Modulation of phosphorylation of tocopherol and phosphatidylinositol by hTAP1/SEC14L2-mediated lipid exchange

Can vitamin E ester derivatives be excellent alternatives of vitamin E: state of art

Vitamin E (VE) is a natural antioxidant which is widely used in the food fields, while the shortcomings of easy oxidative inactivation and poor water solubility limit its application. Vitamin E esters' (VEEs) derivatives, such as vitamin E acetate (VEA), are more stable and easier to be absorbed while have similar biological activities and physiological functions compared with VE. In this systematic review, the digestion, absorption and physiological function of VEEs were summarized. To promote their further industrial applications, the synthesis strategies of VEEs were also summarized in-depth. In particular, as a new generation of green solvents, ionic liquids (ILs) have been widely used in enzymatic reactions due to the stabilization and activation of enzymes. Their applications in enzymatic synthesis of VEEs were summarized and discussed. Finally, several future perspectives for developing more efficiency strategies of VEEs synthesis, such as enzyme engineering and design of novel ILs, were also discussed.

Role of SEC14-like phosphatidylinositol transfer proteins in membrane identity and dynamics

Membrane identity and dynamic processes, that act at membrane sites, provide important cues for regulating transport, signal transduction and communication across membranes. There are still numerous open questions as to how membrane identity changes and the dynamic processes acting at the surface of membranes are regulated in diverse eukaryotes in particular plants and which roles are being played by protein interaction complexes composed of peripheral and integral membrane proteins. One class of peripheral membrane proteins conserved across eukaryotes comprises the SEC14-like phosphatidylinositol transfer proteins (SEC14L-PITPs). These proteins share a SEC14 domain that contributes to membrane identity and fulfills regulatory functions in membrane trafficking by its ability to sense, bind, transport and exchange lipophilic substances between membranes, such as phosphoinositides and diverse other lipophilic substances. SEC14L-PITPs can occur as single-domain SEC14-only proteins in all investigated organisms or with a modular domain structure as multi-domain proteins in animals and streptophytes (comprising charales and land plants). Here, we present an overview on the functional roles of SEC14L-PITPs, with a special focus on the multi-domain SEC14L-PITPs of the SEC14-nodulin and SEC14-GOLD group (PATELLINs, PATLs in plants). This indicates that SEC14L-PITPs play diverse roles from membrane trafficking to organism fitness in plants. We concentrate on the structure of SEC14L-PITPs, their ability to not only bind phospholipids but also other lipophilic ligands, and their ability to regulate complex cellular responses through interacting with proteins at membrane sites.

Modulation of CD36-mediated lipid accumulation and senescence by vitamin E analogs in monocytes and macrophages

The CD36/FAT scavenger receptor/fatty acids transporter regulates cellular lipid accumulation important for inflammation, atherosclerosis, lipotoxicity, and initiation of cellular senescence. Here we compared the regulatory effects of the vitamin E analogs alpha-tocopherol (αT), alpha-tocopheryl phosphate (αTP), and αTP/βCD (a nanocarrier complex between αTP and β-cyclodextrin [βCD]) and investigated their regulatory effects on lipid accumulation, phagocytosis, and senescence in THP-1 monocytes and macrophages. Both, αTP and αTP/βCD inhibited CD36 surface exposition stronger than αT leading to more pronounced CD36-mediated events such as inhibition of DiI-labeled oxLDL uptake, phagocytosis of fluorescent Staphylococcus aureus bioparticles, and cell proliferation. When compared to βCD, the complex of αTP/βCD extracted cholesterol from cellular membranes with higher efficiency and was associated with the delivery of αTP to the cells. Interestingly, both, αTP and more so αTP/βCD inhibited lysosomal senescence-associated beta-galactosidase (SA-β-gal) activity and increased lysosomal pH, suggesting CD36-mediated uptake into the endo-lysosomal phagocytic compartment. Accordingly, the observed pH increase was more pronounced with αTP/βCD in macrophages whereas no significant increase occurred with αT, alpha-tocopheryl acetate (αTA) or βCD. In contrast to αT and αTA, the αTP molecule is di-anionic at neutral pH, but upon moving into the acidic endo-lysosomal compartment becomes protonated and thus is acting as a base. Moreover, it is expected to be retained in lysosomes since it still carries one negative charge, similar to lysosomotropic drugs. Thus, treatment with αTP or αTP/βCD and/or inhibition of conversion of αTP to αT as it occurs in aged cells may counteract CD36-mediated overlapping inflammatory, senescent, and atherosclerotic events.

