Recombinant granulocyte-macrophage colony-stimulating factor increases adenylate cyclase activity in murine peritoneal macrophages.
Granulocyte-macrophage colony stimulating factor (GM-CSF) is a pleiotrophic cytokine which stimulates the function and proliferation of macrophage populations. Although the effects of GM-CSF are diverse and GM-CSF has entered into clinical trials, relatively little is known about signal transduction pathways utilized by GM-CSF. In view of previous studies which have suggested that some of the effects of GM-CSF on monocyte-macrophages can be mimicked by agents which increase intracellular cAMP, we investigated the effect of rGM-CSF on adenylate cyclase (AC) activity in murine peritoneal macrophages. Adenylate cyclase activity was quantitated in macrophage membrane preparations and in intact cells. In seven separate experiments, GM-CSF (50 U/ml) increased AC activity by 61(6)% relative to macrophages treated with carrier medium alone. A dose-dependent increase in AC activity was observed (10 to 100 U/ml) which peaked within 1 to 5 min after the addition of GM-CSF and returned to basal levels by 10 to 20 min. Lineweaver-Burk analysis revealed that the Vmax of macrophage AC was increased from 0.40 to 0.52 pmoles cAMP/min by GM-CSF but the Km was unchanged. Intracellular cAMP was increased by GM-CSF to 129(27)% of control values by 1 min of treatment (n = 6). Under similar experimental conditions, GM-CSF did not increase the activity of PK C (n = 14) or phospholipase A2 (n = 3) in peritoneal macrophages. These data show that macrophage adenylate cyclase activity is rapidly stimulated by GM-CSF. Moreover, these findings support further study of the role of cAMP in transmitting the intracellular signals initiated by GM-CSF in tissue macrophages.
Coleman
D L
DL
Department of Medicine, Veterans Administration Medical Center, West Haven, CT 06516.
Liu
J
J
Bartiss
A H
AH
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D003115:Colony-Stimulating Factors / Q000494:pharmacology*; D004789:Enzyme Activation; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000494:pharmacology*; D007700:Kinetics; D008264:Macrophages / Q000201:enzymology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010529:Peritoneal Cavity; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D011493:Protein Kinase C / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction
D003115:Colony-Stimulating Factors; D006133:Growth Substances; D011994:Recombinant Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D000262:Adenylyl Cyclases