Insulin activates a 70-kDa S6 kinase through serine/threonine-specific phosphorylation of the enzyme polypeptide

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.87.20.7944· OSTI ID:5802457

Price, D J; Gunsalus, J R; Avruch, J ^[1]

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1. Harvard Medical School, Boston, MA (USA)

The dominant insulin-stimulated ribosomal protein S6 kinase activity was purified to near homogeneity from insulin-treated {sup 32}P-labeled rat H4 hepatoma cells and found to copurify with a 70-kDa {sup 32}P-labeled polypeptide. The dominant S6 kinase purified from livers of cycloheximide-treated rats is also a 70-kDa polypeptide. Antiserum raised against rat liver S6 kinase specifically immunoprecipitates the purified {sup 32}P-labeled H4 hepatoma insulin-stimulated S6 kinase. Immune complexes prepared from the cytosol of {sup 32}P-labeled H4 cells contain several {sup 32}P-labeled polypeptides. Insulin treatment increases the {sup 32}P content of the immunoprecipitated 70-kDa S6 kinase polypeptide 3- to 4-fold over basal levels. Tryptic peptide maps indicate that the insulin-stimulated S6 kinase purified from {sup 32}P-labeled H4 cells is phosphorylated at multiple sites distinct from those which participate in autophosphorylation in vitro. The S6 kinases purified from liver of cycloheximide-treated rat and H4 hepatoma insulin-stimulated enzyme are each completely deactivated by incubation with protein phosphatase type 2A in both autophosphorylating and 40S S6 phosphorylating activities. Thus insulin activates the 70-kDa S6 kinase by promoting phosphorylation of specific serine/threonine residues on the enzyme polypeptide, probably through activating an as-yet-unidentified serine/threonine protein kinase distinct from microtubule-associated protein 2 kinase.

• OSTI ID: 5802457
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 87:20; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
INSULIN
BIOLOGICAL EFFECTS
PHOSPHOTRANSFERASES
ENZYME INDUCTION
POLYPEPTIDES
PHOSPHORYLATION
ATP
HEPATOMAS
PHOSPHORUS 32
RATS
SERINE
THREONINE
TUMOR CELLS
AMINO ACIDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DISEASES
ENZYMES
GENE REGULATION
HORMONES
HYDROXY ACIDS
ISOTOPES
LIGHT NUCLEI
MAMMALS
NEOPLASMS
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PEPTIDES
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PROTEINS
RADIOISOTOPES
RODENTS
TRANSFERASES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques