α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells
Liver cells express a cytosolic α-tocopherol transfer protein (αTTP) with high binding affinity for α-tocopherol (αT) and much lower affinities for the non-αT congeners. The role of αTTP in the intracellular distribution of the different vitamin E forms is currently unknown. We therefore investigate...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2018-10-01
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| Series: | Redox Biology |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2213231718305846 |
| _version_ | 1818562160960208896 |
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| author | Andrea Irías-Mata Nadine Sus Sandra Flory Daniela Stock Denise Woerner Maren Podszun Jan Frank |
| author_facet | Andrea Irías-Mata Nadine Sus Sandra Flory Daniela Stock Denise Woerner Maren Podszun Jan Frank |
| author_sort | Andrea Irías-Mata |
| collection | DOAJ |
| description | Liver cells express a cytosolic α-tocopherol transfer protein (αTTP) with high binding affinity for α-tocopherol (αT) and much lower affinities for the non-αT congeners. The role of αTTP in the intracellular distribution of the different vitamin E forms is currently unknown. We therefore investigated the intracellular localization of αT, γ-tocopherol (γT), α-tocotrienol (αT3), and γ-tocotrienol (γT3) in cultured hepatic cells with and without stable expression of αTTP. We first determined cellular uptake of the four congeners and found the methylation of the chromanol ring and saturation of the sidechain to be important factors, with tocotrienols being taken up more efficiently than tocopherols and the γ-congeners more than the α-congeners, irrespective of the expression of αTTP. This, however, could perhaps also be due to an observed higher stability of tocotrienols, compared to tocopherols, in culture media rather than a higher absorption. We then incubated HepG2 cells and αTTP-expressing HepG2 cells with αT, γT, αT3, or γT3, isolated organelle fractions by density gradient centrifugation, and determined the concentrations of the congeners in the subcellular fractions. All four congeners were primarily associated with the lysosomes, endoplasmic reticulum, and plasma membrane, whereas only αT correlated with mitochondria. Neither the chromanol ring methylation or sidechain saturation, nor the expression of αTTP were important factors for the intracellular distribution of vitamin E. In conclusion, αTTP does not appear to regulate the uptake and intracellular localization of different vitamin E congeners in cultured liver cells. Keywords: Endoplasmic reticulum, HepG2 liver cells, Intracellular localization, Lysosomes, Mitochondria, Plasma membrane, α-Tocopherol transfer protein, Tocotrienols, Trafficking, Vitamin E |
| first_indexed | 2024-12-14T01:00:04Z |
| format | Article |
| id | doaj.art-bd18c1bdcfa1427ca9d919fe37e0b50b |
| institution | Directory Open Access Journal |
| issn | 2213-2317 |
| language | English |
| last_indexed | 2024-12-14T01:00:04Z |
| publishDate | 2018-10-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Redox Biology |
| spelling | doaj.art-bd18c1bdcfa1427ca9d919fe37e0b50b2022-12-21T23:23:19ZengElsevierRedox Biology2213-23172018-10-01192836α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cellsAndrea Irías-Mata0Nadine Sus1Sandra Flory2Daniela Stock3Denise Woerner4Maren Podszun5Jan Frank6Institute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyInstitute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyInstitute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyInstitute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyInstitute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyInstitute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyCorresponding author.; Institute of Biological Chemistry and Nutrition, University of Hohenheim, D-70599 Stuttgart, GermanyLiver cells express a cytosolic α-tocopherol transfer protein (αTTP) with high binding affinity for α-tocopherol (αT) and much lower affinities for the non-αT congeners. The role of αTTP in the intracellular distribution of the different vitamin E forms is currently unknown. We therefore investigated the intracellular localization of αT, γ-tocopherol (γT), α-tocotrienol (αT3), and γ-tocotrienol (γT3) in cultured hepatic cells with and without stable expression of αTTP. We first determined cellular uptake of the four congeners and found the methylation of the chromanol ring and saturation of the sidechain to be important factors, with tocotrienols being taken up more efficiently than tocopherols and the γ-congeners more than the α-congeners, irrespective of the expression of αTTP. This, however, could perhaps also be due to an observed higher stability of tocotrienols, compared to tocopherols, in culture media rather than a higher absorption. We then incubated HepG2 cells and αTTP-expressing HepG2 cells with αT, γT, αT3, or γT3, isolated organelle fractions by density gradient centrifugation, and determined the concentrations of the congeners in the subcellular fractions. All four congeners were primarily associated with the lysosomes, endoplasmic reticulum, and plasma membrane, whereas only αT correlated with mitochondria. Neither the chromanol ring methylation or sidechain saturation, nor the expression of αTTP were important factors for the intracellular distribution of vitamin E. In conclusion, αTTP does not appear to regulate the uptake and intracellular localization of different vitamin E congeners in cultured liver cells. Keywords: Endoplasmic reticulum, HepG2 liver cells, Intracellular localization, Lysosomes, Mitochondria, Plasma membrane, α-Tocopherol transfer protein, Tocotrienols, Trafficking, Vitamin Ehttp://www.sciencedirect.com/science/article/pii/S2213231718305846 |
| spellingShingle | Andrea Irías-Mata Nadine Sus Sandra Flory Daniela Stock Denise Woerner Maren Podszun Jan Frank α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells Redox Biology |
| title | α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells |
| title_full | α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells |
| title_fullStr | α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells |
| title_full_unstemmed | α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells |
| title_short | α-Tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α- and γ-tocopherols and -tocotrienols in cultured liver cells |
| title_sort | α tocopherol transfer protein does not regulate the cellular uptake and intracellular distribution of α and γ tocopherols and tocotrienols in cultured liver cells |
| url | http://www.sciencedirect.com/science/article/pii/S2213231718305846 |
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