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Carreras I, Jung Y, Lopez-Benitez J, Tognoni CM, Dedeoglu A. Fingolimod mitigates memory loss in a mouse model of Gulf War Illness amid decreasing the activation of microglia, protein kinase R, and NFκB. Neurotoxicology 2023; 96:197-206. [PMID: 37160207 PMCID: PMC10334821 DOI: 10.1016/j.neuro.2023.05.006] [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: 02/21/2023] [Revised: 05/05/2023] [Accepted: 05/05/2023] [Indexed: 05/11/2023]
Abstract
Gulf War Illness (GWI) is an unrelenting multi-symptom illness with chronic central nervous system and peripheral pathology affecting veterans from the 1991 Gulf War and for which effective treatment is lacking. An increasing number of studies indicate that persistent neuroinflammation is likely the underlying cause of cognitive and mood dysfunction that affects veterans with GWI. We have previously reported that fingolimod, a drug approved for the treatment of relapsing-remitting multiple sclerosis, decreases neuroinflammation and improves cognition in a mouse model of Alzheimer's disease. In this study, we investigated the effect of fingolimod treatment on cognition and neuroinflammation in a mouse model of GWI. We exposed C57BL/6 J male mice to GWI-related chemicals pyridostigmine bromide, DEET, and permethrin, and to mild restraint stress for 28 days (GWI mice). Control mice were exposed to the chemicals' vehicle only. Starting 3 months post-exposure, half of the GWI mice and control mice were orally treated with fingolimod (1 mg/kg/day) for 1 month, and the other half were left untreated. Decreased memory on the Morris water maze test was detected in GWI mice compared to control mice and was reversed by fingolimod treatment. Immunohistochemical analysis of brain sections with antibodies to Iba1 and GFAP revealed that GWI mice had increased microglia activation in the hippocampal dentate gyrus, but no difference in reactive astrocytes was detected. The increased activation of microglia in GWI mice was decreased to the level in control mice by treatment with fingolimod. No effect of fingolimod treatment on gliosis in control mice was detected. To explore the signaling pathways by which decreased memory and increased neuroinflammation in GWI may be protected by fingolimod, we investigated the involvement of the inflammatory signaling pathways of protein kinase R (PKR) in the cerebral cortex of these mice. We found increased phosphorylation of PKR in the brain of GWI mice compared to controls, as well as increased phosphorylation of its most recognized downstream effectors: the α subunit of eukaryotic initiation factor 2 (eIF2α), IκB kinase (IKK), and the p65 subunit of nuclear factor-κB (NFκB-p65). Furthermore, we found that the increased phosphorylation level of these three proteins were suppressed in GWI mice treated with fingolimod. These results suggest that activation of PKR and NFκB signaling may be important for the regulation of cognition and neuroinflammation in the GWI condition and that fingolimod, a drug already approved for human use, may be a potential candidate for the treatment of GWI.
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Affiliation(s)
- Isabel Carreras
- Department of Veterans Affairs, VA Boston Healthcare System,150 S Huntington Av, Boston, MA 02130, USA; Department of Neurology, Boston University School of Medicine, 72 E Concord St, Boston, MA 02118, USA; Department of Biochemistry, Boston University School of Medicine, Boston, MA, 02118, USA.
