Accumulation Of Specific Proteins Research Articles

Single Molecule Tools for Probing Protein Aggregation

Protein aggregation poses a fundamental problem in biophysics, whose solutions have enormous potential for societal benefits. Many devastating and incurable diseases, such as Alzheimer’’s, Parkinson’’s and Type II diabetes, are strongly linked to the misfolding and aggregation of specific proteins. The links between misfolding, aggregation and toxicity, with clues spread across fields from physics and physical chemistry to clinical science and epidemiology, have remained difficult to decipher. In addition, the transience of the aggregation intermediates makes it a difficult challenge. Optical spectroscopy and microscopy, providing unparalleled sensitivity and resolution, are two of the few tools which have been able to provide some effective leads in understanding the process. Here we present a short summary of the applications of fluorescence correlation spectroscopy and total internal reflection fluorescence microscopy to this problem, primarily focusing on the progress made in our laboratory.

The role of macropinocytosis in the propagation of protein aggregation associated with neurodegenerative diseases.

With the onset of the rapidly aging population, the impact of age related neurodegenerative diseases is becoming a predominant health and economic concern. Neurodegenerative diseases such as Alzheimer's disease, Creutzfeldt-Jakob disease (CJD), Parkinson's disease, Huntington's disease, frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS) result from the loss of a specific subsets of neurons, which is closely associated with accumulation and deposition of specific protein aggregates. Protein aggregation, or fibril formation, is a well-studied phenomenon that occurs in a nucleation-dependent growth reaction. Recently, there has been a swell of literature implicating protein aggregation and its ability to propagate cell-to-cell in the rapid progression of these diseases. In order for protein aggregation to be kindled in recipient cells it is a requisite that aggregates must be able to be released from one cell and then taken up by others. In this article we will explore the relationship between protein aggregates, their propagation and the role of macropinocytosis in their uptake. We highlight the ability of neurons to undergo stimulated macropinocytosis and identify potential therapeutic targets.

Spectroscopic and Microscopic Studies of Aggregation and Fibrillation of Lysozyme in Water/Ethanol Solutions.

The thermal aggregation of lysozyme has been analyzed in water/ethanol solutions at low pH to induce the specific protein aggregation pathway which leads to fibrillar structures in a few hours. In this solvating medium, the protein undergoes a conformational rearrangement promoting the formation of fibrils that are structurally similar to amyloid ones. As the process evolves with different steps, a multitechnique approach has been used by means of analytical probes that can be selectively sensitive in the detection of the different stages of protein association. Fourier transform infrared spectroscopy, intrinsic fluorescence, stationary fluorescence anisotropy, transmission electron microscopy (TEM), and atomic force microscopy (AFM) measurements have been carried out at different times to access and characterize the whole aggregation pathway. The data recorded with different experimental setups revealed different sensitivity to different stages of protein assembling. The whole set of data together with the direct visualization of different aggregate structures by use of TEM and AFM imaging enable to discuss a possible mechanism of fibrillation.

Targeting protein aggregation for the treatment of degenerative diseases.

The aggregation of specific proteins is hypothesized to underlie several degenerative diseases, which are collectively known as amyloid disorders. However, the mechanistic connection between the process of protein aggregation and tissue degeneration is not yet fully understood. Here, we review current and emerging strategies to ameliorate aggregation-associated degenerative disorders, with a focus on disease-modifying strategies that prevent the formation of and/or eliminate protein aggregates. Persuasive pharmacological and genetic evidence now supports protein aggregation as the cause of postmitotic tissue dysfunction or loss. However, a more detailed understanding of the factors that trigger and sustain aggregate formation and of the structure-activity relationships underlying proteotoxicity is needed to develop future disease-modifying therapies.

Geldanamycin Reduces Aβ-Associated Anxiety and Depression, Concurrent with Autophagy Provocation.

Neurodegenerative disorders are generally characterized by abnormal aggregation and deposition of specific proteins. Amyloid beta (Aβ)-associated neurodegenerative disorder is characterized by an oxidative damage that, in turn, leads to some behavioral changes before the establishment of dementia such as depression and anxiety. In the current study, we investigated the effect of heat shock protein 90 inhibitor geldanamycin (GA) administration 24 h before Aβ injection. In our experiment, 7 days after Aβ injection, elevated plus maze and forced swimming test were conducted to assess anxiety and depression-like behaviors. Levels of autophagy markers and malondialdehyde (MDA) and also activity of catalase in the hippocampus of rats were evaluated. Our behavioral analyses demonstrated that GA pretreatment can significantly decrease anxiety- and depression-like behaviors in Aβ-injected rats. Also, levels of autophagy markers including Atg12, Atg7, and LC3-II increased, while MDA level decreased and the activity of catalase increased in rats pretreated with GA compared to Aβ-injected rats. Thus, we assumed that GA, at least in part, ameliorated Aβ-mediated anxiety and depression by inducing autophagy and improving antioxidant defense system.

Traumatic Brain Injury, Chronic Traumatic Encephalopathy, and Alzheimer's Disease: Common Pathologies Potentiated by Altered Zinc Homeostasis.

Alzheimer's disease, traumatic brain injury, and chronic traumatic encephalopathy represent conditions that have a profound socioeconomic impact for both the individual and the wider community. They are all characterized by specific protein aggregation that results in synaptic dysfunction, neuronal death, and consequent cognitive decline and memory loss. In this review, we present evidence to support the notion that the common pathologies found in all conditions, and indeed their associated cognitive deficits, may be linked by zinc (Zn²⁺) ion dyshomeostasis. Elucidation of this hypothesis may present new therapeutic avenues for these devastating conditions.

Dopamine induces the accumulation of insoluble prion protein and affects autophagic flux.

Accumulation of protein aggregates is a histopathological hallmark of several neurodegenerative diseases, but in most cases the aggregation occurs without defined mutations or clinical histories, suggesting that certain endogenous metabolites can promote aggregation of specific proteins. One example that supports this hypothesis is dopamine and its metabolites. Dopamine metabolism generates several oxidative metabolites that induce aggregation of α-synuclein, and represents the main etiology of Parkinson's diseases. Because dopamine and its metabolites are unstable and can be highly reactive, we investigated whether these molecules can also affect other proteins that are prone to aggregate, such as cellular prion protein (PrPC). In this study, we showed that dopamine treatment of neuronal cells reduced the number of viable cells and increased the production of reactive oxygen species (ROS) as demonstrated in previous studies. Overall PrPC expression level was not altered by dopamine treatment, but its unglycosylated form was consistently reduced at 100 μM of dopamine. At the same concentration, the level of phosphorylated mTOR and 4EBP1 was also reduced. Moreover, dopamine treatment decreased the solubility of PrPC, and increased its accumulation in autophagosomal compartments with concomitant induction of LC3-II and p62/SQSTM1 levels. In vitro oxidation of dopamine promoted formation of high-order oligomers of recombinant prion protein. These results suggest that dopamine metabolites alter the conformation of PrPC, which in turn is sorted to degradation pathway, causing autophagosome overload and attenuation of protein synthesis. Accumulation of PrPC aggregates is an important feature of prion diseases. Thus, this study brings new insight into the dopamine metabolism as a source of endogenous metabolites capable of altering PrPC solubility and its subcellular localization.

Transglutaminase 2 and neuroinflammation.

Neuroinflammatory processes seem to play a pivotal role in various chronic neurodegenerative diseases, characterized also by the pathogenetic accumulation of specific protein aggregates. Several of these proteins have been shown to be substrates of transglutaminases, calcium-dependent enzymes that catalyze protein crosslinking reactions. However, it has recently been demonstrated that transglutaminase 2 (TG2) may also be involved in molecular mechanisms underlying inflammation. In the central nervous system, astrocytes and microglia are the cell types mainly involved in the inflammatory process. This review is focused on the increases of TG2 protein expression and enzyme activity that occur in astroglial, microglial and monocyte cell models in response to inflammatory stimuli. The transcription factor NF-κB is considered the main regulator of inflammation, being activated by a variety of stimuli including calcium influx, oxidative stress and inflammatory cytokines. Under these conditions, the over-expression of TG2 results in the sustained activation of NF-κB. Several findings emphasize the possible role of the TG2/NF-κB activation pathway in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, multiple sclerosis and amyotrophic lateral sclerosis. Although further studies are needed to characterize the TG2/NF-κB cross-talk in monocytes/macrophages/microglia within the central nervous system, some results show that TG2 and NF-κB are co-localized in cell compartments. Together, evidence suggests that TG2 plays a role in neuroinflammation and contributes to the production of compounds that are potentially deleterious to neuronal cells.

Prion-like Mechanisms in Alzheimer's Disease.

The misfolding and aggregation of specific proteins within nervous system occur in most age-associated neurodegenerative diseases including Alzheimer's disease (AD). This kind of disorders have been classified as the protein misfolding disease or proteopathy which share key biophysical and biochemical characteristics with prion diseases. In AD, β-amyloid (Aβ) and tau protein, capital agents for the senile plaques and intracellular neurofibrillary tangles, are called 'prionoids' indicating that proteins exhibit prion-like properties. In this review, we describe the prion-like mechanisms in the progression that the Aβ and tau are induced to misfold and self-assemble by a process of templated conformational change and then the lesion caused by the pathogenic agents spread out through the cell-to-cell transportation, including release of intracellular seeds by the donor cell, cellular uptake by the recipient and intercellular transport. This hypothesis will suggest new therapeutic strategies for AD, especially valuable in the pre-symptomatic phase.

Agent-based modeling of autophagy reveals emergent regulatory behavior of spatio-temporal autophagy dynamics.

BackgroundAutophagy is a vesicle-mediated pathway for lysosomal degradation, essential under basal and stressed conditions. Various cellular components, including specific proteins, protein aggregates, organelles and intracellular pathogens, are targets for autophagic degradation. Thereby, autophagy controls numerous vital physiological and pathophysiological functions, including cell signaling, differentiation, turnover of cellular components and pathogen defense. Moreover, autophagy enables the cell to recycle cellular components to metabolic substrates, thereby permitting prolonged survival under low nutrient conditions. Due to the multi-faceted roles for autophagy in maintaining cellular and organismal homeostasis and responding to diverse stresses, malfunction of autophagy contributes to both chronic and acute pathologies.ResultsWe applied a systems biology approach to improve the understanding of this complex cellular process of autophagy. All autophagy pathway vesicle activities, i.e. creation, movement, fusion and degradation, are highly dynamic, temporally and spatially, and under various forms of regulation. We therefore developed an agent-based model (ABM) to represent individual components of the autophagy pathway, subcellular vesicle dynamics and metabolic feedback with the cellular environment, thereby providing a framework to investigate spatio-temporal aspects of autophagy regulation and dynamic behavior. The rules defining our ABM were derived from literature and from high-resolution images of autophagy markers under basal and activated conditions. Key model parameters were fit with an iterative method using a genetic algorithm and a predefined fitness function. From this approach, we found that accurate prediction of spatio-temporal behavior required increasing model complexity by implementing functional integration of autophagy with the cellular nutrient state. The resulting model is able to reproduce short-term autophagic flux measurements (up to 3 hours) under basal and activated autophagy conditions, and to measure the degree of cell-to-cell variability. Moreover, we experimentally confirmed two model predictions, namely (i) peri-nuclear concentration of autophagosomes and (ii) inhibitory lysosomal feedback on mTOR signaling.ConclusionAgent-based modeling represents a novel approach to investigate autophagy dynamics, function and dysfunction with high biological realism. Our model accurately recapitulates short-term behavior and cell-to-cell variability under basal and activated conditions of autophagy. Further, this approach also allows investigation of long-term behaviors emerging from biologically-relevant alterations to vesicle trafficking and metabolic state.Electronic supplementary materialThe online version of this article (doi:10.1186/s12964-014-0056-8) contains supplementary material, which is available to authorized users.

Resolving the paradox for protein aggregation diseases: NMR structure and dynamics of the membrane-embedded P56S-MSP causing ALS imply a common mechanism for aggregation-prone proteins to attack membranes.

Paradoxically, aggregation of specific proteins is characteristic of many human diseases and aging, yet aggregates have increasingly been found to be unnecessary for initiating pathogenesis. Here we determined the NMR topology and dynamics of a helical mutant in a membrane environment transformed from the 125-residue cytosolic all-β MSP domain of vesicle-associated membrane protein-associated protein B (VAPB) by the ALS-causing P56S mutation. Despite its low hydrophobicity, the P56S major sperm protein (MSP) domain becomes largely embedded in the membrane environment with high backbone rigidity. Furthermore it is composed of five helices with amphiphilicity comparable to those of the partly-soluble membrane toxin mellitin and α-synuclein causing Parkinson's disease. Consequently, the mechanism underlying this chameleon transformation becomes clear: by disrupting the specific tertiary interaction network stabilizing the native all-β MSP fold to release previously-locked amphiphilic segments, the P56S mutation acts to convert the classic MSP fold into a membrane-active protein that is fundamentally indistinguishable from mellitin and α-synuclein which are disordered in aqueous solution but spontaneously partition into membrane interfaces driven by hydrogen-bond energetics gained from forming α-helix in the membrane environments. As segments with high amphiphilicity exist in all proteins, our study successfully resolves the paradox by deciphering that the proteins with a higher tendency to aggregate have a stronger potential to partition into membranes through the same mechanism as α-synuclein to initially attack membranes to trigger pathogenesis without needing aggregates. This might represent the common first step for various kinds of aggregated proteins to trigger familiar, sporadic and aging diseases. Therefore the homeostasis of aggregated proteins in vivo is the central factor responsible for a variety of human diseases including aging. The number and degree of the membrane attacks by aggregated proteins may act as an endogenous clock to count down the aging process. Consequently, a key approach to fight against them is to develop strategies and agents to maintain or even enhance the functions of the degradation machineries.

