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Abstract
Drug metabolizing enzymes catalyze the biotransformation of many of drugs and chemicals. The drug metabolizing enzymes are distributed among several evolutionary families and catalyze a range of detoxication reactions, including oxidation/reduction, conjugative, and hydrolytic reactions that serve to detoxify potentially toxic compounds. This detoxication function requires that drug metabolizing enzymes exhibit substrate promiscuity. In addition to their catalytic functions, many drug metabolizing enzymes possess functions unrelated to or in addition to catalysis. Such proteins are termed 'moonlighting proteins' and are defined as proteins with multiple biochemical or biophysical functions that reside in a single protein. This review discusses the diverse moonlighting functions of drug metabolizing enzymes and the roles they play in physiological functions relating to reproduction, vision, cell signaling, cancer, and transport. Further research will likely reveal new examples of moonlighting functions of drug metabolizing enzymes.
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Affiliation(s)
- Philip G Board
- John Curtin School of Medical Research, ANU College of Health and Medicine, The Australian National University, Canberra, ACT, Australia
| | - M W Anders
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, NY, USA
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2
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Abstract
The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.
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Affiliation(s)
- Patrick E Hanna
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - M W Anders
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
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Richardson SJ, Steele GA, Gallant EM, Lam A, Schwartz CE, Board PG, Casarotto MG, Beard NA, Dulhunty AF. Association of FK506 binding proteins with RyR channels - effect of CLIC2 binding on sub-conductance opening and FKBP binding. J Cell Sci 2017; 130:3588-3600. [PMID: 28851804 DOI: 10.1242/jcs.204461] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 07/31/2017] [Indexed: 12/22/2022] Open
Abstract
Ryanodine receptor (RyR) Ca2+ channels are central to striated muscle function and influence signalling in neurons and other cell types. Beneficially low RyR activity and maximum conductance opening may be stabilised when RyRs bind to FK506 binding proteins (FKBPs) and destabilised by FKBP dissociation, with submaximal opening during RyR hyperactivity associated with myopathies and neurological disorders. However, the correlation with submaximal opening is debated and quantitative evidence is lacking. Here, we have measured altered FKBP binding to RyRs and submaximal activity with addition of wild-type (WT) CLIC2, an inhibitory RyR ligand, or its H101Q mutant that hyperactivates RyRs, which probably causes cardiac and intellectual abnormalities. The proportion of sub-conductance opening increases with WT and H101Q CLIC2 and is correlated with reduced FKBP-RyR association. The sub-conductance opening reduces RyR currents in the presence of WT CLIC2. In contrast, sub-conductance openings contribute to excess RyR 'leak' with H101Q CLIC2. There are significant FKBP and RyR isoform-specific actions of CLIC2, rapamycin and FK506 on FKBP-RyR association. The results show that FKBPs do influence RyR gating and would contribute to excess Ca2+ release in this CLIC2 RyR channelopathy.
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Affiliation(s)
- Spencer J Richardson
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, PO Box 334, ACT 2601, Australia
| | - Gregory A Steele
- Capital Pathology Laboratory, 70 Kent St, Deakin, ACT 2600, Australia
| | - Esther M Gallant
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, PO Box 334, ACT 2601, Australia
| | - Alexander Lam
- Neurosurgery, Royal Perth Hospital, 197 Wellington St, Perth, WA 6000, Australia
| | - Charles E Schwartz
- JC Self Research Institute, Greenwood Genetic Center, Greenwood, SC 29646, USA
| | - Philip G Board
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, PO Box 334, ACT 2601, Australia
| | - Marco G Casarotto
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, PO Box 334, ACT 2601, Australia
| | - Nicole A Beard
- Cardiac Physiology Department, Health Research Institute, Faculty of Education Science and Mathematics, University of Canberra, Bruce, ACT 2617, Australia
| | - Angela F Dulhunty
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, PO Box 334, ACT 2601, Australia