| | - Younghun Jung
- Department of Veterans Affairs, VA Boston Healthcare System,150 S Huntington Av, Boston, MA 02130, USA; Department of Neurology, Boston University School of Medicine, 72 E Concord St, Boston, MA 02118, USA; The Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, 73 High St, Boston, MA 02114, USA
| | - Jonathan Lopez-Benitez
- Department of Veterans Affairs, VA Boston Healthcare System,150 S Huntington Av, Boston, MA 02130, USA; Department of Neurology, Boston University School of Medicine, 72 E Concord St, Boston, MA 02118, USA
| | - Christina M Tognoni
- Department of Veterans Affairs, VA Boston Healthcare System,150 S Huntington Av, Boston, MA 02130, USA; Department of Neurology, Boston University School of Medicine, 72 E Concord St, Boston, MA 02118, USA
| | - Alpaslan Dedeoglu
- Department of Veterans Affairs, VA Boston Healthcare System,150 S Huntington Av, Boston, MA 02130, USA; Department of Neurology, Boston University School of Medicine, 72 E Concord St, Boston, MA 02118, USA; Department of Radiology, Massachusetts General Hospital and Harvard Medical School, 73 High St, Boston, MA 02114, USA
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2
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Frederick K, Patel RC. Luteolin protects DYT- PRKRA cells from apoptosis by suppressing PKR activation. Front Pharmacol 2023; 14:1118725. [PMID: 36874028 PMCID: PMC9974672 DOI: 10.3389/fphar.2023.1118725] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/06/2023] [Indexed: 02/17/2023] Open
Abstract
DYT-PRKRA is a movement disorder caused by mutations in the PRKRA gene, which encodes for PACT, the protein activator of interferon-induced, double-stranded RNA (dsRNA)-activated protein kinase PKR. PACT brings about PKR's catalytic activation by a direct binding in response to stress signals and activated PKR phosphorylates the translation initiation factor eIF2α. Phosphorylation of eIF2α is the central regulatory event that is part of the integrated stress response (ISR), an evolutionarily conserved intracellular signaling network essential for adapting to environmental stresses to maintain healthy cells. A dysregulation of either the level or the duration of eIF2α phosphorylation in response to stress signals causes the normally pro-survival ISR to become pro-apoptotic. Our research has established that the PRKRA mutations reported to cause DYT-PRKRA lead to enhanced PACT-PKR interactions causing a dysregulation of ISR and an increased sensitivity to apoptosis. We have previously identified luteolin, a plant flavonoid, as an inhibitor of the PACT-PKR interaction using high-throughput screening of chemical libraries. Our results presented in this study indicate that luteolin is markedly effective in disrupting the pathological PACT-PKR interactions to protect DYT-PRKRA cells against apoptosis, thus suggesting a therapeutic option for using luteolin to treat DYT-PRKRA and possibly other diseases resulting from enhanced PACT-PKR interactions.
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Affiliation(s)
- Kenneth Frederick
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
| | - Rekha C Patel
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
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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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Dystonia 16 (DYT16) mutations in PACT cause dysregulated PKR activation and eIF2α signaling leading to a compromised stress response. Neurobiol Dis 2020; 146:105135. [PMID: 33049316 DOI: 10.1016/j.nbd.2020.105135] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 09/17/2020] [Accepted: 10/07/2020] [Indexed: 12/17/2022] Open
Abstract
Dystonia 16 (DYT16) is caused by mutations in PACT, the protein activator of interferon-induced double-stranded RNA-activated protein kinase (PKR). PKR regulates the integrated stress response (ISR) via phosphorylation of the translation initiation factor eIF2α. This post-translational modification attenuates general protein synthesis while concomitantly triggering enhanced translation of a few specific transcripts leading either to recovery and homeostasis or cellular apoptosis depending on the intensity and duration of stress signals. PKR plays a regulatory role in determining the cellular response to viral infections, oxidative stress, endoplasmic reticulum (ER) stress, and growth factor deprivation. In the absence of stress, both PACT and PKR are bound by their inhibitor transactivation RNA-binding protein (TRBP) thereby keeping PKR inactive. Under conditions of cellular stress these inhibitory interactions dissociate facilitating PACT-PACT interactions critical for PKR activation. While both PACT-TRBP and PKR-TRBP interactions are pro-survival, PACT-PACT and PACT-PKR interactions are pro-apoptotic. In this study we evaluate if five DYT16 substitution mutations alter PKR activation and ISR. Our results indicate that the mutant DYT16 proteins show stronger PACT-PACT interactions and enhanced PKR activation. In DYT16 patient derived lymphoblasts the enhanced PACT-PKR interactions and heightened PKR activation leads to a dysregulation of ISR and increased apoptosis. More importantly, this enhanced sensitivity to ER stress can be rescued by luteolin, which disrupts PACT-PKR interactions. Our results not only demonstrate the impact of DYT16 mutations on regulation of ISR and DYT16 etiology but indicate that therapeutic interventions could be possible after a further evaluation of such strategies.
