variant-expressing endothelial cells exhibit autophagic dysfunction and mitochondrial stress.

Polymorphisms in the Apolipoprotein L1 (APOL1) gene are common in ancestrally African populations, and associate with kidney injury and cardiovascular disease. These risk variants (RV) provide an advantage in resisting Trypanosoma brucei, the causal agent of African trypanosomiasis, and are largely absent from non-African genomes. Clinical associations between the APOL1 high risk genotype (HRG) and disease are stronger in those with comorbid infectious or immune disease. To understand the interaction between cytokine exposure and APOL1 cytotoxicity, we established human umbilical vein endothelial cell (HUVEC) cultures representing each APOL1 genotype. Untreated HUVECs were compared to IFNɣ-exposed; and APOL1 expression, mitochondrial function, lysosome integrity, and autophagic flux were measured. IFNɣ increased median APOL1 expression across all genotypes 22.1 (8.3 to 29.8) fold (p=0.02). Compared to zero risk variant-carrying HUVECs (0RV), HUVECs carrying 2 risk variant copies (2RV) showed both depressed baseline and maximum mitochondrial oxygen consumption (p<0.01), and impaired mitochondrial networking on MitoTracker assays. These cells also demonstrated a contracted lysosomal compartment, and an accumulation of autophagosomes suggesting a defect in autophagic flux. Upon blocking autophagy with non-selective lysosome inhibitor, hydroxychloroquine, autophagosome accumulation between 0RV HUVECs and untreated 2RV HUVECs was similar, implicating lysosomal dysfunction in the HRG-associated autophagy defect. Compared to 0RV and 2RV HUVECs, HUVECs carrying 1 risk variant copy (1RV) demonstrated intermediate mitochondrial respiration and autophagic flux phenotypes, which were exacerbated with IFNɣ exposure. Taken together, our data reveal that IFNɣ induces APOL1 expression, and that each additional RV associates with mitochondrial dysfunction and autophagy inhibition. IFNɣ amplifies this phenotype even in 1RV HUVECs, representing the first description of APOL1 pathobiology in variant heterozygous cell cultures.

A neurodegeneration gene, WDR45, links impaired ferritinophagy to iron accumulation.

Neurodegeneration with brain iron accumulation (NBIA) is a clinically and genetically heterogeneous group of neurodegenerative diseases characterized by the abnormal accumulation of brain iron and the progressive degeneration of the nervous system. One of the recently identified subtypes of NBIA is β‐propeller protein‐associated neurodegeneration (BPAN). BPAN is caused by de novo mutations in the WDR45/WIPI4 (WD repeat domain 45) gene. WDR45 is one of the four mammalian homologs of yeast Atg18, a regulator of autophagy. WDR45 deficiency in BPAN patients and animal models may result in defects in autophagic flux. However, how WDR45 deficiency leads to brain iron overload remains unclear. To elucidate the role of WDR45, we generated a WDR45‐knockout (KO) SH‐SY5Y neuroblastoma cell line using CRISPR‐Cas9‐mediated genome editing. Using these cells, we demonstrated that the non‐TF (transferrin)‐bound iron pathway dominantly mediated the accumulation of iron. Moreover, the loss of WDR45 led to defects in ferritinophagy, a form of autophagy that degrades the iron storage protein ferritin. We showed that impaired ferritinophagy contributes to iron accumulation in WDR45‐KO cells. Iron accumulation was also detected in the mitochondria, which was accompanied by impaired mitochondrial respiration, elevated reactive oxygen species, and increased cell death. Thus, our study links WDR45 to specific iron acquisition pathways and ferritinophagy. Cover Image for this issue: https://doi.org/10.1111/jnc.15388

Simvastatin Enhances Muscle Regeneration Through Autophagic Defect-Mediated Inflammation and mTOR Activation in G93ASOD1 Mice.

Amyotrophic lateral sclerosis is a fatal neurodegenerative disease characterised by the selective loss of motor neurons, muscular atrophy, and degeneration. Statins, as 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are the most widely prescribed drugs to lower cholesterol levels and used for the treatment of cardiovascular and cerebrovascular diseases. However, statins are seldom used in muscular diseases, primarily because of their rare statin-associated myopathy. Recently, statins have been shown to reduce muscular damage and improve its function. Here, we investigated the role of statins in myopathy using G93ASOD1 mice. Our results indicated that simvastatin significantly increased the autophagic flux defect and increased inflammation in the skeletal muscles of G93ASOD1 mice. We also found that increased inflammation correlated with aggravated muscle atrophy and fibrosis. Nevertheless, long-term simvastatin treatment promoted the regeneration of damaged muscle by activating the mammalian target of rapamycin pathway. However, administration of simvastatin did not impede vast muscle degeneration and movement dysfunction resulting from the enhanced progressive impairment of the neuromuscular junction. Together, our findings highlighted that simvastatin exacerbated skeletal muscle atrophy and denervation in spite of promoting myogenesis in damaged muscle, providing new insights into the selective use of statin-induced myopathy in ALS.

The GTPase Rab27b regulates the release, autophagic clearance, and toxicity of α-synuclein

α-Synuclein (αsyn) is the primary component of proteinaceous aggregates termed Lewy bodies that pathologically define synucleinopathies including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). αsyn is hypothesized to spread through the brain in a prion-like fashion by misfolded protein forming a template for aggregation of endogenous αsyn. The cell-to-cell release and uptake of αsyn are considered important processes for its prion-like spread. Rab27b is one of several GTPases essential to the endosomal-lysosomal pathway and is implicated in protein secretion and clearance, but its role in αsyn spread has yet to be characterized. In this study, we used a paracrine αsyn in vitro neuronal model to test the impact of Rab27b on αsyn release, clearance, and toxicity. shRNA-mediated knockdown (KD) of Rab27b increased αsyn-mediated paracrine toxicity. Rab27b reduced αsyn release primarily through nonexosomal pathways, but the αsyn released after Rab27b KD was of higher-molecular-weight species, as determined by size-exclusion chromatography. Rab27b KD increased intracellular levels of insoluble αsyn and led to an accumulation of endogenous light chain 3 (LC3)-positive puncta. Rab27b KD also decreased LC3 turnover after treatment with an autophagosome-lysosome fusion inhibitor, chloroquine, indicating that Rab27b KD induces a defect in autophagic flux. Rab27b protein levels were increased in brain lysates obtained from postmortem tissues of individuals with PD and DLB compared with healthy controls. These data indicate a role for Rab27b in the release, clearance, and toxicity of αsyn and, ultimately, in the pathogenesis of synucleinopathies.

WDR45 Contributes to Iron Accumulation Through Dysregulation of Neuronal Iron Homeostasis

Abstract Objectives Neurodegeneration with brain iron accumulation (NBIA) is a clinically and genetically heterogeneous group of neurodegenerative diseases characterized by an abnormal accumulation of brain iron and progressive degeneration of the nervous system. β-propeller protein-associated neurodegeneration (BPAN) (OMIM #300,894) is a recently identified subtype of NBIA. BPAN is caused by de novo mutations in the WD repeat domain 45 (WDR45) gene. WDR45 deficiency in BPAN patients and animal models has shown defects in autophagic flux, suggesting a role for WDR45 in autophagy. How WDR45 deficiency leads to brain iron overload remains unclear. The goal of the present study is to identify the pathogenic mechanisms of WDR45 deficiency that cause iron overload and neurodegeneration. Methods To elucidate the role of WDR45 in dopaminergic neuronal cells, we generated a WDR45-knockout (KO) SH-SY5Y cell line by CRISPR/Cas9-mediated genome editing. To identify mechanisms underlying iron homeostasis and transport, we examined two cellular iron acquisition pathways in these cells using radioactive isotope 59Fe: 1) the canonical transferrin-bound iron (TBI) uptake pathway and 2) the nontransferrin-bound iron (NTBI) pathway. Results Loss of WDR45 increased total iron levels with a concomitant increase in the iron storage protein ferritin in neuronal cells. Specifically, WDR45-KO cells preferentially took up NTBI compared to wild-type cells. Concordant with these functional data, the level of divalent metal transporter-1 (DMT1) expression was upregulated in WDR45-KO cells, providing a causal link to iron overload in WDR45 deficiency. In addition, loss of WDR45 led to defects in autophagic flux and impaired ferritinophagy, a lysosomal process that promotes ferritin degradation, suggesting that iron overload is driven by impaired ferritinophagy. Interestingly, WDR45 deficiency increased iron accumulation in the mitochondria, impaired mitochondrial function, and in turn, elevated reactive oxygen species generation. Conclusions Our study provides the first evidence that WDR45 deficiency alters cellular iron acquisition pathways thereby leading to iron accumulation in neuronal cells. These findings will serve as a basis for developing therapeutic strategies for patients with NBIA. Funding Sources NIH, NBIA Disorder Association.

TFE3, a potential therapeutic target for Spinal Cord Injury via augmenting autophagy flux and alleviating ER stress.

Background and Aim: Increasing evidence suggests that spinal cord injury (SCI)-induced defects in autophagic flux may contribute to an impaired ability for neurological repair following injury. Transcription factor E3 (TFE3) plays a crucial role in oxidative metabolism, lysosomal homeostasis, and autophagy induction. Here, we investigated the role of TFE3 in modulating autophagy following SCI and explored its impact on neurological recovery.Methods: Histological analysis via HE, Nissl and Mason staining, survival rate analysis, and behavioral testing via BMS and footprint analysis were used to determine functional recovery after SCI. Quantitative real-time polymerase chain reaction, Western blotting, immunofluorescence, TUNEL staining, enzyme-linked immunosorbent assays, and immunoprecipitation were applied to examine levels of autophagy flux, ER-stress-induced apoptosis, oxidative stress, and AMPK related signaling pathways. In vitro studies using PC12 cells were performed to discern the relationship between ROS accumulation and autophagy flux blockade.Results: Our results showed that in SCI, defects in autophagy flux contributes to ER stress, leading to neuronal death. Furthermore, SCI enhances the production of reactive oxygen species (ROS) that induce lysosomal dysfunction to impair autophagy flux. We also showed that TFE3 levels are inversely correlated with ROS levels, and increased TFE3 levels can lead to improved outcomes. Finally, we showed that activation of TFE3 after SCI is partly regulated by AMPK-mTOR and AMPK-SKP2-CARM1 signaling pathways.Conclusions: TFE3 is an important regulator in ROS-mediated autophagy dysfunction following SCI, and TFE3 may serve as a promising target for developing treatments for SCI.

Autophagic flux defect in diabetic kidney disease results in megamitochondria formation in podocytes

Podocyte injury is an important factor in the pathogenesis of diabetic nephropathy. Podocytes are characterized by large numbers of mitochondria. However, mitochondrial dysfunction as it relates to kidney pathology remains poorly understood. The present study found that podocyte mitochondria in different animal models of diabetes mellitus became elongated with the development of albuminuria, suggesting a change in mitochondrial dynamics. We then treated cells with a combination of glucose, fatty acids, and angiotensin II (GFA) to mimic the diabetic milieu. Cultured podocytes exposed to GFA showed megamitochondria formation and decreased autophagosome degradation. We also found that GFA treatment decreased the binding of the autophagosome to the lysosome. Our results suggest that megamitochondria are common in podocytes during diabetic nephropathy and that insufficient autophagy flux may underlie this effect. These findings have expanded our understanding of the pathogenesis of diabetic nephropathy and identified a potential pharmacological target for treatment.

Characterization of three TRAPPC11 variants suggests a critical role for the extreme carboxy terminus of the protein

TRAPPC11 was identified as a component of the TRAPP III complex that functions in membrane trafficking and autophagy. Variants in TRAPPC11 have been reported to be associated with a broad spectrum of phenotypes but all affected individuals display muscular pathology. Identifying additional variants will further our understanding of the clinical spectrum of phenotypes and will reveal regions of the protein critical for its functions. Here we report three individuals from unrelated families that have bi-allellic TRAPPC11 variants. Subject 1 harbors a compound heterozygous variant (c.1287 + 5G > A and c.3379_3380insT). The former variant results in a partial deletion of the foie gras domain (p.Ala372_Ser429del), while the latter variant results in a frame-shift and extension at the carboxy terminus (p.Asp1127Valfs*47). Subjects 2 and 3 both harbour a homozygous missense variant (c.2938G > A; p.Gly980Arg). Fibroblasts from all three subjects displayed membrane trafficking defects manifested as delayed endoplasmic reticulum (ER)-to-Golgi transport and/or a delay in protein exit from the Golgi. All three individuals also show a defect in glycosylation of an ER-resident glycoprotein. However, only the compound heterozygous subject displayed an autophagic flux defect. Collectively, our characterization of these individuals with bi-allelic TRAPPC11 variants highlights the functional importance of the carboxy-terminal portion of the protein.

3448 Macrophages, APOL1 Genotype, &amp; Immunometabolism in CVD (MAGIC

OBJECTIVES/SPECIFIC AIMS: This study aims to understand the potential immunomudualtory effect of APOL1 variants in auto-antigen activated myeloid cells by assessing lysosomal integrity in activated cells expressing APOL1. The primary stimuli were: 1. ssRNA hY3 as a proxy for the Ro immune complex; 2. in an bulk RNA seq model, interferon-response gene, Siglec 1, as a read out of interferon activity. The primary outcomes were: 1. Myeloid cell APOL1 expression both in primary macrophage cultures and ex-vivo patient derived macrophages; 2. Lysosome integrity as measured by fluorescence intensity of lysotracker dye on light microscopy. METHODS/STUDY POPULATION: All recruited subjects provided written informed consent as per the NEW YORK UNIVERSITY Division of Rheumatology-wide Specimen and Matched Phenotype Linked Examination (SAMPLE) protocol. Subjects were African American; SLE subjects met 4 American College of Rheumatology criteria for SLE. Healthy donor monocytes representing each genotype in duplicate (reference allele: G0/G0; heterozygote variant: RV/G0; and homozygote variant RV/RV) were cultured with GM-CSF to yield macrophages which were incubated in serum free media or with hY3 ssRNA (TLR 7/8 agonist) to yield inflammatory M1 macrophages. Fold increase of APOL1 in untreated vs hY3 treated macrophages was measured using qPCR. Live cells were then cultured on glass chamber slides with DNA dye, DAPI, and Lysotracker red, a fluorescent dye that stains acidic lysosomes. As a proof of concept, interferon response gene, Signlec1, and APOL1 transcriptional activity in peripheral blood monocytes (PBMCs) were measured and correlated in 17 SLE patients by RNA seq. RESULTS/ANTICIPATED RESULTS: Regardless of genotype, hY3 increased APOL1 expression by 29 (+/−18.4) fold (P = 0.007 vs no treatment). Genotyping of the qPCR product showed concordance with the chromosomal DNA with the RV heterozygotes expressing both alleles. To examine lysosomal membrane integrity, live hY3-treated macrophages were stained with lysosotracker dye and fluorescence intensity was measured. Compared to reference allele carrying macrophages, each additional variant allele corresponded with a lesser degree of lysosome compartment staining. In SLE PBMCs, we found that APOL1 was highly expressed, and significantly correlated with Siglec1 (F=10.5; P = 0.005) supporting an association between circulating interferons and APOL1 accumulation in monocytes. DISCUSSION/SIGNIFICANCE OF IMPACT: Given that the “cytokine milieu” in SLE elicits APOL1 expression, induces inflammatory cell metabolic rewiring, and stimulates autophagy thereby exposing defects in autophagic flux, this gene-environment interaction may underpin the relationship between chronic inflammation and heightened APOL1 polymorphism-attributed cardiovascular risk. These data support further inquiry into the intersection between chronic autoimmunity and APOL1’s functional role in the vascular microenvironment. The in vitro studies herein extend our prior work by demonstrating a mechanistic link between SLE-associated inflammation, APOL1 risk variant status and CVD via a lysosomal defect which converges on common autophagic and metabolic pathways in mononuclear cells.