Vitamin E: Where Are We Now in Vascular Diseases?

Vitamin E is one of the most popular fat-soluble vitamins in pathological research and has been under scrutiny since the 1980s as a vital dietary component of food. The antioxidant effect of vitamin E has been widely studied due to its benefits in the prevention of various cardiovascular diseases. In recent years, alternative effects of vitamin E, in terms of anti-inflammatory pathways and gene regulation, have also been of interest to researchers. This review examines the role of dietary vitamin E (α-tocopherol) as an antioxidant and bioactive molecule in promoting vascular health. While the antioxidant effect of vitamin E is well established, knowledge about its capacity as a promising regulatory molecule in the control of the vascular system is limited. The aim of this review is to discuss some of these mechanisms and summarize their role in the prevention of cardiovascular diseases (CVD). Here, we also briefly discuss foods rich in vitamin E, and deliberate some potential toxicological effects of excessive supplemental vitamin E in the body.

A gold revision of the Golgi Dynamics (GOLD) domain structure and associated cell functionalities

The classical secretory pathway is the key membrane-based delivery system in eukaryotic cells. Several families of proteins involved in the secretory pathway, with functionalities going from cargo sorting receptors to the maintenance and dynamics of secretory organelles, share soluble globular domains predicted to mediate protein-protein interactions. One of them is "Golgi Dynamics" (GOLD) domain, named after its strong association with the Golgi apparatus. There are many GOLD-containing protein families, such as the Transmembrane emp24 domain-containing proteins (TMED/p24 family), animal SEC14-like proteins, Human Golgi resident protein ACBD3, a splice variant of TICAM2 called TRAM with GOLD domain and FYCO1. Here, we critically review the state-of-the-art knowledge of the structures and functions of the main representatives of GOLD-containing proteins in vertebrates. We provide the first unified description of the GOLD domain structure across different families since the first high-resolution structure was determined. With a brand-new update on the definition of the GOLD domain, we also discuss how its tertiary structure fits the β-sandwich-like fold map and give exciting new directions for forthcoming studies.

Vitamin E research: Past, now and future

The early history of vitamin E from its discovery by Herbert M. Evans and Katharine J. S. Bishop in 1922 up to its chemical synthesis by Paul Karrer and coworkers in 1938 and the development of the concept that vitamin E acts as an antioxidant in vivo are recalled. Some more recent results shedding doubt on this hypothesis are reviewed. They comprise influence of vitamin E on enzyme activities, signaling cascades, gene expression and bio-membrane structure. The overall conclusion is that our knowledge of the vitamin's mechanism of action still remains fragmentary. The metabolism of tocopherols and tocotrienols is presented and discussed in respect to bioactivity of the metabolites, interference with drug metabolism and the future design of clinical trials. Some strategies are recommended how to reach the final goal: the identification of the primary vitamin E target(s) and the analysis of the downstream events up to the physiological phenomena.