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Dulhunty AF, Board PG, Beard NA, Casarotto MG. Physiology and Pharmacology of Ryanodine Receptor Calcium Release Channels. ADVANCES IN PHARMACOLOGY 2017; 79:287-324. [DOI: 10.1016/bs.apha.2016.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Hewawasam RP, Liu D, Casarotto MG, Board PG, Dulhunty AF. The GSTM2 C-Terminal Domain Depresses Contractility and Ca2+ Transients in Neonatal Rat Ventricular Cardiomyocytes. PLoS One 2016; 11:e0162415. [PMID: 27612301 PMCID: PMC5017731 DOI: 10.1371/journal.pone.0162415] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 08/22/2016] [Indexed: 11/25/2022] Open
Abstract
The cardiac ryanodine receptor (RyR2) is an intracellular ion channel that regulates Ca2+ release from the sarcoplasmic reticulum (SR) during excitation–contraction coupling in the heart. The glutathione transferases (GSTs) are a family of phase II detoxification enzymes with additional functions including the selective inhibition of RyR2, with therapeutic implications. The C-terminal half of GSTM2 (GSTM2C) is essential for RyR2 inhibition, and mutations F157A and Y160A within GSTM2C prevent the inhibitory action. Our objective in this investigation was to determine whether GSTM2C can enter cultured rat neonatal ventricular cardiomyocytes and influence contractility. We show that oregon green-tagged GSTM2C (at 1 μM) is internalized into the myocytes and it reduces spontaneous contraction frequency and myocyte shortening. Field stimulation of myocytes evoked contraction in the same percentage of myocytes treated either with media alone or media plus 15 μM GSTM2C. Myocyte shortening during contraction was significantly reduced by exposure to 15 μM GSTM2C, but not 5 and 10 μM GSTM2C and was unaffected by exposure to 15 μM of the mutants Y160A or F157A. The amplitude of the Ca2+ transient in the 15 μM GSTM2C - treated myocytes was significantly decreased, the rise time was significantly longer and the decay time was significantly shorter than in control myocytes. The Ca2+ transient was not altered by exposure to Y160A or F157A. The results are consistent with GSTM2C entering the myocytes and inhibiting RyR2, in a manner that indicates a possible therapeutic potential for treatment of arrhythmia in the neonatal heart.
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Affiliation(s)
- Ruwani P. Hewawasam
- John Curtin School of Medical Research, The Australian National University, GPO Box 334, Canberra City, ACT 2600, Australia
| | - Dan Liu
- John Curtin School of Medical Research, The Australian National University, GPO Box 334, Canberra City, ACT 2600, Australia
| | - Marco G. Casarotto
- John Curtin School of Medical Research, The Australian National University, GPO Box 334, Canberra City, ACT 2600, Australia
| | - Philip G. Board
- John Curtin School of Medical Research, The Australian National University, GPO Box 334, Canberra City, ACT 2600, Australia
| | - Angela F. Dulhunty
- John Curtin School of Medical Research, The Australian National University, GPO Box 334, Canberra City, ACT 2600, Australia
- * E-mail:
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Structure, function and disease relevance of Omega-class glutathione transferases. Arch Toxicol 2016; 90:1049-67. [PMID: 26993125 DOI: 10.1007/s00204-016-1691-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 03/10/2016] [Indexed: 12/13/2022]
Abstract
The Omega-class cytosolic glutathione transferases (GSTs) have distinct structural and functional attributes that allow them to perform novel roles unrelated to the functions of other GSTs. Mammalian GSTO1-1 has been found to play a previously unappreciated role in the glutathionylation cycle that is emerging as significant mechanism regulating protein function. GSTO1-1-catalyzed glutathionylation or deglutathionylation of a key signaling protein may explain the requirement for catalytically active GSTO1-1 in LPS-stimulated pro-inflammatory signaling through the TLR4 receptor. The observation that ML175 a specific GSTO1-1 inhibitor can block LPS-stimulated inflammatory signaling has opened a new avenue for the development of novel anti-inflammatory drugs that could be useful in the treatment of toxic shock and other inflammatory disorders. The role of GSTO2-2 remains unclear. As a dehydroascorbate reductase, it could contribute to the maintenance of cellular redox balance and it is interesting to note that the GSTO2 N142D polymorphism has been associated with multiple diseases including Alzheimer's disease, Parkinson's disease, familial amyotrophic lateral sclerosis, chronic obstructive pulmonary disease, age-related cataract and breast cancer.
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