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Volloch V, Rits-Volloch S. Quintessential Synergy: Concurrent Transient Administration of Integrated Stress Response Inhibitors and BACE1 and/or BACE2 Activators as the Optimal Therapeutic Strategy for Alzheimer's Disease. Int J Mol Sci 2024; 25:9913. [PMID: 39337400 PMCID: PMC11432332 DOI: 10.3390/ijms25189913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2024] [Revised: 09/01/2024] [Accepted: 09/03/2024] [Indexed: 09/30/2024] Open
Abstract
The present study analyzes two potential therapeutic approaches for Alzheimer's disease (AD). One is the suppression of the neuronal integrated stress response (ISR). Another is the targeted degradation of intraneuronal amyloid-beta (iAβ) via the activation of BACE1 (Beta-site Aβ-protein-precursor Cleaving Enzyme) and/or BACE2. Both approaches are rational. Both are promising. Both have substantial intrinsic limitations. However, when combined in a carefully orchestrated manner into a composite therapy they display a prototypical synergy and constitute the apparently optimal, potentially most effective therapeutic strategy for AD.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children's Hospital, Boston, MA 02115, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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Volloch V, Rits-Volloch S. ACH2.0/E, the Consolidated Theory of Conventional and Unconventional Alzheimer's Disease: Origins, Progression, and Therapeutic Strategies. Int J Mol Sci 2024; 25:6036. [PMID: 38892224 PMCID: PMC11172602 DOI: 10.3390/ijms25116036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/19/2024] [Accepted: 05/21/2024] [Indexed: 06/21/2024] Open
Abstract
The centrality of amyloid-beta (Aβ) is an indisputable tenet of Alzheimer's disease (AD). It was initially indicated by the detection (1991) of a mutation within Aβ protein precursor (AβPP) segregating with the disease, which served as a basis for the long-standing Amyloid Cascade Hypothesis (ACH) theory of AD. In the intervening three decades, this notion was affirmed and substantiated by the discovery of numerous AD-causing and AD-protective mutations with all, without an exception, affecting the structure, production, and intraneuronal degradation of Aβ. The ACH postulated that the disease is caused and driven by extracellular Aβ. When it became clear that this is not the case, and the ACH was largely discredited, a new theory of AD, dubbed ACH2.0 to re-emphasize the centrality of Aβ, was formulated. In the ACH2.0, AD is caused by physiologically accumulated intraneuronal Aβ (iAβ) derived from AβPP. Upon reaching the critical threshold, it triggers activation of the autonomous AβPP-independent iAβ generation pathway; its output is retained intraneuronally and drives the AD pathology. The bridge between iAβ derived from AβPP and that generated independently of AβPP is the neuronal integrated stress response (ISR) elicited by the former. The ISR severely suppresses cellular protein synthesis; concurrently, it activates the production of a small subset of proteins, which apparently includes components necessary for operation of the AβPP-independent iAβ generation pathway that are absent under regular circumstances. The above sequence of events defines "conventional" AD, which is both caused and driven by differentially derived iAβ. Since the ISR can be elicited by a multitude of stressors, the logic of the ACH2.0 mandates that another class of AD, referred to as "unconventional", has to occur. Unconventional AD is defined as a disease where a stressor distinct from AβPP-derived iAβ elicits the neuronal ISR. Thus, the essence of both, conventional and unconventional, forms of AD is one and the same, namely autonomous, self-sustainable, AβPP-independent production of iAβ. What distinguishes them is the manner of activation of this pathway, i.e., the mode of causation of the disease. In unconventional AD, processes occurring at locations as distant from and seemingly as unrelated to the brain as, say, the knee can potentially trigger the disease. The present study asserts that these processes include traumatic brain injury (TBI), chronic traumatic encephalopathy, viral and bacterial infections, and a wide array of inflammatory conditions. It considers the pathways which are common to all these occurrences and culminate in the elicitation of the neuronal ISR, analyzes the dynamics of conventional versus unconventional AD, shows how the former can morph into the latter, explains how a single TBI can hasten the occurrence of AD and why it takes multiple TBIs to trigger the disease, and proposes the appropriate therapeutic strategies. It posits that yet another class of unconventional AD may occur where the autonomous AβPP-independent iAβ production pathway is initiated by an ISR-unrelated activator, and consolidates the above notions in a theory of AD, designated ACH2.0/E (for expanded ACH2.0), which incorporates the ACH2.0 as its special case and retains the centrality of iAβ produced independently of AβPP as the driving agent of the disease.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA 02115, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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Volloch V, Rits-Volloch S. On the Inadequacy of the Current Transgenic Animal Models of Alzheimer's Disease: The Path Forward. Int J Mol Sci 2024; 25:2981. [PMID: 38474228 PMCID: PMC10932000 DOI: 10.3390/ijms25052981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 02/27/2024] [Accepted: 02/28/2024] [Indexed: 03/14/2024] Open
Abstract
For at least two reasons, the current transgenic animal models of Alzheimer's disease (AD) appear to be patently inadequate. They may be useful in many respects, the AD models; however, they are not. First, they are incapable of developing the full spectrum of the AD pathology. Second, they respond spectacularly well to drugs that are completely ineffective in the treatment of symptomatic AD. These observations indicate that both the transgenic animal models and the drugs faithfully reflect the theory that guided the design and development of both, the amyloid cascade hypothesis (ACH), and that both are inadequate because their underlying theory is. This conclusion necessitated the formulation of a new, all-encompassing theory of conventional AD-the ACH2.0. The two principal attributes of the ACH2.0 are the following. One, in conventional AD, the agent that causes the disease and drives its pathology is the intraneuronal amyloid-β (iAβ) produced in two distinctly different pathways. Two, following the commencement of AD, the bulk of Aβ is generated independently of Aβ protein precursor (AβPP) and is retained inside the neuron as iAβ. Within the framework of the ACH2.0, AβPP-derived iAβ accumulates physiologically in a lifelong process. It cannot reach levels required to support the progression of AD; it does, however, cause the disease. Indeed, conventional AD occurs if and when the levels of AβPP-derived iAβ cross the critical threshold, elicit the neuronal integrated stress response (ISR), and trigger the activation of the AβPP-independent iAβ generation pathway; the disease commences only when this pathway is operational. The iAβ produced in this pathway reaches levels sufficient to drive the AD pathology; it also propagates its own production and thus sustains the activity of the pathway and perpetuates its operation. The present study analyzes the reason underlying the evident inadequacy of the current transgenic animal models of AD. It concludes that they model, in fact, not Alzheimer's disease but rather the effects of the neuronal ISR sustained by AβPP-derived iAβ, that this is due to the lack of the operational AβPP-independent iAβ production pathway, and that this mechanism must be incorporated into any successful AD model faithfully emulating the disease. The study dissects the plausible molecular mechanisms of the AβPP-independent iAβ production and the pathways leading to their activation, and introduces the concept of conventional versus unconventional Alzheimer's disease. It also proposes the path forward, posits the principles of design of productive transgenic animal models of the disease, and describes the molecular details of their construction.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA 02115, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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Volloch V, Rits-Volloch S. Next Generation Therapeutic Strategy for Treatment and Prevention of Alzheimer's Disease and Aging-Associated Cognitive Decline: Transient, Once-in-a-Lifetime-Only Depletion of Intraneuronal Aβ ( iAβ) by Its Targeted Degradation via Augmentation of Intra- iAβ-Cleaving Activities of BACE1 and/or BACE2. Int J Mol Sci 2023; 24:17586. [PMID: 38139415 PMCID: PMC10744314 DOI: 10.3390/ijms242417586] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 12/04/2023] [Accepted: 12/05/2023] [Indexed: 12/24/2023] Open
Abstract
Although the long-standing Amyloid Cascade Hypothesis (ACH) has been largely discredited, its main attribute, the centrality of amyloid-beta (Aβ) in Alzheimer's disease (AD), remains the cornerstone of any potential interpretation of the disease: All known AD-causing mutations, without a single exception, affect, in one way or another, Aβ. The ACH2.0, a recently introduced theory of AD, preserves this attribute but otherwise differs fundamentally from the ACH. It posits that AD is a two-stage disorder where both stages are driven by intraneuronal (rather than extracellular) Aβ (iAβ) albeit of two distinctly different origins. The first asymptomatic stage is the decades-long accumulation of Aβ protein precursor (AβPP)-derived iAβ to the critical threshold. This triggers the activation of the self-sustaining AβPP-independent iAβ production pathway and the commencement of the second, symptomatic AD stage. Importantly, Aβ produced independently of AβPP is retained intraneuronally. It drives the AD pathology and perpetuates the operation of the pathway; continuous cycles of the iAβ-stimulated propagation of its own AβPP-independent production constitute an engine that drives AD, the AD Engine. It appears that the dynamics of AβPP-derived iAβ accumulation is the determining factor that either drives Aging-Associated Cognitive Decline (AACD) and triggers AD or confers the resistance to both. Within the ACH2.0 framework, the ACH-based drugs, designed to lower levels of extracellular Aβ, could be applicable in the prevention of AD and treatment of AACD because they reduce the rate of accumulation of AβPP-derived iAβ. The present study analyzes their utility and concludes that it is severely limited. Indeed, their short-term employment is ineffective, their long-term engagement is highly problematic, their implementation at the symptomatic stages of AD is futile, and their evaluation in conventional clinical trials for the prevention of AD is impractical at best, impossible at worst, and misleading in between. In contrast, the ACH2.0-guided Next Generation Therapeutic Strategy for the treatment and prevention of both AD and AACD, namely the depletion of iAβ via its transient, short-duration, targeted degradation by the novel ACH2.0-based drugs, has none of the shortcomings of the ACH-based drugs. It is potentially highly effective, easily evaluable in clinical trials, and opens up the possibility of once-in-a-lifetime-only therapeutic intervention for prevention and treatment of both conditions. It also identifies two plausible ACH2.0-based drugs: activators of physiologically occurring intra-iAβ-cleaving capabilities of BACE1 and/or BACE2.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA 02115, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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Chatanaka MK, Sohaei D, Diamandis EP, Prassas I. Beyond the amyloid hypothesis: how current research implicates autoimmunity in Alzheimer's disease pathogenesis. Crit Rev Clin Lab Sci 2023; 60:398-426. [PMID: 36941789 DOI: 10.1080/10408363.2023.2187342] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 03/01/2023] [Indexed: 03/23/2023]
Abstract
The amyloid hypothesis has so far been at the forefront of explaining the pathogenesis of Alzheimer's Disease (AD), a progressive neurodegenerative disorder that leads to cognitive decline and eventual death. Recent evidence, however, points to additional factors that contribute to the pathogenesis of this disease. These include the neurovascular hypothesis, the mitochondrial cascade hypothesis, the inflammatory hypothesis, the prion hypothesis, the mutational accumulation hypothesis, and the autoimmunity hypothesis. The purpose of this review was to briefly discuss the factors that are associated with autoimmunity in humans, including sex, the gut and lung microbiomes, age, genetics, and environmental factors. Subsequently, it was to examine the rise of autoimmune phenomena in AD, which can be instigated by a blood-brain barrier breakdown, pathogen infections, and dysfunction of the glymphatic system. Lastly, it was to discuss the various ways by which immune system dysregulation leads to AD, immunomodulating therapies, and future directions in the field of autoimmunity and neurodegeneration. A comprehensive account of the recent research done in the field was extracted from PubMed on 31 January 2022, with the keywords "Alzheimer's disease" and "autoantibodies" for the first search input, and "Alzheimer's disease" with "IgG" for the second. From the first search, 19 papers were selected, because they contained recent research on the autoantibodies found in the biofluids of patients with AD. From the second search, four papers were selected. The analysis of the literature has led to support the autoimmune hypothesis in AD. Autoantibodies were found in biofluids (serum/plasma, cerebrospinal fluid) of patients with AD with multiple methods, including ELISA, Mass Spectrometry, and microarray analysis. Through continuous research, the understanding of the synergistic effects of the various components that lead to AD will pave the way for better therapeutic methods and a deeper understanding of the disease.