Distal renal tubules are deficient in aggresome formation and autophagy upon aldosterone administration.

Prolonged elevations of plasma aldosterone levels are associated with renal pathogenesis. We hypothesized that renal distress could be imposed by an augmented aldosterone-induced protein turnover challenging cellular protein degradation systems of the renal tubular cells. Cellular accumulation of specific protein aggregates in rat kidneys was assessed after 7 days of aldosterone administration. Aldosterone induced intracellular accumulation of 60 s ribosomal protein L22 in protein aggregates, specifically in the distal convoluted tubules. The mineralocorticoid receptor inhibitor spironolactone abolished aldosterone-induced accumulation of these aggregates. The aldosterone-induced protein aggregates also contained proteasome 20 s subunits. The partial de-ubiquitinase ataxin-3 was not localized to the distal renal tubule protein aggregates, and the aggregates only modestly colocalized with aggresome transfer proteins dynactin p62 and histone deacetylase 6. Intracellular protein aggregation in distal renal tubules did not lead to development of classical juxta-nuclear aggresomes or to autophagosome formation. Finally, aldosterone treatment induced foci in renal cortex of epithelial vimentin expression and a loss of E-cadherin expression, as signs of cellular stress. The cellular changes occurred within high, but physiological aldosterone concentrations. We conclude that aldosterone induces protein accumulation in distal renal tubules; these aggregates are not cleared by autophagy that may lead to early renal tubular damage.

Protein phosphorylation in neurodegeneration: friend or foe?

Protein misfolding and aggregation is a common hallmark in neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and fronto-temporal dementia (FTD). In these disorders, the misfolding and aggregation of specific proteins occurs alongside neuronal degeneration in somewhat specific brain areas, depending on the disorder and the stage of the disease. However, we still do not fully understand the mechanisms governing protein aggregation, and whether this constitutes a protective or detrimental process. In PD, alpha-synuclein (aSyn) forms protein aggregates, known as Lewy bodies, and is phosphorylated at serine 129. Other residues have also been shown to be phosphorylated, but the significance of phosphorylation in the biology and pathophysiology of the protein is still controversial. In AD and in FTD, hyperphosphorylation of tau protein causes its misfolding and aggregation. Again, our understanding of the precise consequences of tau phosphorylation in the biology and pathophysiology of the protein is still limited. Through the use of a variety of model organisms and technical approaches, we are now gaining stronger insight into the effects of phosphorylation in the behavior of these proteins. In this review, we cover recent findings in the field and discuss how targeting phosphorylation events might be used for therapeutic intervention in these devastating diseases of the nervous system.

Resolving the paradox for protein aggregation diseases: NMR structure and dynamics of the membrane-embedded P56S-MSP causing ALS imply a common mechanism for aggregation-prone proteins to attack membranes

Paradoxically, aggregation of specific proteins is characteristic of many human diseases and aging, yet aggregates have increasingly been found to be unnecessary for initiating pathogenesis. Here we determined the NMR topology and dynamics of a helical mutant in a membrane environment transformed from the 125-residue cytosolic all-β MSP domain of vesicle-associated membrane protein-associated protein B (VAPB) by the ALS-causing P56S mutation. Despite its low hydrophobicity, the P56S major sperm protein (MSP) domain becomes largely embedded in the membrane environment with high backbone rigidity. Furthermore it is composed of five helices with amphiphilicity comparable to those of the partly-soluble membrane toxin mellitin and α-synuclein causing Parkinson's disease. Consequently, the mechanism underlying this chameleon transformation becomes clear: by disrupting the specific tertiary interaction network stabilizing the native all-β MSP fold to release previously-locked amphiphilic segments, the P56S mutation acts to convert the classic MSP fold into a membrane-active protein that is fundamentally indistinguishable from mellitin and α-synuclein which are disordered in aqueous solution but spontaneously partition into membrane interfaces driven by hydrogen-bond energetics gained from forming α-helix in the membrane environments. As segments with high amphiphilicity exist in all proteins, our study successfully resolves the paradox by deciphering that the proteins with a higher tendency to aggregate have a stronger potential to partition into membranes through the same mechanism as α-synuclein to initially attack membranes to trigger pathogenesis without needing aggregates. This might represent the common first step for various kinds of aggregated proteins to trigger familiar, sporadic and aging diseases. Therefore the homeostasis of aggregated proteins in vivo is the central factor responsible for a variety of human diseases including aging. The number and degree of the membrane attacks by aggregated proteins may act as an endogenous clock to count down the aging process. Consequently, a key approach to fight against them is to develop strategies and agents to maintain or even enhance the functions of the degradation machineries.

