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

Journal Article · · Am. J. Physiol.; (United States)
OSTI ID:6500316
; ; ; ;

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 /sup 32/Pi before amino acid deprivation. Incorporation of /sup 32/Pi 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.

Research Organization:
Pennsylvania State Univ., Hershey (USA)
OSTI ID:
6500316
Journal Information:
Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 256; ISSN AJPHA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMAL CELLS
ANIMALS
AROMATICS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
BODY
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DRUGS
ENZYMES
ESTERASES
GROWTH FACTORS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROLASES
INDOLES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIPOTROPIC FACTORS
LIVER CELLS
LYSINE
MAMMALS
METHIONINE
MITOGENS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
PERFUSED ORGANS
PHOSPHATASES
PHOSPHATES
PHOSPHORUS 32
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
PROTEINS
PYRROLES
RADIOISOTOPES
RATS
REACTION KINETICS
RODENTS
SOMATIC CELLS
SYNTHESIS
TRACER TECHNIQUES
TRANSFERASES
TRYPTOPHAN
VERTEBRATES