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Bond S, Lopez-Lloreda C, Gannon PJ, Akay-Espinoza C, Jordan-Sciutto KL. The Integrated Stress Response and Phosphorylated Eukaryotic Initiation Factor 2α in Neurodegeneration. J Neuropathol Exp Neurol 2020; 79:123-143. [PMID: 31913484 DOI: 10.1093/jnen/nlz129] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 11/07/2019] [Indexed: 02/06/2023] Open
Abstract
The proposed molecular mechanisms underlying neurodegenerative pathogenesis are varied, precluding the development of effective therapies for these increasingly prevalent disorders. One of the most consistent observations across neurodegenerative diseases is the phosphorylation of eukaryotic initiation factor 2α (eIF2α). eIF2α is a translation initiation factor, involved in cap-dependent protein translation, which when phosphorylated causes global translation attenuation. eIF2α phosphorylation is mediated by 4 kinases, which, together with their downstream signaling cascades, constitute the integrated stress response (ISR). While the ISR is activated by stresses commonly observed in neurodegeneration, such as oxidative stress, endoplasmic reticulum stress, and inflammation, it is a canonically adaptive signaling cascade. However, chronic activation of the ISR can contribute to neurodegenerative phenotypes such as neuronal death, memory impairments, and protein aggregation via apoptotic induction and other maladaptive outcomes downstream of phospho-eIF2α-mediated translation inhibition, including neuroinflammation and altered amyloidogenic processing, plausibly in a feed-forward manner. This review examines evidence that dysregulated eIF2a phosphorylation acts as a driver of neurodegeneration, including a survey of observations of ISR signaling in human disease, inspection of the overlap between ISR signaling and neurodegenerative phenomenon, and assessment of recent encouraging findings ameliorating neurodegeneration using developing pharmacological agents which target the ISR. In doing so, gaps in the field, including crosstalk of the ISR kinases and consideration of ISR signaling in nonneuronal central nervous system cell types, are highlighted.
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Affiliation(s)
- Sarah Bond
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Claudia Lopez-Lloreda
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Patrick J Gannon
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Cagla Akay-Espinoza
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Kelly L Jordan-Sciutto
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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6
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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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7
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Increased PKR level in human CADASIL brains. Virchows Arch 2018; 473:771-774. [PMID: 30073405 DOI: 10.1007/s00428-018-2425-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 07/22/2018] [Indexed: 10/28/2022]
Abstract
Cerebral autosomal dominant arteriolopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is the most common form of hereditary small vessel disease (SVD) of the brain. Neuronal apoptosis has been demonstrated in the cortex of patients. Whether it is associated with an activation of the pro-apoptotic protein PKR pathway is unknown. Similarly, activation of autophagy in CADASIL has never been explored. Immunostaining of four CADASIL brains previously analyzed for cortical neuronal apoptosis and five control brains for PKR (phosphoPKR) and autophagy (ATG5, LC3II) activation markers. Significant nuclear pPKR staining was observed in CADASIL neurons comparatively to controls (p = 0.001). No difference was observed between patients and controls with autophagy markers. We demonstrated the activation of PKR pathway in CADASIL. This was not associated with a detectable modulation of autophagy. These results open a new field to explore in order to better understand the mechanisms underlying cortical neurons apoptosis.
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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: 138] [Impact Index Per Article: 19.7] [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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10
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Li H, Chen J, Qi Y, Dai L, Zhang M, Frank JA, Handshoe JW, Cui J, Xu W, Chen G. Deficient PKR in RAX/PKR Association Ameliorates Ethanol-Induced Neurotoxicity in the Developing Cerebellum. THE CEREBELLUM 2016; 14:386-97. [PMID: 25592072 DOI: 10.1007/s12311-015-0644-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Ethanol-induced neuronal loss is closely related to the pathogenesis of fetal alcohol spectrum disorders. The cerebellum is one of the brain areas that are most sensitive to ethanol. The mechanism underlying ethanol neurotoxicity remains unclear. Our previous in vitro studies have shown that the double-stranded RNA (dsRNA)-activated protein kinase (PKR) regulates neuronal apoptosis upon ethanol exposure and ethanol activates PKR through association with its intracellular activator RAX. However, the role of PKR and its interaction with RAX in vivo have not been investigated. In the current study, by utilizing N-PKR-/- mice, C57BL/6J mice with a deficient RAX-binding domain in PKR, we determined the critical role of RAX/PKR association in PKR-regulated ethanol neurotoxicity in the developing cerebellum. Our data indicate that while N-PKR-/- mice have a similar BAC profile as wild-type mice, ethanol induces less brain/body mass reduction as well as cerebellar neuronal loss. In addition, ethanol promotes interleukin-1β (IL-1β) secretion, and IL-1β is a master cytokine regulating inflammatory response. Importantly, ethanol-promoted IL-1β secretion is inhibited in the developing cerebellum of N-PKR-/- mice. Thus, RAX/PKR interaction and PKR activation regulate ethanol neurotoxicity in the developing cerebellum, which may involve ethanol-induced neuroinflammation. Further, PKR could be a possible target for pharmacological intervention to prevent or treat fetal alcohol spectrum disorder (FASD).