Resolving the paradox for protein aggregation diseases: a common mechanism for aggregated proteins to initially attack membranes without needing aggregates

Paradoxically, aggregation of specific proteins is characteristic of many human diseases and aging, yet aggregates have been found to be unnecessary for initiating pathogenesis. Here we determined the NMR topology and dynamics of a helical mutant in a membrane environment transformed from the 125-residue cytosolic all-β MSP by the ALS-causing P56S mutation. Unexpectedly, despite its low hydrophobicity, the P56S major sperm protein (MSP) domain becomes largely embedded in the membrane environment with high backbone rigidity. Furthermore it is composed of five helices with amphiphilicity comparable to those of the partly-soluble membrane toxin mellitin and α-synuclein causing Parkinson's disease. Consequently, the mechanism underlying this chameleon transformation becomes clear: by disrupting the specific tertiary interaction network stabilizing the native all-β MSP fold to release previously-locked amphiphilic segments, the P56S mutation acts to convert the classic MSP fold into a membrane-active protein that is fundamentally indistinguishable from mellitin and α-synuclein which are disordered in aqueous solution but spontaneously partition into membrane interfaces driven by hydrogen-bond energetics gained from forming α-helix in the membrane environments. As segments with high amphiphilicity exist in all proteins, our study successfully resolves the paradox by deciphering that the proteins with a higher tendency to aggregate have a stronger potential to partition into membranes through the same mechanism as α-synuclein to initially attack membranes to trigger pathogenesis without needing aggregates. This might represent the common first step for various kinds of aggregated proteins to trigger familiar, sporadic and aging diseases. Therefore the homeostasis of aggregated proteins in vivo is the central factor responsible for a variety of human diseases including aging. The number and degree of the membrane attacks by aggregated proteins may act as an endogenous clock to count down the aging process. Consequently, a key approach to fight against them is to develop strategies and agents to maintain or even enhance the functions of the degradation machineries.

Neurodegenerative lesions: Seeding and spreading

Accumulation of specific proteins has replaced loss of specific populations of neurons in the definition of most neurodegenerative diseases. In some cases, the amino-acid sequence of the protein that accumulates is altered by a mutation in the gene that codes for it but most generally, the primary structure is normal. Much evidence from human neuropathology has been collected over the years indicating that the progression of the lesions in such neurodegenerative diseases as Alzheimer's disease, Parkinson's disease and progressive supranuclear palsy follow the neuroanatomical connections. More recently, injection of aggregates of the specific proteins in the brain of experimental animals has been attempted in various experimental settings. Brain homogenates containing Aβ aggregates induce the early development of Aβ deposits in APP transgenic mice. Brain homogenates from various human tauopathies induce tau aggregates in transgenic mice expressing normal human tau. Finally, synthetic preformed fibrils of alpha-synuclein initiate the development of alpha-synuclein accumulation resembling Parkinson's disease in wild-type mice. Experiments in cell cultures suggest that the protein has to be in some specific state of oligomerization or fibrillation to be endocytosed and transported by the neuron. These data suggest that the protein that accumulates in a specific disease is initially misfolded and that this misfolding contaminates normal protein in a prion-like manner – in some cases through the neuronal connections.