Reflections on a century of vitamin E research: Looking at the past with an eye on the future

The name vitamin E, was given by Barnett and Sure who suggested that the factor proposed by Evans and Bishop as substance "X," be termed vitamin "E" as the next vitamin after the A, B, C and D vitamins had been already described. The identification of vitamin E with a-tocopherol was made in 1936 by Evans' group. One year later β-tocopherol and 11 years later δ-tocopherol were isolated. Tocotrienol (named zetatocopherol) was first described in 1957 and later isolated in 1961. The antioxidant property of tocopherols was reported by Olcott and Emerson in 1937. Inherited vitamin E deficiency, AVED, characterized by a form of neuromyopathy was first described in 1981. The disease, was localized to chromosome 8q and found to be caused by a mutation of the a-TTP gene. The subsequent paragraphs are not a comprehensive review but only critical reflections on some important aspects of vitamin E research.

Vitamin E: Regulatory Role on Signal Transduction

Vitamin E modulates signal transduction pathways by several molecular mechanisms. As a hydrophobic molecule located mainly in membranes it contributes together with other lipids to the physical and structural characteristics such as membrane stability, curvature, fluidity, and the organization into microdomains (lipid rafts). By acting as the main lipid-soluble antioxidant, it protects other lipids such as mono- and poly-unsaturated fatty acids (MUFA and PUFA, respectively) against chemical reactions with reactive oxygen and nitrogen species (ROS and RNS, respectively) and prevents membrane destabilization and cellular dysfunction. In cells, vitamin E affects signaling in redox-dependent and redox-independent molecular mechanisms by influencing the activity of enzymes and receptors involved in modulating specific signal transduction and gene expression pathways. By protecting and preventing depletion of MUFA and PUFA it indirectly enables regulatory effects that are mediated by the numerous lipid mediators derived from these lipids. In recent years, some vitamin E metabolites have been observed to affect signal transduction and gene expression and their relevance for the regulatory function of vitamin E is beginning to be elucidated. In particular, the modulation of the CD36/FAT scavenger receptor/fatty acids transporter by vitamin E may influence many cellular signaling pathways relevant for lipid homeostasis, inflammation, survival/apoptosis, angiogenesis, tumorigenesis, neurodegeneration, and senescence. Thus, vitamin E has an important role in modulating signal transduction and gene expression pathways relevant for its uptake, distribution, metabolism, and molecular action that when impaired affect physiological and patho-physiological cellular functions relevant for the prevention of a number of diseases. © 2018 IUBMB Life, 71(4):456-478, 2019.

Vitamin E - The Next 100 Years

α-Tocopherol is the only tocopherol that has been shown to prevent the human deficiency disease Ataxia with Isolated Vitamin E Deficiency (AVED), and thus it is the only one that, for humans, can be called vitamin E. Vitamin E in addition to preventing AVED has documented immune boosting properties and an activity against nonalcoholic hepatosteatosis and low-grade inflammation. Epidemiological studies indicating that vitamin E could prevent cardiovascular events, neurodegenerative disease, macular degeneration, and cancer were in general not confirmed by clinical intervention studies. Vitamin E and some of its metabolites modulate cell signaling and gene transcription. Future research is needed to achieve a better understanding of the molecular events leading to gene regulation by vitamin E, especially in its phosphorylated form. Isolation and characterization of the vitamin E kinase and vitamin E phosphate phosphatase will help in the understanding of cell regulation processes modulated by vitamin E. A clarification of the pathogenesis of AVED remains an important goal to be achieved. © 2018 IUBMB Life, 71(4):411-415, 2019.