Silver nanoparticles induce lysosomal-autophagic defects and decreased expression of transcription factor EB in A549 human lung adenocarcinoma cells

Although silver nanoparticles (AgNPs) are widely used in consumer and medical products, the mechanism by which AgNPs cause pulmonary damage is unclear. AgNPs are incorporated into cells and processed via the autophagy pathway. We examined the effects of AgNP exposure on autophagic flux and expression of transcription factor EB (TFEB) in A549 lung adenocarcinoma cells. In cells exposed to citrate-coated 60-nm AgNPs, confocal laser microscopic examination showed a decrease in the LysoTracker fluorescence signal and an increase in that of Cyto-ID, indicating lysosomal pH alkalization and autophagosome formation, respectively. The proteins p62 and microtubule-associated protein light chain 3B-II (LC3B-II) are both degraded by autophagy, and their levels increased depending on AgNP dose. Furthermore, AgNP-induced increase in LC3B-II was not enhanced by treatment with the autophagic inhibitor bafilomycin A1. TFEB mRNA levels, and protein levels in cytosolic and nuclear fractions, were suppressed by exposure to AgNPs, suggesting transcriptional inhibition of TFEB expression. Overexpression of TFEB did not suppress AgNP-induced LC3B-II accumulation and cellular damage, indicating that impairment of autophagic flux and cellular damage by AgNPs might not be primarily caused by reduced TFEB expression. The present study suggests that AgNP-induced lysosomal dysfunction plays a principal role in the autophagic flux defect.

Glucagon-Like Peptide 1 Protects Pancreatic β-Cells From Death by Increasing Autophagic Flux and Restoring Lysosomal Function.

Studies in animal models of type 2 diabetes have shown that glucagon-like peptide 1 (GLP-1) receptor agonists prevent β-cell loss. Whether GLP-1 mediates β-cell survival via the key lysosomal-mediated process of autophagy is unknown. In this study, we report that treatment of INS-1E β-cells and primary islets with glucolipotoxicity (0.5 mmol/L palmitate and 25 mmol/L glucose) increases LC3 II, a marker of autophagy. Further analysis indicates a blockage in autophagic flux associated with lysosomal dysfunction. Accumulation of defective lysosomes leads to lysosomal membrane permeabilization and release of cathepsin D, which contributes to cell death. Our data further demonstrated defects in autophagic flux and lysosomal staining in human samples of type 2 diabetes. Cotreatment with the GLP-1 receptor agonist exendin-4 reversed the lysosomal dysfunction, relieving the impairment in autophagic flux and further stimulated autophagy. Small interfering RNA knockdown showed the restoration of autophagic flux is also essential for the protective effects of exendin-4. Collectively, our data highlight lysosomal dysfunction as a critical mediator of β-cell loss and shows that exendin-4 improves cell survival via restoration of lysosomal function and autophagic flux. Modulation of autophagy/lysosomal homeostasis may thus define a novel therapeutic strategy for type 2 diabetes, with the GLP-1 signaling pathway as a potential focus.

Circulation : Clinical Summaries

<i>Circulation</i> : Clinical Summaries

Leucine-Rich Repeat Kinase 1 Regulates Autophagy through Turning On TBC1D2-Dependent Rab7 Inactivation.

Autophagy is a conserved process that enables catabolic and degradative pathways. Rab family proteins, which are active in the GTP-bound form, regulate the transport and fusion of autophagosomes. However, it remains unclear how each cycle of Rab activation and inactivation is precisely regulated. Here, we show that leucine-rich repeat kinase 1 (LRRK1) regulates autophagic flux by controlling Rab7 activity in autolysosome formation. Upon induction of autophagy, LRRK1 was recruited via an association with VAMP7 to the autolysosome, where it activated the Rab7 GTPase-activating protein (GAP) TBC1D2, thereby switching off Rab7 signaling. Consistent with this model, LRRK1 deletion caused mice to be vulnerable to starvation and disrupted autolysosome formation, as evidenced by the accumulation of enlarged autolysosomes with undegraded LC3-II and persistently high levels of Rab7-GTP. This defect in autophagic flux was partially rescued by a mutant form of TBC1D2 with elevated Rab7-GAP activity. Thus, the spatiotemporal regulation of Rab7 activity during tunicamycin-induced autophagy is regulated by LRRK1.

