Sala AJ et al. (2017) J Cell Biol "Shaping proteostasis at the cellular, tissue, and organismal level."

Morimoto RI, Bott LC, Sala AJ

[J Cell Biol, 2017]

The proteostasis network (PN) regulates protein synthesis, folding, transport, and degradation to maintain proteome integrity and limit the accumulation of protein aggregates, a hallmark of aging and degenerative diseases. In multicellular organisms, the PN is regulated at the cellular, tissue, and systemic level to ensure organismal health and longevity. Here we review these three layers of PN regulation and examine how they collectively maintain cellular homeostasis, achieve cell type-specific proteomes, and coordinate proteostasis across tissues. A precise understanding of these layers of control has important implications for organismal health and could offer new therapeutic approaches for neurodegenerative diseases and other chronic disorders related to PN dysfunction.

Duke BO et al. (2002) Parasitology "Neoplastic change in Onchocerca volvulus and its relation to ivermectin treatment."

Pion SD, Gardo J, Boussinesq M, Kamgno J, Marty AM, Duke BO, Peett DL

[Parasitology, 2002]

A pleomorphic neoplasm (PN) is described from sections of Onchocerca volvulus worms in nodules excised from Cameroonian patients. PN is confined to older, non-fecund, female worms, and those classed as moribund/dead. It is mainly composed of small, roundish, basophilic cells of diverse sizes, often forming a 'rosette' pattern around amorphous eosinophilic centres. The cells have a high nuclear/cytoplasmic ratio and up to 2-3 mitoses/high-power field; some become grossly enlarged, highly polymorphic and contain large, irregular blocks of chromatin. The eukaryotic PN cells first appear posteriorly in the pseudocoelom, probably from ovarian cells; they spread anteriorly, invading or compressing the uteri. Ivermectin treatment increased the prevalence PN from 3.7% of 1422 female worms in 637 patients before treatment to 17.5% of 1134 worms in 511 patients after 3 years treatment. Ivermectin at 400-800 microg/kg annually, or at 150 microg/kg or 400-800 microg/kg 3-monthly, over 3 years, did not increase the PN prevalence significantly, as compared with standard doses of 150 microg/kg annually. In other small series of African patients, PN prevalence increased in worms 2, 4, 6 and 10 months after ivermectin treatment; but there was no increase after treatment with amocarzine, albendazole or diethylcarbamazine and suramin. PN may partly account for the increased macrofilaricidal action of ivermectin on female O. volvulus in patients treated for 3 years at 3-monthly intervals.

O'Reilly LP et al. (2014) Expert Opin Drug Discov "Worming our way to novel drug discovery with the Caenorhabditis elegans proteostasis network, stress response and insulin-signaling pathways."

Pak SC, Silverman GA, O'Reilly LP, Perlmutter DH, Cummings EE, Benson JA

[Expert Opin Drug Discov, 2014]

INTRODUCTION: Many human diseases result from a failure of a single protein to achieve the correct folding and tertiary conformation. These so-called 'conformational diseases' involve diverse proteins and distinctive cellular pathologies. They all engage the proteostasis network (PN), to varying degrees in an attempt to mange cellular stress and restore protein homeostasis. The insulin/insulin-like growth factor signaling (IIS) pathway is a master regulator of cellular stress response, which is implicated in regulating components of the PN. AREAS COVERED: This review focuses on novel approaches to target conformational diseases. The authors discuss the evidence supporting the involvement of the IIS pathway in modulating the PN and regulating proteostasis in Caenorhabditis elegans. Furthermore, they review previous PN and IIS drug screens and explore the possibility of using C. elegans for whole organism-based drug discovery for modulators of IIS-proteostasis pathways. EXPERT OPINION: An alternative approach to develop individualized therapy for each conformational disease is to modulate the global PN. The involvement of the IIS pathway in regulating longevity and response to a variety of stresses is well documented. Increasing data now provide evidence for the close association between the IIS and the PN pathways. The authors believe that high-throughput screening campaigns, which target the C. elegans IIS pathway, may identify drugs that are efficacious in treating numerous conformational diseases.

Boocholez H et al. (2022) Cell Rep "Neuropeptide signaling and SKN-1 orchestrate differential responses of the proteostasis network to dissimilar proteotoxic insults."

Zhu H, Roitenberg N, Boocholez H, Siddiqui AA, Marques FC, Cohen E, Grushko D, Levine A, Elami T, Moll L, Haimson RB

[Cell Rep, 2022]

The protein homeostasis (proteostasis) network (PN) encompasses mechanisms that maintain proteome integrity by controlling various biological functions. Loss of proteostasis leads to toxic protein aggregation (proteotoxicity), which underlies the manifestation of neurodegeneration. How the PN responds to dissimilar proteotoxic challenges and how these responses are regulated at the organismal level are largely unknown. Here, we report that, while torsin chaperones protect from the toxicity of neurodegeneration-causing polyglutamine stretches, they exacerbate the toxicity of the Alzheimer's disease-causing Aβ peptide in neurons and muscles. These opposing effects are accompanied by differential modulations of gene expression, including that of three neuropeptides that are involved in tailoring the organismal response to dissimilar proteotoxic insults. This mechanism is regulated by insulin/IGF signaling and the transcription factor SKN-1/NRF. Our work delineates a mechanism by which the PN orchestrates differential responses to dissimilar proteotoxic challenges and points at potential targets for therapeutic interventions.

Alper S et al. (2001) Development "REF-1, a protein with two bHLH domains, alters the pattern of cell fusion in C. elegans by regulating Hox protein activity."

Kenyon C, Alper S

[Development, 2001]

Hox genes control the choice of cell fates along the anteroposterior (AP) body axis of many organisms. In C. elegans, two Hox genes, lin-39 and mab-5, control the cell fusion decision of the 12 ventrally located Pn.p cells. Specific Pn,p cells fuse with an epidermal syncytium, hyp7, in a sexually dimorphic pattern. In hermaphrodites, Pn.p cells in the mid-body region remain unfused whereas in males, Pn,p cells adopt an alternating pattern of syncytial and unfused fates. The complexity of these fusion patterns arises because the activities of these two Hox proteins are regulated in a sex-specific manner. MAB-5 activity is inhibited in hermaphrodite Pn.p cells and thus MAB-5 normally only affects the male Pn,p fusion pattern. Here we identify a gene, ref-1, that regulates the hermaphrodite Pn,p cell fusion pattern largely by regulating MAB-5 activity in these cells. Mutation of ref-l also affects the fate of other epidermal cells in distinct AP body regions. ref-l encodes a protein with two basic helix-loop-helix domains distantly related to those of the hairy/Enhancer of split family. ref-l, and another hairy homolog, lin-22, regulate similar cell fate decisions in different body regions along the C. elegans AP body axis.

O'Reilly LP et al. (2014) Hum Mol Genet "A genome-wide RNAi screen identifies potential drug targets in a C. elegans model of 1-antitrypsin deficiency."

Cobanoglu MC, Silverman GA, Pak SC, Perlmutter DH, Miedel MT, Benson JA, Long OS, Bahar I, Hale P, O'Reilly LP, Luke CJ

[Hum Mol Genet, 2014]

1-Antitrypsin deficiency (ATD) is a common genetic disorder that can lead to end-stage liver and lung disease. Although liver transplantation remains the only therapy currently available, manipulation of the proteostasis network (PN) by small molecule therapeutics offers great promise. To accelerate the drug-discovery process for this disease, we first developed a semi-automated high-throughput/content-genome-wide RNAi screen to identify PN modifiers affecting the accumulation of the 1-antitrypsin Z mutant (ATZ) in a Caenorhabditis elegans model of ATD. We identified 104 PN modifiers, and these genes were used in a computational strategy to identify human ortholog-ligand pairs. Based on rigorous selection criteria, we identified four FDA-approved drugs directed against four different PN targets that decreased the accumulation of ATZ in C. elegans. We also tested one of the compounds in a mammalian cell line with similar results. This methodology also proved useful in confirming drug targets in vivo, and predicting the success of combination therapy. We propose that small animal models of genetic disorders combined with genome-wide RNAi screening and computational methods can be used to rapidly, economically and strategically prime the preclinical discovery pipeline for rare and neglected diseases with limited therapeutic options.

van Oosten-Hawle P et al. (2014) Genes Dev "Organismal proteostasis: role of cell-nonautonomous regulation and transcellular chaperone signaling."

Morimoto RI, van Oosten-Hawle P

[Genes Dev, 2014]

Protein quality control is essential in all organisms and regulated by the proteostasis network (PN) and cell stress response pathways that maintain a functional proteome to promote cellular health. In this review, we describe how metazoans employ multiple modes of cell-nonautonomous signaling across tissues to integrate and transmit the heat-shock response (HSR) for balanced expression of molecular chaperones. The HSR and other cell stress responses such as the unfolded protein response (UPR) can function autonomously in single-cell eukaryotes and tissue culture cells; however, within the context of a multicellular animal, the PN is regulated by cell-nonautonomous signaling through specific sensory neurons and by the process of transcellular chaperone signaling. These newly identified forms of stress signaling control the PN between neurons and nonneuronal somatic tissues to achieve balanced tissue expression of chaperones in response to environmental stress and to ensure that metastable aggregation-prone proteins expressed within any single tissue do not generate local proteotoxic risk. Transcellular chaperone signaling leads to the compensatory expression of chaperones in other somatic tissues of the animal, perhaps preventing the spread of proteotoxic damage. Thus, communication between subcellular compartments and across different cells and tissues maintains proteostasis when challenged by acute stress and upon chronic expression of metastable proteins. We propose that transcellular chaperone signaling provides a critical control step for the PN to maintain cellular and organismal health span.

Scharf A et al. (2011) Nucleic Acids Res "Distant positioning of proteasomal proteolysis relative to actively transcribed genes."

