Granulocyte colony-stimulating factor upregulates the vacuolar proton ATPase in human neutrophils.
We have previously shown that granulocyte colony-stimulating factor (G-CSF ) delays spontaneous neutrophil apoptosis through activation of the vacuolar proton ATPase (v-ATPase). We have now examined the regulation of the v-ATPase in neutrophils exposed to G-CSF in vitro. When neutrophils were cultivated in the absence of G-CSF, the 57-kD cytosolic B subunit of the v-ATPase disappeared within 1 to 2 hours, its loss preceding the nuclear changes of apoptosis and coinciding with the onset of acidification. By contrast, in neutrophils cultured for 2 hours in the presence of G-CSF, the amount of the 57-kD subunit was similar to that in freshly isolated neutrophils. However, inhibition of protein synthesis with cycloheximide and actinomycin D led to loss of the 57-kD subunit even in the presence of G-CSF. These results indicated that ongoing protein synthesis was required to maintain the v-ATPase, and further suggested that G-CSF acted, at least in part, by maintaining synthesis of the 57-kD cytosolic subunit. G-CSF also promoted the translocation of the 57-and 33-kD cytosolic v-ATPase subunits to the membrane. Our findings suggested two coordinate mechanisms by which the activity of the v-ATPase could be increased by G-CSF: the synthesis of cytosolic v-ATPase subunits and their translocation to the membrane.
Niessen
H
H
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA 92037.
Meisenholder
G W
GW
Li
H L
HL
Gluck
S L
SL
Lee
B S
BS
Bowman
B
B
Engler
R L
RL
Babior
B M
BM
Gottlieb
R A
RA
D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018942:Macrolides; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000096:biosynthesis*; D015854:Up-Regulation / Q000187:drug effects*; D025262:Vacuolar Proton-Translocating ATPases
D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D018942:Macrolides; D011500:Protein Synthesis Inhibitors; C057620:bafilomycin A; D016179:Granulocyte Colony-Stimulating Factor; D003513:Cycloheximide; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases