Insulin-stimulated microtubule-associated protein kinase is phosphorylated on tyrosine and threonine in vivo

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.85.11.3753· OSTI ID:5365254

Ray, L B; Sturgill, T W ^[1]

---

1. Univ. of Virginia School of Medicine, Charlottesville (USA)

Exposure of 3T3-L1 cells to insulin stimulates a soluble, serine(threonine)-specific protein kinase that phosphorylates microtubule-associated protein 2 (MAP-2) in vitro. The enzyme, termed MAP kinase, was isolated from insulin-treated or control cells radiolabeled with {sup 32}P{sub i}. A 40-kDa phosphoprotein was found to elute in exact correspondence with enzymatic activity during hydrophobic interaction and gel filtration chromatography of extracts from cells stimulated with insulin. Both MAP kinase activity and the phosphoprotein were absent in fractions prepared from untreated cells. The {sup 32}P incorporated into the 40-kDa protein was stable during treatment with alkali. Phospho amino acid analysis confirmed that the radiolabel was primarily incorporated into phosphotyrosine and to a lesser extend phosphothreonine. In addition, MAP kinase was incompletely but specifically adsorbed by antibodies to phosphotyrosine. The authors conclude, based on these data and additional studies from this laboratory, that MAP kinase is phosphorylated on tyrosine in vivo. The data are consistent with the possibility that MAP kinase may be a substrate for the insulin receptor or another insulin-regulated tyrosine kinase.

• OSTI ID: 5365254
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 85:11; ISSN 0027-8424; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
ELECTROPHORESIS
ENZYME ACTIVITY
ENZYME INDUCTION
ENZYMES
FIBROBLASTS
GENE REGULATION
HORMONES
HYDROXY ACIDS
IN VIVO
INSULIN
ISOTOPES
LIGHT NUCLEI
MICROTUBULES
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
RADIOISOTOPES
SOMATIC CELLS
THREONINE
TRANSFERASES
TYROSINE