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Iwata Y, Nakade Y, Kitajima S, Nakagawa SY, Oshima M, Sakai N, Ogura H, Sato K, Toyama T, Yamamura Y, Miyagawa T, Yamazaki H, Hara A, Shimizu M, Furuichi K, Mita M, Hamase K, Tanaka T, Nishida M, Muramatsu W, Yamamoto H, Shichino S, Ueha S, Matsushima K, Wada T. Protective Effect of D-Alanine Against Acute Kidney Injury. Am J Physiol Renal Physiol 2022; 322:F667-F679. [PMID: 35435002 DOI: 10.1152/ajprenal.00198.2021] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Recent studies revealed the connection between amino acid chirality and diseases. We previously reported that the gut microbiota produced various D-amino acids in a murine acute kidney injury (AKI) model. Here, we further explore the pathophysiological role of D-Alanine (Ala) in AKI. METHODS We analyzed the transcripts of the N-methyl-D-aspartate (NMDA) receptor, a receptor for D-Ala, in tubular epithelial cells (TECs). Then, the therapeutic effect of D-Ala was assessed in vivo and in vitro. Lastly, the plasma level of D-Ala was evaluated in AKI patients. RESULTS The Grin genes encoding NMDA receptor subtypes were expressed in TECs. Hypoxia condition changes the gene expressions of Grin1, Grin2A and Grin2B. D-Ala protected TECs from hypoxia-related cell injury and induced proliferation after hypoxia. These protective effects are associated with the chirality of D-Ala. D-Ala inhibits ROS production and improves mitochondrial membrane potential, through NMDA receptor signaling. The ratio of D-Ala/L-Ala was increased in feces, plasma, and urine after the induction of I/R. Moreover, enterobacteriaceae, such as Escherichia coli, Klebsiella oxytoca produced D-Ala. The oral administration of D-Ala ameliorated kidney injury after I/R induction in mice. The deficiency of NMDA subunit NR1 on tubular cell worsened kidney damage in AKI. In addition, the plasma level of D-Ala was increased and reflected the level of renal function in AKI patients. CONCLUSIONS D-Ala has protective effects on I/R-induced kidney injury. Moreover, the plasma level of D-Ala reflects the eGFR in AKI patients. D-Ala could be a promising therapeutic target and potential biomarker for AKI.
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Affiliation(s)
- Yasunori Iwata
- Division of Infection Control, Kanazawa University Hospital, Kanazawa, Japan.,Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Yusuke Nakade
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Shinji Kitajima
- Division of Blood Purification, Kanazawa University Hospital, Kanazawa, Japan.,Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | | | - Megumi Oshima
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Norihiko Sakai
- Division of Blood Purification, Kanazawa University Hospital, Kanazawa, Japan.,Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Hisayuki Ogura
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Koichi Sato
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Tadashi Toyama
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Yuta Yamamura
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Taro Miyagawa
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Hiroka Yamazaki
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Akinori Hara
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Miho Shimizu
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
| | - Kengo Furuichi
- Division of Nephrology, Kanazawa Medical University School of Medicine, Ishikawa, Kanazawa, Japan
| | | | - Kenji Hamase
- Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Tomohiro Tanaka
- National Institute for Physiological Sciences and Exploratory Research Center on Life and Living Systems and Center for Novel Science Initiatives, National Institutes of Natural Sciences, Aichi, Japan
| | - Motohiro Nishida
- National Institute for Physiological Sciences and Exploratory Research Center on Life and Living Systems and Center for Novel Science Initiatives, National Institutes of Natural Sciences, Aichi, Japan
| | - Wataru Muramatsu
- Molecular Catalyst Research Center, Chubu University, Aichi, Japan
| | - Hisashi Yamamoto
- Molecular Catalyst Research Center, Chubu University, Aichi, Japan
| | - Shigeyuki Shichino
- Division of Molecular Regulation of Inflammatory and Immune Diseases, Research Institute of Biomedical Sciences, Chiba, Tokyo University of Science, Tokyo, Japan
| | - Satoshi Ueha
- Division of Molecular Regulation of Inflammatory and Immune Diseases, Research Institute of Biomedical Sciences, Chiba, Tokyo University of Science, Tokyo, Japan
| | - Kouji Matsushima
- Division of Molecular Regulation of Inflammatory and Immune Diseases, Research Institute of Biomedical Sciences, Chiba, Tokyo University of Science, Tokyo, Japan
| | - Takashi Wada
- Department of Nephrology and Laboratory Medicine, Kanazawa University, Kanazawa, Japan
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Sacchi S, Rabattoni V, Miceli M, Pollegioni L. Yin and Yang in Post-Translational Modifications of Human D-Amino Acid Oxidase. Front Mol Biosci 2021; 8:684934. [PMID: 34041270 PMCID: PMC8141710 DOI: 10.3389/fmolb.2021.684934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 04/23/2021] [Indexed: 11/30/2022] Open
Abstract
In the central nervous system, the flavoprotein D-amino acid oxidase is responsible for catabolizing D-serine, the main endogenous coagonist of N-methyl-D-aspartate receptor. Dysregulation of D-serine brain levels in humans has been associated with neurodegenerative and psychiatric disorders. This D-amino acid is synthesized by the enzyme serine racemase, starting from the corresponding L-enantiomer, and degraded by both serine racemase (via an elimination reaction) and the flavoenzyme D-amino acid oxidase. To shed light on the role of human D-amino acid oxidase (hDAAO) in D-serine metabolism, the structural/functional relationships of this enzyme have been investigated in depth and several strategies aimed at controlling the enzymatic activity have been identified. Here, we focused on the effect of post-translational modifications: by using a combination of structural analyses, biochemical methods, and cellular studies, we investigated whether hDAAO is subjected to nitrosylation, sulfhydration, and phosphorylation. hDAAO is S-nitrosylated and this negatively affects its activity. In contrast, the hydrogen sulfide donor NaHS seems to alter the enzyme conformation, stabilizing a species with higher affinity for the flavin adenine dinucleotide cofactor and thus positively affecting enzymatic activity. Moreover, hDAAO is phosphorylated in cerebellum; however, the protein kinase involved is still unknown. Taken together, these findings indicate that D-serine levels can be also modulated by post-translational modifications of hDAAO as also known for the D-serine synthetic enzyme serine racemase.
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Affiliation(s)
- Silvia Sacchi
- "The Protein Factory 2.0", Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi Dell'Insubria, Varese, Italy
| | - Valentina Rabattoni
- "The Protein Factory 2.0", Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi Dell'Insubria, Varese, Italy
| | - Matteo Miceli
- "The Protein Factory 2.0", Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi Dell'Insubria, Varese, Italy
| | - Loredano Pollegioni
- "The Protein Factory 2.0", Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi Dell'Insubria, Varese, Italy
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3
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Murtas G, Sacchi S, Pollegioni L. Substitution of Arginine 120 in Human D-Amino Acid Oxidase Favors FAD-Binding and Nuclear Mistargeting. Front Mol Biosci 2019; 6:125. [PMID: 31799256 PMCID: PMC6862323 DOI: 10.3389/fmolb.2019.00125] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 10/28/2019] [Indexed: 01/23/2023] Open
Abstract
The peroxisomal enzyme human D-amino acid oxidase (hDAAO) is attracting attention owing to its role in degrading D-serine, the main co-agonist of N-methyl D-aspartate receptors in brain, and its involvement in brain functions and diseases. Here, we focused on arginine 120, a residue located at the protein interface, 20 Å from the assumed second ligand-binding site, showing a different orientation of the side chain in the hDAAO-benzoate complex, and corresponding to Ser119 in rat DAAO, which is part of a putative nuclear translocation signal (NTS). By substituting Arg120 in hDAAO with a glutamate (to mimic the active NTS) or a leucine (to eliminate the positive charge) the protein conformation, thermal stability, and kinetic properties are slightly altered, while the dimeric structure and the ligand-binding properties are unchanged. The most relevant alteration in Arg120 variants is the strongest interaction with FAD. Nevertheless, the activity assayed at low D-serine and FAD concentrations (resembling physiological conditions) was quite similar for wild-type and Arg120 hDAAO variants. These results resemble the ones obtained substituting another residue located at the interface region (i.e., the W209R variant), indicating that substitutions at the monomer-monomer interface mainly affects the FAD binding in hDAAO. Indeed, U87 glioblastoma cells transiently transfected for hDAAO variants show that substitution of Arg120 favors mistargeting: the increase in cytosolic localization observed for the variants promotes nuclear targeting, especially for the R120E hDAAO, without affecting cell viability. Notably, mistargeting to the nucleus is an innate process as it is apparent for the wild-type hDAAO, too: whether such a process is related to specific pathologic processes is still unknown.
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Affiliation(s)
- Giulia Murtas
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
| | - Silvia Sacchi
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
| | - Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
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Bastings JJ, van Eijk HM, Olde Damink SW, Rensen SS. d-amino Acids in Health and Disease: A Focus on Cancer. Nutrients 2019; 11:nu11092205. [PMID: 31547425 PMCID: PMC6770864 DOI: 10.3390/nu11092205] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/06/2019] [Accepted: 09/09/2019] [Indexed: 01/09/2023] Open
Abstract
d-amino acids, the enantiomeric counterparts of l-amino acids, were long considered to be non-functional or not even present in living organisms. Nowadays, d-amino acids are acknowledged to play important roles in numerous physiological processes in the human body. The most commonly studied link between d-amino acids and human physiology concerns the contribution of d-serine and d-aspartate to neurotransmission. These d-amino acids and several others have also been implicated in regulating innate immunity and gut barrier function. Importantly, the presence of certain d-amino acids in the human body has been linked to several diseases including schizophrenia, amyotrophic lateral sclerosis, and age-related disorders such as cataract and atherosclerosis. Furthermore, increasing evidence supports a role for d-amino acids in the development, pathophysiology, and treatment of cancer. In this review, we aim to provide an overview of the various sources of d-amino acids, their metabolism, as well as their contribution to physiological processes and diseases in man, with a focus on cancer.
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Affiliation(s)
- Jacco J.A.J. Bastings
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200 MD Maastricht, The Netherlands (H.M.v.E.); (S.W.O.D.)
- Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200 MD Maastricht, The Netherlands
| | - Hans M. van Eijk
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200 MD Maastricht, The Netherlands (H.M.v.E.); (S.W.O.D.)
| | - Steven W. Olde Damink
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200 MD Maastricht, The Netherlands (H.M.v.E.); (S.W.O.D.)
- Department of General, Visceral and Transplantation Surgery, RWTH University Hospital Aachen, 52074 Aachen, Germany
| | - Sander S. Rensen
- Department of Surgery, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200 MD Maastricht, The Netherlands (H.M.v.E.); (S.W.O.D.)
- Correspondence:
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Pollegioni L, Sacchi S, Murtas G. Human D-Amino Acid Oxidase: Structure, Function, and Regulation. Front Mol Biosci 2018; 5:107. [PMID: 30547037 PMCID: PMC6279847 DOI: 10.3389/fmolb.2018.00107] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 11/12/2018] [Indexed: 12/11/2022] Open
Abstract
D-Amino acid oxidase (DAAO) is an FAD-containing flavoenzyme that catalyzes with absolute stereoselectivity the oxidative deamination of all natural D-amino acids, the only exception being the acidic ones. This flavoenzyme plays different roles during evolution and in different tissues in humans. Its three-dimensional structure is well conserved during evolution: minute changes are responsible for the functional differences between enzymes from microorganism sources and those from humans. In recent years several investigations focused on human DAAO, mainly because of its role in degrading the neuromodulator D-serine in the central nervous system. D-Serine is the main coagonist of N-methyl D-aspartate receptors, i.e., excitatory amino acid receptors critically involved in main brain functions and pathologic conditions. Human DAAO possesses a weak interaction with the FAD cofactor; thus, in vivo it should be largely present in the inactive, apoprotein form. Binding of active-site ligands and the substrate stabilizes flavin binding, thus pushing the acquisition of catalytic competence. Interestingly, the kinetic efficiency of the enzyme on D-serine is very low. Human DAAO interacts with various proteins, in this way modulating its activity, targeting, and cell stability. The known properties of human DAAO suggest that its activity must be finely tuned to fulfill a main physiological function such as the control of D-serine levels in the brain. At present, studies are focusing on the epigenetic modulation of human DAAO expression and the role of post-translational modifications on its main biochemical properties at the cellular level.