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Affiliation(s)
- Miyo K Chatanaka
- Department of Laboratory and Medicine Pathobiology, University of Toronto, Toronto, Canada
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Dorsa Sohaei
- Faculty of Medicine and Health Sciences, McGill University, Montreal, Canada
| | - Eleftherios P Diamandis
- Department of Laboratory and Medicine Pathobiology, University of Toronto, Toronto, Canada
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
- Department of Clinical Biochemistry, University Health Network, Toronto, Canada
| | - Ioannis Prassas
- Laboratory Medicine Program, University Health Network, Toronto, Canada
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Volloch V, Rits-Volloch S. Principles of Design of Clinical Trials for Prevention and Treatment of Alzheimer's Disease and Aging-Associated Cognitive Decline in the ACH2.0 Perspective: Potential Outcomes, Challenges, and Solutions. J Alzheimers Dis Rep 2023; 7:921-955. [PMID: 37849639 PMCID: PMC10578334 DOI: 10.3233/adr-230037] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 07/31/2023] [Indexed: 10/19/2023] Open
Abstract
With the Amyloid Cascade Hypothesis (ACH) largely discredited, the ACH2.0 theory of Alzheimer's disease (AD) has been recently introduced. Within the framework of the ACH2.0, AD is triggered by amyloid-β protein precursor (AβPP)-derived intraneuronal Aβ (iAβ) and is driven by iAβ produced in the AβPP-independent pathway and retained intraneuronally. In this paradigm, the depletion of extracellular Aβ or suppression of Aβ production by AβPP proteolysis, the two sources of AβPP-derived iAβ, would be futile in symptomatic AD, due to its reliance on iAβ generated independently of AβPP, but effective in preventing AD and treating Aging-Associated Cognitive Decline (AACD) driven, in the ACH2.0 framework, by AβPP-derived iAβ. The observed effect of lecanemab and donanemab, interpreted in the ACH2.0 perspective, supports this notion and mandates AD-preventive clinical trials. Such trials are currently in progress. They are likely, however, to fail or to yield deceptive results if conducted conventionally. The present study considers concepts of design of clinical trials of lecanemab, donanemab, or any other drug, targeting the influx of AβPP-derived iAβ, in prevention of AD and treatment of AACD. It analyzes possible outcomes and explains why selection of high-risk asymptomatic participants seems reasonable but is not. It argues that outcomes of such AD preventive trials could be grossly misleading, discusses inevitable potential problems, and proposes feasible solutions. It advocates the initial evaluation of this type of drugs in clinical trials for treatment of AACD. Whereas AD protective trials of these drugs are potentially of an impractical length, AACD clinical trials are expected to yield unequivocal results within a relatively short duration. Moreover, success of the latter, in addition to its intrinsic value, would constitute a proof of concept for the former. Furthermore, this study introduces concepts of the active versus passive iAβ depletion, contends that targeted degradation of iAβ is the best therapeutic strategy for both prevention and treatment of AD and AACD, proposes potential iAβ-degrading drugs, and describes their feasible and unambiguous evaluation in clinical trials.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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Volloch V, Rits-Volloch S. The Amyloid Cascade Hypothesis 2.0 for Alzheimer's Disease and Aging-Associated Cognitive Decline: From Molecular Basis to Effective Therapy. Int J Mol Sci 2023; 24:12246. [PMID: 37569624 PMCID: PMC10419172 DOI: 10.3390/ijms241512246] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 08/13/2023] Open
Abstract
With the long-standing amyloid cascade hypothesis (ACH) largely discredited, there is an acute need for a new all-encompassing interpretation of Alzheimer's disease (AD). Whereas such a recently proposed theory of AD is designated ACH2.0, its commonality with the ACH is limited to the recognition of the centrality of amyloid-β (Aβ) in the disease, necessitated by the observation that all AD-causing mutations affect, in one way or another, Aβ. Yet, even this narrow commonality is superficial since AD-causing Aβ of the ACH differs distinctly from that specified in the ACH2.0: Whereas in the former, the disease is caused by secreted extracellular Aβ, in the latter, it is triggered by Aβ-protein-precursor (AβPP)-derived intraneuronal Aβ (iAβ) and driven by iAβ generated independently of AβPP. The ACH2.0 envisions AD as a two-stage disorder. The first, asymptomatic stage is a decades-long accumulation of AβPP-derived iAβ, which occurs via internalization of secreted Aβ and through intracellular retention of a fraction of Aβ produced by AβPP proteolysis. When AβPP-derived iAβ reaches critical levels, it activates a self-perpetuating AβPP-independent production of iAβ that drives the second, devastating AD stage, a cascade that includes tau pathology and culminates in neuronal loss. The present study analyzes the dynamics of iAβ accumulation in health and disease and concludes that it is the prime factor driving both AD and aging-associated cognitive decline (AACD). It discusses mechanisms potentially involved in AβPP-independent generation of iAβ, provides mechanistic interpretations for all principal aspects of AD and AACD including the protective effect of the Icelandic AβPP mutation, the early onset of FAD and the sequential manifestation of AD pathology in defined regions of the affected brain, and explains why current mouse AD models are neither adequate nor suitable. It posits that while drugs affecting the accumulation of AβPP-derived iAβ can be effective only protectively for AD, the targeted degradation of iAβ is the best therapeutic strategy for both prevention and effective treatment of AD and AACD. It also proposes potential iAβ-degrading drugs.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA 02115, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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Waigi EW, Webb RC, Moss MA, Uline MJ, McCarthy CG, Wenceslau CF. Soluble and insoluble protein aggregates, endoplasmic reticulum stress, and vascular dysfunction in Alzheimer's disease and cardiovascular diseases. GeroScience 2023; 45:1411-1438. [PMID: 36823398 PMCID: PMC10400528 DOI: 10.1007/s11357-023-00748-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 01/28/2023] [Indexed: 02/25/2023] Open
Abstract
Dementia refers to a particular group of symptoms characterized by difficulties with memory, language, problem-solving, and other thinking skills that affect a person's ability to perform everyday activities. Alzheimer's disease (AD) is the most common form of dementia, affecting about 6.2 million Americans aged 65 years and older. Likewise, cardiovascular diseases (CVDs) are a major cause of disability and premature death, impacting 126.9 million adults in the USA, a number that increases with age. Consequently, CVDs and cardiovascular risk factors are associated with an increased risk of AD and cognitive impairment. They share important age-related cardiometabolic and lifestyle risk factors, that make them among the leading causes of death. Additionally, there are several premises and hypotheses about the mechanisms underlying the association between AD and CVD. Although AD and CVD may be considered deleterious to health, the study of their combination constitutes a clinical challenge, and investigations to understand the mechanistic pathways for the cause-effect and/or shared pathology between these two disease constellations remains an active area of research. AD pathology is propagated by the amyloid β (Aβ) peptides. These peptides give rise to small, toxic, and soluble Aβ oligomers (SPOs) that are nonfibrillar, and it is their levels that show a robust correlation with the extent of cognitive impairment. This review will elucidate the interplay between the effects of accumulating SPOs in AD and CVDs, the resulting ER stress response, and their role in vascular dysfunction. We will also address the potential underlying mechanisms, including the possibility that SPOs are among the causes of vascular injury in CVD associated with cognitive decline. By revealing common mechanistic underpinnings of AD and CVD, we hope that novel experimental therapeutics can be designed to reduce the burden of these devastating diseases. Graphical abstract Alzheimer's disease (AD) pathology leads to the release of Aβ peptides, and their accumulation in the peripheral organs has varying effects on various components of the cardiovascular system including endoplasmic reticulum (ER) stress and vascular damage. Image created with BioRender.com.
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Affiliation(s)
- Emily W Waigi
- Cardiovascular Translational Research Cententer (CTRC), Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, SC, USA
| | - R Clinton Webb
- Cardiovascular Translational Research Cententer (CTRC), Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, SC, USA
- Biomedical Engineering Program, Univeristy of South Carolina, Columbia, SC, USA
| | - Melissa A Moss
- Biomedical Engineering Program, Univeristy of South Carolina, Columbia, SC, USA
- Department of Chemical Engineering, University of South Carolina, Columbia, SC, USA
| | - Mark J Uline
- Biomedical Engineering Program, Univeristy of South Carolina, Columbia, SC, USA
- Department of Chemical Engineering, University of South Carolina, Columbia, SC, USA
| | - Cameron G McCarthy
- Cardiovascular Translational Research Cententer (CTRC), Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, SC, USA
- Biomedical Engineering Program, Univeristy of South Carolina, Columbia, SC, USA
| | - Camilla Ferreira Wenceslau
- Cardiovascular Translational Research Cententer (CTRC), Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, SC, USA.
- Biomedical Engineering Program, Univeristy of South Carolina, Columbia, SC, USA.
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Takano C, Takano T, Masumura M, Nakamura R, Koda S, Bochimoto H, Yoshida S, Bando Y. Involvement of Degenerating 21.5 kDa Isoform of Myelin Basic Protein in the Pathogenesis of the Relapse in Murine Relapsing-Remitting Experimental Autoimmune Encephalomyelitis and MS Autopsied Brain. Int J Mol Sci 2023; 24:ijms24098160. [PMID: 37175866 PMCID: PMC10179612 DOI: 10.3390/ijms24098160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 04/22/2023] [Accepted: 04/27/2023] [Indexed: 05/15/2023] Open
Abstract
Multiple sclerosis (MS) is the chronic inflammatory demyelinating disease of the CNS. Relapsing-remitting MS (RRMS) is the most common type of MS. However, the mechanisms of relapse and remission in MS have not been fully understood. While SJL mice immunized with proteolipid protein (PLP) develop relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE), we have recently observed that some of these mice were resistant to the active induction of relapsing EAE after initial clinical and histological symptoms of EAE with a severity similar to the relapsing EAE mice. To clarify the mechanism of relapsing, we examined myelin morphology during PLP139-151-induced RR-EAE in the SJL mice. While RR-EAE mice showed an increased EAE severity (relapse) with CNS inflammation, demyelination with abnormal myelin morphology in the spinal cord, the resistant mice exhibited a milder EAE phenotype with diminished relapse. Compared with the RR-EAE mice, the resistant mice showed less CNS inflammation, demyelination, and abnormalities of the myelin structure. In addition, scanning electron microscopic (SEM) analysis with the osmium-maceration method displayed ultrastructural abnormalities of the myelin structure in the white matter of the RR-EAE spinal cord, but not in that of the resistant mice. While the intensity of myelin staining was reduced in the relapsing EAE spinal cord, immunohistochemistry and immunoblot analysis revealed that the 21.5 kDa isoform of degenerating myelin basic protein (MBP) was specifically induced in the relapsing EAE spinal cord. Taken together, the neuroinflammation-induced degenerating 21 kDa isoform of MBP sheds light on the development of abnormal myelin on the relapse of MS pathogenesis.
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Affiliation(s)
- Chie Takano
- Department of Functional Anatomy and Neuroscience, Asahikawa Medical University, Asahikawa 078-8510, Japan
- Department of Neurosurgery, Asahikawa Medical University, Asahikawa 078-8510, Japan
| | - Takuma Takano
- Department of Functional Anatomy and Neuroscience, Asahikawa Medical University, Asahikawa 078-8510, Japan
- Department of Neurosurgery, Asahikawa Medical University, Asahikawa 078-8510, Japan
| | - Makoto Masumura
- Institute for Social Innovation and Cooperation, Niigata University, Niigata 951-8510, Japan
| | | | | | - Hiroki Bochimoto
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Shigetaka Yoshida
- Department of Functional Anatomy and Neuroscience, Asahikawa Medical University, Asahikawa 078-8510, Japan
| | - Yoshio Bando
- Department of Functional Anatomy and Neuroscience, Asahikawa Medical University, Asahikawa 078-8510, Japan
- Department of Anatomy, Akita University Graduate School of Medicine, Hondo 1-1-1, Akita 010-8543, Japan
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Volloch V, Rits-Volloch S. The Amyloid Cascade Hypothesis 2.0: Generalization of the Concept. J Alzheimers Dis Rep 2023; 7:21-35. [PMID: 36777328 PMCID: PMC9912825 DOI: 10.3233/adr-220079] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 12/09/2022] [Indexed: 12/31/2022] Open
Abstract
Recently, we proposed the Amyloid Cascade Hypothesis 2.0 (ACH2.0), a reformulation of the ACH. In the former, in contrast to the latter, Alzheimer's disease (AD) is driven by intraneuronal amyloid-β (iAβ) and occurs in two stages. In the first, relatively benign stage, Aβ protein precursor (AβPP)-derived iAβ activates, upon reaching a critical threshold, the AβPP-independent iAβ-generating pathway, triggering a devastating second stage resulting in neuronal death. While the ACH2.0 remains aligned with the ACH premise that Aβ is toxic, the toxicity is exerted because of intra- rather than extracellular Aβ. In this framework, a once-in-a-lifetime-only iAβ depletion treatment via transient activation of BACE1 and/or BACE2 (exploiting their Aβ-cleaving activities) or by any means appears to be the best therapeutic strategy for AD. Whereas the notion of differentially derived iAβ being the principal moving force at both AD stages is both plausible and elegant, a possibility remains that the second AD stage is enabled by an AβPP-derived iAβ-activated self-sustaining mechanism producing a yet undefined deleterious "substance X" (sX) which anchors the second AD stage. The present study generalizes the ACH2.0 by incorporating this possibility and shows that, in this scenario, the iAβ depletion therapy may be ineffective at symptomatic AD stages but fully retains its preventive potential for both AD and the aging-associated cognitive decline, which is defined in the ACH2.0 framework as the extended first stage of AD.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA,Correspondence to: Vladimir Volloch, Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA. and Sophia Rits-Volloch, Division of Molecular Medicine, Children’s Hospital, Boston, MA, USA. E-mail:
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA, USA,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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11
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Baerends E, Soud K, Folke J, Pedersen AK, Henmar S, Konrad L, Lycas MD, Mori Y, Pakkenberg B, Woldbye DPD, Dmytriyeva O, Pankratova S. Modeling the early stages of Alzheimer's disease by administering intracerebroventricular injections of human native Aβ oligomers to rats. Acta Neuropathol Commun 2022; 10:113. [PMID: 35974377 PMCID: PMC9380371 DOI: 10.1186/s40478-022-01417-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 07/29/2022] [Indexed: 11/10/2022] Open
Abstract
Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease characterized by the accumulation of aggregated amyloid beta (Aβ) and hyperphosphorylated tau along with a slow decline in cognitive functions. Unlike advanced AD, the initial steps of AD pathophysiology have been poorly investigated, partially due to limited availability of animal models focused on the early, plaque-free stages of the disease. The aim of this study was to evaluate the early behavioral, anatomical and molecular alterations in wild-type rats following intracerebroventricular injections of human Aβ oligomers (AβOs). Bioactive human AD and nondemented control brain tissue extracts were characterized using ELISA and proteomics approaches. Following a bilateral infusion, rats underwent behavioral testing, including the elevated plus maze, social recognition test, Morris water maze and Y-maze within 6 weeks postinjection. An analysis of brain structure was performed with manganese-enhanced MRI. Collected brain tissues were analyzed using stereology, immunohistochemistry, ELISA and qPCR. No sensorimotor deficits affecting motor performance on different maze tasks were observed, nor was spatial memory disturbed in AD rats. In contrast, a significant impairment of social memory became evident at 21 days postinjection. This deficit was associated with a significantly decreased volume of the lateral entorhinal cortex and a tendency toward a decrease in the total brain volume. Significant increase of cleaved caspase-3-positive cells, microglial activation and proinflammatory responses accompanied by altered expression of synaptic markers were observed in the hippocampus of AD rats with immunohistochemical and qPCR approaches at 6 weeks postinjection. Our data suggest that the social memory impairment observed in AβO-injected rats might be determined by neuroinflammatory responses and synaptopathy. An infusion of native oligomeric Aβ in the rat brain represents a feasible tool to model early plaque-free events associated with AD.
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Affiliation(s)
- Eva Baerends
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Katia Soud
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Jonas Folke
- Centre for Neuroscience and Stereology, Department of Neurology,, Bispebjerg-Frederiksberg Hospital, Copenhagen University Hospital, Copenhagen, Denmark.,Copenhagen Center for Translational Research, Bispebjerg-Frederiksberg Hospital, Copenhagen University Hospital, Copenhagen, Denmark
| | - Anna-Kathrine Pedersen
- Proteomics Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Simon Henmar
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Lisa Konrad
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Matthew D Lycas
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Yuki Mori
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Pakkenberg
- Centre for Neuroscience and Stereology, Department of Neurology,, Bispebjerg-Frederiksberg Hospital, Copenhagen University Hospital, Copenhagen, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - David P D Woldbye
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Oksana Dmytriyeva
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Stanislava Pankratova
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark. .,Comparative Pediatrics and Nutrition, Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark.
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12
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Volloch V, Rits-Volloch S. The Amyloid Cascade Hypothesis 2.0: On the Possibility of Once-in-a-Lifetime-Only Treatment for Prevention of Alzheimer’s Disease and for Its Potential Cure at Symptomatic Stages. J Alzheimers Dis Rep 2022; 6:369-399. [PMID: 36072366 PMCID: PMC9397896 DOI: 10.3233/adr-220031] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 06/08/2022] [Indexed: 11/15/2022] Open
Abstract
We posit that Alzheimer’s disease (AD) is driven by amyloid-β (Aβ) generated in the amyloid-β protein precursor (AβPP) independent pathway activated by AβPP-derived Aβ accumulated intraneuronally in a life-long process. This interpretation constitutes the Amyloid Cascade Hypothesis 2.0 (ACH2.0). It defines a tandem intraneuronal-Aβ (iAβ)-anchored cascade occurrence: intraneuronally-accumulated, AβPP-derived iAβ triggers relatively benign cascade that activates the AβPP-independent iAβ-generating pathway, which, in turn, initiates the second, devastating cascade that includes tau pathology and leads to neuronal loss. The entire output of the AβPP-independent iAβ-generating pathway is retained intraneuronally and perpetuates the pathway’s operation. This process constitutes a self-propagating, autonomous engine that drives AD and ultimately kills its host cells. Once activated, the AD Engine is self-reliant and independent from Aβ production in the AβPP proteolytic pathway; operation of the former renders the latter irrelevant to the progression of AD and brands its manipulation for therapeutic purposes, such as BACE (beta-site AβPP-cleaving enzyme) inhibition, as futile. In the proposed AD paradigm, the only valid direct therapeutic strategy is targeting the engine’s components, and the most effective feasible approach appears to be the activation of BACE1 and/or of its homolog BACE2, with the aim of exploiting their Aβ-cleaving activities. Such treatment would collapse the iAβ population and ‘reset’ its levels below those required for the operation of the AD Engine. Any sufficiently selective iAβ-depleting treatment would be equally effective. Remarkably, this approach opens the possibility of a short-duration, once-in-a-lifetime-only or very infrequent, preventive or curative therapy for AD; this therapy would be also effective for prevention and treatment of the ‘common’ pervasive aging-associated cognitive decline. The ACH2.0 clarifies all ACH-unresolved inconsistencies, explains the widespread ‘resilience to AD’ phenomenon, predicts occurrences of a category of AD-afflicted individuals without excessive Aβ plaque load and of a novel type of familial insusceptibility to AD; it also predicts the lifespan-dependent inevitability of AD in humans if untreated preventively. The article details strategy and methodology to generate an adequate AD model and validate the hypothesis; the proposed AD model may also serve as a research and drug development platform.
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Affiliation(s)
- Vladimir Volloch
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - Sophia Rits-Volloch
- Division of Molecular Medicine, Children’s Hospital, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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13
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Lopez-Grancha M, Bernardelli P, Moindrot N, Genet E, Vincent C, Roudieres V, Krick AI, Sabuco JF, Machnik D, Ibghi D, Pradier L, Taupin V. A Novel Selective PKR Inhibitor Restores Cognitive Deficits and Neurodegeneration in Alzheimer Disease Experimental Models. J Pharmacol Exp Ther 2021; 378:262-275. [PMID: 34531308 DOI: 10.1124/jpet.121.000590] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 06/09/2021] [Indexed: 11/22/2022] Open
Abstract
In Alzheimer disease (AD), the double-strand RNA-dependent kinase protein kinase R (PKR )/EIF2AK2 is activated in brain with increased phosphorylation of its substrate eukaryotic initiation factor 2α (eIF2α). AD risk-promoting factors, such as ApoE4 allele or the accumulation of neurotoxic amyloid-β oligomers (AβOs), have been associated with activation of PKR-dependent signaling. Here, we report the discovery of a novel potent and selective PKR inhibitor (SAR439883) and demonstrate its neuroprotective pharmacological activity in AD experimental models. In ApoE4 human replacement male mice, 1-week oral treatment with SAR439883 rescued short-term memory impairment in the spatial object recognition test and dose-dependently reduced learning and memory deficits in the Barnes maze test. Moreover, in AβO-injected male mice, a 2-week administration of SAR439883 in diet dose-dependently ameliorated the AβO-induced cognitive impairment in both Y-maze and Morris Water Maze, prevented loss of synaptic proteins, and reduced levels of the proinflammatory cytokine interleukin-1β In both mouse models, these effects were associated with a dose-dependent inhibition of brain PKR activity as measured by both PKR occupancy and partial lowering of peIF2α levels. Our results provide evidence that selective pharmacological inhibition of PKR by a small selective molecule can rescue memory deficits and prevent neurodegeneration in animal models of AD-like pathology, suggesting that inhibition of PKR is a potential therapeutic approach for AD. SIGNIFICANCE STATEMENT: This study reports the identification of a new small molecule potent and selective protein kinase R (PKR) inhibitor that can prevent cognitive deficits and neurodegeneration in Alzheimer disease (AD) experimental models, including a mouse model expressing the most prevalent AD genetic risk factor ApoE4. With high potency and selectivity, this PKR inhibitor represents a unique tool for investigating the physiological role of PKR and a starting point for developing new drug candidates for AD.
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Affiliation(s)
- Matilde Lopez-Grancha
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Patrick Bernardelli
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Nicolas Moindrot
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Elisabeth Genet
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Carine Vincent
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Valerie Roudieres
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - AIain Krick
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Jean-François Sabuco
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - David Machnik
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Delphine Ibghi
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Laurent Pradier
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
| | - Veronique Taupin
- Neurodegeneration Cluster, Rare and Neurologic Disease Research TA (M.L.-G., N.M., E.G., C.V., V.R., D.I., L.P., V.T.), Integrated Drug Discovery (P.B., J.-F.S., D.M.), and DMPK (A.K.), Sanofi R&D, Chilly-Mazarin, France
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14
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Silva VAO, André ND, E Sousa TA, Alves VM, Do Carmo Kettelhut I, De Lucca FL. Nuclear PKR in retinal neurons in the early stage of diabetic retinopathy in streptozotocin‑induced diabetic rats. Mol Med Rep 2021; 24:614. [PMID: 34184090 PMCID: PMC8258468 DOI: 10.3892/mmr.2021.12253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 02/16/2021] [Indexed: 01/01/2023] Open
Abstract
Retinal neuron apoptosis is a key component of diabetic retinopathy (DR), one of the most common complications of diabetes. Stress due to persistent hyperglycaemia and corresponding glucotoxicity represents one of the primary pathogenic mechanisms of diabetes and its complications. Apoptosis of retinal neurons serves a critical role in the pathogenesis of DR observed in patients with diabetes and streptozotocin (STZ)‑induced diabetic rats. Retinal neuron apoptosis occurs one month after STZ injection, which is considered the early stage of DR. The molecular mechanism involved in the suppression of retinal neuron apoptosis during the early stage of DR remains unclear. RNA‑dependent protein kinase (PKR) is a stress‑sensitive pro‑apoptotic kinase. Our previous study indicated that PKR‑associated protein X, a stress‑sensitive activator of PKR, is upregulated in the early stage of STZ‑induced diabetes. In order to assess the role of PKR in DR prior to apoptosis of retinal neurons, immunofluorescence and western blotting were performed to investigate the cellular localization and expression of PKR in the retina in the early stage of STZ‑induced diabetes in rats. PKR activity was indirectly assessed by expression levels of phosphorylated eukaryotic translation initiation factor 2α (p‑eIF2‑α) and the presence of apoptotic cells in the retina was investigated by TUNEL assay. The findings revealed that PKR was localized in the nucleus of retinal ganglion and inner nuclear layer cells from normal and diabetic rats. To the best of our knowledge, the present study is the first to demonstrate nuclear localization of PKR in retinal neurons. Immunofluorescence analysis demonstrated that PKR was expressed in the nuclei of retinal neurons at 3 and 6 days and its expression was decreased at 15 days after STZ treatment. In addition, p‑eIF2‑α expression and cellular localization followed the trend of PKR, suggesting that this pro‑apoptotic kinase was active in the nuclei of retinal neurons. These findings are consistent with the hypothesis that nuclear translocation of PKR may be a mechanism to sequester active PKR, thus preventing upregulation of cytosolic signalling pathways that induce apoptosis in retinal neurons. Apoptotic cells were not detected in the retina in the early stage of DR. A model was proposed to explain the mechanism by which apoptosis of retinal neurons by PKR is suppressed in the early stage of DR. The possible role of mitochondrial RNA (mtRNA) and Alu RNA in this phenomenon is also discussed since it was demonstrated that the cellular stress due to prolonged hyperglycaemia induces the release of mtRNA and transcription of Alu RNA. Moreover, it mtRNA activates PKR, whereas Alu RNA inhibits the activation of this protein kinase.
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Affiliation(s)
| | | | - Thaís Amaral E Sousa
- Federal Institute of Education, Science and Technology of Goiás, Formosa, Goiás 73813-816, Brazil
| | - Vâni Maria Alves
- Department of Biochemistry and Immunology, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil
| | - Isis Do Carmo Kettelhut
- Department of Biochemistry and Immunology, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil
| | - Fernando Luiz De Lucca
- Department of Biochemistry and Immunology, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil
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15
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Reinharz V, Ishida Y, Tsuge M, Durso-Cain K, Chung TL, Tateno C, Perelson AS, Uprichard SL, Chayama K, Dahari H. Understanding Hepatitis B Virus Dynamics and the Antiviral Effect of Interferon Alpha Treatment in Humanized Chimeric Mice. J Virol 2021; 95:e0049220. [PMID: 33910953 PMCID: PMC8223956 DOI: 10.1128/jvi.00492-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 04/20/2021] [Indexed: 12/16/2022] Open
Abstract
Whereas the mode of action of lamivudine (LAM) against hepatitis B virus (HBV) is well established, the inhibition mechanism(s) of interferon alpha (IFN-α) is less completely defined. To advance our understanding, we mathematically modeled HBV kinetics during 14-day pegylated IFN-α-2a (pegIFN), LAM, or pegIFN-plus-LAM (pegIFN+LAM) treatment of 39 chronically HBV-infected humanized uPA/SCID chimeric mice. Serum HBV DNA and intracellular HBV DNA were measured frequently. We developed a multicompartmental mathematical model and simultaneously fit it to the serum and intracellular HBV DNA data. Unexpectedly, even in the absence of an adaptive immune response, a biphasic decline in serum HBV DNA and intracellular HBV DNA was observed in response to all treatments. Kinetic analysis and modeling indicate that the first phase represents inhibition of intracellular HBV DNA synthesis and secretion, which was similar under all treatments with an overall mean efficacy of 98%. In contrast, there were distinct differences in HBV decline during the second phase, which was accounted for in the model by a time-dependent inhibition of intracellular HBV DNA synthesis, with the steepest decline observed during pegIFN+LAM treatment (1.28/day) and the slowest (0.1/day) during pegIFN monotherapy. Reminiscent of observations in patients treated with pegIFN and/or LAM, a biphasic HBV decline was observed in treated humanized mice in the absence of an adaptive immune response. Interestingly, combination treatment did not increase the initial inhibition of HBV production but rather enhanced second-phase decline, providing insight into the dynamics of HBV treatment response and the mode of action of IFN-α against HBV. IMPORTANCE Chronic hepatitis B virus (HBV) infection remains a global health care problem, as we lack sufficient curative treatment options. Elucidating the dynamics of HBV infection and treatment response at the molecular level could facilitate the development of novel, more effective HBV antivirals. Currently, the only well-established small animal HBV infection model available is the chimeric uPA/SCID mice with humanized livers; however, the HBV inhibition kinetics under pegylated IFN-α-2a (pegIFN) in this model system have not been determined in sufficient detail. In this study, viral kinetics in 39 humanized mice treated with pegIFN and/or lamivudine were monitored and analyzed using a mathematical modeling approach. We found that the main mode of action of IFN-α is blocking HBV DNA synthesis and that the majority of synthesized HBV DNA is secreted. Our study provides novel insights into HBV DNA dynamics within infected human hepatocytes.
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Affiliation(s)
- Vladimir Reinharz
- Department of Computer Science, Université du Québec à Montréal, Montreal, Quebec, Canada
| | - Yuji Ishida
- Research Center for Hepatology and Gastroenterology, Hiroshima University, Hiroshima, Japan
- PhoenixBio Co., Ltd., Hiroshima, Japan
| | - Masataka Tsuge
- Research Center for Hepatology and Gastroenterology, Hiroshima University, Hiroshima, Japan
- The Program for Experimental and Theoretical Modeling, Division of Hepatology, Department of Medicine, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, USA
- Natural Science Center for Basic Research and Development, Hiroshima University, Hiroshima, Japan
| | - Karina Durso-Cain
- The Program for Experimental and Theoretical Modeling, Division of Hepatology, Department of Medicine, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, USA
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Medical Center, Maywood, Illinois, USA
- Infectious Disease and Immunology Research Institute, Stritch School of Medicine, Loyola University Medical Center, Maywood, Illinois, USA
| | - Tje Lin Chung
- The Program for Experimental and Theoretical Modeling, Division of Hepatology, Department of Medicine, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, USA
- Institut für Biostatistik and Mathematische Modellierung, Fachbereich Medizin, Goethe Universität, Frankfurt, Germany
| | - Chise Tateno
- Research Center for Hepatology and Gastroenterology, Hiroshima University, Hiroshima, Japan
- PhoenixBio Co., Ltd., Hiroshima, Japan
| | - Alan S. Perelson
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
| | - Susan L. Uprichard
- The Program for Experimental and Theoretical Modeling, Division of Hepatology, Department of Medicine, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, USA
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Medical Center, Maywood, Illinois, USA
- Infectious Disease and Immunology Research Institute, Stritch School of Medicine, Loyola University Medical Center, Maywood, Illinois, USA
| | - Kazuaki Chayama
- Research Center for Hepatology and Gastroenterology, Hiroshima University, Hiroshima, Japan
- Institute of Physical and Chemical Research (RIKEN) Center for Integrative Medical Sciences, Yokohama, Japan
- Collaborative Research Laboratory of Medical Innovation, Hiroshima University, Hiroshima, Japan
| | - Harel Dahari
- The Program for Experimental and Theoretical Modeling, Division of Hepatology, Department of Medicine, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, USA
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16
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Stanciu GD, Rusu RN, Bild V, Filipiuc LE, Tamba BI, Ababei DC. Systemic Actions of SGLT2 Inhibition on Chronic mTOR Activation as a Shared Pathogenic Mechanism between Alzheimer's Disease and Diabetes. Biomedicines 2021; 9:biomedicines9050576. [PMID: 34069618 PMCID: PMC8160780 DOI: 10.3390/biomedicines9050576] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 05/15/2021] [Accepted: 05/17/2021] [Indexed: 02/07/2023] Open
Abstract
Alzheimer's disease (AD) affects tens of millions of people worldwide. Despite the advances in understanding the disease, there is an increased urgency for pharmacological approaches able of impacting its onset and progression. With a multifactorial nature, high incidence and prevalence in later years of life, there is growing evidence highlighting a relationship between metabolic dysfunction related to diabetes and subject's susceptibility to develop AD. The link seems so solid that sometimes AD and type 3 diabetes are used interchangeably. A candidate for a shared pathogenic mechanism linking these conditions is chronically-activated mechanistic target of rapamycin (mTOR). Chronic activation of unrestrained mTOR could be responsible for sustaining metabolic dysfunction that causes the breakdown of the blood-brain barrier, tau hyperphosphorylation and senile plaques formation in AD. It has been suggested that inhibition of sodium glucose cotransporter 2 (SGLT2) mediated by constant glucose loss, may restore mTOR cycle via nutrient-driven, preventing or even decreasing the AD progression. Currently, there is an unmet need for further research insight into molecular mechanisms that drive the onset and AD advancement as well as an increase in efforts to expand the testing of potential therapeutic strategies aimed to counteract disease progression in order to structure effective therapies.
