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SW Evans, D Rennick and WL Farrar
In order to investigate early signal transduction events in myeloid cells,
the phosphosubstrates of an interleukin 3 (IL 3)-dependent cell line,
FDC-P1, have been analyzed. Using synthetic diacylglycerol as a direct
activator of the unique calcium-phospholipid-dependent phosphotransferase
protein kinase C (PK-C) and genetically engineered homogeneous IL 3, we
have demonstrated a common element to signal transduction events associated
with these stimulants. One novel substrate, p68 (68,000 kd), was rapidly
phosphorylated in either IL 3- or diacylglycerol-stimulated cells. The
phosphorylation of p68 was dose- dependent, with both the physiological
ligand and diacylglycerol inducing the same maximal level of
phosphorylation. Phosphorylation of p68 occurred in a time-dependent manner
analogous to previously described kinetics of PK-C subcellular
redistribution in the FDC-P1 cell line. The p68 substrate was also
phosphorylated in a cell-free system under conditions designed to activate
PK-C. Phosphoamino acid analysis demonstrated that the p68 molecule
phosphorylated in intact cells as well as in a
calcium-phospho-lipid-dependent cell-free system was phosphorylated on
threonine residues, not tyrosine. These data support the hypothesis that
the activation of PK-C that occurs after IL 3-receptor interaction which
leads to the rapid phosphorylation of cellular proteins is an important
element of the signal transduction mechanism in FDC-P1 cells. We propose
that phosphorylation of the p68 molecule is a physiochemical marker for the
activation of PK-C in myeloid cells, in response to the growth-promoting
physiological ligand.
This article has been cited by other articles:
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| Copyright © 1986 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
