Priming of the respiratory burst of bone marrow-derived macrophages is associated with an increase in protein kinase C content.
The biochemical mechanism(s) underlying the priming of the macrophage for an enhanced PMA-induced respiratory burst is not understood. Because the cellular receptor for PMA is thought to be protein kinase C (PKC), we have investigated the effects of priming agents on cellular PKC levels. Sonicates from unprimed bone marrow-derived macrophages (BMM) were found to contain PKC activity (309 +/- 51 pmol 32P-incorporated/mg/min; mean +/- SE, n = 17) as measured by the phospholipid-, diacylglycerol-, and calcium-dependent phosphorylation of histone. Exposure of BMM to priming agents such as TNF-alpha, LPS, and granulocyte/macrophage-CSF resulted in a significant increase in both histone-phosphorylating activity and levels of immunoreactive PKC protein in these cells. A minimum of 6-h exposure, with an increasing effect up to 48 h, was required for a detectable increase in PKC level. The activity from primed BMM, like that of the untreated cells, was predominantly cytosolic. The kinetics and concentration dependence of the priming agent-induced increase in the PKC content of BMM closely paralleled the enhancing effects of these agents on the PMA-stimulated respiratory burst. Furthermore, CSF-1, a cytokine that does not prime BMM, failed to increase PKC activity. We propose that the exposure of BMM to priming agents leads to an increase in the expression of a stimulatory isozyme(s) of PKC, resulting in an enhanced ability to mount a respiratory burst in response to stimulation with PMA.
Phillips
W A
WA
Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Victoria, Australia.
Croatto
M
M
Hamilton
J A
JA
D000818:Animals; D001854:Bone Marrow Cells; D004305:Dose-Response Relationship, Drug; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000008:administration & dosage; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008808:Mice, Inbred CBA; D008970:Molecular Weight; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D016897:Respiratory Burst; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D008070:Lipopolysaccharides; D010750:Phosphoproteins; D014409:Tumor Necrosis Factor-alpha; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011493:Protein Kinase C