Granulocyte-macrophage colony-stimulating factor: signals for its mRNA accumulation.
Granulocyte-monocyte colony-stimulating factor (GM-CSF) is an important hematopoietic growth factor. Mesenchymal cells produce abundant GM-CSF in response to tumor necrosis factor alpha (TNF). We wished to determine (1) what cellular pathways enhanced levels of GM-CSF mRNA, and (2) if TNF used any of these pathways. Modulation in levels of GM-CSF mRNA in human fibroblasts (WI-38) was studied by using Northern blot analysis. Markedly increased levels of GM-CSF mRNA occurred in these cells after exposure to sodium fluoride (NaF) and the effect of NaF was slightly enhanced by aluminum chloride; these results suggest that accumulation of GM-CSF mRNA can occur by activating a G-binding protein. Stimulators of protein kinase C dramatically increased levels of GM-CSF mRNA; however, blockade of protein kinase C activity did not attenuate accumulation of GM-CSF mRNA stimulated by TNF and NaF. Exposure to ouabain increased levels of GM-CSF mRNA and this effect was prominently enhanced in the presence of low concentrations of extracellular K+ and was almost abolished in high concentrations of extracellular K+. A monovalent ionophore (monensin) also increased levels of GM-CSF mRNA. Both ouabain and monensin can increase intracellular Ca++ concentration (Cai++) through Na+-Ca++ exchange. A calcium channel blocker (diltiazem) blocked the increased levels of GM-CSF mRNA mediated by ouabain, but could not block the stimulation mediated by TNF alpha. Ca++ ionophores also increased levels of GM-CSF mRNA and rapidly increased levels of Cai++. TNF did not increase Cai++ and, moreover, was able to stimulate accumulation of GM-CSF mRNA in the absence of extracellular Ca++. Taken together, we have found that several different cellular pathways can lead to prominent accumulation of GM-CSF mRNA in mesenchymal cells including (1) activation of protein kinase C, (2) increase in Cai++, and (3) stimulation of G-binding protein. Our studies show that TNF appears to increase levels of GM-CSF mRNA independent of protein kinase C activity or levels of Cai++.
Yamato
K
K
UCLA Department of Medicine, Los Angeles, CA 90024-1678.
El-Hajjaoui
Z
Z
Kuo
J F
JF
Koeffler
H P
HP
D000535:Aluminum / Q000494:pharmacology; D000077410:Aluminum Chloride; D017607:Aluminum Compounds; D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D003115:Colony-Stimulating Factors / Q000378:metabolism* / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008168:Lung; D008985:Monensin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D012969:Sodium Fluoride / Q000494:pharmacology
D017607:Aluminum Compounds; D002712:Chlorides; D003115:Colony-Stimulating Factors; D006133:Growth Substances; D012333:RNA, Messenger; D000001:Calcimycin; D000077410:Aluminum Chloride; D010042:Ouabain; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D012969:Sodium Fluoride; D008985:Monensin; D000535:Aluminum; D011493:Protein Kinase C