Biophysical Parameters of the Sec14 Phospholipid Exchange Cycle

Sec14, the major yeast phosphatidylcholine (PC)/phosphatidylinositol (PI) transfer protein (PITP), coordinates PC and PI metabolism to facilitate an appropriate and essential lipid signaling environment for membrane trafficking from trans-Golgi membranes. The Sec14 PI/PC exchange cycle is essential for its essential biological activity, but fundamental aspects of how this PITP executes its lipid transfer cycle remain unknown. To address some of these outstanding issues, we applied time-resolved small-angle neutron scattering for the determination of protein-mediated intervesicular movement of deuterated and hydrogenated phospholipids in vitro. Quantitative analysis by small-angle neutron scattering revealed that Sec14 PI- and PC-exchange activities were sensitive to both the lipid composition and curvature of membranes. Moreover, we report that these two parameters regulate lipid exchange activity via distinct mechanisms. Increased membrane curvature promoted both membrane binding and lipid exchange properties of Sec14, indicating that this PITP preferentially acts on the membrane site with a convexly curved face. This biophysical property likely constitutes part of a mechanism by which spatial specificity of Sec14 function is determined in cells. Finally, wild-type Sec14, but not a mixture of Sec14 proteins specifically deficient in either PC- or PI-binding activity, was able to effect a net transfer of PI or PC down opposing concentration gradients in vitro.

Comparative proteomic analysis reveals the regulatory network of the veA gene during asexual and sexual spore development of Aspergillus cristatus

Aspergillus cristatus is the predominant fungal population during fermentation of Chinese Fuzhuan brick tea, and belongs to the homothallic fungal group that undergoes a sexual stage without asexual conidiation under hypotonic conditions, while hypertonic medium induces initiation of the asexual stage and completely blocks sexual development. However, the veA deletion mutant only produces conidia in hypotonic medium after a 24-h culture, but both asexual and sexual spores are observed after 72 h. The veA gene is one of the key genes that positively regulates sexual and negatively regulates asexual development in A. cristatus. To elucidate the molecular mechanism of how VeA regulates asexual and sexual spore development in A. cristatus, 2D electrophoresis (2-DE) combined with MALDI-tandem ToF MS analysis were applied to identify 173 differentially expressed proteins (DEPs) by comparing the agamotype (24 h) and teleomorph (72 h) with wild-type (WT) A. cristatus strains. Further analysis revealed that the changed expression pattern of Pmk1-MAPK and Ser/Thr phosphatase signaling, heat shock protein (Hsp) 90 (HSP90), protein degradation associated, sulphur-containing amino acid biosynthesis associated, valine, leucine, isoleucine, and arginine biosynthesis involved, CYP450 and cytoskeletal formation associated proteins were involved in the production of conidia in agamotype of A. cristatus. Furthermore, the deletion of veA in A. cristatus resulted in disturbed process of transcription, translation, protein folding, amino acid metabolism, and secondary metabolism. The carbohydrate and energy metabolism were also greatly changed, which lied in the suppression of anabolism through pentose phosphate pathway (PPP) but promotion of catabolism through glycolysis and tricarboxylic acid (TCA) cycle. The energy compounds produced in the agamotype were mainly ATP and NADH, whereas they were NADPH and FAD in the teleomorph. These results will contribute to the existing knowledge on the complex role of VeA in the regulation of spore development in Aspergillus and provide a framework for functional investigations on the identified proteins.

Water-Soluble Vitamin E-Tocopheryl Phosphate

The hydrophobicity of vitamin E poses transport and metabolic challenges to regulate its bioavailability and to prevent its accumulation in lipid-rich tissues such as adipose tissue, brain, and liver. Water-soluble precursors of vitamin E (α-tocopherol, αT), such as its esters with acetate (αTA), succinate (αTS), or phosphate (αTP), have increased solubility in water and stability against reaction with free radicals, but they are rapidly converted during their uptake into the lipid-soluble vitamin E. Therefore, the bioavailability of these precursors as intact molecules is low; nevertheless, at least for αTS and αTP, the recent research has revealed unique regulatory effects on signal transduction and gene expression and the modulation of cellular events ranging from proliferation, survival/apoptosis, lipid uptake and metabolism, phagocytosis, long term potentiation, cell migration, telomere maintenance, and angiogenesis. Moreover, water-soluble derivatives of vitamin E including some based on αTP are increasingly used as components of nanocarriers for enhanced and targeted delivery of drugs and other molecules (vitamins, including αT and αTP itself, vitamin D3, carnosine, caffeine, docosahexaenoic acid (DHA), insulin) and cofactors such as coenzyme Q10. In this review, the chemical characteristics, transport, metabolic pathways, and molecular mechanisms of action of αTP in cells and tissues are summarized and put into perspective with its possible role in the prevention of a number of diseases.