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Affiliation(s)
- Gabriela Dumitrita Stanciu
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
| | - Razvan Nicolae Rusu
- Pharmacodynamics and Clinical Pharmacy Department, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (R.N.R.); (D.C.A.)
| | - Veronica Bild
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
- Pharmacodynamics and Clinical Pharmacy Department, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (R.N.R.); (D.C.A.)
| | - Leontina Elena Filipiuc
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
- Department of Pharmacology, Clinical Pharmacology and Algesiology, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania
| | - Bogdan-Ionel Tamba
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
- Department of Pharmacology, Clinical Pharmacology and Algesiology, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania
- Correspondence:
| | - Daniela Carmen Ababei
- Pharmacodynamics and Clinical Pharmacy Department, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (R.N.R.); (D.C.A.)
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17
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Martinez NW, Gómez FE, Matus S. The Potential Role of Protein Kinase R as a Regulator of Age-Related Neurodegeneration. Front Aging Neurosci 2021; 13:638208. [PMID: 33994991 PMCID: PMC8113420 DOI: 10.3389/fnagi.2021.638208] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Accepted: 03/10/2021] [Indexed: 01/25/2023] Open
Abstract
There is a growing evidence describing a decline in adaptive homeostasis in aging-related diseases affecting the central nervous system (CNS), many of which are characterized by the appearance of non-native protein aggregates. One signaling pathway that allows cell adaptation is the integrated stress response (ISR), which senses stress stimuli through four kinases. ISR activation promotes translational arrest through the phosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2α) and the induction of a gene expression program to restore cellular homeostasis. However, depending on the stimulus, ISR can also induce cell death. One of the ISR sensors is the double-stranded RNA-dependent protein kinase [protein kinase R (PKR)], initially described as a viral infection sensor, and now a growing evidence supports a role for PKR on CNS physiology. PKR has been largely involved in the Alzheimer’s disease (AD) pathological process. Here, we reviewed the antecedents supporting the role of PKR on the efficiency of synaptic transmission and cognition. Then, we review PKR’s contribution to AD and discuss the possible participation of PKR as a player in the neurodegenerative process involved in aging-related pathologies affecting the CNS.
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Affiliation(s)
- Nicolás W Martinez
- Fundación Ciencia & Vida, Santiago, Chile.,Departamento de Ciencias Básicas, Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile.,Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
| | | | - Soledad Matus
- Fundación Ciencia & Vida, Santiago, Chile.,Departamento de Ciencias Básicas, Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile.,Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
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Knowles A, Campbell S, Cross N, Stafford P. Bacterial Manipulation of the Integrated Stress Response: A New Perspective on Infection. Front Microbiol 2021; 12:645161. [PMID: 33967983 PMCID: PMC8100032 DOI: 10.3389/fmicb.2021.645161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 02/16/2021] [Indexed: 11/13/2022] Open
Abstract
Host immune activation forms a vital line of defence against bacterial pathogenicity. However, just as hosts have evolved immune responses, bacteria have developed means to escape, hijack and subvert these responses to promote survival. In recent years, a highly conserved group of signalling cascades within the host, collectively termed the integrated stress response (ISR), have become increasingly implicated in immune activation during bacterial infection. Activation of the ISR leads to a complex web of cellular reprogramming, which ultimately results in the paradoxical outcomes of either cellular homeostasis or cell death. Therefore, any pathogen with means to manipulate this pathway could induce a range of cellular outcomes and benefit from favourable conditions for long-term survival and replication. This review aims to outline what is currently known about bacterial manipulation of the ISR and present key hypotheses highlighting areas for future research.
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Affiliation(s)
- Alex Knowles
- Biomolecular Sciences Research Centre, Department of Biosciences and Chemistry, Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, United Kingdom
| | - Susan Campbell
- Biomolecular Sciences Research Centre, Department of Biosciences and Chemistry, Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, United Kingdom
| | - Neil Cross
- Biomolecular Sciences Research Centre, Department of Biosciences and Chemistry, Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, United Kingdom
| | - Prachi Stafford
- Biomolecular Sciences Research Centre, Department of Biosciences and Chemistry, Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, United Kingdom
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19
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Weber AJ, Herskowitz JH. Perspectives on ROCK2 as a Therapeutic Target for Alzheimer's Disease. Front Cell Neurosci 2021; 15:636017. [PMID: 33790742 PMCID: PMC8005730 DOI: 10.3389/fncel.2021.636017] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/19/2021] [Indexed: 12/12/2022] Open
Abstract
Rho-associated coiled-coil containing kinase isoform 2 (ROCK2) is a member of the AGC family of serine/threonine kinases and an extensively studied regulator of actin-mediated cytoskeleton contractility. Over the past decade, new evidence has emerged that suggests ROCK2 regulates autophagy. Recent studies indicate that dysregulation of autophagy contributes to the development of misfolded tau aggregates among entorhinal cortex (EC) excitatory neurons in early Alzheimer's disease (AD). While the accumulation of tau oligomers and fibrils is toxic to neurons, autophagy facilitates the degradation of these pathologic species and represents a major cellular pathway for tau disposal in neurons. ROCK2 is expressed in excitatory neurons and pharmacologic inhibition of ROCK2 can induce autophagy pathways. In this mini-review, we explore potential mechanisms by which ROCK2 mediates autophagy and actin dynamics and discuss how these pathways represent therapeutic avenues for Alzheimer's disease.
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Affiliation(s)
| | - Jeremy H. Herskowitz
- Center for Neurodegeneration and Experimental Therapeutics, Departments of Neurology and Neurobiology, University of Alabama at Birmingham, Birmingham, AL, United States
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20
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Engin AB, Engin A. Alzheimer's Disease and Protein Kinases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1275:285-321. [PMID: 33539020 DOI: 10.1007/978-3-030-49844-3_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disorder and accounts for more than 60-80% of all cases of dementia. Loss of pyramidal neurons, extracellular amyloid beta (Abeta) accumulated senile plaques, and neurofibrillary tangles that contain hyperphosphorylated tau constitute the main pathological alterations in AD.Synaptic dysfunction and extrasynaptic N-methyl-D-aspartate receptor (NMDAR) hyperactivation contributes to excitotoxicity in patients with AD. Amyloid precursor protein (APP) and Abeta promoted neurodegeneration develop through the activation of protein kinase signaling cascade in AD. Furthermore, ultimate neuronal death in AD is under control of protein kinases-related signaling pathways. In this chapter, critical check-points within the cross-talk between neuron and protein kinases have been defined regarding the initiation and progression of AD. In this context, amyloid cascade hypothesis, neuroinflammation, oxidative stress, granulovacuolar degeneration, loss of Wnt signaling, Abeta-related synaptic alterations, prolonged calcium ions overload and NMDAR-related synaptotoxicity, damage signals hypothesis and type-3 diabetes are discussed briefly.In addition to clinical perspective of AD pathology, recommendations that might be effective in the treatment of AD patients have been reviewed.
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Affiliation(s)
- Ayse Basak Engin
- Department of Toxicology, Faculty of Pharmacy, Gazi University, Ankara, Turkey.
| | - Atilla Engin
- Department of General Surgery, Faculty of Medicine, Gazi University, Ankara, Turkey
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21
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Moradi Majd R, Mayeli M, Rahmani F. Pathogenesis and promising therapeutics of Alzheimer disease through eIF2α pathway and correspondent kinases. Metab Brain Dis 2020; 35:1241-1250. [PMID: 32681467 DOI: 10.1007/s11011-020-00600-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 07/05/2020] [Indexed: 01/10/2023]
Abstract
Eukaryotic initiation factor 2 (eIF2α) pathway is overactivated in Alzheimer disease and is probably associated with synaptic and memory deficiencies. EIF2α protein is principally in charge of the regulation of protein synthesis in eukaryotic cells. Four kinases responsible for eIF2α phosphorylation at ser-51 are: General control non-derepressible-2 kinase (GCN2), double-stranded RNA-activated protein kinase (PKR), PKR-like endoplasmic reticulum kinase (PERK), and heme-regulated inhibitor kinase (HRI) are the four kinases. They lead to reduced levels of general translation and paradoxical increase of stress-responsive mRNAs expression including the B-secretase (BACE1) and the transcriptional modulator activating transcription factor 4 (ATF4), which in turn accelerates the beta-amyloidogenesis, tau phosphorylation, proapoptotic pathway induction and autophagy elements formation leading to the main pathological hallmarks of AD. Findings suggest that genetic or pharmacological inhibition of correspondent kinases can restore memory and prevent neurodegeneration. This implies that inhibition of eIF2α phosphorylation through respondent kinases is indeed a feasible prospect of clinical application. This review discusses recent therapeutic approaches targeting eIF2α pathway and provides an overview of the links between correspondent kinases overactivation with neurodegeneration in AD.
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Affiliation(s)
- Reza Moradi Majd
- Tehran University of Medical Sciences, Tehran, Islamic Republic of Iran
| | - Mahsa Mayeli
- Tehran University of Medical Sciences, Tehran, Islamic Republic of Iran.
| | - Farzaneh Rahmani
- Tehran University of Medical Sciences, Tehran, Islamic Republic of Iran
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22
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Lee WYJ, Jones M, Wing PAC, Rajagopal S, Foster GR. The A150V Polymorphism of Genotype 3 Hepatitis C Virus Polymerase Inhibits Interferon Alfa by Suppressing Protein Kinase R Activation. Cell Mol Gastroenterol Hepatol 2020; 11:1163-1175. [PMID: 33248325 PMCID: PMC7903130 DOI: 10.1016/j.jcmgh.2020.11.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 11/17/2020] [Accepted: 11/17/2020] [Indexed: 12/10/2022]
Abstract
BACKGROUND & AIMS Despite recent advances in antiviral therapy for hepatitis C virus (HCV), a proportion of patients with genotype 3 (G3) HCV infection do not respond to current all oral treatment regimens. Genomic analyses have identified key polymorphisms correlating with increased resistance to direct-acting antivirals. We previously reported that amino the acid polymorphism, A150V, in the polymerase (NS5B) of G3 HCV reduces response to sofosbuvir. We now demonstrate that this polymorphism alters the response to interferon alpha. METHODS Quantitative polymerase chain reaction, immunofluorescence, luciferase activity assay, immunoblotting, and flow cytometry were used to study the antiviral effect of interferon (IFN) on DBN G3 HCV-infected cells and G3 HCV replicons. RESULTS We show the presence of the A150V polymorphism markedly reduces the response to IFN alpha (IC50 of S52_WT = 1.162 IU/mL and IC50 of S52_A150V = 14.45 IU/mL, 12.4-fold difference). The induction of IFN-stimulated genes in A150V replicon cells is unaffected, but nuclear localization of active protein kinase R (PKR) is reduced. Blockade of PKR activity reduced the antiviral effect of IFN on wild-type replicons, whereas augmented PKR activation promoted the antiviral effect of IFN on A150V replicons. Furthermore, we show that impaired activation of PKR in A150V replicon cells diminishes cellular apoptosis. CONCLUSIONS These results demonstrate that polymorphisms reducing response rates to direct-acting antivirals may function beyond conferring drug resistance by modulating the intrinsic cellular antiviral response.
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Affiliation(s)
- Wing-Yiu Jason Lee
- Centre of Immunobiology, Blizard Institute, Queen Mary University of London, London
| | - Meleri Jones
- Centre of Immunobiology, Blizard Institute, Queen Mary University of London, London
| | - Peter A C Wing
- Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Swathi Rajagopal
- Centre of Immunobiology, Blizard Institute, Queen Mary University of London, London
| | - Graham R Foster
- Centre of Immunobiology, Blizard Institute, Queen Mary University of London, London.
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23
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Bocai NI, Marcora MS, Belfiori-Carrasco LF, Morelli L, Castaño EM. Endoplasmic Reticulum Stress in Tauopathies: Contrasting Human Brain Pathology with Cellular and Animal Models. J Alzheimers Dis 2020; 68:439-458. [PMID: 30775999 DOI: 10.3233/jad-181021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The accumulation and spreading of protein tau in the human brain are major features of neurodegenerative disorders known as tauopathies. In addition to several subcellular abnormalities, tau aggregation within neurons seems capable of triggering endoplasmic reticulum (ER) stress and the consequent unfolded protein response (UPR). In metazoans, full activation of a complex ER-UPR network may restore proteostasis and ER function or, if stress cannot be solved, commit cells to apoptosis. Due to these alternative outcomes (survival or death), the pharmacological manipulation of ER-UPR has become the focus of potential therapies in many human diseases, including tauopathies. Here we update and analyze the experimental data from human brain, cellular, and animal models linking tau accumulation and ER-UPR. We further discuss mechanistic aspects and put the ER-UPR into perspective as a possible therapeutic target in this group of diseases.
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Affiliation(s)
- Nadia I Bocai
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - María S Marcora
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Lautaro F Belfiori-Carrasco
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Laura Morelli
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Eduardo M Castaño
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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24
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Yagyu K, Hasegawa Y, Sato M, Oh-Hashi K, Hirata Y. Activation of protein kinase R in the manganese-induced apoptosis of PC12 cells. Toxicology 2020; 442:152526. [PMID: 32574669 DOI: 10.1016/j.tox.2020.152526] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/30/2020] [Accepted: 06/11/2020] [Indexed: 11/16/2022]
Abstract
Manganese neurotoxicity leads to Parkinson-like symptoms associated with the apoptotic cell death of dopaminergic neurons. Protein kinase R (PKR) is a serine/threonine-specific protein kinase that has been implicated in several cellular signal transduction pathways, including the induction of apoptosis. Here, we investigated the role of PKR in the manganese-induced apoptosis of dopamine-producing pheochromocytoma PC12 cells. Manganese (0.5 mM) induced the proteolytic cleavage of PKR and caspase-3, DNA fragmentation, and cell death, which were prevented by the co-treatment of PC12 cells with a PKR specific inhibitor, C16 in a concentration-dependent manner. C16 did not affect the manganese-induced activation of the c-Jun N-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) pathway, indicating that PKR functions downstream of JNK and p38 MAPK. In contrast, C16 triggered the activation of the p44/42 MAPK (ERK1/2) pathway and induced hemoxygenase-1, both in the absence and presence of manganese. PKR is reportedly involved in endoplasmic reticulum (ER) stress-induced apoptosis. Manganese activated all three branches of the unfolded protein response in PC12 cells; however, this effect was very weak compared with the ER stress induced by the well-known ER stress inducers thapsigargin and tunicamycin. Moreover, C16 did not affect manganese-induced ER stress at concentrations that almost prevented caspase-3 activation and DNA fragmentation. These results suggest that PKR is involved in manganese-induced apoptotic cell death and stress response, such as the activation of the p44/42 MAPK pathway and the induction of hemoxygenase-1. Although manganese induced a faint, but typical, ER stress, these events contributed little to manganese-induced apoptosis.
