S6 kinase in quiescent Swiss mouse 3T3 cells is activated by phosphorylation in response to serum treatment

Journal Article · Sat Oct 01 00:00:00 EDT 1988 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.85.19.7154· OSTI ID:5478178

Ballou, L M; Siegmann, M; Thomas, G ^[1]

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1. Friedrich Miescher-Institut, Basel (Switzerland)

To investigate the role of phosphorylation in the activation of S6 kinase, the enzyme was isolated from {sup 32}P-labeled Swiss mouse 3T3 cells before and after stimulation with serum. The kinase activity was followed through several purification steps, and a radioactive protein of M{sub r} 70,000 was obtained from the stimulated cells. This band was not detected in resting cells. The M{sub r} 70,000 protein exhibited the same size upon NaDodSO{sub 4}/PAGE as the homogeneous kinase, and it comigrated with the in vitro autophosphorylated form of the enzyme. Treatment of the in vivo-labeled material with phosphatase 2A led to a loss of kinase activity concomitant with a release of {sup 32}P{sub i} from the M{sub r} 70,000 protein. The partially dephosphorylated protein migrated faster during PAGE, displaying distinct species of M{sub r} 69,000 and 68,000. Most importantly, phospho amino acid analysis of the labeled S6 kinase showed only phosphoserine and phosphothreonine. These results argue that the S6 kinase is phosphorylated at multiple sites in vivo and that it is activated by serine/threonine phosphorylation.

• OSTI ID: 5478178
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 85:19; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CELL PROLIFERATION
BIOCHEMISTRY
PHOSPHOTRANSFERASES
PHOSPHORYLATION
ELECTROPHORESIS
ENZYME INDUCTION
FIBROBLASTS
IN VIVO
MICE
PHOSPHORUS 32
SERINE
THREONINE
AMINO ACIDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
ENZYMES
GENE REGULATION
HYDROXY ACIDS
ISOTOPES
LIGHT NUCLEI
MAMMALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
RADIOISOTOPES
RODENTS
SOMATIC CELLS
TRANSFERASES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques