Acetylation targets mutant huntingtin to autophagosomes for degradation.

Huntington's disease (HD) is an incurable neurodegenerative disease caused by neuronal accumulation of the mutant protein huntingtin. Improving clearance of the mutant protein is expected to prevent cellular dysfunction and neurodegeneration in HD. We report here that such clearance can be achieved by posttranslational modification of the mutant Huntingtin (Htt) by acetylation at lysine residue 444 (K444). Increased acetylation at K444 facilitates trafficking of mutant Htt into autophagosomes, significantly improves clearance of the mutant protein by macroautophagy, and reverses the toxic effects of mutant huntingtin in primary striatal and cortical neurons and in a transgenic C. elegans model of HD. In contrast, mutant Htt that is rendered resistant to acetylation dramatically accumulates and leads to neurodegeneration in cultured neurons and in mouse brain. These studies identify acetylation as a mechanism for removing accumulated protein in HD, and more broadly for actively targeting proteins for degradation by autophagy.

Advanced glycation end-products (AGEs) are lower in prostate tumor tissue and inversely related to proportion of West African ancestry.

BACKGROUND: The metabolism of normal prostate relies on glycolysis, with prostate cancer having reduced glycolysis and increased aerobic metabolism. Advanced glycation end products (AGEs) accumulate in tissues as a result of age and glycolytic rate. Differential AGE levels were recently observed in prostate cancer tissues. Herein we sought to quantify AGEs in benign and cancer prostate tissue in a diverse cohort of patients. METHODS: Levels of the AGE Nε-(carboxylethyl)lysine (CML) were quantified by immunohistochemistry (IHC) in a tissue microarray which consisted of 3 cores from tumor and 2 cores from benign areas from 118 patients (87 African American and 31 European American). Ancestry informative markers for African Ancestry were available for 79 patients. Epithelial and stromal areas were quantified separately using an E-cadherin mask. CML levels were compared with clinical grade group and ancestry by mixed linear effect models. Age, prostate-specific antigen (PSA) levels, body mass index (BMI), and hemoglobin A1C were included as covariates. RESULTS: CML levels were lower in areas of the tumor, for both epithelium and surrounding stroma, compared with benign, but did not significantly change with tumor grade group. Age, PSA levels, BMI, and hemoglobin A1C did not associate with CML levels. CML levels were inversely associated with the percentage of African Ancestry in all tissues. CONCLUSIONS: The low CML levels in cancer may reflect the reduced glycolytic state of the tissue. The inverse relationship between African Ancestry and CML levels in both benign and cancer areas suggests a state of reduced glycolysis. It is yet to be determined whether altered glycolysis and CML levels are bystanders or drivers of carcinogenesis.

Chaperone networks: tipping the balance in protein folding diseases.

Adult-onset neurodegeneration and other protein conformational diseases are associated with the appearance, persistence, and accumulation of misfolded and aggregation-prone proteins. To protect the proteome from long-term damage, the cell expresses a highly integrated protein homeostasis (proteostasis) machinery to ensure that proteins are properly expressed, folded, and cleared, and to recognize damaged proteins. Molecular chaperones have a central role in proteostasis as they have been shown to be essential to prevent the accumulation of alternate folded proteotoxic states as occurs in protein conformation diseases exemplified by neurodegeneration. Studies using invertebrate models expressing proteins associated with Huntington's disease, Alzheimer's disease, ALS, and Parkinson's disease have provided insights into the genetic networks and stress signaling pathways that regulate the proteostasis machinery to prevent cellular dysfunction, tissue pathology, and organismal failure. These events appear to be further amplified by aging and provide evidence that age-related failures in proteostasis may be a common element in many diseases.

Reducing INS-IGF1 signaling protects against non-cell autonomous vesicle rupture caused by SNCA spreading.

Aging is associated with a gradual decline of cellular proteostasis, giving rise to devastating protein misfolding diseases, such as Alzheimer disease (AD) or Parkinson disease (PD). These diseases often exhibit a complex pathology involving non-cell autonomous proteotoxic effects, which are still poorly understood. Using Caenorhabditis elegans we investigated how local protein misfolding is affecting neighboring cells and tissues showing that misfolded PD-associated SNCA/α-synuclein is accumulating in highly dynamic endo-lysosomal vesicles. Irrespective of whether being expressed in muscle cells or dopaminergic neurons, accumulated proteins were transmitted into the hypodermis with increasing age, indicating that epithelial cells might play a role in remote degradation when the local endo-lysosomal degradation capacity is overloaded. Cell biological and genetic approaches revealed that inter-tissue dissemination of SNCA was regulated by endo- and exocytosis (neuron/muscle to hypodermis) and basement membrane remodeling (muscle to hypodermis). Transferred SNCA conformers were, however, inefficiently cleared and induced endo-lysosomal membrane permeabilization. Remarkably, reducing INS (insulin)-IGF1 (insulin-like growth factor 1) signaling provided protection by maintaining endo-lysosomal integrity. This study suggests that the degradation of lysosomal substrates is coordinated across different tissues in metazoan organisms. Because the chronic dissemination of poorly degradable disease proteins into neighboring tissues exerts a non-cell autonomous toxicity, this implies that restoring endo-lysosomal function not only in cells with pathological inclusions, but also in apparently unaffected cell types might help to halt disease progression.Abbreviations: AD: Alzheimer disease; BM: basement membrane; BWM: body wall muscle; CEP: cephalic sensilla; CLEM: correlative light and electron microscopy; CTNS-1: cystinosin (lysosomal protein) homolog; DA: dopaminergic; DAF-2: abnormal dauer formation; ECM: extracellular matrix; FLIM: fluorescence lifetime imaging microscopy; fps: frames per second; GFP: green fluorescent protein; HPF: high pressure freezing; IGF1: insulin-like growth factor 1; INS: insulin; KD: knockdown; LMP: lysosomal membrane permeabilization; MVB: multivesicular body; NOC: nocodazole; PD: Parkinson disease; RFP: red fluorescent protein; RNAi: RNA interference; sfGFP: superfolder GFP; SNCA: synuclein alpha; TEM: transmission electron microscopy; TNTs: tunneling nanotubes; TCSPC: time correlated single photon counting; YFP: yellow fluorescent protein.

Prostate Stroma Increases the Viability and Maintains the Branching Phenotype of Human Prostate Organoids.

The fibromuscular stroma of the prostate regulates normal epithelial differentiation and contributes to carcinogenesis in vivo. We developed and characterized a human 3D prostate organoid co-culture model that incorporates prostate stroma. Primary prostate stromal cells increased organoid formation and directed organoid morphology into a branched acini structure similar to what is observed in vivo. Organoid branching occurred distal to physical contact with stromal cells, demonstrating non-random branching. Stroma-induced phenotypes were similar in all patients examined, yet they maintained inter-patient heterogeneity in the degree of response. Stromal cells expressed growth factors involved in epithelial differentiation, which was not observed in non-prostatic fibroblasts. Organoids derived from areas of prostate cancer maintained differential expression of alpha-methylacyl-CoA racemase and showed increased viability and passaging when co-cultured with stroma. The addition of stroma to epithelial cells in vitro improves the ability of organoids to recapitulate features of the tissue and enhances the viability of organoids.

Model systems of protein-misfolding diseases reveal chaperone modifiers of proteotoxicity.

Chaperones and co-chaperones enable protein folding and degradation, safeguarding the proteome against proteotoxic stress. Chaperones display dynamic responses to exogenous and endogenous stressors and thus constitute a key component of the proteostasis network (PN), an intricately regulated network of quality control and repair pathways that cooperate to maintain cellular proteostasis. It has been hypothesized that aging leads to chronic stress on the proteome and that this could underlie many age-associated diseases such as neurodegeneration. Understanding the dynamics of chaperone function during aging and disease-related proteotoxic stress could reveal specific chaperone systems that fail to respond to protein misfolding. Through the use of suppressor and enhancer screens, key chaperones crucial for proteostasis maintenance have been identified in model organisms that express misfolded disease-related proteins. This review provides a literature-based analysis of these genetic studies and highlights prominent chaperone modifiers of proteotoxicity, which include the HSP70-HSP40 machine and small HSPs. Taken together, these studies in model systems can inform strategies for therapeutic regulation of chaperone functionality, to manage aging-related proteotoxic stress and to delay the onset of neurodegenerative diseases.

The nematode Caenorhabditis elegans displays a chemotaxis behavior to tuberculosis-specific odorants.

A simple, affordable diagnostic test for pulmonary tuberculosis (TB) is urgently needed to improve detection of active Mycobacterium tuberculosis. Recently, it has been suggested that animal behavior can be used as a biosensor to signal the presence of human disease. For example, the giant African pouched rats can detect tuberculosis by sniffing sputum specimens while trained honeybees respond to three of the volatile organic compounds (VOCs) detected in the breath of TB positive patients by proboscis extension. However, both rats and honeybees require animal housing facilities and professional trainers, which are outside the scope of most disease testing facilities. Here, we report that the innate olfactory behavioral response of the roundworm nematode Caenorhabditis elegans can be used to detect the TB-specific VOCs methyl p-anisate, methyl nicotinate, methyl phenylacetate and o-phenylanisole, in chemotaxis assays. Dauer larvae, a long-lived stress resistant alternative development state of C. elegans in which the animals can survive for extended periods of time in dry conditions with no food, were also demonstrated to detect the VOCs. We propose that exposing naive dauer larvae to TB-related VOCs and recording their response in this behavioral assay could lead to the development of a new method for TB diagnostics using breath as the sample type.

Caenorhabditis elegans as a model system for triplet repeat diseases.

Common features underlie the generation and function of neurons in multicellular animals. It is likely that conserved pathways and genes also are involved in neuronal degeneration and malfunction. To address the molecular mechanisms of complex human neurological disorders, many investigators are choosing to study these diseases in simpler organisms. The nematode Caenorhabditis elegans provides an excellent model system to address genetically the mechanisms of triplet repeat diseases. Advantages of using C. elegans as a model system include the ease of genetic manipulation, the sequenced genome, and a short life cycle. Furthermore, researchers can precisely identify specific neurons and follow their development or survival throughout the animal's lifetime. This chapter describes the tools and approaches for modeling triplet repeat diseases in C. elegans with a specific emphasis on polyglutamine (polyQ) diseases. Although the bulk of the chapter is devoted to generating a polyQ disease model in C. elegans, it also addresses potential avenues for assessing the impact of specific candidate genes/pathways on the disease process, including cell death and aging.

A chaperome subnetwork safeguards proteostasis in aging and neurodegenerative disease.

Chaperones are central to the proteostasis network (PN) and safeguard the proteome from misfolding, aggregation, and proteotoxicity. We categorized the human chaperome of 332 genes into network communities using function, localization, interactome, and expression data sets. During human brain aging, expression of 32% of the chaperome, corresponding to ATP-dependent chaperone machines, is repressed, whereas 19.5%, corresponding to ATP-independent chaperones and co-chaperones, are induced. These repression and induction clusters are enhanced in the brains of those with Alzheimer's, Huntington's, or Parkinson's disease. Functional properties of the chaperome were assessed by perturbation in C. elegans and human cell models expressing Aß, polyglutamine, and Huntingtin. Of 219 C. elegans orthologs, knockdown of 16 enhanced both Aß and polyQ-associated toxicity. These correspond to 28 human orthologs, of which 52% and 41% are repressed, respectively, in brain aging and disease and 37.5% affected Huntingtin aggregation in human cells. These results identify a critical chaperome subnetwork that functions in aging and disease.

Arylazanylpyrazolone derivatives as inhibitors of mutant superoxide dismutase 1 dependent protein aggregation for the treatment of amyotrophic lateral sclerosis.

The arylsulfanylpyrazolone and aryloxanylpyrazolone scaffolds previously were reported to inhibit Cu/Zn superoxide dismutase 1 dependent protein aggregation and to extend survival in the ALS mouse model. However, further evaluation of these compounds indicated weak pharmacokinetic properties and a relatively low maximum tolerated dose. On the basis of an ADME analysis, a new series of compounds, the arylazanylpyrazolones, has been synthesized, and structure-activity relationships were determined. The SAR results showed that the pyrazolone ring is critical to cellular protection. The NMR, IR, and computational analyses suggest that phenol-type tautomers of the pyrazolone ring are the active pharmacophore with the arylazanylpyrazolone analogues. A comparison of experimental and calculated IR spectra is shown to be a valuable method to identify the predominant tautomer.

Identification of potential therapeutic drugs for huntington's disease using Caenorhabditis elegans.

BACKGROUND: The prolonged time course of Huntington's disease (HD) neurodegeneration increases both the time and cost of testing potential therapeutic compounds in mammalian models. An alternative is to initially assess the efficacy of compounds in invertebrate models, reducing time of testing from months to days. METHODOLOGY/PRINCIPAL FINDINGS: We screened candidate therapeutic compounds that were identified previously in cell culture/animal studies in a C. elegans HD model and found that two FDA approved drugs, lithium chloride and mithramycin, independently and in combination suppressed HD neurotoxicity. Aging is a critical contributor to late onset neurodegenerative diseases. Using a genetic strategy and a novel assay, we demonstrate that lithium chloride and mithramycin remain neuroprotective independent of activity of the forkhead transcription factor DAF-16, which mediates the effects of the insulin-like signaling pathway on aging. CONCLUSIONS/SIGNIFICANCE: These results suggest that pathways involved in polyglutamine-induced degeneration are distinct from specific aging pathways. The assays presented here will be useful for rapid and inexpensive testing of other potential HD drugs and elucidating pathways of drug action. Additionally, the neuroprotection conferred by lithium chloride and mithramycin suggests that these drugs may be useful for polyglutamine disease therapy.

Inhibitors of metabolism rescue cell death in Huntington's disease models.

Huntington's disease (HD) is a fatal inherited neurodegenerative disorder. HD is caused by polyglutamine expansions in the huntingtin (htt) protein that result in neuronal loss and contribute to HD pathology. The mechanisms of neuronal loss in HD are elusive, and there is no therapy to alleviate HD. To find small molecules that slow neuronal loss in HD, we screened 1,040 biologically active molecules to identify suppressors of cell death in a neuronal cell culture model of HD. We found that inhibitors of mitochondrial function or glycolysis rescued cell death in this cell culture and in in vivo HD models. These inhibitors prevented cell death by activating prosurvival ERK and AKT signaling but without altering cellular ATP levels. ERK and AKT inhibition through the use of specific chemical inhibitors abrogated the rescue, whereas their activation through the use of growth factors rescued cell death, suggesting that this activation could explain the protective effect of metabolic inhibitors. Both ERK and AKT signaling are disrupted in HD, and activating these pathways is protective in several HD models. Our results reveal a mechanism for activating prosurvival signaling that could be exploited for treating HD and possibly other neurodegenerative disorders.

Selective inhibitors of death in mutant huntingtin cells.

Huntington disease (HD) is an inherited neurodegenerative disorder with unclear pathophysiology. We developed a high-throughput assay in a neuronal cell culture model of HD, screened 43,685 compounds and identified 29 novel selective inhibitors of cell death in mutant huntingtin-expressing cells. Four compounds were active in diverse HD models, which suggests a role for cell death in HD; these compounds are mechanistic probes and potential drug leads for HD.

Glutamine/proline-rich PQE-1 proteins protect Caenorhabditis elegans neurons from huntingtin polyglutamine neurotoxicity.

Huntington's disease is a progressive neurodegenerative disease caused by a polyglutamine (polyQ) repeat expansion in the huntingtin protein [Huntington's Disease Collaborative Research Group (1993) Cell 72, 971-983]. To understand the mechanism by which polyQ repeats cause neurodegeneration and cell death, we modeled polyQ neurotoxicity in Caenorhabditis elegans. In our model, expression of N-terminal fragments of human huntingtin causes polyQ-dependent degeneration of neurons. We conducted a genetic screen to identify proteins that protect neurons from the toxic effects of expanded polyQ tracts. Loss of polyQ enhancer-1 (pqe-1) gene function strongly and specifically exacerbates neurodegeneration and cell death, whereas overexpression of a pqe-1 cDNA protects C. elegans neurons from the toxic effects of expanded huntingtin fragments. A glutamineproline-rich domain, along with a charged domain, is critical for PQE-1 protein function. Analysis of pqe-1 suggests that proteins exist that specifically protect neurons from the toxic effects of expanded polyQ disease proteins.