Phosphorylation at a tyrosine residue of lipomodulin in mitogen-stimulated murine thymocytes.

When murine thymocytes were stimulated by mitogens such as concanavalin A, the Ca2+ ionophore A23187, or 4 beta-phorbol 12-myristate 13-acetate, there was a marked increase of 32P incorporation into immunoprecipitable lipomodulin, a phospholipase inhibitory protein. These compounds enhanced 45Ca2+ influx into thymocytes, which, in turn, increased protein phosphorylation, probably by Ca2+- and phospholipid-dependent protein kinase (protein kinase C). Cyclic 8-bromo-AMP, an inhibitor of lymphocyte mitogenesis, blocked the mitogen-stimulated phosphorylation of lipomodulin, although it stimulated the protein phosphorylation via cyclic AMP-dependent kinase (protein kinase A). On electrophoresis, the hydrolysates of 32P-labeled lipomodulin showed a single radioactive spot, which comigrated with authentic phosphotyrosine. The partially purified middle-sized tumor antigen was able to phosphorylate lipomodulin after being phosphorylated by protein kinase C but not by the catalytic subunit of protein kinase A. Our findings suggest that the activity of a tyrosine-specific kinase, which phosphorylates lipomodulin in vivo as well as in vitro, is stimulated by protein kinase C and inhibited by protein kinase A.
AuthorsF Hirata, K Matsuda, Y Notsu, T Hattori, R del Carmine
JournalProceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 81 Issue 15 Pg. 4717-21 (Aug 1984) ISSN: 0027-8424 [Print] UNITED STATES
PMID6205401 (Publication Type: Journal Article)
Chemical References
  • Annexins
  • Calcium-Binding Proteins
  • Glycoproteins
  • Phosphoproteins
  • Proteins
  • lipomodulin
  • Phosphotyrosine
  • Tyrosine
  • Cyclic AMP
  • Protein Kinases
  • Protein Kinase C
  • Animals
  • Annexins
  • Calcium-Binding Proteins
  • Cells, Cultured
  • Cyclic AMP (pharmacology)
  • Glycoproteins
  • Lymphocyte Activation
  • Mice
  • Mitosis
  • Phosphoproteins (metabolism)
  • Phosphotyrosine
  • Protein Kinase C
  • Protein Kinases (metabolism)
  • Proteins (metabolism)
  • Thymus Gland (metabolism)
  • Tyrosine (analogs & derivatives, metabolism)

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