Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.108 (TAT)
 2,389 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new pH-sensitive micelle delivery system based on TAT cell penetrating peptide and biodegradable sulfonamide grafted disulfide polymer is presented. The system consists of two components: (1) A polymeric micelle made of Poly(L-lactic acid)-b-poly(ethylene glycol) (PLLA-b-PEG) conjugated to TAT (TAT-micelle), (2) A pH-sensitive diblock copolymer (poly(L-cystine bisamide-g-sulfadiazine))-b-PEG (PCBS-b-PEG). The anionic PCBS complexed with cationic TAT of TAT-micelles forms the final carrier. PCBS showed rapid degradation in the presence of cysteine. The TAT-micelles showed increase in particle size between pH 8.0 and 7.0 upon mixing with PCBS-b-PEG indicating complexation. As the pH was further decreased (pH 6.8 to 6.0) two populations were observed, one of normal TAT-micelles and the other of aggregated PCBS-b-PEG. Flow cytometry showed significantly higher uptake of TAT-micelles at pH 6.6 indicating deshielding compared to pH 7.4. The anticancer drug doxorubicin (DOX) was encapsulated into the TAT-micelles, and the in vitro cytotoxicity at different pHs was evaluated. The system was able to distinguish pHs 7.2 and 7.0 in terms of cytotoxicity.
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PMID:A biodegradable pH-sensitive micelle system for targeting acidic solid tumors. 1799 64

We report an early detection of cancer in a child with Li-Fraumeni syndrome. The proband was a 3-year-old male with a primitive mesenchymal tumor. Genetic analysis showed a germline TP53 mutation in codon 220 exon 6, which changed TAT --> TGT and resulted in a tyrosine-to-cysteine amino acid substitution (Tyr220Cys). The younger sister at risk was followed, and an asymptomatic adrenal cortical carcinoma was detected 3 years later. The report highlights the importance of genetic counseling and provides an example of early detection of cancers in childhood LFS carriers.
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PMID:Early detection of adrenocortical carcinoma in a child with Li-Fraumeni syndrome. 1910 93

As part of a study on aminotransferases, genes coding for putative enzymes from Trypanosoma brucei and Leishmania major (alanine aminotransferases: ALATs, Tb927.1.3950 and LmjF12.0630; kynurenine aminotransferase: KAT, Tb10.389.1810; and tyrosine aminotransferase: TAT, LmjF36.2360) were cloned and functionally expressed in Escherichia coli. The putative T. brucei KAT, in fact coded for a glutamine aminotransferase (GlnAT), which exhibited a notably high affinity (in the micromolar range) towards glutamine and cysteine; in addition, like bacterial GlnATs and mammalian KATs, it was able to utilize different 2-oxoacids as amino acceptors. L. major TAT resembled T. cruzi TAT in substrate specificity, although the leishmanial enzyme did not exhibit ALAT activity. On the other hand, T. brucei ALAT, shortened by the first 65 amino acids assigned in the data bases, was functional and actively transaminated the substrate pair l-alanine and 2-oxoglutarate. Moreover in Western blots, the molecular size of the protein detected in crude extracts of T. brucei procyclics was identical to the value of the recombinant enzyme. Like T. brucei and T. cruzi orthologues, L. major ALAT displayed narrow substrate specificity. The leishmanial ALAT, like the T. cruzi enzyme, exhibited a dual subcellular localization, in the cytosol and in the mitochondrion. In line with the findings of comparative proteomic analyses of insect and mammalian stages of T. brucei and Leishmania parasites, our results also showed that T. cruzi ALAT is constitutively expressed, with remarkably higher levels being detected in amastigotes than in epimastigotes. ALATs are expressed in the clinically important stages of TriTryps, probably fulfilling an essential role, which deserves further studies.
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PMID:Functional characterization of stage-specific aminotransferases from trypanosomatids. 1944 56

TAT peptide functionalized shell-core ZnS-CdSe quantum dots (QDs) have been prepared by three different methods, direct ligand exchange with cysteine-terminated TAT (TAT-QD(lig exch)), and covalent conjugation to QDs coated with silanes (TAT-QD(silica)) and polyacrylate derivatives (TAT-QD(polyacrylate)). The silica and polyacrylate coatings incorporated multiple primary and secondary amines, introducing positive surface charges onto the QDs, providing high water solubility and sites for peptide conjugation, while inducing the "proton sponge effect". The different coating methods produced particles of different sizes, surface charges, and colloidal stability; these factors jointly influenced the cellular uptake and subcellular localization of these particles. As the particle size increased, (TAT-QD(lig exch) (6 nm) < TAT-QD(silica) (10 nm) < QD(polyacrylate) (25 nm)), both the particle surface charge and cellular uptake increased. The smaller TAT-QD(lig exch) and TAT-QD(silica) particles were localized mainly in the perinuclear regions, while the larger TAT-QD(polyacrylate) particles were localized in both the perinuclear regions and the lysosomes. Compared to the other TAT-QDs, TAT-QD(lig-exch) has a lower colloidal stability and was more cytotoxic due to the weak binding of the ligands.
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PMID:Surface coating directed cellular delivery of TAT-functionalized quantum dots. 1968 98