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Affiliation(s)
- Hui Li
- Department Pharmacology & Nutritional Sciences, University of Kentucky College of Medicine, MN306, UKMC, 800 Rose street, Lexington, KY, 40536, USA
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11
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Mouton-Liger F, Rebillat AS, Gourmaud S, Paquet C, Leguen A, Dumurgier J, Bernadelli P, Taupin V, Pradier L, Rooney T, Hugon J. PKR downregulation prevents neurodegeneration and β-amyloid production in a thiamine-deficient model. Cell Death Dis 2015; 6:e1594. [PMID: 25590804 PMCID: PMC4669750 DOI: 10.1038/cddis.2014.552] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 10/30/2014] [Accepted: 11/03/2014] [Indexed: 12/22/2022]
Abstract
Brain thiamine homeostasis has an important role in energy metabolism and displays reduced activity in Alzheimer's disease (AD). Thiamine deficiency (TD) induces regionally specific neuronal death in the animal and human brains associated with a mild chronic impairment of oxidative metabolism. These features make the TD model amenable to investigate the cellular mechanisms of neurodegeneration. Once activated by various cellular stresses, including oxidative stress, PKR acts as a pro-apoptotic kinase and negatively controls the protein translation leading to an increase of BACE1 translation. In this study, we used a mouse TD model to assess the involvement of PKR in neuronal death and the molecular mechanisms of AD. Our results showed that the TD model activates the PKR-eIF2α pathway, increases the BACE1 expression levels of Aβ in specific thalamus nuclei and induces motor deficits and neurodegeneration. These effects are reversed by PKR downregulation (using a specific inhibitor or in PKR knockout mice).
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Affiliation(s)
- F Mouton-Liger
- 1] Inserm UMR-S942, Paris 75010, France [2] Department of Histology, Pathology and Biochemistry, Saint Louis Lariboisière Fernand Hospital, Service AP-HP, University of Paris Diderot, Paris, France
| | | | - S Gourmaud
- 1] Inserm UMR-S942, Paris 75010, France [2] Department of Histology, Pathology and Biochemistry, Saint Louis Lariboisière Fernand Hospital, Service AP-HP, University of Paris Diderot, Paris, France
| | - C Paquet
- 1] Inserm UMR-S942, Paris 75010, France [2] Department of Histology, Pathology and Biochemistry, Saint Louis Lariboisière Fernand Hospital, Service AP-HP, University of Paris Diderot, Paris, France [3] Clinical and Research Memory Center, Paris Nord Ile de France Saint Louis Lariboisière Fernand Hospital, AP-HP, University of Paris Diderot, Paris, France
| | - A Leguen
- Inserm UMR-S942, Paris 75010, France
| | - J Dumurgier
- 1] Department of Histology, Pathology and Biochemistry, Saint Louis Lariboisière Fernand Hospital, Service AP-HP, University of Paris Diderot, Paris, France [2] Clinical and Research Memory Center, Paris Nord Ile de France Saint Louis Lariboisière Fernand Hospital, AP-HP, University of Paris Diderot, Paris, France
| | - P Bernadelli
- Sanofi-Aventis Therapeutic Strategy Unit Aging, Chilly-Mazarin, France
| | - V Taupin
- Sanofi-Aventis Therapeutic Strategy Unit Aging, Chilly-Mazarin, France
| | - L Pradier
- Sanofi-Aventis Therapeutic Strategy Unit Aging, Chilly-Mazarin, France
| | - T Rooney
- Sanofi-Aventis Therapeutic Strategy Unit Aging, Chilly-Mazarin, France
| | - J Hugon
- 1] Inserm UMR-S942, Paris 75010, France [2] Department of Histology, Pathology and Biochemistry, Saint Louis Lariboisière Fernand Hospital, Service AP-HP, University of Paris Diderot, Paris, France [3] Clinical and Research Memory Center, Paris Nord Ile de France Saint Louis Lariboisière Fernand Hospital, AP-HP, University of Paris Diderot, Paris, France
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12
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Zech M, Castrop F, Schormair B, Jochim A, Wieland T, Gross N, Lichtner P, Peters A, Gieger C, Meitinger T, Strom TM, Oexle K, Haslinger B, Winkelmann J. DYT16 revisited: exome sequencing identifies PRKRA mutations in a European dystonia family. Mov Disord 2014; 29:1504-10. [PMID: 25142429 DOI: 10.1002/mds.25981] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 06/26/2014] [Accepted: 07/11/2014] [Indexed: 01/02/2023] Open
Abstract
Recessive DYT16 dystonia associated with mutations in PRKRA has until now been reported only in seven Brazilian patients. The aim of this study was to elucidate the genetic cause underlying disease in a Polish family with autosomal-recessive, early-onset generalized dystonia and slight parkinsonism, and to explore further the role of PRKRA in a dystonia series of European ancestry. We employed whole-exome sequencing in two affected siblings of the Polish family and filtered for rare homozygous and compound heterozygous variants shared by both exomes. Validation of the identified variants as well as homozygosity screening and copy number variation analysis was carried out in the two affected individuals and their healthy siblings. PRKRA was analyzed in 339 German patients with various forms of dystonia and 376 population-based controls by direct sequencing or high-resolution melting. The previously described homozygous p.Pro222Leu mutation in PRKRA was found to segregate with the disease in the studied family, contained in a 1.2 Mb homozygous region identical by state with all Brazilian patients in chromosome 2q31.2. The clinical presentation with young-onset, progressive generalized dystonia and mild parkinsonism resembled the phenotype of the original DYT16 cases. PRKRA mutational screening in additional dystonia samples revealed three novel heterozygous changes (p.Thr34Ser, p.Asn102Ser, c.-14A>G), each in a single subject with focal/segmental dystonia. Our study provides the first independent replication of the DYT16 locus at 2q31.2 and strongly confirms the causal contribution of the PRKRA gene to DYT16. Our data suggest worldwide involvement of PRKRA in dystonia.
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Affiliation(s)
- Michael Zech
- Neurologische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, Munich, Germany; Institut für Humangenetik, Helmholtz Zentrum München, Munich, Germany
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13
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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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14
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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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Casper C, Kalliolia E, Warner TT. Recent advances in the molecular pathogenesis of dystonia-plus syndromes and heredodegenerative dystonias. Curr Neuropharmacol 2013; 11:30-40. [PMID: 23814535 PMCID: PMC3580789 DOI: 10.2174/157015913804999432] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 08/17/2012] [Accepted: 08/29/2012] [Indexed: 12/04/2022] Open
Abstract
The majority of studies investigating the molecular pathogenesis and cell biology underlying dystonia have been performed in individuals with primary dystonia. This includes monogenic forms such as DYT1and DYT6 dystonia, and primary focal dystonia which is likely to be multifactorial in origin. In recent years there has been renewed interest in non-primary forms of dystonia including the dystonia-plus syndromes and heredodegenerative disorders. These are caused by a variety of genetic mutations and their study has contributed to our understanding of the neuronal dysfunction that leads to dystonia These findings have reinforced themes identified from study of primary dystonia including abnormal dopaminergic signalling, cellular trafficking and mitochondrial function. In this review we highlight recent advances in the understanding of the dystonia-plus syndromes and heredodegenerative dystonias.
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Affiliation(s)
- Catharina Casper
- Department of Clinical Neurosciences, UCL Institute of Neurology, Royal Free Campus, Rowland Hill Street, London NW3 2PF, United Kingdom
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16
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Trinh MA, Klann E. Translational control by eIF2α kinases in long-lasting synaptic plasticity and long-term memory. Neurobiol Learn Mem 2013; 105:93-9. [PMID: 23707798 DOI: 10.1016/j.nlm.2013.04.013] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 04/25/2013] [Accepted: 04/25/2013] [Indexed: 01/10/2023]
Abstract
Although the requirement for new protein synthesis in synaptic plasticity and memory has been well established, recent genetic, molecular, electrophysiological, and pharmacological studies have broadened our understanding of the translational control mechanisms that are involved in these processes. One of the critical translational control points mediating general and gene-specific translation depends on the phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α) by four regulatory kinases. Here, we review the literature highlighting the important role for proper translational control via regulation of eIF2α phosphorylation by its kinases in long-lasting synaptic plasticity and long-term memory.
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Affiliation(s)
- Mimi A Trinh
- Pharmaceutical Research Division, CNS Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa 251-8555, Japan
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17
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Blocking the eIF2α kinase (PKR) enhances positive and negative forms of cortex-dependent taste memory. J Neurosci 2013; 33:2517-25. [PMID: 23392680 DOI: 10.1523/jneurosci.2322-12.2013] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Age-associated memory deterioration (and the decline in ability to acquire new information) is one of the major diseases of our era. Cognitive enhancement can be achieved by using psycho-stimulants, such as caffeine or nicotine, but very little is known about drugs that can enhance the consolidation phase of memories in the cortex, the brain structure considered to store, at least partially, long-term memories. We used cortex-dependent taste-learning paradigms to test the hypothesis that pharmacological manipulation of the translation initiation eIF2α, which plays a role in hippocampus-dependent memory, can enhance positive or negative forms of taste memories. We found that dephosphorylation (Ser51) of eIF2α, specifically in the cortex, is both correlated with and necessary for normal memory consolidation. To reduce eIF2α phosphorylation and improve memory consolidation, we pharmacologically inhibited one of the eIF2α kinases, PKR, which is known to be involved in brain aging and Alzheimer's disease. Systemic or local microinjection of PKR inhibitor to the gustatory cortex enhanced both positive and negative forms of taste memory in rats and mice. Our results provide clear evidence that PKR plays a major role in cortex-dependent memory consolidation and, therefore, that pharmacological inhibition of PKR is a potential target for drugs to enhance cognition.
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Abstract
The double-stranded RNA-dependent protein kinase PKR plays multiple roles in cells, in response to different stress situations. As a member of the interferon (IFN)‑Stimulated Genes, PKR was initially recognized as an actor in the antiviral action of IFN, due to its ability to control translation, through phosphorylation, of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). As such, PKR participates in the generation of stress granules, or autophagy and a number of viruses have designed strategies to inhibit its action. However, PKR deficient mice resist most viral infections, indicating that PKR may play other roles in the cell other than just acting as an antiviral agent. Indeed, PKR regulates several signaling pathways, either as an adapter protein and/or using its kinase activity. Here we review the role of PKR as an eIF2α kinase, its participation in the regulation of the NF-κB, p38MAPK and insulin pathways, and we focus on its role during infection with the hepatitis C virus (HCV). PKR binds the HCV IRES RNA, cooperates with some functions of the HCV core protein and may represent a target for NS5A or E2. Novel data points out for a role of PKR as a pro-HCV agent, both as an adapter protein and as an eIF2α-kinase, and in cooperation with the di-ubiquitin-like protein ISG15. Developing pharmaceutical inhibitors of PKR may help in resolving some viral infections as well as stress-related damages.
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Affiliation(s)
- Stéphanie Dabo
- Unit Hepacivirus and Innate Immunity, Department Virology, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France.
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Abstract
OBJECTIVE DYT16 is an autosomal recessive dystonia-parkinsonism due to putative mutations at PRKRA gene. The aim of this study was to describe clinical features providing video documentation of patients with DYT16 dystonia. METHODS We examined and videotaped all homozygous carriers of the DYT16 gene. RESULTS We identified two phenotypes, generalised dystonia and dystonia-parkinsonism non-responsive to levo-dopa, with three patients belonging to each of the groups. There was inter-individual and intra-family phenotypic heterogeneity. CONCLUSIONS DYT16 is a rare autosomal recessive dystonia characterised by generalised dystonia or dystonia-parkinsonism. Patients are refractory to pharmacological therapy.
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Affiliation(s)
- Sarah Camargos
- Movement Disorders Clinic, Hospital das Clínicas, Departamento de Clínica, Médica, Faculdade de Medicina da Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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Increased cerebrospinal fluid levels of double-stranded RNA-dependant protein kinase in Alzheimer's disease. Biol Psychiatry 2012; 71:829-35. [PMID: 22281122 DOI: 10.1016/j.biopsych.2011.11.031] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 11/16/2011] [Accepted: 11/16/2011] [Indexed: 12/31/2022]
Abstract
BACKGROUND The pathological hallmarks of Alzheimer's disease (AD) include accumulation of amyloid-β (Aß) peptide forming extracellular senile plaques, neurofibrillary tangles made of hyperphosphorylated tau protein with neuronal loss. Aβ peptide (1-42), total tau (T-tau), and phosphorylated tau at threonine 181 (p181tau) levels in the cerebrospinal fluid (CSF) are now validated biomarkers. The proapoptotic kinase R (PKR), is activated by Aβ accumulates in degenerating neurons in AD brains and controls protein synthesis and indirectly tau phosphorylation. METHODS In a prospective cohort study, the CSF of 91 patients were studied (AD: 45; amnestic mild cognitive impairment: 11; neurological disease control subjects [NDC]: 35). The levels of total PKR (T-PKR), phosphorylated PKR (pPKR), Aß 1-42, T-tau, and p181tau were assessed by immunoblotting or enzyme-linked immunosorbent assay methods. Receivers operating characteristic curves were used to examine the discriminatory power of T-PKR, pPKR, and pPKR/T-PKR ratio between AD and NDC patients. RESULTS Total PKR and pPKR concentrations were elevated in AD and amnestic mild cognitive impairment subjects. We have determined a pPKR value (optical density units) that could discriminate AD patients from control subjects with a sensitivity of 91.1% and a specificity of 94.3%. Among AD patients, T-PKR and pPKR levels correlate with CSF p181tau levels. Some AD patients with normal CSF Aß, T-tau, or p181tau levels had abnormal T-PKR and pPKR levels. CONCLUSIONS The evaluation of CSF T-PKR and pPKR can discriminate between AD patients and NDC and could help to improve the biochemical diagnosis of AD.
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Zhu PJ, Huang W, Kalikulov D, Yoo JW, Placzek AN, Stoica L, Zhou H, Bell JC, Friedlander MJ, Krnjević K, Noebels JL, Costa-Mattioli M. Suppression of PKR promotes network excitability and enhanced cognition by interferon-γ-mediated disinhibition. Cell 2012; 147:1384-96. [PMID: 22153080 DOI: 10.1016/j.cell.2011.11.029] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 09/06/2011] [Accepted: 11/02/2011] [Indexed: 01/20/2023]
Abstract
The double-stranded RNA-activated protein kinase (PKR) was originally identified as a sensor of virus infection, but its function in the brain remains unknown. Here, we report that the lack of PKR enhances learning and memory in several behavioral tasks while increasing network excitability. In addition, loss of PKR increases the late phase of long-lasting synaptic potentiation (L-LTP) in hippocampal slices. These effects are caused by an interferon-γ (IFN-γ)-mediated selective reduction in GABAergic synaptic action. Together, our results reveal that PKR finely tunes the network activity that must be maintained while storing a given episode during learning. Because PKR activity is altered in several neurological disorders, this kinase presents a promising new target for the treatment of cognitive dysfunction. As a first step in this direction, we show that a selective PKR inhibitor replicates the Pkr(-/-) phenotype in WT mice, enhancing long-term memory storage and L-LTP.
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Affiliation(s)
- Ping Jun Zhu
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
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Bryk R, Wu K, Raimundo BC, Boardman PE, Chao P, Conn GL, Anderson E, Cole JL, Duffy NP, Nathan C, Griffin JH. Identification of new inhibitors of protein kinase R guided by statistical modeling. Bioorg Med Chem Lett 2011; 21:4108-14. [DOI: 10.1016/j.bmcl.2011.04.149] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 04/05/2011] [Accepted: 04/07/2011] [Indexed: 11/30/2022]
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Blalock WL, Bavelloni A, Piazzi M, Tagliavini F, Faenza I, Martelli AM, Follo MY, Cocco L. Multiple forms of PKR present in the nuclei of acute leukemia cells represent an active kinase that is responsive to stress. Leukemia 2010; 25:236-45. [PMID: 21072047 DOI: 10.1038/leu.2010.264] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A number of cancers possess constitutive activity of the dsRNA-dependent kinase, PKR. Inhibition of PKR in these cancers leads to tumor cell death. We recently reported the increased presence of PKR phosphorylated on Thr451 (p-T451 PKR) in clinical samples from myelodysplastic syndrome (MDS) patients and acute leukemia cell lines. Whereas p-T451 PKR in low-risk patient samples or PTEN-positive acute leukemia cell lines was mostly cytoplasmic, in high-risk patient samples and acute leukemia cell lines deficient in PTEN, p-T451 PKR was mainly nuclear. As nuclear activity of PKR has not been previously characterized, we examined the status of nuclear PKR in acute leukemia cell lines. Using antibodies to N-terminus, C-terminus and the kinase domain in conjunction with a proteomics approach, we found that PKR exists in diverse molecular weight forms in the nucleus. Analysis of PKR transcripts by reverse transcriptase-PCR, and PKR-derived peptides by MS/MS revealed that these forms were the result of post-translational modifications (PTMs). Biochemical analysis demonstrated that nuclear PKR is an active kinase that can respond to stress. Given the association of PKR with PTEN and the Fanconi complex, these results indicate that PKR likely has other previously unrecognized roles in nuclear signaling that may contribute to leukemic development.
