TY - JOUR
T1 - Phosphorylation at a tyrosine residue of lipomodulin in mitogen-stimulated murine thymocytes
AU - Hirata, F.
AU - Matsuda, K.
AU - Notsu, Y.
AU - Hattori, T.
AU - del Carmine, R.
PY - 1984
Y1 - 1984
N2 - When murine thymocytes were stimulated by mitogens such as concanavalin A, the Ca2+ ionophore A23187, or 4β-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.
AB - When murine thymocytes were stimulated by mitogens such as concanavalin A, the Ca2+ ionophore A23187, or 4β-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.
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U2 - 10.1073/pnas.81.15.4717
DO - 10.1073/pnas.81.15.4717
M3 - Article
C2 - 6205401
AN - SCOPUS:0021272948
VL - 81
SP - 4717
EP - 4721
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 15 I
ER -