Expression Profile of Genes Regulating Steroid Biosynthesis and Metabolism in Human Ovarian Granulosa Cells-A Primary Culture Approach

Because of the deep involvement of granulosa cells in the processes surrounding the cycles of menstruation and reproduction, there is a great need for a deeper understanding of the ways in which they function during the various stages of those cycles. One of the main ways in which the granulosa cells influence the numerous sex associated processes is hormonal interaction. Expression of steroid sex hormones influences a range of both primary and secondary sexual characteristics, as well as regulate the processes of oogenesis, folliculogenesis, ovulation, and pregnancy. Understanding of the exact molecular mechanisms underlying those processes could not only provide us with deep insight into the regulation of the reproductive cycle, but also create new clinical advantages in detection and treatment of various diseases associated with sex hormone abnormalities. We have used the microarray approach validated by RT-qPCR, to analyze the patterns of gene expression in primary cultures of human granulosa cells at days 1, 7, 15, and 30 of said cultures. We have especially focused on genes belonging to ontology groups associated with steroid biosynthesis and metabolism, namely “Regulation of steroid biosynthesis process” and “Regulation of steroid metabolic process”. Eleven genes have been chosen, as they exhibited major change under a culture condition. Out of those, ten genes, namely STAR, SCAP, POR, SREBF1, GFI1, SEC14L2, STARD4, INSIG1, DHCR7, and IL1B, belong to both groups. Patterns of expression of those genes were analyzed, along with brief description of their functions. That analysis helped us achieve a better understanding of the exact molecular processes underlying steroid biosynthesis and metabolism in human granulosa cells.

Many tocopherols, one vitamin E

Four tocopherols are available in nature and are absorbed with the diet, but only one RRR-α-tocopherol satisfies the criteria of being a vitamin. The biological activity of the different tocopherols studied in the rat by the resorption-gestation test has been inconsistently extrapolated to human beings where the tocopherols have no influence on a successful pregnancy. Diminution of RRR-α-tocopherol intake results in diseases characterized by ataxia, whose pathogenetic mechanism, despite vigorous claims, has not been clarified. The calculation of the Daily Reference Intake (DRI), necessary to prevent disease, is based on an obsolete test, the peroxide-induced erythrocyte hemolysis, called the gold standard, but of highly questioned validity. If many epidemiological studies have given positive results, showing prevention by high vitamin E containing diets of cardiovascular events, neurodegenerative disease, macular degeneration and cancer, the clinical confirmatory intervention studies were mostly negative. On the positive side, besides preventing vitamin E deficiency diseases, vitamin E has shown efficacy as anti-inflammatory and immune boosting compound. It has also shown some efficacy in protecting against nonalcoholic hepato-steatosis. At a molecular level, vitamin E and some of its metabolites have shown capacity of regulating cell signaling and modulating gene transcription.