Histone deacetylase 6 delays motor neuron degeneration by ameliorating the autophagic flux defect in a transgenic mouse model of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective loss of motor neurons. Abnormal protein aggregation and impaired protein degradation are believed to contribute to the pathogenesis of this disease. Our previous studies showed that an autophagic flux defect is involved in motor neuron degeneration in the SOD1(G93A) mouse model of ALS. Histone deacetylase 6 (HDAC6) is a class II deacetylase that promotes autophagy by inducing the fusion of autophagosomes to lysosomes. In the present study, we showed that HDAC6 expression was decreased at the onset of disease and became extremely low at the late stage in ALS mice. Using lentivirus-HDAC6 gene injection, we found that HDAC6 overexpression prolonged the lifespan and delayed the motor neuron degeneration in ALS mice. Moreover, HDAC6 induced the formation of autolysosomes and accelerated the degradation of SOD1 protein aggregates in the motor neurons of ALS mice. Collectively, our results indicate that HDAC6 has neuroprotective effects in an animal model of ALS by improving the autophagic flux in motor neurons, and autophagosome-lysosome fusion might be a therapeutic target for ALS.

Abstract A02: PKCι in pancreatic cancer development: A possible role for autophagy

Abstract Pancreatic cancer is the fourth leading cause of cancer death in the United States with current 5-year survival rates at 6%. Greater than 90% of all pancreatic cancers harbor an activating mutation in codon 12 of the Kras gene (KrasG12D). Protein Kinase C iota (PKCι) has been shown to mediate KrasG12D downstream signaling and acinar-to-ductal metaplasia in an explant model of pancreatic cancer initiation. Additionally, inhibition of PKCι in human pancreatic cancer cells leads to decreased tumor size, angiogenesis, and metastasis in an orthotopic tumor model, suggesting that PKCι plays a role in maintaining the oncogenic phenotype of pancreatic cancer cells. We sought to test the hypothesis that PKCι plays a role development and maintenance of pancreatic cancer using a mouse model of KrasG12D-induced pancreatic cancer. Purpose: To identify the effect of PKCι loss on pancreas function and development of KrasG12D-induced pancreatic cancer. Procedures: Pancreata from mice with pancreas-specific deletion of PKCι, with and without pancreas-specific KrasG12D expression, were analyzed for histological and protein expression alterations. Acinar cells isolated from these transgenic mouse models were subjected to in vitro analyses to determine the role of PKCι in pancreatic cell homeostasis. Results: Mice lacking pancreatic PKCι survived and developed normally. Pancreatic knockout of PKCι expression resulted in a phenotype consistent with a defect in autophagic flux. In vitro analyses of isolated acinar cells supported the hypothesis that PKCι promotes autophagy in pancreatic cells. Autophagy exhibits a dual functionality in pancreatic cancer, acting as a tumor suppressor in normal cells and a tumor promoter in established tumor cells. We sought to determine the effect of PKCι knock-out on both of these cell types in a mouse model of pancreatic cancer. Using the LSL mouse model of K-ras induced pancreatic cancer, we demonstrated that pancreatic loss of PKCι lead to an increase in the number of Pancreatic Intraepithelial (PanIN) lesions formed in young mice. However, these lesions were protected from progressing past the early PanIN1/2 stage such that no mice lacking PKCι developed cancer, even after 1.5 years of age. By contrast, over 50% of mice with wild-type PKCι developed cancer; of those without cancer, many had progressed to the PanIN-3 stage, a stage representative of carcinoma in-situ. These data are similar to that seen in mouse models of pancreatic cancer with genetic inhibition of autophagy. Analysis of PanINs in these mice revealed that those lacking PKCι expressed significantly more P62 protein, a selective autophagy substrate, compared to PanINs with wild-type PKCι, supporting a block in the autophagic flux. These data suggest that PKCι plays an important role in both the initiation and progression of pancreatic cancer, possibly by regulating autophagic flux. Impact: Inhibition of pancreatic PKCι expression prevented progression of PanIN lesions past the early PanIN1/2 stage, resulting in a complete block in cancer development in mouse models of pancreatic cancer. Our preliminary data suggests that PKCι promotes cancer progression by regulating autophagic flux, a process that has been shown to be essential for KrasG12D-mediated pancreatic cancers. Pancreatic cancer is characterized by resistance to current therapies. Novel targets for new and more effective therapies are critical to improve outcomes for patients with this deadly disease. Inhibitors of PKCι are currently in clinical trials for ovarian and lung cancers. Our data supports the feasibility of using PKCι inhibitors for therapy in pancreatic cancer. Citation Format: Kristin S. Inman, Amanda A. Francis, Nicole R. Murray. PKCι in pancreatic cancer development: A possible role for autophagy. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A02.

