Disease relevance of Ttpa

• Lack of protein-mediated alpha-tocopherol transfer between membranes in the cytoplasm of ascites hepatomas [1].

High impact information on Ttpa

• Brefeldin A, which effectively inhibits VLDL secretion by disrupting the Golgi apparatus, had no effect on alpha-tocopherol secretion, indicating that alphaTTP-mediated alpha-tocopherol secretion is not coupled to VLDL secretion [2].
• These results suggest that alphaTTP present in the liver cytosol functions to stimulate secretion of cellular alpha-tocopherol into the extracellular medium and that the reaction utilizes a novel non-Golgi-mediated pathway that may be linked to cellular cholesterol metabolism and/or transport [2].
• alpha-tocopherol transfer protein stimulates the secretion of alpha-tocopherol from a cultured liver cell line through a brefeldin A-insensitive pathway [2].
• In the present paper, we have isolated a cDNA clone with 2194 base pairs encoding alpha TTP from a rat liver cDNA library [3].
• From the longest open reading frame of the cloned cDNA, one isoform of rat liver alpha TTP is predicted to be composed of 278 amino acid residues of calculated molecular weight 31,845 [3].

Biological context of Ttpa

• Double-staining experiments with endocytosis markers revealed that alpha-TTP accumulates transiently on the cytoplasmic surface of late endosomal membranes [4].
• The results suggested that dietary vitamin E does not affect alpha-TTP gene expression except that the protein levels in the liver were lowered by vitamin E deficiency [5].
• These findings indicate that mRNA for hepatic alpha TTP, rather than Mn-SOD or GPX, may be highly responsive to oxidative stress [6].

Anatomical context of Ttpa

• alpha-Tocopherol transfer protein (alpha TTP) present in rat liver cytosol specifically binds this vitamin and enhances its transfer between separate membranes [3].
• These data show that alpha-tocopherol transfer activity of LPL in adipose tissue and muscle is not important for alpha-tocopherol transport to the tissue after alpha-tocopherol intake or that the amount transferred is small relative to the tissue concentration [7].
• This transient binding may explain the mechanism of how alpha-tocopherol is transferred from late endosomes to cytosolic alpha-TTP [4].
• This distribution pattern strongly suggests that the message for alpha-TTP is expressed in the Bergmann glial cells [8].
• alpha-Tocopherol transfer from liposomes to mitochondria was enhanced by a cytosolic protein in rat liver [9].

Associations of Ttpa with chemical compounds

• The aim of this experiment was to clarify the contribution of the alpha-tocopherol transfer activity of lipoprotein lipase (LPL) to vitamin E transport to tissues in vivo [7].
• We investigated whether the expression of the hepatic alpha-TTP can be induced by dietary tocopherols [10].
• Refeeding a diet containing either alpha- or delta-tocopherol, or both, caused a steady increase of the expression of alpha-TTP mRNA [10].
• We found that alpha-tocopherylquinone binds to a liver protein with a molecular mass of about 40 kDa that is distinct from alphaTTP [11].
• Under chloroquine treatment, the diffuse cytosolic distribution of alpha-TTP changes to a punctate pattern [4].

Regulatory relationships of Ttpa

• alpha- and delta-tocopherol induce expression of hepatic alpha-tocopherol-transfer-protein mRNA [10].

Other interactions of Ttpa

• The decrease in alpha-TTP expression was exacerbated by adding epidermal growth factor to the culture medium and was inhibited by adding dexamethasone [12].

Analytical, diagnostic and therapeutic context of Ttpa

• Both Western and Northern blot analyses revealed that alpha TTP is expressed exclusively in the liver in rats. alpha TTP has been found to exhibit a structural homology with the cellular retinaldehyde-binding protein present only in visual tissues [3].
• As shown by the Northern and Western Blot Analysis, the expression of alpha-TTP in the liver of the DE group was significantly lower than, while that of the HE group was not different from, that of the controls [5].
• In the brain, the alpha-TTP transcript was detected predominantly in the cerebellar cortex, as revealed by in situ hybridization histochemistry [8].

References