Kubitscheck U, Meier UT, von Mikecz A, Veith R, Scharf A, Grozdanov PN

[Nucleic Acids Res, 2011]

While it is widely acknowledged that the ubiquitin-proteasome system plays an important role in transcription, little is known concerning the mechanistic basis, in particular the spatial organization of proteasome-dependent proteolysis at the transcription site. Here, we show that proteasomal activity and tetraubiquitinated proteins concentrate to nucleoplasmic microenvironments in the euchromatin. Such proteolytic domains are immobile and distinctly positioned in relation to transcriptional processes. Analysis of gene arrays and early genes in Caenorhabditis elegans embryos reveals that proteasomes and proteasomal activity are distantly located relative to transcriptionally active genes. In contrast, transcriptional inhibition generally induces local overlap of proteolytic microdomains with components of the transcription machinery and degradation of RNA polymerase II. The results establish that spatial organization of proteasomal activity differs with respect to distinct phases of the transcription cycle in at least some genes, and thus might contribute to the plasticity of gene expression in response to environmental stimuli.

Lazaro-Pena, Maria et al. (2021) International Worm Meeting "HPK-1 prevents the decline of proteostasis through neuroendocrine control of the proteostatic network"

Diaz-Balzac, Carlos, Samuelson, Andrew, Das, Ritika, Lazaro-Pena, Maria

[International Worm Meeting, 2021]

The progressive decline of cellular proteostasis is a hallmark of normal organismal aging, and is the basis for the onset and progression of a growing number of neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's disease. These diseases share a common characteristic: the accumulation of proteotoxic aggregates that result in cellular dysfunction and death. Proteotoxic disease is opposed by a cellular proteostatic network (PN) of approximately 1500-2000 proteins, which maintain the proteome by balancing rates of protein synthesis, degradation, folding, and sequestration. We have identified the transcriptional cofactor HPK-1 (homeodomain-interacting protein kinase) as an important PN component that preserves proteostasis and extends longevity. We find HPK-1 is primarily expressed in the nervous system during adulthood. Loss of neuronal hpk-1 shortens lifespan, while neuronal overexpression of hpk-1 is sufficient to increase lifespan. Neuronal HPK-1 is responsive to both acute heat shock and chronic nutritional stress, suggesting HPK-1 may act within the nervous system to integrate diverse signals and coordinate adaptive responses within the PN. We investigated whether HPK-1 acts cell autonomously in neurons to mediate stress response and proteostasis, or alternatively functions cell non-autonomously from neurons to regulate these processes in peripheral tissues. Neuronal loss of hpk-1 hastens the collapse of both neuronal and muscle proteostasis. Conversely, neuronal overexpression of hpk-1 delays the progressive decline of both neuronal and muscle proteostasis. Neuronal HPK-1 overexpression produces a paracrine signal to hyper-induce molecular chaperone expression locally and a neuroendocrine signal to induce autophagy in peripheral tissues. To further investigate the non-cell autonomous regulation of neuronal HPK-1, we expressed HPK-1 in different types of neurons and found that overexpression of HPK-1 in serotonergic and GABAergic neurons is sufficient to preserve proteostasis in the muscle. Interestingly, overexpression of HPK-1 in serotonergic neurons, but not in GABAergic neurons, is sufficient to increase heat stress resistance, suggesting HPK-1 exerts a different PN function in these types of neurons to preserve proteostasis. Overexpression of HPK-1 in single types of neurons is not sufficient to increase lifespan, suggesting that its combinatorial roles in neuronal cell-types is required to extend longevity. Collectively, our results position HPK-1 at a central regulatory node acting from the nervous system, upstream of the greater PN, by exerting distinct but complementary roles in different types of neurons.

Pigazzini ML et al. (2020) J Vis Exp "Characterization of Amyloid Structures in Aging C. Elegans Using Fluorescence Lifetime Imaging."

Gallrein C, Kaminski Schierle G, Kirstein J, Pigazzini ML, Iburg M

[J Vis Exp, 2020]

Amyloid fibrils are associated with a number of neurodegenerative diseases such as Huntington's, Parkinson's, or Alzheimer's disease. These amyloid fibrils can sequester endogenous metastable proteins as well as components of the proteostasis network (PN) and thereby exacerbate protein misfolding in the cell. There are a limited number of tools available to assess the aggregation process of amyloid proteins within an animal. We present a protocol for fluorescence lifetime microscopy (FLIM) that allows monitoring as well as quantification of the amyloid fibrilization in specific cells, such as neurons, in a noninvasive manner and with the progression of aging and upon perturbation of the PN. FLIM is independent of the expression levels of the fluorophore and enables an analysis of the aggregation process without any further staining or bleaching. Fluorophores are quenched when they are in close vicinity of amyloid structures, which results in a decrease of the fluorescence lifetime. The quenching directly correlates with the aggregation of the amyloid protein. FLIM is a versatile technique that can be applied to compare the fibrilization process of different amyloid proteins, environmental stimuli, or genetic backgrounds in vivo in a non-invasive manner.