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Affiliation(s)
- Kazuya Yagyu
- United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Yuto Hasegawa
- Graduate School of Natural Science and Technology, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Mina Sato
- Graduate School of Natural Science and Technology, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Kentaro Oh-Hashi
- United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu, 501-1193, Japan; Graduate School of Natural Science and Technology, Gifu University, Yanagido, Gifu, 501-1193, Japan; Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan
| | - Yoko Hirata
- United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu, 501-1193, Japan; Graduate School of Natural Science and Technology, Gifu University, Yanagido, Gifu, 501-1193, Japan; Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193, Japan.
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25
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Mao D, Reuter CM, Ruzhnikov MR, Beck AE, Farrow EG, Emrick LT, Rosenfeld JA, Mackenzie KM, Robak L, Wheeler MT, Burrage LC, Jain M, Liu P, Calame D, Küry S, Sillesen M, Schmitz-Abe K, Tonduti D, Spaccini L, Iascone M, Genetti CA, Koenig MK, Graf M, Tran A, Alejandro M, Lee BH, Thiffault I, Agrawal PB, Bernstein JA, Bellen HJ, Chao HT, Acosta MT, Adam M, Adams DR, Agrawal PB, Alejandro ME, Allard P, Alvey J, Amendola L, Andrews A, Ashley EA, Azamian MS, Bacino CA, Bademci G, Baker E, Balasubramanyam A, Baldridge D, Bale J, Bamshad M, Barbouth D, Batzli GF, Bayrak-Toydemir P, Beck A, Beggs AH, Bejerano G, Bellen HJ, Bennet J, Berg-Rood B, Bernier R, Bernstein JA, Berry GT, Bican A, Bivona S, Blue E, Bohnsack J, Bonnenmann C, Bonner D, Botto L, Briere LC, Brokamp E, Burke EA, Burrage LC, Butte MJ, Byers P, Carey J, Carrasquillo O, Chang TCP, Chanprasert S, Chao HT, Clark GD, Coakley TR, Cobban LA, Cogan JD, Cole FS, Colley HA, Cooper CM, Cope H, Craigen WJ, Cunningham M, D’Souza P, Dai H, Dasari S, Davids M, Dayal JG, Dell’Angelica EC, Dhar SU, Dipple K, Doherty D, Dorrani N, Douine ED, Draper DD, Duncan L, Earl D, Eckstein DJ, Emrick LT, Eng CM, Esteves C, Estwick T, Fernandez L, Ferreira C, Fieg EL, Fisher PG, Fogel BL, Forghani I, Fresard L, Gahl WA, Glass I, Godfrey RA, Golden-Grant K, Goldman AM, Goldstein DB, Grajewski A, Groden CA, Gropman AL, Hahn S, Hamid R, Hanchard NA, Hayes N, High F, Hing A, Hisama FM, Holm IA, Hom J, Horike-Pyne M, Huang A, Huang Y, Isasi R, Jamal F, Jarvik GP, Jarvik J, Jayadev S, Jiang YH, Johnston JM, Karaviti L, Kelley EG, Kiley D, Kohane IS, Kohler JN, Krakow D, Krasnewich DM, Korrick S, Koziura M, Krier JB, Lalani SR, Lam B, Lam C, Lanpher BC, Lanza IR, Lau CC, LeBlanc K, Lee BH, Lee H, Levitt R, Lewis RA, Lincoln SA, Liu P, Liu XZ, Longo N, Loo SK, Loscalzo J, Maas RL, Macnamara EF, MacRae CA, Maduro VV, Majcherska MM, Malicdan MCV, Mamounas LA, Manolio TA, Mao R, Maravilla K, Markello TC, Marom R, Marth G, Martin BA, Martin MG, Martínez-Agosto JA, Marwaha S, McCauley J, McConkie-Rosell A, McCormack CE, McCray AT, Mefford H, Merritt JL, Might M, Mirzaa G, Morava-Kozicz E, Moretti PM, Morimoto M, Mulvihill JJ, Murdock DR, Nath A, Nelson SF, Newman JH, Nicholas SK, Nickerson D, Novacic D, Oglesbee D, Orengo JP, Pace L, Pak S, Pallais JC, Palmer CG, Papp JC, Parker NH, Phillips JA, Posey JE, Postlethwait JH, Potocki L, Pusey BN, Quinlan A, Raskind W, Raja AN, Renteria G, Reuter CM, Rives L, Robertson AK, Rodan LH, Rosenfeld JA, Rowley RK, Ruzhnikov M, Sacco R, Sampson JB, Samson SL, Saporta M, Scott CR, Schaechter J, Schedl T, Schoch K, Scott DA, Shakachite L, Sharma P, Shashi V, Shin J, Signer R, Sillari CH, Silverman EK, Sinsheimer JS, Sisco K, Smith KS, Solnica-Krezel L, Spillmann RC, Stoler JM, Stong N, Sullivan JA, Sun A, Sutton S, Sweetser DA, Sybert V, Tabor HK, Tamburro CP, Tan QKG, Tekin M, Telischi F, Thorson W, Tifft CJ, Toro C, Tran AA, Urv TK, Velinder M, Viskochil D, Vogel TP, Wahl CE, Wallace S, Walley NM, Walsh CA, Walker M, Wambach J, Wan J, Wang LK, Wangler MF, Ward PA, Wegner D, Wener M, Westerfield M, Wheeler MT, Wise AL, Wolfe LA, Woods JD, Yamamoto S, Yang J, Yoon AJ, Yu G, Zastrow DB, Zhao C, Zuchner S. De novo EIF2AK1 and EIF2AK2 Variants Are Associated with Developmental Delay, Leukoencephalopathy, and Neurologic Decompensation. Am J Hum Genet 2020; 106:570-583. [PMID: 32197074 PMCID: PMC7118694 DOI: 10.1016/j.ajhg.2020.02.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 02/28/2020] [Indexed: 02/03/2023] Open
Abstract
EIF2AK1 and EIF2AK2 encode members of the eukaryotic translation initiation factor 2 alpha kinase (EIF2AK) family that inhibits protein synthesis in response to physiologic stress conditions. EIF2AK2 is also involved in innate immune response and the regulation of signal transduction, apoptosis, cell proliferation, and differentiation. Despite these findings, human disorders associated with deleterious variants in EIF2AK1 and EIF2AK2 have not been reported. Here, we describe the identification of nine unrelated individuals with heterozygous de novo missense variants in EIF2AK1 (1/9) or EIF2AK2 (8/9). Features seen in these nine individuals include white matter alterations (9/9), developmental delay (9/9), impaired language (9/9), cognitive impairment (8/9), ataxia (6/9), dysarthria in probands with verbal ability (6/9), hypotonia (7/9), hypertonia (6/9), and involuntary movements (3/9). Individuals with EIF2AK2 variants also exhibit neurological regression in the setting of febrile illness or infection. We use mammalian cell lines and proband-derived fibroblasts to further confirm the pathogenicity of variants in these genes and found reduced kinase activity. EIF2AKs phosphorylate eukaryotic translation initiation factor 2 subunit 1 (EIF2S1, also known as EIF2α), which then inhibits EIF2B activity. Deleterious variants in genes encoding EIF2B proteins cause childhood ataxia with central nervous system hypomyelination/vanishing white matter (CACH/VWM), a leukodystrophy characterized by neurologic regression in the setting of febrile illness and other stressors. Our findings indicate that EIF2AK2 missense variants cause a neurodevelopmental syndrome that may share phenotypic and pathogenic mechanisms with CACH/VWM.
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Chen X, Ji B, Hao X, Li X, Eisele F, Nyström T, Petranovic D. FMN reduces Amyloid-β toxicity in yeast by regulating redox status and cellular metabolism. Nat Commun 2020; 11:867. [PMID: 32054832 PMCID: PMC7018843 DOI: 10.1038/s41467-020-14525-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 01/07/2020] [Indexed: 01/09/2023] Open
Abstract
Alzheimer's disease (AD) is defined by progressive neurodegeneration, with oligomerization and aggregation of amyloid-β peptides (Aβ) playing a pivotal role in its pathogenesis. In recent years, the yeast Saccharomyces cerevisiae has been successfully used to clarify the roles of different human proteins involved in neurodegeneration. Here, we report a genome-wide synthetic genetic interaction array to identify toxicity modifiers of Aβ42, using yeast as the model organism. We find that FMN1, the gene encoding riboflavin kinase, and its metabolic product flavin mononucleotide (FMN) reduce Aβ42 toxicity. Classic experimental analyses combined with RNAseq show the effects of FMN supplementation to include reducing misfolded protein load, altering cellular metabolism, increasing NADH/(NADH + NAD+) and NADPH/(NADPH + NADP+) ratios and increasing resistance to oxidative stress. Additionally, FMN supplementation modifies Htt103QP toxicity and α-synuclein toxicity in the humanized yeast. Our findings offer insights for reducing cytotoxicity of Aβ42, and potentially other misfolded proteins, via FMN-dependent cellular pathways.
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Affiliation(s)
- Xin Chen
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE41296, Gothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE41296, Gothenburg, Sweden
| | - Boyang Ji
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE41296, Gothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE41296, Gothenburg, Sweden
| | - Xinxin Hao
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, SE40530, Gothenburg, Sweden
| | - Xiaowei Li
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE41296, Gothenburg, Sweden
| | - Frederik Eisele
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, SE40530, Gothenburg, Sweden
| | - Thomas Nyström
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, SE40530, Gothenburg, Sweden
| | - Dina Petranovic
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, SE41296, Gothenburg, Sweden.
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE41296, Gothenburg, Sweden.
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27
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Hirata Y, Iwasaki T, Makimura Y, Okajima S, Oh-Hashi K, Takemori H. Inhibition of double-stranded RNA-dependent protein kinase prevents oxytosis and ferroptosis in mouse hippocampal HT22 cells. Toxicology 2019; 418:1-10. [PMID: 30817950 DOI: 10.1016/j.tox.2019.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 01/26/2019] [Accepted: 02/22/2019] [Indexed: 01/20/2023]
Abstract
Double-stranded RNA-dependent protein kinase (PKR) is a component of signal transduction pathways mediating various stress signals including oxidative stress and endoplasmic reticulum (ER) stress and is suggested to be implicated in several neurodegenerative diseases. Cell death in neurodegenerative conditions has been linked to oxidative stress; however, the involvement of PKR in endogenous oxidative stress such as oxytosis and ferroptosis which is quite distinct from classical apoptosis remains unknown. We investigated here the effect of a PKR inhibitor C16 (an imidazole-oxindole derivative) on oxytosis and ferroptosis in cultured HT22 mouse hippocampal cells. C16 prevented glutamate- and erastin-induced cell death, reactive oxygen species accumulation, Ca2+ influx, phosphorylation of inositol-requiring enzyme 1 (IRE1), one of the three branches of ER stress signaling and its downstream signaling components. On the other hand, C16 did not prevent oxidative stress-induced heme oxygenase-1 expression; instead, C16 activated the extracellular signal-regulated kinase pathway. The protective effect of C16 is diminished in PKR knockout HT22 cells. Real time measurements of the oxygen consumption rate and extracellular acidification rate over a long period of time leading to cell death showed that C16 partially prevented erastin-induced mitochondrial and glycolytic dysfunction. These results suggest that PKR is an important component of oxytosis and ferroptosis and the inhibition of PKR is neuroprotective against endogenous oxidative stress-induced cell death and provide an effective strategy for neuroprotection.
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Affiliation(s)
- Yoko Hirata
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan; United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan.
| | - Takuya Iwasaki
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Yukimi Makimura
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Sayaka Okajima
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Kentaro Oh-Hashi
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan; United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Hiroshi Takemori
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan; United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan.
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Okamoto K, Rausch JW, Wakashin H, Fu Y, Chung JY, Dummer PD, Shin MK, Chandra P, Suzuki K, Shrivastav S, Rosenberg AZ, Hewitt SM, Ray PE, Noiri E, Le Grice SFJ, Hoek M, Han Z, Winkler CA, Kopp JB. APOL1 risk allele RNA contributes to renal toxicity by activating protein kinase R. Commun Biol 2018; 1:188. [PMID: 30417125 PMCID: PMC6220249 DOI: 10.1038/s42003-018-0188-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 10/03/2018] [Indexed: 01/09/2023] Open
Abstract
APOL1 risk alleles associate with chronic kidney disease in African Americans, but the mechanisms remain to be fully understood. We show that APOL1 risk alleles activate protein kinase R (PKR) in cultured cells and transgenic mice. This effect is preserved when a premature stop codon is introduced to APOL1 risk alleles, suggesting that APOL1 RNA but not protein is required for the effect. Podocyte expression of APOL1 risk allele RNA, but not protein, in transgenic mice induces glomerular injury and proteinuria. Structural analysis of the APOL1 RNA shows that the risk variants possess secondary structure serving as a scaffold for tandem PKR binding and activation. These findings provide a mechanism by which APOL1 variants damage podocytes and suggest novel therapeutic strategies.
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Affiliation(s)
- Koji Okamoto
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
- Division of Nephrology, Endocrinology and Vascular Medicine, Department of Medicine, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8574, Japan
- Department of Nephrology, Endocrinology, Hemodialysis & Apheresis, University Hospital, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 133-8655, Japan
| | - Jason W Rausch
- Reverse Transcriptase Biochemistry Section, Basic Research Program, Frederick National Laboratory for Cancer Research, 1050 Boyle Street, Frederick, MD, 21702, USA
| | - Hidefumi Wakashin
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Yulong Fu
- Children's National Health System, 111 Michigan Ave NW, Washington, DC, 20010, USA
| | - Joon-Yong Chung
- Experimental Pathology Lab, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Patrick D Dummer
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Myung K Shin
- Merck Research Laboratories, Merck and Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA
| | - Preeti Chandra
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, 655 W. Baltimore Street, Baltimore, MD, 21201, USA
| | - Kosuke Suzuki
- Division of Nephrology, Endocrinology and Vascular Medicine, Department of Medicine, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8574, Japan
| | - Shashi Shrivastav
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Avi Z Rosenberg
- Department of Pathology, Johns Hopkins Medical Institutions, 720 Rutland Avenue, Baltimore, MD, 21287, USA
| | - Stephen M Hewitt
- Experimental Pathology Lab, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Patricio E Ray
- Children's National Health System, 111 Michigan Ave NW, Washington, DC, 20010, USA
| | - Eisei Noiri
- Department of Nephrology, Endocrinology, Hemodialysis & Apheresis, University Hospital, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 133-8655, Japan
| | - Stuart F J Le Grice
- Reverse Transcriptase Biochemistry Section, Basic Research Program, Frederick National Laboratory for Cancer Research, 1050 Boyle Street, Frederick, MD, 21702, USA
| | - Maarten Hoek
- Merck Research Laboratories, Merck and Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ, 07033, USA
| | - Zhe Han
- Children's National Health System, 111 Michigan Ave NW, Washington, DC, 20010, USA
| | - Cheryl A Winkler
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Leidos Biomedical Research, Frederick National Laboratory, 8560 Progress Dr., Frederick, MD, 21702, USA
| | - Jeffrey B Kopp
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA.
