Genetics of the mammalian phenylalanine hydroxylase system. II. Immunological and two-dimensional gel electrophoretic studies of phenylalanine hydroxylase in cultured normal and mutant rat hepatoma cells

1979 ◽  
Vol 17 (9-10) ◽  
pp. 921-946 ◽  
Author(s):  
K. H. Choo ◽  
R. G. H. Cotton
Keyword(s):  
Phenylalanine Hydroxylase ◽  
Hepatoma Cells ◽  
Two Dimensional ◽  
Mutant Rat ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

Glucocorticoid stimulation of tetrahydrobiopterin levels and phenylalanine hydroxylase activity in rat hepatoma cells

1989 ◽  
Vol 67 (6) ◽  
pp. 293-296 ◽  
Author(s):  
Michael A. Parniak ◽  
Janice Pilkington
Keyword(s):  
Culture Medium ◽  
Phenylalanine Hydroxylase ◽  
Hepatoma Cells ◽  
Rapid Loss ◽  
Maximum Elevation ◽  
Rat Liver Cells ◽  
Important Regulator ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells ◽  
Stimulation Of

Incubation of H4-II-E-C3 rat hepatoma cells with either hydrocortisone or dexamethasone resulted in 3- to 5-fold increases in the levels of both phenylalanine hydroxylase and its essential cofactor, tetrahydrobiopterin. Maximum elevation of phenylalanine hydroxylase was noted after 24 h of incubation, whereas significant increases in tetrahydrobiopterin were found only after 48 h exposure of the cells to glucocorticoids. Removal of hormone from the culture medium resulted in rapid loss of cell tetrahydrobiopterin, but a much slower decline in the level of phenylalanine hydroxylase. Thus, although the levels of both phenylalanine hydroxylase and tetrahydrobiopterin in rat hepatoma cells are regulated by glucocorticoids, this regulation is apparently not strictly coordinated. Nevertheless, control of cellular tetrahydrobiopterin levels may be an important regulator of hepatic phenylalanine catabolism since significant increases in the ability of intact rat liver cells to hydroxylate phenylalanine were observed only after 48 h exposure to glucocorticoids, in correlation with increases in cell tetrahydrobiopterin content.Key words: phenylalanine hydroxylase, tetrahydrobiopterin, glucocorticoid, hepatoma cells.

scholarly journals Preferential degradation of the terminal carbohydrate moiety of membrane glycoproteins in rat hepatoma cells and after transfer to the membranes of mouse fibroblasts.

1983 ◽  
Vol 96 (1) ◽  
pp. 139-150 ◽  
Author(s):  
H Baumann ◽  
E Hou ◽  
G P Jahreis
Keyword(s):  
Plasma Membrane ◽  
Protein Fraction ◽  
Hepatoma Cells ◽  
Total Cell ◽  
Cell Protein ◽  
Two Dimensional ◽  
Membrane Glycoproteins ◽  
Membrane Components ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

Glycoproteins in the plasma membrane of rat hepatoma cells were labeled at their externally exposed tyrosine residues with 131I and at their galactose and sialic acid residues with 3H. The degradation of both isotopes in the total cell protein fraction, in glycoproteins purified by concanavalin A, and in glycoproteins separated on two-dimensional gels was determined. Similarly, the total cellular membrane glycoproteins were metabolically labeled with [35S]methionine and [3H]fucose. The fate of both incorporated labels was followed by lectin chromatography or by precipitation of the proteins with specific antibodies followed by electrophoretic gel separation. In both labeling experiments, the carbohydrate markers were lost from the ligand-recognized fraction with similar kinetics as from the total cell protein fraction. In some glycoprotein species which were separated by two-dimensional gel electrophoresis, the polypeptide portion exhibited up to a twofold slower rate of degradation relative to that of the carbohydrate moiety. This difference is most pronounced in carbohydrate-rich glycoproteins. To corroborate this finding, double-labeled membrane glycoproteins were incorporated into reconstituted phospholipid vesicles which were then transferred via fusion into the plasma membrane of mouse fibroblasts. Both the polypeptide and carbohydrate moieties of the transferred membrane glycoproteins were degraded with the same relative kinetics as in the original hepatoma cells. The rate of degradation is mostly a function of the structural properties of the membrane components as shown by the preservation of metabolically stable fucogangliosides of Reuber H-35 hepatoma cells transferred onto the fibroblasts. The technique of insertion of membrane components into the plasma membrane of another cell should assist in the elucidation of the exact route and mechanism of membrane protein destruction.

scholarly journals Identification of the insulin receptor tyrosine residues undergoing insulin-stimulated phosphorylation in intact rat hepatoma cells.

1988 ◽  
Vol 263 (1) ◽  
pp. 350-359 ◽  
Author(s):  
H E Tornqvist ◽  
J R Gunsalus ◽  
R A Nemenoff ◽  
A R Frackelton ◽  
M W Pierce ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Hepatoma Cells ◽  
Tyrosine Residues ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells
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