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Affiliation(s)
- Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
| | - Silvia Sacchi
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
| | - Giulia Murtas
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
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Identification of d-amino acid oxidase and propiverine interaction partners and their potential role in the propiverine-mediated nephropathy. Chem Biol Interact 2017; 281:69-80. [PMID: 29273565 DOI: 10.1016/j.cbi.2017.12.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 12/11/2017] [Accepted: 12/13/2017] [Indexed: 11/20/2022]
Abstract
Propiverine, a frequently-prescribed pharmaceutical for the treatment of symptoms associated with overactive bladder syndrome, provoked massive intranuclear and cytosolic protein inclusions in rat proximal tubule epithelium, primarily consisting of the peroxisomal targeting signal 1 (PTS1) containing protein d-amino acid oxidase (DAAO). As this type of nephropathy was also observed for other drugs, the aim was to determine whether propiverine interferes with trafficking and/or import of peroxisomal proteins. To elucidate this, DAAO- and propiverine-specific interaction partners from human HEK293 and rat WKPT cell lines and rat kidney and liver homogenate were determined using co-immunoprecipitation with subsequent nano-ESI-LC-MS/MS analyses. Corroboration of the role of DAAO- and/or propiverine-specific interaction partners in the drug-induced DAAO accumulation was sought via specific immunofluorescence staining of rat kidney sections from control and propiverine-treated rats. Above analyses demonstrated the interaction of propiverine with several protein classes, foremost peroxisomal proteins (DAAO, MFE2, HAOX2) and proteins of the protein quality control system, i.e. chaperones (HSP70 and DnaJ co-chaperones), proteases and proteasomal proteins (regulatory subunits of the 26S proteasome; Rpn1/2). The immunofluorescence analysis revealed mislocalization of many PTS1-proteins (DAAO, CAT, MFE2, ACOX1, EHHADH) in rat renal sections, strongly suggesting that propiverine primarily binds to PTS1 proteins resulting in the formation of PTS1 but not PTS2 or peroxisomal membrane protein (PMP) accumulations. Moreover, chaperones involved in peroxisomal trafficking (HSC70, DnaJB1) and peroxisomal biogenesis factor proteins (PEX3, PEX5, PEX7), also presented with distinct mislocalization patterns. Concomitantly, an increased number of peroxisomes was observed, suggestive of a compensatory mechanism for the presumably suboptimally functioning peroxisomes. Overall, the data presented suggested that propiverine interacts exclusively with DAAO or with a selected number of PTS1 proteins. The consequence of this interaction is the abrogated trafficking and peroxisomal import of PTS1 proteins concomitant with their nuclear and cytosolic accumulation due to inhibited degradation and imbalanced protein homeostasis.
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Murtas G, Sacchi S, Valentino M, Pollegioni L. Biochemical Properties of Human D-Amino Acid Oxidase. Front Mol Biosci 2017; 4:88. [PMID: 29326945 PMCID: PMC5737116 DOI: 10.3389/fmolb.2017.00088] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 12/05/2017] [Indexed: 02/03/2023] Open
Abstract
D-amino acid oxidase catalyzes the oxidative deamination of D-amino acids. In the brain, the NMDA receptor coagonist D-serine has been proposed as its physiological substrate. In order to shed light on the mechanisms regulating D-serine concentration at the cellular level, we biochemically characterized human DAAO (hDAAO) in greater depth. In addition to clarify the physical-chemical properties of the enzyme, we demonstrated that divalent ions and nucleotides do not affect flavoenzyme function. Moreover, the definition of hDAAO substrate specificity demonstrated that D-cysteine is the best substrate, which made it possible to propose it as a putative physiological substrate in selected tissues. Indeed, the flavoenzyme shows a preference for hydrophobic amino acids, some of which are molecules relevant in neurotransmission, i.e., D-kynurenine, D-DOPA, and D-tryptophan. hDAAO shows a very low affinity for the flavin cofactor. The apoprotein form exists in solution in equilibrium between two alternative conformations: the one at higher affinity for FAD is favored in the presence of an active site ligand. This may represent a mechanism to finely modulate hDAAO activity by substrate/inhibitor presence. Taken together, the peculiar properties of hDAAO seem to have evolved in order to use this flavoenzyme in different tissues to meet different physiological needs related to D-amino acids.
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Affiliation(s)
- Giulia Murtas
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy
| | - Silvia Sacchi
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy.,The Protein Factory, Politecnico di Milano and Università degli Studi dell'Insubria, Milan, Italy
| | - Mattia Valentino
- The Protein Factory, Politecnico di Milano and Università degli Studi dell'Insubria, Milan, Italy.,Sezione Adolfo Quilico, Istituto di Chimica del Riconoscimento Molecolare, CNR, Milan, Italy
| | - Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy.,The Protein Factory, Politecnico di Milano and Università degli Studi dell'Insubria, Milan, Italy
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Koga R, Miyoshi Y, Sakaue H, Hamase K, Konno R. Mouse d-Amino-Acid Oxidase: Distribution and Physiological Substrates. Front Mol Biosci 2017; 4:82. [PMID: 29255714 PMCID: PMC5722847 DOI: 10.3389/fmolb.2017.00082] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/14/2017] [Indexed: 01/05/2023] Open
Abstract
d-Amino-acid oxidase (DAO) catalyzes the oxidative deamination of d-amino acids. DAO is present in a wide variety of organisms and has important roles. Here, we review the distribution and physiological substrates of mouse DAO. Mouse DAO is present in the kidney, brain, and spinal cord, like DAOs in other mammals. However, in contrast to other animals, it is not present in the mouse liver. Recently, DAO has been detected in the neutrophils, retina, and small intestine in mice. To determine the physiological substrates of mouse DAO, mutant mice lacking DAO activity are helpful. As DAO has wide substrate specificity and degrades various d-amino acids, many d-amino acids accumulate in the tissues and body fluids of the mutant mice. These amino acids are d-methionine, d-alanine, d-serine, d-leucine, d-proline, d-phenylalanine, d-tyrosine, and d-citrulline. Even in wild-type mice, administration of DAO inhibitors elevates D-serine levels in the plasma and brain. Among the above d-amino acids, the main physiological substrates of mouse DAO are d-alanine and d-serine. These two d-amino acids are most abundant in the tissues and body fluids of mice. d-Alanine derives from bacteria and produces bactericidal reactive oxygen species by the action of DAO. d-Serine is synthesized by serine racemase and is present especially in the central nervous system, where it serves as a neuromodulator. DAO is responsible for the metabolism of d-serine. Since DAO has been implicated in the etiology of neuropsychiatric diseases, mouse DAO has been used as a representative model. Recent reports, however, suggest that mouse DAO is different from human DAO with respect to important properties.
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Affiliation(s)
- Reiko Koga
- Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan
| | - Yurika Miyoshi
- Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Hiroaki Sakaue
- Department of Biochemistry, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
| | - Kenji Hamase
- Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Ryuichi Konno
- Department of Pharmacological Sciences, International University of Health and Welfare, Ohtawara, Japan
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Understanding renal nuclear protein accumulation: an in vitro approach to explain an in vivo phenomenon. Arch Toxicol 2017; 91:3599-3611. [PMID: 28451739 DOI: 10.1007/s00204-017-1970-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 04/19/2017] [Indexed: 01/01/2023]
Abstract
Proper subcellular trafficking is essential to prevent protein mislocalization and aggregation. Transport of the peroxisomal enzyme D-amino acid oxidase (DAAO) appears dysregulated by specific pharmaceuticals, e.g., the anti-overactive bladder drug propiverine or a norepinephrine/serotonin reuptake inhibitor (NSRI), resulting in massive cytosolic and nuclear accumulations in rat kidney. To assess the underlying molecular mechanism of the latter, we aimed to characterize the nature of peroxisomal and cyto-nuclear shuttling of human and rat DAAO overexpressed in three cell lines using confocal microscopy. Indeed, interference with peroxisomal transport via deletion of the PTS1 signal or PEX5 knockdown resulted in induced nuclear DAAO localization. Having demonstrated the absence of active nuclear import and employing variably sized mCherry- and/or EYFP-fusion proteins of DAAO and catalase, we showed that peroxisomal proteins ≤134 kDa can passively diffuse into mammalian cell nuclei-thereby contradicting the often-cited 40 kDa diffusion limit. Moreover, their inherent nuclear presence and nuclear accumulation subsequent to proteasome inhibition or abrogated peroxisomal transport suggests that nuclear localization is a characteristic in the lifecycle of peroxisomal proteins. Based on this molecular trafficking analysis, we suggest that pharmaceuticals like propiverine or an NSRI may interfere with peroxisomal protein targeting and import, consequently resulting in massive nuclear protein accumulation in vivo.
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