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Strong and sustained activation of the anticipatory unfolded protein response induces necrotic cell death. Cell Death Differ 2018; 25:1796-1807. [PMID: 29899383 DOI: 10.1038/s41418-018-0143-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 05/18/2018] [Accepted: 05/24/2018] [Indexed: 02/07/2023] Open
Abstract
The endoplasmic reticulum stress sensor, the unfolded protein response (UPR), regulates intracellular protein homeostasis. While transient activation of the reactive UPR by unfolded protein is protective, prolonged and sustained activation of the reactive UPR triggers CHOP-mediated apoptosis. In the recently characterized, evolutionarily conserved anticipatory UPR, mitogenic hormones and other effectors pre-activate the UPR; how strong and sustained activation of the anticipatory UPR induces cell death was unknown. To characterize this cell death pathway, we used BHPI, a small molecule that activates the anticipatory UPR through estrogen receptor α (ERα) and induces death of ERα+ cancer cells. We show that sustained activation of the anticipatory UPR by BHPI kills cells by inducing depletion of intracellular ATP, resulting in classical necrosis phenotypes, including plasma membrane disruption and leakage of intracellular contents. Unlike reactive UPR activation, BHPI-induced hyperactivation of the anticipatory UPR does not induce apoptosis or sustained autophagy. BHPI does not induce CHOP protein or PARP cleavage, and two pan-caspase inhibitors, or Bcl2 overexpression, have no effect on BHPI-induced cell death. Moreover, BHPI does not increase expression of autophagy markers, or work through recently identified programmed-necrosis pathways, such as necroptosis. Opening of endoplasmic reticulum IP3R calcium channels stimulates cell swelling, cPLA2 activation, and arachidonic acid release. Notably, cPLA2 activation requires ATP depletion. Importantly, blocking rapid cell swelling or production of arachidonic acid does not prevent necrotic cell death. Rapid cell death is upstream of PERK activation and protein synthesis inhibition, and results from strong and sustained activation of early steps in the anticipatory UPR. Supporting a central role for ATP depletion, reversing ATP depletion blocks rapid cell death, and the onset of necrotic cell death is correlated with ATP depletion. Necrotic cell death initiated by strong and sustained activation of the anticipatory UPR is a newly discovered role of the UPR.
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Cho C, Michailidis V, Martin LJ. Revealing brain mechanisms of mTOR-mediated translational regulation: Implications for chronic pain. NEUROBIOLOGY OF PAIN 2018; 4:27-34. [PMID: 31194026 PMCID: PMC6550104 DOI: 10.1016/j.ynpai.2018.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 03/15/2018] [Accepted: 03/16/2018] [Indexed: 12/27/2022]
Abstract
mTOR is a major regulator of protein translation. mTOR serves an important role in neural plasticity. mTOR signalling in the brain as a pathology for neurological disorder is known. mTOR signalling in the brain as a chronic pain mechanism is understudied.
In the spinal cord, altered protein transcription and translation have received a lot of recent attention for their role in neural plasticity, a major mechanism leading to the development of chronic pain. However, changes in brain plasticity are also associated with the maintenance of pain symptoms, but these cellular mechanisms remain less clear. The mechanistic/mammalian target of rapamycin (mTOR) is a master regulator of protein synthesis, and controls several neuronal functions, including neural plasticity. While aberrant changes in mTOR signaling are associated with sensitization of the pain pathway (sensory neurons and spinal cord), there are various nervous system diseases that have pain as a comorbidity and altered mTOR activity in the brain. Here, we provide a brief review of mTOR changes in the brain that are associated with some neurological disorders and focus on how these changes may be relevant to the pain of the underlying condition and chronic pain itself.
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Affiliation(s)
- Chulmin Cho
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Vassilia Michailidis
- Deptartment of Cell and Systems Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Loren J. Martin
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Deptartment of Cell and Systems Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Corresponding author at: Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Rd., Mississauga, ON L5L 1C6, Canada.
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Krishna KH, Kumar MS. Molecular evolution and functional divergence of eukaryotic translation initiation factor 2-alpha kinases. PLoS One 2018. [PMID: 29538447 PMCID: PMC5851622 DOI: 10.1371/journal.pone.0194335] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Eukaryotic translation initiation factor 2-alpha kinase (EIF2AK) proteins inhibit protein synthesis at translation initiation level, in response to various stress conditions, including oxidative stress, heme deficiency, osmotic shock, and heat shock. Origin and functional diversification of EIF2AK sequences remain ambiguous. Here we determine the origin and molecular evolution of EIF2AK proteins in lower eukaryotes and studied the molecular basis of divergence among sub-family sequences. Present work emphasized primitive origin of EIF2AK4 sub-family gene in lower eukaryotes of protozoan lineage. Phylogenetic analysis supported common origin and sub-family based classification of EIF2AKs. Functional divergence studies across sub-families revealed several putative amino acid sites, which assist in altered protein interactions of kinase domains. The data can facilitate designing site-directed experimental studies aiming at elucidating diverse functional aspects of kinase domains regarding down-regulation of protein synthesis.
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Affiliation(s)
- K. Hari Krishna
- Centre for Bioinformatics, Pondicherry University, Kalapet, Pondicherry, India
- Department of Biotechnology, Vignan's Foundation for Science, Technology & Research (VFSTR) University, Vadlamudi, Andhra Pradesh, India
| | - Muthuvel Suresh Kumar
- Centre for Bioinformatics, Pondicherry University, Kalapet, Pondicherry, India
- * E-mail:
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Rahman S, Archana A, Jan AT, Minakshi R. Dissecting Endoplasmic Reticulum Unfolded Protein Response (UPR ER) in Managing Clandestine Modus Operandi of Alzheimer's Disease. Front Aging Neurosci 2018; 10:30. [PMID: 29467648 PMCID: PMC5808164 DOI: 10.3389/fnagi.2018.00030] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/24/2018] [Indexed: 01/12/2023] Open
Abstract
Alzheimer's disease (AD), a neurodegenerative disorder, is most common cause of dementia witnessed among aged people. The pathophysiology of AD develops as a consequence of neurofibrillary tangle formation which consists of hyperphosphorylated microtubule associated tau protein and senile plaques of amyloid-β (Aβ) peptide in specific brain regions that result in synaptic loss and neuronal death. The feeble buffering capacity of endoplasmic reticulum (ER) proteostasis in AD is evident through alteration in unfolded protein response (UPR), where UPR markers express invariably in AD patient's brain samples. Aging weakens UPRER causing neuropathology and memory loss in AD. This review highlights molecular signatures of UPRER and its key molecular alliance that are affected in aging leading to the development of intriguing neuropathologies in AD. We present a summary of recent studies reporting usage of small molecules as inhibitors or activators of UPRER sensors/effectors in AD that showcase avenues for therapeutic interventions.
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Affiliation(s)
- Safikur Rahman
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan, South Korea
| | - Ayyagari Archana
- Department of Microbiology, Swami Shraddhanand College, University of Delhi, New Delhi, India
| | - Arif Tasleem Jan
- School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri, India
| | - Rinki Minakshi
- Institute of Home Economics, University of Delhi, New Delhi, India
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Kapur M, Monaghan CE, Ackerman SL. Regulation of mRNA Translation in Neurons-A Matter of Life and Death. Neuron 2017; 96:616-637. [PMID: 29096076 DOI: 10.1016/j.neuron.2017.09.057] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 09/20/2017] [Accepted: 09/28/2017] [Indexed: 12/14/2022]
Abstract
Dynamic regulation of mRNA translation initiation and elongation is essential for the survival and function of neural cells. Global reductions in translation initiation resulting from mutations in the translational machinery or inappropriate activation of the integrated stress response may contribute to pathogenesis in a subset of neurodegenerative disorders. Aberrant proteins generated by non-canonical translation initiation may be a factor in the neuron death observed in the nucleotide repeat expansion diseases. Dysfunction of central components of the elongation machinery, such as the tRNAs and their associated enzymes, can cause translational infidelity and ribosome stalling, resulting in neurodegeneration. Taken together, dysregulation of mRNA translation is emerging as a unifying mechanism underlying the pathogenesis of many neurodegenerative disorders.
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Affiliation(s)
- Mridu Kapur
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Caitlin E Monaghan
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Susan L Ackerman
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA.
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Hugon J, Mouton-Liger F, Dumurgier J, Paquet C. PKR involvement in Alzheimer's disease. ALZHEIMERS RESEARCH & THERAPY 2017; 9:83. [PMID: 28982375 PMCID: PMC5629792 DOI: 10.1186/s13195-017-0308-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Accepted: 09/08/2017] [Indexed: 12/15/2022]
Abstract
BACKGROUND Brain lesions in Alzheimer's disease (AD) are characterized by Aβ accumulation, neurofibrillary tangles, and synaptic and neuronal vanishing. According to the amyloid cascade hypothesis, Aβ1-42 oligomers could trigger a neurotoxic cascade with kinase activation that leads to tau phosphorylation and neurodegeneration. Detrimental pathways that are associated with kinase activation could also be linked to the triggering of direct neuronal death, the production of free radicals, and neuroinflammation. RESULTS Among these kinases, PKR (eukaryotic initiation factor 2α kinase 2) is a pro-apoptotic enzyme that inhibits translation and that has been implicated in several molecular pathways that lead to AD brain lesions and disturbed memory formation. PKR accumulates in degenerating neurons and is activated by Aβ1-42 neurotoxicity. It might modulate Aβ synthesis through BACE 1 induction. PKR is increased in cerebrospinal fluid from patients with AD and mild cognitive impairment and can induce the activation of pro-inflammatory pathways leading to TNFα and IL1-β production. In addition, experimentally, PKR seems to down-regulate the molecular processes of memory consolidation. This review highlights the major findings linking PKR and abnormal brain metabolism associated with AD lesions. CONCLUSIONS Studying the detrimental role of PKR signaling in AD could pave the way for a neuroprotective strategy in which PKR inhibition could reduce neuronal demise and alleviate cognitive decline as well as the cumbersome burden of AD for patients.
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Affiliation(s)
- Jacques Hugon
- Center of Cognitive Neurology and Inserm U942 Lariboisière Hospital AP-HP University Paris Diderot, 75010, Paris, France. .,Center of Cognitive Neurology, Lariboisière FW Hospital, 200 rue du Faubourg Saint Denis, 75010, Paris, France.
| | | | - Julien Dumurgier
- Center of Cognitive Neurology and Inserm U942 Lariboisière Hospital AP-HP University Paris Diderot, 75010, Paris, France
| | - Claire Paquet
- Center of Cognitive Neurology and Inserm U942 Lariboisière Hospital AP-HP University Paris Diderot, 75010, Paris, France
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Halliday M, Hughes D, Mallucci GR. Fine-tuning PERK signaling for neuroprotection. J Neurochem 2017; 142:812-826. [PMID: 28643372 PMCID: PMC5601187 DOI: 10.1111/jnc.14112] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/06/2017] [Accepted: 06/16/2017] [Indexed: 12/11/2022]
Abstract
Protein translation and folding are tightly controlled processes in all cells, by proteostasis, an important component of which is the unfolded protein response (UPR). During periods of endoplasmic reticulum stress because of protein misfolding, the UPR activates a coordinated response in which the PERK branch activation restricts translation, while a variety of genes involved with protein folding, degradation, chaperone expression and stress responses are induced through signaling of the other branches. Chronic overactivation of the UPR, particularly the PERK branch, is observed in the brains of patients in a number of protein misfolding neurodegenerative diseases, including Alzheimer's, and Parkinson's diseases and the tauopathies. Recently, numerous genetic and pharmacological studies in mice have demonstrated the effectiveness of inhibiting the UPR for eliciting therapeutic benefit and boosting memory. In particular, fine-tuning the level of PERK inhibition to provide neuroprotection without adverse side effects has emerged as a safe, effective approach. This includes the recent discovery of licensed drugs that can now be repurposed in clinical trials for new human treatments for dementia. This review provides an overview of the links between UPR overactivation and neurodegeneration in protein misfolding disorders. It discusses recent therapeutic approaches targeting this pathway, with a focus on treatments that fine-tune PERK signaling.
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Affiliation(s)
| | | | - Giovanna R. Mallucci
- MRC Toxicology UnitLeicesterUK
- Department of Clinical NeurosciencesUniversity of CambridgeCambridge Biomedical CampusCambridgeUK
- UK Dementia Research Institute at University of CambridgeIsland Research BuildingCambridge Biomedical CampusCambridgeUK
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Clinical and therapeutic potential of protein kinase PKR in cancer and metabolism. Expert Rev Mol Med 2017; 19:e9. [PMID: 28724458 DOI: 10.1017/erm.2017.11] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The protein kinase R (PKR, also called EIF2AK2) is an interferon-inducible double-stranded RNA protein kinase with multiple effects on cells that plays an active part in the cellular response to numerous types of stress. PKR has been extensively studied and documented for its relevance as an antiviral agent and a cell growth regulator. Recently, the role of PKR related to metabolism, inflammatory processes, cancer and neurodegenerative diseases has gained interest. In this review, we summarise and discuss the involvement of PKR in several cancer signalling pathways and the dual role that this kinase plays in cancer disease. We emphasise the importance of PKR as a molecular target for both conventional chemotherapeutics and emerging treatments based on novel drugs, and its potential as a biomarker and therapeutic target for several pathologies. Finally, we discuss the impact that the recent knowledge regarding PKR involvement in metabolism has in our understanding of the complex processes of cancer and metabolism pathologies, highlighting the translational research establishing the clinical and therapeutic potential of this pleiotropic kinase.
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Human Herpesvirus 6A Exhibits Restrictive Propagation with Limited Activation of the Protein Kinase R-eIF2α Stress Pathway. J Virol 2017; 91:JVI.02120-16. [PMID: 28202752 PMCID: PMC5391470 DOI: 10.1128/jvi.02120-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/06/2017] [Indexed: 11/28/2022] Open
Abstract
The eIF2α protein plays a critical role in the regulation of translation. The production of double-stranded RNA (dsRNA) during viral replication can activate protein kinase R (PKR), which phosphorylates eIF2α, leading to inhibition of the initial step of translation. Many viruses have evolved gene products targeting the PKR-eIF2a pathway, indicating its importance in antiviral defense. In the present study, we focused on alternations of PKR-eIF2a pathway during human herpesvirus 6A (HHV-6A) infection while monitoring viral gene expression and infectious viral yields. We have found increased phosphorylated PKR as well as phosphorylated eIF2α coincident with accumulation of the late gp82-105 viral protein. The level of total PKR was relatively constant, but it decreased by 144 h postinfection. The phosphorylation of eIF2a led to a moderate increase in activating transcription factor 4 (ATF4) accumulation, indicating moderate inhibition of protein translation during HHV-6A infection. The overexpression of PKR led to decreased viral propagation coincident with increased accumulation of phosphorylated PKR and phosphorylated eIF2a. Moreover, addition of a dominant negative PKR mutant resulted in a moderate increase in viral replication. HHV-6A exhibits relatively low efficiency of propagation of progeny virus secreted into the culture medium. This study suggests that the replicative strategy of HHV-6A involves a mild infection over a lengthy life cycle in culture, while preventing severe activation of the PKR-eIF2α pathway. IMPORTANCE Human herpesvirus 6A (HHV-6A) and HHV-6B are common, widely prevalent viruses, causing from mild to severe disease. Our study focused on the PKR-eIF2α stress pathway, which limits viral replication. The HHV-6 genome carries multiple genes transcribed from the two strands, predicting accumulation of dsRNAs which can activate PKR and inhibition of protein synthesis. We report that HHV-6A induced the accumulation of phosphorylated PKR and phosphorylated eIF2α and a moderate increase of activating transcription factor 4 (ATF4), which is known to transcribe stress genes. Overexpression of PKR led to increased eIF2α phosphorylation and decreased viral replication, whereas overexpression of a dominant negative PKR mutant resulted in a moderate increase in viral replication. These results suggest that the HHV-6A replication strategy involves restricted activation of the PKR-eIF2α pathway, partial translation inhibition, and lower yields of infectious virus. In essence, HHV-6A limits its own replication due to the inability to bypass the eIF2α phosphorylation.
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Mengke NS, Hu B, Han QP, Deng YY, Fang M, Xie D, Li A, Zeng HK. Rapamycin inhibits lipopolysaccharide-induced neuroinflammation in vitro and in vivo. Mol Med Rep 2016; 14:4957-4966. [PMID: 27779711 PMCID: PMC5355655 DOI: 10.3892/mmr.2016.5883] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 07/08/2016] [Indexed: 01/05/2023] Open
Abstract
Alzheimer's disease (AD) is the most common type of progressive neurodegenerative disorder, and is responsible for the most common form of dementia in the elderly. Inflammation occurs in the brains of patients with AD, and is critical for disease progression. In the present study, the effects of rapamycin (RAPA) on neuroinflammation lipopolysaccharide (LPS)-induced were investigated. SH-SY5Y human neuroblastoma cells were treated with 20 µg/ml LPS and 0.1, 1 or 10 nmol/l RAPA, and were analyzed at various time points (6, 12 and 24 h). The mRNA expression levels of interleukin (IL) 1β, IL6 and hypoxia-inducible factor 1α (HIF1α) were determined using reverse transcription-quantitative polymerase chain reaction. The protein expression levels of phosphorylated (p-)S6, p-nuclear factor κB (NFκB), p-inhibitor of NFκB kinase subunit β (IKKβ) and p-tau protein were measured by western blot analysis. p-IKKβ, p-NFκB, p-S6 and p-tau were significantly decreased at 6, 12 and 24 h when cells were treated with ≥0.1 nmol/ml RAPA. In addition, female Sprague Dawley rats were intracranially injected with a single dose of 100 µg/kg LPS in the absence or presence of 1 mg/kg RAPA pretreatment. Brain tissues were subjected to immunohistochemical analysis 6–24 h later, which revealed that the expression levels of HIF1α and p-S6 in rat cerebral cortex were increased following LPS injection; however, this increase was abrogated by RAPA treatment. RAPA may therefore be considered a potential therapeutic agent for the early or emergency treatment of neuroinflammation.
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Affiliation(s)
- Na-Shun Mengke
- Faculty of Graduate Studies, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Bei Hu
- Faculty of Graduate Studies, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Qian-Peng Han
- Faculty of Graduate Studies, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Yi-Yu Deng
- Department of Emergency and Critical Care Medicine, Guangdong General Hospital & Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Ming Fang
- Department of Emergency and Critical Care Medicine, Guangdong General Hospital & Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, P.R. China
| | - Di Xie
- Faculty of Graduate Studies, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Ang Li
- Department of Histoembryology, Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Hong-Ke Zeng
- Faculty of Graduate Studies, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
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Duncan JW, Johnson S, Zhang X, Zheng B, Luo J, Ou XM, Stockmeier CA, Wang JM. Up-Regulation of PKR Signaling Pathway by Ethanol Displays an Age of Onset-Dependent Relationship. Alcohol Clin Exp Res 2016; 40:2320-2328. [PMID: 27647657 DOI: 10.1111/acer.13209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 08/01/2016] [Indexed: 12/16/2022]
Abstract
BACKGROUND Ethanol (EtOH) neurotoxicity can result in devastating effects on brain and behavior by disrupting homeostatic signaling cascades and inducing cell death. One such mechanism involves double-stranded RNA activated protein kinase (PKR), a primary regulator of protein translation and cell viability in the presence of a virus or other external stimuli. EtOH-mediated up-regulation of interferon-gamma (IFN-γ; the oxidative stress-inducible regulator of PKR), PKR, and its target, p53, are still being fully elucidated. METHODS Using Western blot analysis, immunofluorescence, and linear regression analyses, changes in the IFN-γ-PKR-p53 pathway following chronic EtOH treatment in the frontal cortex of rodents were examined. The role of PKR on cell viability was also assessed in EtOH-treated cells using PKR overexpression vector and PKR inhibitor (PKRI). RESULTS In rats chronically fed EtOH, PKR, phosphorylated PKR (p-PKR), IFN-γ, and p53 were significantly increased following chronic EtOH exposure. Linear regression revealed a significant correlation between IFN-γ and p-PKR protein levels, as well as p-PKR expression and age of EtOH exposure. Overexpression of PKR resulted in greater cell death, while use of PKRI enhanced cell viability in EtOH-treated cells. CONCLUSIONS Chronic EtOH exposure activates the IFN-γ-PKR-p53 pathway in the frontal cortex of rodents. p-PKR expression is greater in brains of rodents exposed to EtOH at earlier ages compared to later life, suggesting a mechanism by which young brains could be more susceptible to EtOH-related brain injury. PKR and p-PKR were also colocalized in neurons and astrocytes of rats. This study provides additional insight into biochemical mechanisms underlying alcohol use disorder related neuropathology and warrants further investigation of PKR as a potential pharmacotherapeutic target to combat EtOH-related neurotoxicity, loss of protein translation and brain injury.
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Affiliation(s)
- Jeremy W Duncan
- Program in Neuroscience , University of Mississippi Medical Center, Jackson, Mississippi.,Department of Psychiatry and Human Behavior , University of Mississippi Medical Center, Jackson, Mississippi
| | - Shakevia Johnson
- Department of Psychiatry and Human Behavior , University of Mississippi Medical Center, Jackson, Mississippi
| | - Xiao Zhang
- Program in Neuroscience , University of Mississippi Medical Center, Jackson, Mississippi.,Department of Psychiatry and Human Behavior , University of Mississippi Medical Center, Jackson, Mississippi
| | - Baoying Zheng
- Department of Pathology, University of Mississippi Medical Center, Jackson, Mississippi
| | - Jia Luo
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky.,Department of Internal Medicine, University of Kentucky, Lexington, Kentucky
| | - Xiao-Ming Ou
- Department of Psychiatry and Human Behavior , University of Mississippi Medical Center, Jackson, Mississippi
| | - Craig A Stockmeier
- Department of Psychiatry and Human Behavior , University of Mississippi Medical Center, Jackson, Mississippi
| | - Jun Ming Wang
- Program in Neuroscience , University of Mississippi Medical Center, Jackson, Mississippi. .,Department of Psychiatry and Human Behavior , University of Mississippi Medical Center, Jackson, Mississippi. .,Department of Pathology, University of Mississippi Medical Center, Jackson, Mississippi.
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Hong MN, Nam KY, Kim KK, Kim SY, Kim I. The small molecule '1-(4-biphenylylcarbonyl)-4-(5-bromo-2-methoxybenzyl) piperazine oxalate' and its derivatives regulate global protein synthesis by inactivating eukaryotic translation initiation factor 2-alpha. Cell Stress Chaperones 2016; 21:485-97. [PMID: 26873011 PMCID: PMC4837177 DOI: 10.1007/s12192-016-0677-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 01/29/2016] [Accepted: 01/30/2016] [Indexed: 10/22/2022] Open
Abstract
By environmental stresses, cells can initiate a signaling pathway in which eukaryotic translation initiation factor 2-alpha (eIF2-α) is involved to regulate the response. Phosphorylation of eIF2-α results in the reduction of overall protein neogenesis, which allows cells to conserve resources and to reprogram energy usage for effective stress control. To investigate the role of eIF2-α in cell stress responses, we conducted a viability-based compound screen under endoplasmic reticulum (ER) stress condition, and identified 1-(4-biphenylylcarbonyl)-4-(5-bromo-2-methoxybenzyl) piperazine oxalate (AMC-01) and its derivatives as eIF2-α-inactivating chemical. Molecular characterization of this signaling pathway revealed that AMC-01 induced inactivation of eIF2-α by phosphorylating serine residue 51 in a dose- and time-dependent manner, while the negative control compounds did not affect eIF2-α phosphorylation. In contrast with ER stress induction by thapsigargin, phosphorylation of eIF2-α persisted for the duration of incubation with AMC-01. By pathway analysis, AMC-01 clearly induced the activation of protein kinase RNA-activated (PKR) kinase and nuclear factor-κB (NF-κB), whereas it did not modulate the activity of PERK or heme-regulated inhibitor (HRI). Finally, we could detect a lower protein translation rate in cells incubated with AMC-01, establishing AMC-01 as a potent chemical probe that can regulate eIF2-α activity. We suggest from these data that AMC-01 and its derivative compounds can be used as chemical probes in future studies of the role of eIF2-α in protein synthesis-related cell physiology.
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Affiliation(s)
- Mi-Na Hong
- Department of Convergence Medicine, Asan Institute for Life Sciences, Asan Medical Center, Convergence Medicine Research Building, 43 gil Olympicro, Pungnapdong, Songpagu, Seoul, 138-736, Republic of Korea
| | - Ky-Youb Nam
- Department of Convergence Medicine, Asan Institute for Life Sciences, Asan Medical Center, Convergence Medicine Research Building, 43 gil Olympicro, Pungnapdong, Songpagu, Seoul, 138-736, Republic of Korea
| | - Kyung Kon Kim
- Department of Convergence Medicine, Asan Institute for Life Sciences, Asan Medical Center, Convergence Medicine Research Building, 43 gil Olympicro, Pungnapdong, Songpagu, Seoul, 138-736, Republic of Korea
- Department of Convergence Medicine, College of Medicine, University of Ulsan, Seoul, Republic of Korea
| | - So-Young Kim
- Department of Convergence Medicine, Asan Institute for Life Sciences, Asan Medical Center, Convergence Medicine Research Building, 43 gil Olympicro, Pungnapdong, Songpagu, Seoul, 138-736, Republic of Korea
| | - InKi Kim
- Department of Convergence Medicine, Asan Institute for Life Sciences, Asan Medical Center, Convergence Medicine Research Building, 43 gil Olympicro, Pungnapdong, Songpagu, Seoul, 138-736, Republic of Korea.
- Department of Convergence Medicine, College of Medicine, University of Ulsan, Seoul, Republic of Korea.
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The mammalian target of rapamycin at the crossroad between cognitive aging and Alzheimer's disease. NPJ Aging Mech Dis 2015; 1:15008. [PMID: 28721257 PMCID: PMC5514987 DOI: 10.1038/npjamd.2015.8] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 08/10/2015] [Accepted: 09/01/2015] [Indexed: 12/12/2022] Open
Abstract
Age-dependent cognitive decline is a major debilitating event affecting even individuals who are otherwise healthy. Understanding the molecular basis underlying these changes may increase the healthspan of the elderly population. It may also reveal insights into the pathogenesis of numerous neurodegenerative disorders characterized by cognitive deficits, as aging is the major risk factor for most of these disorders. Alzheimer’s disease (AD), the most common neurodegenerative disorder, first manifests itself as deficits in encoding new memories. As AD progresses, these deficits spread to other cognitive domains that further debilitate the person before contributing to their demise. Suppression of the mammalian target of rapamycin (mTOR) increases healthspan and lifespan in several organisms. Numerous reports have linked alterations in mTOR signaling to age-dependent cognitive decline and the pathogenesis of AD. This review will discuss recent work highlighting the complex role of mTOR in cognitive aging and in the pathogenesis of AD.
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Paquet C, Dumurgier J, Hugon J. Pro-Apoptotic Kinase Levels in Cerebrospinal Fluid as Potential Future Biomarkers in Alzheimer's Disease. Front Neurol 2015; 6:168. [PMID: 26300842 PMCID: PMC4523792 DOI: 10.3389/fneur.2015.00168] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/20/2015] [Indexed: 12/22/2022] Open
Abstract
Alzheimer’s disease (AD) is characterized by the accumulation of Aβ peptides, hyperphosphorylated tau proteins, and neuronal loss in the brain of affected patients. The causes of neurodegeneration in AD are not clear, but apoptosis could be one of the cell death mechanisms. According to the amyloid hypothesis, abnormal aggregation of Aβ leads to altered kinase activities inducing tau phosphorylation and neuronal degeneration. Several studies have shown that pro-apoptotic kinases could be a link between Aβ and tau anomalies. Here, we present recent evidences from AD experimental models and human studies that three pro-apoptotic kinases (double-stranded RNA kinase (PKR), glycogen synthase kinase-3β, and C-Jun terminal kinase (JNK) could be implicated in AD physiopathology. These kinases are detectable in human fluids and the analysis of their levels could be used as potential surrogate markers to evaluate cell death and clinical prognosis. In addition to current biomarkers (Aβ1–42, tau, and phosphorylated tau), these new evaluations could bring about valuable information on potential innovative therapeutic targets to alter the clinical evolution.
