scholarly journals Microcystin-LR induced an inhibition of protein synthesis in isolated rat hepatocytes

1995 ◽  
Vol 306 (3) ◽  
pp. 693-696 ◽  
Author(s):  
S Claeyssens ◽  
A Francois ◽  
A Chedeville ◽  
A Lavoinne
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Hepatocytes ◽  
Mitochondrial Fraction ◽  
Maximum Effect ◽  
Isolated Rat Hepatocytes ◽  
Phosphatase Inhibitors ◽  
Protein Phosphatase Inhibitors ◽  
Phosphatase Activation ◽  
Isolated Rat

The effect of microcystin-LR, an inhibitor of protein phosphatases PP1 and PP2A, was studied on protein synthesis by measuring the incorporation of labelled amino acid into protein in isolated rat hepatocytes. Microcystin-LR inhibited protein synthesis in the first minutes of the incubation period, and half-maximum effect was obtained at about 60 nM. Such an inhibition was also observed in the presence of different protein phosphatase inhibitors, i.e. okadaic acid, calyculin A and microcystin-RR. This effect was observed in whole hepatocytes, in the supernatant of the post-mitochondrial fraction and in the microsomal fraction. It was independent of a substrate supply and of the labelled amino acid used. Furthermore, this inhibition preceded the previously reported glucose-6-phosphatase activation induced by microcystin-LR [Claeyssens, Chédeville and Lavoinne (1993) FEBS Lett. 315, 7-10].

AMINO ACID CONTROL OF PROTEIN SYNTHESIS AND DEGRADATION IN ISOLATED RAT HEPATOCYTES*

1980 ◽  
Vol 349 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Per O. Seglen ◽  
Anne E. Solheim ◽  
Bjørn Grinde ◽  
Paul B. Gordon ◽  
Per E. Schwarze ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Acid Control ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation ◽  
Isolated Rat

Effect of amino acid deprivation on initiation of protein synthesis in rat hepatocytes

1989 ◽  
Vol 256 (1) ◽  
pp. C18-C27 ◽  
Author(s):  
W. V. Everson ◽  
K. E. Flaim ◽  
D. M. Susco ◽  
S. R. Kimball ◽  
L. S. Jefferson
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Hepatocytes ◽  
Initiation Factor ◽  
Synthetic Activity ◽  
Perfused Liver ◽  
Amino Acid Deprivation ◽  
Isolated Rat Hepatocytes ◽  
Reticulocyte Lysate

Conditions were defined for maintaining optimal protein synthetic activity in suspensions of freshly isolated rat hepatocytes. Under these conditions, isolated hepatocytes exhibited rates of protein synthesis and levels of polysomal aggregation equivalent to those observed in vivo and in perfused liver. Deprivation of total amino acids or single, essential amino acids resulted in a rapid decrease in the rate of protein synthesis, which was readily reversed by readdition of the deficient amino acid(s). The decrease was accompanied by a disaggregation of polysomes and an inhibition of 43S initiation complex formation, which was indicative of a limitation in the rate of initiation of protein synthesis. Extracts prepared from perfused liver deprived of amino acids were inhibitory to initiation of protein synthesis in reticulocyte lysate. The inhibition in reticulocyte lysate was accompanied by an increase in phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 (eIF-2), suggesting activation of an eIF-2 alpha kinase or inhibition of a phosphatase in amino acid-deprived hepatocytes. This suggestion was confirmed by prelabeling hepatocytes with 32Pi before amino acid deprivation. Incorporation of 32Pi into eIF-2 alpha was two- to threefold higher in lysine-deprived cells than in hepatocytes incubated in fully supplemented medium. Overall, the results indicated that an increase in eIF-2 alpha phosphorylation was responsible for the defect in initiation of protein synthesis caused by amino acid deprivation.

Initiation of protein synthesis in a cell-free system prepared from rat hepatocytes

1989 ◽  
Vol 256 (1) ◽  
pp. C28-C34 ◽  
Author(s):  
S. R. Kimball ◽  
W. V. Everson ◽  
K. E. Flaim ◽  
L. S. Jefferson
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Hepatocytes ◽  
Initiation Factor ◽  
Nucleotide Exchange ◽  
Isolated Rat Hepatocytes ◽  
Intact Cells ◽  
Free System ◽  
Cell Free System ◽  
A Cell

A cell-free system, which maintained a linear rate of protein synthesis for up to 20 min of incubation, was prepared from isolated rat hepatocytes. The rate of protein synthesis in the cell-free system was approximately 20% of the rate obtained in isolated hepatocytes or perfused liver. More than 70% of total protein synthesis in the cell-free system was due to reinitiation, as indicated by addition of inhibitors of initiation, i.e., edeine or polyvinyl sulfate. The rate of protein synthesis and formation of 43S initiation complexes in the cell-free system were reduced to 60 and 30% of the control values, respectively, after incubation of hepatocytes in medium deprived of an essential amino acid. Therefore, the cell-free system maintained the defect in initiation induced in the intact cells by amino acid deprivation. The defect in initiation was corrected by addition of either rat liver eukaryotic initiation factor 2 or the guanine nucleotide exchange factor (GEF) to the cell-free system. A role for GEF in the defect in initiation was further implicated by experiments that showed that the activity of the factor was decreased in extracts from livers perfused with medium deficient in amino acids. The cell-free system should provide a valuable tool for investigation of mechanisms involved in the regulation of initiation of protein synthesis.

Amiloride inhibits protein synthesis in isolated rat hepatocytes

Life Sciences ◽  
1981 ◽  
Vol 28 (11) ◽  
pp. 1295-1302 ◽  
Author(s):  
Max Fehlmann ◽  
Michel Samson ◽  
Katherine S. Koch ◽  
Hyam L. Leffert ◽  
Pierre Freychet
Keyword(s):  
Protein Synthesis ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Isolated Rat
Sign in / Sign up

Export Citation Format

Share Document