Measuring autophagic flux by assessing LC3, p62 and LAMP1 co-localization using imaging flow cytometry (TECH2P.908)

Abstract Autophagy is a catabolic pathway in which normal or dysfunctional cellular components that accumulate during growth and differentiation are degraded via the lysosome; during starvation it is a survival mechanism that reallocates nutrients from unnecessary processes to more vital processes in the cell. In autophagy, cytoplasmic LC3 protein is processed and recruited to the autophagosomal membranes. The autophagosome then fuses with the lysosome to cause the breakdown of the autophagosome vesicle and its contents. The ubiquitin-associated protein p62 which binds to LC3 can also be used to measure autophagy. p62 is an important marker for the induction of autophagy, clearance of protein aggregates and the inhibition of autophagy. In addition, p62 positive cytoplasmic inclusions have been found in several neurodegenerative diseases. Immunofluorescence microscopy has been used to visually identify LC3 puntca, p62 and/or lysosomes on a per-cell basis; however, an objective and statistically rigorous assessment can be difficult to obtain. To overcome these problems, we employed the ImageStreamX Mark II imaging cytometry platform. We collected large numbers of cell images to assess autophagy and co-localization of LC3, p62 and the lysosomal marker LAMP1 in an objective, quantitative, and statistically robust manner. Defects in autophagic flux have been linked to immune-mediated diseases; we believe this technique may bring insight to these diseases.

Nucleocytosolic Depletion of the Energy Metabolite Acetyl-Coenzyme A Stimulates Autophagy and Prolongs Lifespan

SummaryHealthy aging depends on removal of damaged cellular material that is in part mediated by autophagy. The nutritional status of cells affects both aging and autophagy through as-yet-elusive metabolic circuitries. Here, we show that nucleocytosolic acetyl-coenzyme A (AcCoA) production is a metabolic repressor of autophagy during aging in yeast. Blocking the mitochondrial route to AcCoA by deletion of the CoA-transferase ACH1 caused cytosolic accumulation of the AcCoA precursor acetate. This led to hyperactivation of nucleocytosolic AcCoA-synthetase Acs2p, triggering histone acetylation, repression of autophagy genes, and an age-dependent defect in autophagic flux, culminating in a reduced lifespan. Inhibition of nutrient signaling failed to restore, while simultaneous knockdown of ACS2 reinstated, autophagy and survival of ach1 mutant. Brain-specific knockdown of Drosophila AcCoA synthetase was sufficient to enhance autophagic protein clearance and prolong lifespan. Since AcCoA integrates various nutrition pathways, our findings may explain diet-dependent lifespan and autophagy regulation.

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 SOD1G93A 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 SOD1G93A mice. We have found that trehalose significantly delays disease onset prolongs life span, and reduces motor neuron loss in the spinal cord of SOD1G93A 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 SOD1G93A mice. Moreover, we have demonstrated that trehalose can reduce skeletal muscle denervation, protect mitochondria, and inhibit the proapoptotic pathway in SOD1G93A 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.