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Affiliation(s)
- Claire Paquet
- INSERM UMR-S942, Centre Mémoire de Ressources et de Recherche (CMRR) Paris Nord Ile de France, Groupe Hospitalier Lariboisière Fernand-Widal Saint-Louis, AP-HP, Université Paris Diderot , Paris , France
| | - Julien Dumurgier
- INSERM UMR-S942, Centre Mémoire de Ressources et de Recherche (CMRR) Paris Nord Ile de France, Groupe Hospitalier Lariboisière Fernand-Widal Saint-Louis, AP-HP, Université Paris Diderot , Paris , France
| | - Jacques Hugon
- INSERM UMR-S942, Centre Mémoire de Ressources et de Recherche (CMRR) Paris Nord Ile de France, Groupe Hospitalier Lariboisière Fernand-Widal Saint-Louis, AP-HP, Université Paris Diderot , Paris , France
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43
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Buffington SA, Huang W, Costa-Mattioli M. Translational control in synaptic plasticity and cognitive dysfunction. Annu Rev Neurosci 2015; 37:17-38. [PMID: 25032491 DOI: 10.1146/annurev-neuro-071013-014100] [Citation(s) in RCA: 251] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Activity-dependent changes in the strength of synaptic connections are fundamental to the formation and maintenance of memory. The mechanisms underlying persistent changes in synaptic strength in the hippocampus, specifically long-term potentiation and depression, depend on new protein synthesis. Such changes are thought to be orchestrated by engaging the signaling pathways that regulate mRNA translation in neurons. In this review, we discuss the key regulatory pathways that govern translational control in response to synaptic activity and the mRNA populations that are specifically targeted by these pathways. The critical contribution of regulatory control over new protein synthesis to proper cognitive function is underscored by human disorders associated with either silencing or mutation of genes encoding proteins that directly regulate translation. In light of these clinical implications, we also consider the therapeutic potential of targeting dysregulated translational control to treat cognitive disorders of synaptic dysfunction.
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Affiliation(s)
- Shelly A Buffington
- Department of Neuroscience, Memory and Brain Research Center, Baylor College of Medicine, Houston, Texas 77030; , ,
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44
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Zhu Z, Zhong H, Zhou Q, Hu X, Chen D, Wang J, Wu J, Cai J, Zhou S, Chen AF. Inhibition of PKR impairs angiogenesis through a VEGF pathway. Am J Physiol Endocrinol Metab 2015; 308:E518-24. [PMID: 25587101 DOI: 10.1152/ajpendo.00469.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Peripheral artery disease (PAD) is a common clinical problem, and its pathophysiological mechanisms are incompletely understood. Double-stranded RNA-activated protein kinase (PKR) is a ubiquitously expressed serine/threonine protein kinase. Although PKR has been reported in antivirus and the immune system, the role of PKR in vascular function, especially in angiogenesis, is still unclear. PKR(-/-) mice were used in our experiments. Blood flow recovery was significantly delayed in PKR(-/-) vs. WT mice (Laser Doppler detection, n = 9, P < 0.01), accompanied by 34% reduced CD31-positive stain in ischemic muscle 28 days after procedure (immunohistochemistry, n = 9, P < 0.05). PKR expression decreased in the first 12 h and increased to peak at 24 h in human umbilical vein endothelial cells (HUVECs) in response to hypoxia (Western blot analyses, n = 3, P < 0.05). Accordingly, phospho-PKR expression increased in HUVECs 24 h after treatment with hypoxia (Western blot analyses, n = 3, P < 0.05). Inhibition of PKR (siRNA transfection) reduced microtubule formation (Matrigel tube formation, n = 3, vs. control siRNA, P < 0.05) and migration (wound healing, n = 3, vs. control siRNA, P < 0.05) by 33 and 59%, respectively. Vascular endothelial growth factor (VEGF) expression in ischemic muscle from PKR(-/-) mice was significantly decreased by 54% 1 day after procedure (n = 3, P < 0.05, vs. WT) and by 63% 7 days after procedure (n = 3, P < 0.01, vs. WT), respectively. At the same time, VEGF expression in HUVECs decreased by 21% (n = 3, P < 0.05, PKR siRNA vs. control siRNA). These findings demonstrate that PKR mediates angiogenesis through a VEGF pathway, which may form the basis for future intervention of PAD.
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Affiliation(s)
- Zhaowei Zhu
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Hua Zhong
- The Third Xiangya Hospital and the College of Pharmacy, Central South University, Changsha, China
| | - Qin Zhou
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Xinqun Hu
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Dandan Chen
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Jiemei Wang
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Jinze Wu
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Jingjing Cai
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
| | - Shenghua Zhou
- The Third Xiangya Hospital and the College of Pharmacy, Central South University, Changsha, China
| | - Alex F Chen
- Department of Cardiology, the Second Xiangya Hospital, Central South University, Changsha, China; and
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45
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Blalock WL, Piazzi M, Bavelloni A, Raffini M, Faenza I, D'Angelo A, Cocco L. Identification of the PKR nuclear interactome reveals roles in ribosome biogenesis, mRNA processing and cell division. J Cell Physiol 2014; 229:1047-60. [PMID: 24347309 DOI: 10.1002/jcp.24529] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 12/05/2013] [Indexed: 01/08/2023]
Abstract
The double-strand RNA-dependent protein kinase, PKR, plays a central role in inflammatory/chronic stress-mediated pathologies such as cancer, diabetes, and neuro/muscular degenerative diseases. Although a significant amount of research has been conducted to elucidate the role of PKR signaling in the cytosol, only recently has attention been paid to the role of PKR in the nuclear compartment. Previously our group reported that phosphorylated forms of PKR are present in the nucleus of acute leukemic cell lines, representing a reservoir of active kinase that responds to stress. Using the CCRF-CEM acute T-cell leukemia cell line, a PKR-specific inhibitor, co-immunoprecipitation and a proteomics approach, which included affinity purified mass spectrometry analysis (AP/MS), we identified the proteins present in active and inactive PKR nuclear complexes. Of the proteins identified in the PKR complexes, sixty-nine (69) were specific to the active complex, while thirty-eight (38) were specific to the inactive complex. An additional thirteen (13) proteins associated specifically with both complexes. The majority of the proteins identified are involved in, ribosome biogenesis, RNA splicing, mRNA stability, gene expression, cell cycle, or chromatin organization, including several with known significance to normal hematopoiesis and/or hematological disease. In agreement with the AP/MS data, basal- or over-expression of PKR under normal growth conditions favored cell proliferation in the tested cell lines, whereas pharmacological inhibition of PKR or shRNA-mediated knock-down did not. PKR was also found to influence the isoform and the level of expression of the proto-oncogene MYC.
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Affiliation(s)
- William L Blalock
- CNR-NationalResearch Council of Italy, Institute of Molecular Genetics, Bologna, Italy; SC Laboratory of Musculoskeletal Cell Biology, Rizzoli Orthopedic Institute, Bologna, Italy
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46
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Marchal JA, Lopez GJ, Peran M, Comino A, Delgado JR, García-García JA, Conde V, Aranda FM, Rivas C, Esteban M, Garcia MA. The impact of PKR activation: from neurodegeneration to cancer. FASEB J 2014; 28:1965-74. [PMID: 24522206 DOI: 10.1096/fj.13-248294] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
An inverse association between cancer and neurodegeneration is plausible because these biological processes share several genes and signaling pathways. Whereas uncontrolled cell proliferation and decreased apoptotic cell death governs cancer, excessive apoptosis contributes to neurodegeneration. Protein kinase R (PKR), an interferon-inducible double-stranded RNA protein kinase, is involved in both diseases. PKR activation blocks global protein synthesis through eIF2α phosphorylation, leading to cell death in response to a variety of cellular stresses. However, PKR also has the dual role of activating the nuclear factor κ-B pathway, promoting cell proliferation. Whereas PKR is recognized for its negative effects on neurodegenerative diseases, in part, inducing high level of apoptosis, the role of PKR activation in cancer remains controversial. In general, PKR is considered to have a tumor suppressor function, and some clinical data show a correlation between suppressed or inactivated PKR and a poor prognosis for several cancers. However, other studies show high PKR expression and activation levels in various cancers, suggesting that PKR might contribute to neoplastic progression. Understanding the cellular factors and signals involved in the regulation of PKR in these age-related diseases is relevant and may have important clinical implications. The present review highlights the current knowledge on the role of PKR in neurodegeneration and cancer, with special emphasis on its regulation and clinical implications.
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Affiliation(s)
- Juan A Marchal
- 1University Hospital Virgen de las Nieves, Azpitarte sn., Granada E-18012, Spain.
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47
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Vaughn LS, Snee B, Patel RC. Inhibition of PKR protects against tunicamycin-induced apoptosis in neuroblastoma cells. Gene 2013; 536:90-6. [PMID: 24334130 DOI: 10.1016/j.gene.2013.11.074] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 10/29/2013] [Accepted: 11/26/2013] [Indexed: 01/07/2023]
Abstract
Endoplasmic reticulum (ER) dysfunction is thought to play a significant role in several neurological disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, amyotrophic lateral sclerosis, cerebral ischemia, and the prion diseases. ER dysfunction can be mimicked by cellular stress signals such as disruption of calcium homeostasis, inhibition of protein glycosylation, and reduction of disulfide bonds, which results in accumulation of misfolded proteins in the ER and leads to cell death by apoptosis. Tunicamycin, which is an inhibitor of protein glycosylation, induces ER stress and apoptosis. In this study, we examined the involvement of double stranded (ds) RNA-activated protein kinase PKR in tunicamycin-induced apoptosis. We used overexpression of the trans-dominant negative, catalytically inactive mutant K296R to inhibit PKR activity in neuroblastoma cells. We demonstrate that inhibition of PKR activation in response to tunicamycin protects neuronal cells from undergoing apoptosis. Furthermore, K296R overexpressing cells show defective PKR activation, delayed eIF2α phosphorylation, dramatically delayed ATF4 expression. In addition, both caspase-3 activation and C/EBP homologous protein (CHOP, also known as GADD153) induction, which are markers of apoptotic cells, are absent from K296R overexpression cells in response to tunicamycin. These results establish that PKR activation plays a major regulatory role in induction of apoptosis in response to ER stress and indicates the potential of PKR as possible target for neuroprotective therapeutics.
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Affiliation(s)
- Lauren S Vaughn
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Brittany Snee
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Rekha C Patel
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
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48
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Expression of the CHOP-inducible carbonic anhydrase CAVI-b is required for BDNF-mediated protection from hypoxia. Brain Res 2013; 1543:28-37. [PMID: 24275196 DOI: 10.1016/j.brainres.2013.11.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 10/29/2013] [Accepted: 11/17/2013] [Indexed: 01/19/2023]
Abstract
Carbonic anhydrases (CAs) comprise a family of zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide. CAs contribute to a myriad of physiological processes, including pH regulation, anion transport and water balance. To date, 16 known members of the mammalian alpha-CA family have been identified. Given that the catalytic family members share identical reaction chemistry, their physiologic roles are influenced greatly by their tissue and sub-cellular locations. CAVI is the lone secreted CA and exists in both saliva and the gastrointestinal mucosa. An alternative, stress-inducible isoform of CAVI (CAVI-b) has been shown to be expressed from a cryptic promoter that is activated by the CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP). The CAVI-b isoform is not secreted and is currently of unknown physiological function. Here we use neuronal models, including a model derived using Car6 and CHOP gene ablations, to delineate a role for CAVI-b in ischemic protection. Our results demonstrate that CAVI-b expression, which is increased through CHOP-signaling in response to unfolded protein stress, is also increased by oxygen-glucose deprivation (OGD). While enforced expression of CAVI-b is not sufficient to protect against ischemia, CHOP regulation of CAVI-b is necessary for adaptive changes mediated by BDNF that reduce subsequent ischemic damage. These results suggest that CAVI-b comprises a necessary component of a larger adaptive signaling pathway downstream of CHOP.
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49
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Donnelly N, Gorman AM, Gupta S, Samali A. The eIF2α kinases: their structures and functions. Cell Mol Life Sci 2013; 70:3493-511. [PMID: 23354059 PMCID: PMC11113696 DOI: 10.1007/s00018-012-1252-6] [Citation(s) in RCA: 609] [Impact Index Per Article: 55.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 12/16/2012] [Accepted: 12/20/2012] [Indexed: 01/02/2023]
Abstract
Cell signaling in response to an array of diverse stress stimuli converges on the phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2). Phosphorylation of eIF2α on serine 51 results in a severe decline in de novo protein synthesis and is an important strategy in the cell's armory against stressful insults including viral infection, the accumulation of misfolded proteins, and starvation. The phosphorylation of eIF2α is carried out by a family of four kinases, PERK (PKR-like ER kinase), PKR (protein kinase double-stranded RNA-dependent), GCN2 (general control non-derepressible-2), and HRI (heme-regulated inhibitor). Each primarily responds to a distinct type of stress or stresses. Thus, while significant sequence similarity exists between the eIF2α kinases in their kinase domains, underlying their common role in phosphorylating eIF2α, additional unique features determine the regulation of these four proteins, that is, what signals activate them. This review will describe the structure of each eIF2α kinase and discuss how this is linked to their activation and function. In parallel to the general translational attenuation elicited by eIF2α kinase activation the translation of stress-induced mRNAs, most notably activating transcription factor 4 (ATF4) is enhanced and these set in motion cascades of gene expression constituting the integrated stress response (ISR), which seek to remediate stress and restore homeostasis. Depending on the cellular context and concurrent signaling pathways active, however, translational attenuation can also facilitate apoptosis. Accordingly, the role of the kinases in determining cell fate will also be discussed.
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Affiliation(s)
- Neysan Donnelly
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Natural Sciences, National University of Ireland, Galway, Ireland
- Present Address: Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried, Munich, 82152 Germany
| | - Adrienne M. Gorman
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Sanjeev Gupta
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Medicine, National University of Ireland, Galway, Ireland
| | - Afshin Samali
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Natural Sciences, National University of Ireland, Galway, Ireland
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50
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Joshi M, Kulkarni A, Pal JK. Small molecule modulators of eukaryotic initiation factor 2α kinases, the key regulators of protein synthesis. Biochimie 2013; 95:1980-90. [PMID: 23939221 DOI: 10.1016/j.biochi.2013.07.030] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 07/26/2013] [Indexed: 01/25/2023]
Abstract
Eukaryotic initiation factor 2 alpha kinases (eIF-2α kinases) are key mediators of stress response in cells. In mammalian cells, there are four eIF-2α kinases, namely HRI (Heme-Regulated Inhibitor), PKR (RNA-dependent Protein Kinase), PERK (PKR-like ER Kinase) and GCN2 (General Control Non-derepressible 2). These kinases get activated during diverse cytoplasmic stress conditions and phosphorylate the alpha-subunit of eIF2, leading to global protein synthesis inhibition. Therefore, eIF-2α kinases play a vital role in various cellular processes such as proliferation, differentiation, apoptosis and cell signaling. Deregulation of eIF-2α kinases and protein synthesis has been linked to numerous pathological conditions such as certain cancers, anemia and neurodegenerative disorders. Thus, modulation of these kinases by small molecules holds a great therapeutic promise. In this review we have compiled the available information on inhibitors and activators of these four eIF-2α kinases. The review concludes with a note on the selectivity issue of currently available modulators and future perspectives for the design of specific small molecule probes.
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Affiliation(s)
- Manali Joshi
- Bioinformatics Center, University of Pune, Pune - 411007, Maharashtra, India.
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