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Affiliation(s)
- W L Blalock
- Department of Human Anatomical Sciences, University of Bologna, Bologna, Italy
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Prion protein interaction with stress-inducible protein 1 enhances neuronal protein synthesis via mTOR. Proc Natl Acad Sci U S A 2010; 107:13147-52. [PMID: 20615969 DOI: 10.1073/pnas.1000784107] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Transmissible spongiform encephalopathies are fatal neurodegenerative diseases caused by the conversion of prion protein (PrP(C)) into an infectious isoform (PrP(Sc)). How this event leads to pathology is not fully understood. Here we demonstrate that protein synthesis in neurons is enhanced via PrP(C) interaction with stress-inducible protein 1 (STI1). We also show that neuroprotection and neuritogenesis mediated by PrP(C)-STI1 engagement are dependent upon the increased protein synthesis mediated by PI3K-mTOR signaling. Strikingly, the translational stimulation mediated by PrP(C)-STI1 binding is corrupted in neuronal cell lines persistently infected with PrP(Sc), as well as in primary cultured hippocampal neurons acutely exposed to PrP(Sc). Consistent with this, high levels of eukaryotic translation initiation factor 2alpha (eIF2alpha) phosphorylation were found in PrP(Sc)-infected cells and in neurons acutely exposed to PrP(Sc). These data indicate that modulation of protein synthesis is critical for PrP(C)-STI1 neurotrophic functions, and point to the impairment of this process during PrP(Sc) infection as a possible contributor to neurodegeneration.
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Abstract
Infection of cultured cells with lytic animal viruses often results in the selective inhibition of host protein synthesis, whereas viral mRNA is efficiently translated under these circumstances. This phenomenon, known as "shut off," has been well described at the molecular level for some viruses, but there is not yet any direct or indirect evidence supporting the idea that it also should operate in animals infected with viruses. To address this issue, we constructed recombinant Sindbis virus (SV)-expressing reporter mRNA, the translation of which is sensitive or resistant to virus-induced shut off. As found in cultured cells, replication of SV in mouse brain was associated with a strong phosphorylation of eukaryotic initiation factor (eIF2) that prevented translation of reporter mRNA (luciferase and EGFP). Translation of these reporters was restored in vitro, in vivo, and ex vivo when a viral RNA structure, termed downstream hairpin loop, present in viral 26S mRNA, was placed at the 5' end of reporter mRNAs. By comparing the expression of shut off-sensitive and -resistant reporters, we unequivocally concluded that replication of SV in animal tissues is associated with a profound inhibition of nonviral mRNA translation. A strategy as simple as that followed here might be applicable to other viruses to evaluate their interference on host translation in infected animals.
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Blalock WL, Bavelloni A, Piazzi M, Faenza I, Cocco L. A role for PKR in hematologic malignancies. J Cell Physiol 2010; 223:572-91. [PMID: 20232306 DOI: 10.1002/jcp.22092] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The double-stranded RNA-dependent kinase PKR has been described for many years as strictly a pro-apoptotic kinase. Recent data suggest that the main purpose of this kinase is damage control and repair following stress and, if all else fails, apoptosis. Aberrant activation of PKR has been reported in numerous neurodegenerative diseases and cancer. Although a subset of myelodysplastic syndromes (MDS) and chronic lymphocytic leukemia contain low levels of PKR expression and activity, elevated PKR activity and/or expression have been detected in a wide range of hematologic malignancies, from bone marrow failure disorders to acute leukemia. With the recent findings that cancers containing elevated PKR activity are highly sensitive to PKR inhibition, we explore the role of PKR in hematologic malignancies, signal transduction pathways affected by PKR, and how PKR may contribute to leukemic transformation.
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Affiliation(s)
- William L Blalock
- Department of Human Anatomical Sciences, University of Bologna, Bologna, Italy
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Distribution of apoptosis-related proteins in sporadic Creutzfeldt–Jakob disease. Brain Res 2010; 1323:192-9. [DOI: 10.1016/j.brainres.2010.01.089] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 01/29/2010] [Accepted: 01/30/2010] [Indexed: 02/06/2023]
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Hugon J, Paquet C, Chang RCC. Could PKR inhibition modulate human neurodegeneration? Expert Rev Neurother 2009; 9:1455-7. [PMID: 19831834 DOI: 10.1586/ern.09.92] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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