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Balczon R, Choi CS, deWeever A, Zhou C, Gwin MS, Kolb C, Francis CM, Lin MT, Stevens T. Infection promotes Ser-214 phosphorylation important for generation of cytotoxic tau variants. FASEB J 2023; 37:e23042. [PMID: 37358817 DOI: 10.1096/fj.202300620rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/02/2023] [Accepted: 06/07/2023] [Indexed: 06/27/2023]
Abstract
Patients who recover from hospital-acquired pneumonia exhibit a high incidence of end-organ dysfunction following hospital discharge, including cognitive deficits. We have previously demonstrated that pneumonia induces the production and release of cytotoxic oligomeric tau from pulmonary endothelial cells, and these tau oligomers can enter the circulation and may be a cause of long-term morbidities. Endothelial-derived oligomeric tau is hyperphosphorylated during infection. The purpose of these studies was to determine whether Ser-214 phosphorylation of tau is a necessary stimulus for generation of cytotoxic tau variants. The results of these studies demonstrate that Ser-214 phosphorylation is critical for the cytotoxic properties of infection-induced oligomeric tau. In the lung, Ser-214 phosphorylated tau contributes to disruption of the alveolar-capillary barrier, resulting in increased permeability. However, in the brain, both the Ser-214 phosphorylated tau and the mutant Ser-214-Ala tau, which cannot be phosphorylated, disrupted hippocampal long-term potentiation suggesting that inhibition of long-term potentiation was relatively insensitive to the phosphorylation status of Ser-214. Nonetheless, phosphorylation of tau is essential to its cytotoxicity since global dephosphorylation of the infection-induced cytotoxic tau variants rescued long-term potentiation. Collectively, these data demonstrate that multiple forms of oligomeric tau are generated during infectious pneumonia, with different forms of oligomeric tau being responsible for dysfunction of distinct end-organs during pneumonia.
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Affiliation(s)
- Ron Balczon
- Department of Biochemistry and Molecular Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Chung-Sik Choi
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Althea deWeever
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Chun Zhou
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Meredith S Gwin
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Claire Kolb
- Department of Biochemistry and Molecular Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - C Michael Francis
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Mike T Lin
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
| | - Troy Stevens
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, USA
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Montalto G, Ricciarelli R. Tau, tau kinases, and tauopathies: An updated overview. Biofactors 2023. [PMID: 36688478 DOI: 10.1002/biof.1930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 12/13/2022] [Indexed: 01/24/2023]
Abstract
Tau is a macrotubule-associated protein primarily involved in the stabilization of the cytoskeleton. Under normal conditions, phosphorylation reduces the affinity of tau for tubulin, allowing the protein to detach from microtubules and ensuring the system dynamics in neuronal cells. However, hyperphosphorylated tau aggregates into paired helical filaments, the main constituents of neurofibrillary tangles found in the brains of patients with Alzheimer's disease and other tauopathies. In this review, we provide an overview of the structure of tau and the pathophysiological roles of tau phosphorylation. We also evaluate the major protein kinases involved and discuss the progress made in the development of drug therapies aimed at inhibiting tau kinases.
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Affiliation(s)
- Giulia Montalto
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
| | - Roberta Ricciarelli
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
- IRCCS Ospedale Policlinico San Martino, Genoa, Italy
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Villa V, Montalto G, Caudano F, Fedele E, Ricciarelli R. Selective inhibition of phosphodiesterase 4D increases tau phosphorylation at Ser214 residue. Biofactors 2022; 48:1111-1117. [PMID: 35561079 PMCID: PMC9790528 DOI: 10.1002/biof.1847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 04/29/2022] [Indexed: 12/30/2022]
Abstract
Tau is a protein that normally participates in the assembly and stability of microtubules. However, it can form intraneuronal hyperphosphorylated aggregates that are hallmarks of Alzheimer's disease and other neurodegenerative disorders known as tauopathies. Tau can be phosphorylated by multiple kinases at several sites. Among such kinases, the cAMP-dependent protein kinase A (PKA) phosphorylates tau at Ser214 (pTAU-S214), an event that was shown to reduce the pathological assembly of the protein. Given that the neuronal cAMP/PKA-activated cascade is involved in synaptic plasticity and memory, and that cAMP-enhancing strategies demonstrated promising therapeutic potential for the treatment of cognitive deficits, we investigated the impact of cAMP on pTAU-S214 in N2a cells and rat hippocampal slices. Our results confirm that the activation of adenylyl cyclase increases pTAU-S214 in both model systems and, more interestingly, this effect is mimicked by GEBR-7b, a phosphodiesterase 4D inhibitor with proven pro-cognitive efficacy in rodents.
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Affiliation(s)
- Viviana Villa
- Department of Experimental Medicine, Section of General Pathology, School of Medical and Pharmaceutical SciencesUniversity of GenoaGenoaItaly
| | - Giulia Montalto
- Department of Experimental Medicine, Section of General Pathology, School of Medical and Pharmaceutical SciencesUniversity of GenoaGenoaItaly
| | - Francesca Caudano
- Department of Experimental Medicine, Section of General Pathology, School of Medical and Pharmaceutical SciencesUniversity of GenoaGenoaItaly
| | - Ernesto Fedele
- Department of Pharmacy, Section of Pharmacology and Toxicology, School of Medical and Pharmaceutical SciencesUniversity of GenoaGenoaItaly
- IRCCS Ospedale Policlinico San MartinoGenoaItaly
| | - Roberta Ricciarelli
- Department of Experimental Medicine, Section of General Pathology, School of Medical and Pharmaceutical SciencesUniversity of GenoaGenoaItaly
- IRCCS Ospedale Policlinico San MartinoGenoaItaly
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A New Bistable Switch Model of Alzheimer’s Disease Pathogenesis. Int J Mol Sci 2022; 23:ijms23137061. [PMID: 35806088 PMCID: PMC9267076 DOI: 10.3390/ijms23137061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 06/23/2022] [Accepted: 06/24/2022] [Indexed: 02/04/2023] Open
Abstract
We propose a model to explain the pathogenesis of Alzheimer’s disease (AD) based on the theory that any disease affecting a healthy organism originates from a bistable feedback loop that shifts the system from a physiological to a pathological condition. We focused on the known double inhibitory loop involving the cellular prion protein (PrPC) and the enzyme BACE1 that produces amyloid-beta (Aβ) peptides. BACE1 is inhibited by PrPC, but its inhibitory activity is lost when PrPC binds to Aβ oligomers (Aβo). Excessive Aβo formation would switch the loop to a pathogenic condition involving the Aβo-PrPC-mGluR5 complex, Fyn kinase activation, tau, and NMDAR phosphorylation, ultimately leading to neurodegeneration. Based on the emerging role of cyclic nucleotides in Aβ production, and thereby in synaptic plasticity and cognitive processes, cAMP and cGMP can be considered as modulatory factors capable of inducing the transition from a physiological steady state to a pathogenic one. This would imply that critical pharmacological targets for AD treatment lie within pathways that lead to an imbalance of cyclic nucleotides in neurons. If this hypothesis is confirmed, it will provide precise indications for the development of preventive or therapeutic treatments for the disease.
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Jehle A, Garaschuk O. The Interplay between cGMP and Calcium Signaling in Alzheimer’s Disease. Int J Mol Sci 2022; 23:ijms23137048. [PMID: 35806059 PMCID: PMC9266933 DOI: 10.3390/ijms23137048] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 05/31/2022] [Accepted: 06/22/2022] [Indexed: 02/04/2023] Open
Abstract
Cyclic guanosine monophosphate (cGMP) is a ubiquitous second messenger and a key molecule in many important signaling cascades in the body and brain, including phototransduction, olfaction, vasodilation, and functional hyperemia. Additionally, cGMP is involved in long-term potentiation (LTP), a cellular correlate of learning and memory, and recent studies have identified the cGMP-increasing drug Sildenafil as a potential risk modifier in Alzheimer’s disease (AD). AD development is accompanied by a net increase in the expression of nitric oxide (NO) synthases but a decreased activity of soluble guanylate cyclases, so the exact sign and extent of AD-mediated imbalance remain unclear. Moreover, human patients and mouse models of the disease present with entangled deregulation of both cGMP and Ca2+ signaling, e.g., causing changes in cGMP-mediated Ca2+ release from the intracellular stores as well as Ca2+-mediated cGMP production. Still, the mechanisms governing such interplay are poorly understood. Here, we review the recent data on mechanisms underlying the brain cGMP signaling and its interconnection with Ca2+ signaling. We also discuss the recent evidence stressing the importance of such interplay for normal brain function as well as in Alzheimer’s disease.
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