Isoquinolinesulfonamide protein kinase inhibitors H7 and H8 enhance the
effects of granulocyte-macrophage colony-stimulating factor (GM-CSE) on
neutrophil function and inhibit GM-CSF receptor internalization
A Khwaja, PJ Roberts, HM Jones, K Yong, MS Jaswon and DC Linch
Department of Haematology, University College Middlesex School of Medicine,
London, UK.
Human granulocyte-macrophage colony-stimulating factor (GM-CSF) increases
neutrophil surface expression of the cellular adhesion molecule CD11b and
primes the respiratory burst stimulated by the bacterial peptide
f-met-leuphe (FMLP). We have examined the effects of the
isoquinolinesulfonamide protein kinase inhibitors H7 and H8 on these
functions of GM-CSF using whole blood assays. Concentrations of H7 and H8
that inhibited the 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulated
upregulation of CD11b expression and activation of the respiratory burst,
both augmented the effects of GM-CSF. H7 and H8 enhanced the
GM-CSF-stimulated increase in CD11b expression to 215% +/- 10% (P less than
.05) and 233% +/- 45% (P less than .05), respectively, of the value
obtained with GM-CSF alone. The GM-CSF priming of the FMLP- stimulated
oxidative burst was increased to 190% +/- 44% (P less than .01) by
preincubation with H7 and to 172% +/- 25% (P less than .01) with H8.
Preincubation with H8 did not affect overall binding of 125I- GM-CSF to
neutrophils, but inhibited GM-CSF receptor internalization after ligand
binding (P less than .05). These data indicate that the effects of GM-CSF
are not mediated by protein kinase C and that a phosphorylation event
down-modulates the neutrophil response to GM-CSF. It suggests that
internalization of the receptor-ligand complex is not a rate-limiting step
in signal transduction, and that regulation of the rate of internalization
may be an important level of control of the activity of GM-CSF.
Volume 76,
Issue 5,
pp. 996-1003,
09/01/1990
Copyright © 1990 by The American Society of Hematology
