Functional Characterization of Ergothioneine Transport by Rat Organic Cation/Carnitine Transporter Octn1 (slc22a4)

Department of Membrane Transport and Pharmacokinetics, Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
Biological & Pharmaceutical Bulletin (Impact Factor: 1.83). 09/2008; 31(8):1580-4. DOI: 10.1248/bpb.31.1580
Source: PubMed


It has been reported that organic cation/carnitine transporter 1 (OCTN1) is associated with rheumatoid arthritis and Crohn's disease. Additionally, we reported that OCTN1 is expressed in hematopoietic cells, and is associated with proliferation and differentiation of erythroid cells. However, physiological role of OCTN1 is still unclear. Ergothioneine, an anti-oxidant, was recently reported to be a good substrate of human OCTN1. However, the transport characteristics of ergothioneine in rat remains to be clarified. The present study, is to further investigate the role of rat Octn1 on transport of ergothioneine in rat Octn1 transfected cells and natively expressing cell line PC12 derived from rat adrenal pheochromocytoma. [(3)H]Ergothioneine uptake by rat Octn1 stably transfected HEK293 cells was saturable, sodium dependent with 1 : 1 stoichiometry of ergothioneine, and pH dependent. Since ergothioneine was reported to presumably play a protective role against oxidative stress-induced apoptosis in PC12 cells, its transport in this cell line was investigated. The expression of rat Octn1 and a saturable and Na(+)-dependent transport of ergothioneine were observed in PC12 cells, suggesting that ergothioneine transport in this cell line may be mediated by rat Octn1. These findings suggested that rat Octn1 may act as a survival factor by taking up ergothioneine to suppress oxidative stress in this cell line. In conclusion, functional characteristics of ergothioneine transport by rat Octn1 is similar to that of human OCTN1 and it is suggested that rat Octn1 is important by transporting anti-oxidant ergothioneine in PC12 cells, though its role in vivo is to be investigated.

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Available from: Toshimichi Nakamura, Jan 28, 2015
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    • "Human fibroblasts possess the OCTN1 transporter and transport ergothioneine in a saturable manner (Figs. 3 and 4). The kinetic constants for ergothioneine transport by human fibroblasts were in the same order of magnitude of those observed for the OCTN1 transporter when expressed in other cells (Grundemann, et al., 2005; Nakamura, et al., 2008). There were no significant differences in ergothioneine transport between control cells and cells from patients with primary carnitine deficiency (Fig. 5). "
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    ABSTRACT: Primary carnitine deficiency is caused by defective OCTN2 carnitine transporters encoded by the SLC22A5 gene. Lack of carnitine impairs fatty acid oxidation resulting in hypoketotic hypoglycemia, hepatic encephalopathy, skeletal and cardiac myopathy. Recently, asymptomatic mothers with primary carnitine deficiency were identified by low carnitine levels in their infant by newborn screening. Here, we evaluate mutations in the SLC22A5 gene and carnitine transport in fibroblasts from symptomatic patients and asymptomatic women. Carnitine transport was significantly reduced in fibroblasts obtained from all patients with primary carnitine deficiency, but was significantly higher in the asymptomatic women's than in the symptomatic patients' fibroblasts (P < 0.01). By contrast, ergothioneine transport (a selective substrate of the OCTN1 transporter, tested here as a control) was similar in cells from controls and patients with carnitine deficiency. DNA sequencing indicated an increased frequency of nonsense mutations in symptomatic patients (P < 0.001). Expression of the missense mutations in Chinese hamster ovary (CHO) cells indicated that many mutations retained residual carnitine transport activity, with no difference in the average activity of missense mutations identified in symptomatic versus asymptomatic patients. These results indicate that cells from asymptomatic women have on average higher levels of residual carnitine transport activity as compared to that of symptomatic patients due to the presence of at least one missense mutation.
    Full-text · Article · Jan 2012 · Human Mutation
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    • "Since ergothioneine is a low molecular weight antioxidant that is plasma membrane impermeable that accumulates in cells subjected to high levels of oxidative stress, its protective function is restricted to cells that express the ergothionene-specific receptor/transporter, organic cation/carnitine transporter 1 (OCTN1) (Gründemann et al., 2005). OCTN1 (gene symbol SLC22A4) is expressed in hematopoietic cells and associated with proliferation and differentiation of erythroid cells (Nakamura et al., 2008). The transporter is functionally expressed in non-parenchymal liver cells and serves to enhance small intestinal absorption of ergothioneine, as demonstrated using OCTN1 gene knockout mice (Sugiura et al., 2010). "
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    ABSTRACT: The dietary antioxidant L-(+)-ergothioneine was tested for its potential mutagenic activity using the bacterial reverse mutation assay. The experiments were carried out using histidine-requiring auxotrophic strains of Salmonella typhimurium (Salmonella typhimurium TA98, TA100, TA1535 and TA1537), and the tryptophan-requiring auxotrophic strain of Escherichia coli (Escherichia coli WP2 uvrA) in the presence and absence of a post-mitochondrial supernatant (S9) prepared from livers of phenobarbital/β-naphthoflavone-induced rats. The revertant colony numbers of vehicle control plates with and without S9 Mix were within the corresponding historical control data ranges. The reference mutagen treatments (positive controls) showed the expected, biologically relevant increases in induced revertant colonies in all experimental phases in all tester strains. No biologically relevant increases were observed in revertant colony numbers of any of the five test strains following treatment with L-(+)-ergothioneine at any concentration level, either in the presence or absence of metabolic activation (S9 Mix) in the performed experiments. On the basis of the data reported, it can be concluded that L-(+)-ergothioneine did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used. Thus L-(+)-ergothioneine has no mutagenic activity on the applied bacteria tester strains under the test conditions used in this study. Research is continuing to define the role of L-(+)-ergothioneine in disease pathophysiology. Further studies on its safety are suggested.
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