α-Tocopheryl Phosphate Induces VEGF Expression via CD36/PI3Kγ in THP-1 Monocytes

The CD36 scavenger receptor binds several ligands and mediates ligand uptake and ligand-dependent signal transduction and gene expression, events that may involve CD36 internalization. Here we show that CD36 internalization in THP-1 monocytes is triggered by α-tocopherol (αT) and more strongly by α-tocopheryl phosphate (αTP) and EPC-K1, a phosphate diester of αTP and L-ascorbic acid. αTP-triggered CD36 internalization is prevented by the specific covalent inhibitor of selective lipid transport by CD36, sulfo-N-succinimidyl oleate (SSO). Moreover, SSO inhibited the CD36-mediated uptake of 14C-labelled αTP suggesting that αTP binding and internalization of CD36 is involved in cellular αTP uptake, whereas the uptake of αT was less affected. Similar to that, inhibition of selective lipid transport of the SR-BI scavenger receptor resulted mainly in reduction of αTP and not αT uptake. In contrast, uptake of αT was mainly inhibited by Dynasore, an inhibitor of clathrin-mediated endocytosis, suggesting that the differential regulatory effects of αTP and αT on signaling may be influenced by their different routes of uptake. Interestingly, αTP and EPC-K1 also reduced the neutral lipid content of THP-1 cells and the phagocytosis of fluorescent Staphylococcus aureus bioparticles. Moreover, induction of the vascular endothelial growth factor (VEGF) promoter activity by αTP occurred via CD36/PI3Kγ/Akt, as it could be inhibited by specific inhibitors of this pathway (SSO, Wortmannin, AS-605240). These results suggest that αTP activates PI3Kγ/Akt signaling leading to VEGF expression in monocytes after binding to and/or transport by CD36, a receptor known to modulate angiogenesis in response to amyloid beta, oxLDL, and thrombospondin. J. Cell. Biochem. 118: 1855-1867, 2017. © 2017 Wiley Periodicals, Inc.

Vitamin E: Emerging aspects and new directions

The discovery of vitamin E will have its 100th anniversary in 2022, but we still have more questions than answers regarding the biological functions and the essentiality of vitamin E for human health. Discovered as a factor essential for rat fertility and soon after characterized for its properties of fat-soluble antioxidant, vitamin E was identified to have signaling and gene regulation effects in the 1980s. In the same years the cytochrome P-450 dependent metabolism of vitamin E was characterized and a first series of studies on short-chain carboxyethyl metabolites in the 1990s paved the way to the hypothesis of a biological role for this metabolism alternative to vitamin E catabolism. In the last decade other physiological metabolites of vitamin E have been identified, such as α-tocopheryl phosphate and the long-chain metabolites formed by the ω-hydroxylase activity of cytochrome P-450. Recent findings are consistent with gene regulation and homeostatic roles of these metabolites in different experimental models, such as inflammatory, neuronal and hepatic cells, and in vivo in animal models of acute inflammation. Molecular mechanisms underlying these responses are under investigation in several laboratories and side-glances to research on other fat soluble vitamins may help to move faster in this direction. Other emerging aspects presented in this review paper include novel insights on the mechanisms of reduction of the cardiovascular risk, immunomodulation and antiallergic effects, neuroprotection properties in models of glutamate excitotoxicity and spino-cerebellar damage, hepatoprotection and prevention of liver toxicity by different causes and even therapeutic applications in non-alcoholic steatohepatitis. We here discuss these topics with the aim of stimulating the interest of the scientific community and further research activities that may help to celebrate this anniversary of vitamin E with an in-depth knowledge of its action as vitamin.

The rise, the fall and the renaissance of vitamin E

This review deals with the expectations of vitamin E ability of preventing or curing, as a potent antioxidant, alleged oxidative stress based ailments including cardiovascular disease, cancer, neurodegenerative diseases, cataracts, macular degeneration and more. The results obtained with clinical intervention studies have highly restricted the range of effectiveness of this vitamin. At the same time, new non-antioxidant mechanisms have been proposed. The new functions of vitamin E have been shown to affect cell signal transduction and gene expression, both in vitro and in vivo. Phosphorylation of vitamin E, which takes place in vivo, results in a molecule provided with functions that are in part stronger and in part different from those of the non-phosphorylate compound. The in vivo documented functions of vitamin E preventing the vitamin E deficiency ataxia (AVED), slowing down the progression of non-alcoholic steato-hepatitis (NASH), decreasing inflammation and potentiating the immune response are apparently based on these new molecular mechanisms. It should be stressed however that vitamin E, when present at higher concentrations in the body, should exert antioxidant properties to the extent that its chromanol ring is unprotected or un-esterified.