The glutathione (GSH) antioxidant defense system plays a central role in protecting mammalian cells against oxidative injury. Glutamate cysteine ligase (GCL) is the rate-limiting enzyme in GSH biosynthesis and is a heterodimeric holoenzyme composed of catalytic (GCLC) and modifier (GCLM) subunits. As a means of assessing the cytoprotective effects of enhanced GSH biosynthetic capacity, we have developed a protein transduction approach whereby recombinant GCL protein can be rapidly and directly transferred into cells when coupled to the HIV TAT protein transduction domain. Bacterial expression vectors encoding TAT fusion proteins of both GCL subunits were generated and recombinant fusion proteins were synthesized and purified to near homogeneity. The TAT-GCL fusion proteins were capable of heterodimerization and formation of functional GCL holoenzyme in vitro. Exposure of Hepa-1c1c7 cells to the TAT-GCL fusion proteins resulted in the time- and dose-dependent transduction of both GCL subunits and increased cellular GCL activity and GSH levels. A heterodimerization-competent, enzymatically deficient GCLC-TAT mutant was also generated in an attempt to create a dominant-negative suppressor of GCL. Transduction of cells with a catalytically inactive GCLC(E103A)-TAT mutant decreased cellular GCL activity in a dose-dependent manner. TAT-mediated manipulation of cellular GCL activity was also functionally relevant as transduction with wild-type GCLC(WT)-TAT or mutant GCLC(E103A)-TAT conferred protection or enhanced sensitivity to H(2)O(2)-induced cell death, respectively. These findings demonstrate that TAT-mediated transduction of wild-type or dominant-inhibitory mutants of the GCL subunits is a viable means of manipulating cellular GCL activity to assess the effects of altered GSH biosynthetic capacity.
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PMID:Manipulation of cellular GSH biosynthetic capacity via TAT-mediated protein transduction of wild-type or a dominant-negative mutant of glutamate cysteine ligase alters cell sensitivity to oxidant-induced cytotoxicity. 1991 71

Here we report and validate a new method, suitable broadly, for use in differentiated cells and tissues, for the direct visualization of actin polymerization under physiological conditions. We have designed and tested different versions of fluorescently labeled actin, reversibly attached to the protein transduction tag TAT, and have introduced this novel reagent into intact differentiated vascular smooth muscle cells (dVSMCs). A thiol-reactive version of the TAT peptide was synthesized by adding the amino acids glycine and cysteine to its NH(2)-terminus and forming a thionitrobenzoate adduct: viz. TAT-Cys-S-STNB. This peptide reacts readily with G-actin, and the complex is rapidly taken up by freshly enzymatically isolated dVSMC, as indicated by the fluorescence of a FITC tag on the TAT peptide. By comparing different versions of the construct, we determined that the optimal construct for biological applications is a nonfluorescently labeled TAT peptide conjugated to rhodamine-labeled actin. When TAT-Cys-S-STNB-tagged rhodamine actin (TSSAR) was added to live, freshly enzymatically isolated cells, we observed punctae of incorporated actin at the cortex of the cell. The punctae are indistinguishable from those we have previously reported to occur in the same cell type when rhodamine G-actin is added to permeabilized cells. Thus this new method allows the delivery of labeled G-actin into intact cells without disrupting the native state and will allow its further use to study the effect of physiological intracellular Ca(2+) concentration transients and signal transduction on actin dynamics in intact cells.
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PMID:A new method for direct detection of the sites of actin polymerization in intact cells and its application to differentiated vascular smooth muscle. 2068 75

Recently, PEGylation has been extensively employed to increase the circulation time of liposomes and enhance their accumulation in tumor tissue via the enhanced permeability and retention (EPR) effect; however, poly(ethylene glycol) (PEG) is unfavorable for the uptake of liposomes by tumor cells because of its steric hindrance. In this study, thiolytic cleavable PEG modified liposomes were used to solve this dilemma. Before arrival at the tumor tissue, PEG presents on the surface of liposomes, which is useful for passive accumulation in tumor tissue. Upon reaching the tumor tissues, the PEG chain could be removed by a safe cleaving reagent l-cysteine (l-Cys), and thus, the steric hindrance of PEG could be overcome conveniently. To further improve the uptake of liposomes, a "functional molecule" cell-penetrating peptide TAT was attached to the distal end of a shorter PEG spacer anchored to the surface of the liposomes, which could be shielded by cleavable PEG during circulation; upon arriving at tumor tissue, PEG was removed and thus the "functional molecule" TAT was exposed, and then TAT could mediate the uptake of the liposomes with high efficiency. In this study, thiolytic cleavable PEG was synthesized via a disulfide bridge, DOPE-PEG(1600)-TAT was synthesized by sulfhydryl-maleimide reaction, and then Rh-PE labeled liposomes composed of 2% DOPE-PEG(1600)-TAT and various amounts of cleavable PEG(5000) (2%, 4%, and 8%) were prepared, with particle size around 100 nm and slightly negative charge. These liposomes showed good stability in the presence of 10% serum. Their uptake by tumor cells HepG2 in vitro was assessed qualitatively and quantitatively. Liposomes modified with 2% DOPE-PEG(1600)-TAT and 8% DOPE-S-S-mPEG(5000) were regarded as the optimal formulation. In this preparation, nearly no uptake could be observed before addition of l-Cys, which meant undesired uptake during circulation could be avoided, while the uptake upon addition of l-Cys was 4 times as high as that in the absence of l-Cys. For the uptake in vivo, calcein loaded and Rh-PE labeled 8% cleavable PEG + 2% TAT modified liposomes were injected intratumorally into H22 tumor bearing mice. Confocal laser scanning microscopy (CLSM) showed that the uptake of 8% cleavable PEG + 2% TAT modified liposomes was much higher than that of 8% noncleavable PEG + 2% TAT modified liposomes in the presence of l-Cys. Thus, tumor targeted delivery could be achieved efficiently by the liposomal drug delivery system developed here in a controlled manner.
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PMID:Efficient delivery of payload into tumor cells in a controlled manner by TAT and thiolytic cleavable PEG co-modified liposomes. 2070 Dec 88

A retro-inverso, TAT-like peptide wherein lysine residues are replaced with cysteine residues bearing a disulfide-linked cysteamine group is found to engage in thiol-disulfide exchange with cysteine. These peptides are transported into cells and localize to lysosomes. Cellular uptake is enhanced in peptides bearing two cysteamine groups over those with one or none, by factors of approximately 1.5 and 12, respectively.
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PMID:A retro-inverso TAT-like peptide designed to deliver cysteamine to cells. 2084 89

A liposomal delivery system with a high efficiency of accumulation in tumor tissue and then transportation of the cargo into tumor cells was developed here and evaluated via systemic administration. 1,2-Distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol)(2000) (DSPE-PEG(2000))-TAT and protective DSPE-PEG(2000) modified liposomes possessing good stability in 50% FBS (fetal bovine serum) and good uptake efficiency were used as the basic formulation (TAT-SL; SL = stealth liposome), and then longer cysteine (Cys)-cleavable PEG(5000) was incorporated to modulate the function of TAT. All of the formulations to be used in vivo had sizes in a range of 80-100 nm and were stable in the presence of 50% FBS. Optical imaging showed that the incorporation of cleavable PEG(5000) into TAT-SL (i.e., C-TAT-SL) led to much more tumor accumulation and much less liver distribution compared with TAT-SL. The in vivo delivery profiles of C-TAT-SL were investigated using DiD as a fluorescent probe. Confocal laser scanning microscopy and flow cytometry showed that C-TAT-SL had a 48% higher (p < 0.001) delivery efficiency in the absence of Cys and a 130% higher (p < 0.001) delivery efficiency in the presence of Cys than the control (SL), indicating the successful targeted delivery of cargo was achieved by C-TAT-SL via systemic administration especially with a subsequent administration of Cys.
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PMID:Targeted delivery of cargoes into a murine solid tumor by a cell-penetrating peptide and cleavable poly(ethylene glycol) comodified liposomal delivery system via systemic administration. 2198 83

The cell penetrating peptide TAT, which appears to enter cells with alacrity, can pass through the BBB efficiently. It has been indentified to enhance the brain delivery of the liposome. However, little was known about its mechanism. TAT contains a basic region consisting of six arginine and two lysine residues. These eight basic amino acids seem to be the key to its highly efficient membrane translocation and brain delivery. In this study, four selected peptides are synthesized. (1) TAT peptide with terminal Cysteine (Cys-AYGRKKRRQRRR). (2) TAT peptide with disordered sequence (Cys-RKARYRGRKRQR). (3) Glycine and glutamic acid substituted TAT peptide (Cys-AYGGQQGGQGGG). (4) R8 (Cys-RRRRRRRR). Liposomes were chosen as the delivery vehicle. The peptide was covalently bonded with the liposome. We compare four peptides for their brain targeting potential, and investigate their ability to target liposomes to the brain in vitro and in vivo. The cellular uptake of these four liposomes by brain capillary endothelial cells (BCECs) of rats and C6s and the mechanism of the pathway of endocytosis were explored. Biodistribution in vivo was also investigated qualitatively and quantitatively. The results showed that the charge of the peptide played an important role in enhancing its brain delivery. The sequence had little to do with its membrane translocation and brain delivery indicated there might be no specific receptor or transporter for the Tat peptide.
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PMID:Comparison of four different peptides to enhance accumulation of liposomes into the brain. 2218 12


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