Therapeutic activity of inhibition of the soluble epoxide hydrolase in a mouse model of scrapie

AimsThe misfolding and the aggregation of specific proteins are key features of neurodegenerative diseases, specifically Transmissible Spongiform Encephalopathies (TSEs). In TSEs, neuronal loss and inflammation are associated with the accumulation of the misfolded isoform (PrPsc) of the cellular prion protein (PrPc). Therefore we tested the hypothesis that augmenting a natural anti-inflammatory pathway mediated by epoxygenated fatty acids (EpFAs) will delay lethality. EpFAs are highly potent but enzymatically labile molecules produced by the actions of a number of cytochrome P450 enzymes. Stabilization of these bioactive lipids by inhibiting their degradation mediated by the soluble epoxide hydrolase (sEH) results in potent anti-inflammatory effects in multiple disease models. Main methodsMice were infected with the mouse-adapted RML strain of scrapie by intracerebral or intraperitoneal routes. Animals received the sEH inhibitor, by oral route, administrated in drinking water or vehicle (PEG400). Infected mice were euthanized at a standard clinical end point. Histopathological, immunohistochemical and Western blot analyses of brain tissue confirmed the presence of pathology related to prion infection. Key findingsOral administration of the sEHI did not affect the very short survival time of the intracerebral prion infection group. However, mice infected by intraperitoneal route and treated with t-AUCB survived significantly longer than the control group mice (p<0.001). SignificanceThese findings support the idea that inhibition of sEH or augmentation of the natural EpFA signaling in the brain offers a potential and different route to understand prion diseases and may become a therapeutic strategy for diseases involving neuroinflammation.

The cell biology of prion-like spread of protein aggregates: mechanisms and implication in neurodegeneration

The misfolding and aggregation of specific proteins is a common hallmark of many neurodegenerative disorders, including highly prevalent illnesses such as Alzheimer's and Parkinson's diseases, as well as rarer disorders such as Huntington's and prion diseases. Among these, only prion diseases are 'infectious'. By seeding misfolding of the PrP(C) (normal conformer prion protein) into PrP(Sc) (abnormal disease-specific conformation of prion protein), prions spread from the periphery of the body to the central nervous system and can also be transmitted between individuals of the same or different species. However, recent exciting data suggest that the transmissibility of misfolded proteins within the brain is a property that goes way beyond the rare prion diseases. Evidence indicates that non-prion aggregates [tau, α-syn (α-synuclein), Aβ (amyloid-β) and Htt (huntingtin) aggregates] can also move between cells and seed the misfolding of their normal conformers. These findings have enormous implications. On the one hand they question the therapeutical use of transplants, and on the other they indicate that it may be possible to bring these diseases to an early arrest by preventing cell-to-cell transmission. To better understand the prion-like spread of these protein aggregates it is essential to identify the underlying cellular and molecular factors. In the present review we analyse and discuss the evidence supporting prion-like spreading of amyloidogenic proteins, especially focusing on the cellular and molecular mechanisms and their significance.

Ribosomal Protein L22 (RPL22) accumulates as aggregates in distal renal tubules after aldosterone administration

The mineralocorticoid aldosterone is important in the delevelopment of renal disease. We hypothesized that aldosterone increase protein turnover and challenge the cellular protein degradation systems in renal tubules as a primary event in tubular damage. The cellular accumulation of specific protein aggregates and aggresome formation was assessed in kidneys from rats receiving either 50 μg aldosterone/kg body weight/day for 7 days or vehicle in osmotic minipumps. Aldosterone induced accumulation of 60s ribosomal subunit L22 (RPL22) in protein aggregates specifically in the aldosterone sensitive distal renal tubules. RPL22 showed 80% co‐localization with proteasome 20s, while co‐localization with endosomal and lysosomal markers was neglible. A 1.5‐fold increase in proteasome 20s abundance was observed in distal renal tubules with a concomitant increase in proteasome aggregate count. Finally, aldosterone treatment induced foci of early epithelial to mesenchymal transition in renal cortex as judged by vimentin expression and lymphocyte infiltration. We conclude that aldosterone administration leads to accumulation of non‐classical protein aggregates in the distal renal tubule that are not cleared by autophagy.

Mechanisms of Protein Seeding in Neurodegenerative Diseases

Most age-associated neurodegenerative diseases involve the aggregation of specific proteins within the nervous system. In Alzheimer disease, the insidious pathogenic process begins many years before the symptoms emerge, and the lesions that characterize the disease—senile plaques and neurofibrillary tangles—ramify systematically through the brain. We review evidence that the -amyloid and tau proteins, which aggregate to form senile plaques and neurofibrillary tangles, respectively, are induced to misfold and self-assemble by a process of templated conformational change that amplifies a toxic species. Recent data also indicate that the spread of these lesions from one site to another is mediated by the cellular uptake, transport, and release of endogenous seeds formed by the cognate proteins. This simple pathogenic principle suggests that the formation, trafficking, and metabolism of pathogenic protein seeds are promising therapeutic targets for Alzheimer disease and other neurodegenerative disorders.