H. Niessen et al., GRANULOCYTE-COLONY-STIMULATING FACTOR UP-REGULATES THE VACUOLAR PROTON ATPASE IN HUMAN NEUTROPHILS, Blood, 90(11), 1997, pp. 4598-4601
We have previously shown that granulocyte colony-stimulating factor (G
-CSF) delays spontaneous neutrophil apoptosis through activation of th
e vacuolar proton ATPase (v-ATPase). We have now examined the regulati
on of the v-ATPase in neutrophils exposed to G-CSF in vitro. When neut
rophils 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 pre
ceding 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 s
ynthesis with cycloheximide and actinomycin D led to loss of the 57-kD
subunit even in the presence of G-CSF. These results indicated that o
ngoing protein synthesis was required to maintain the v-ATPase, and fu
rther suggested that G-CSF acted, at least in part, by maintaining syn
thesis of the 57-kD cytosolic subunit. G-CSF also promoted the translo
cation of the 57- and 33-kD cytosolic v-ATPase subunits to the membran
e. Our findings suggested two coordinate mechanisms by which the activ
ity of the v-ATPase could be increased by G-CSF: the synthesis of cyto
solic v-ATPase subunits and their translocation to the membrane. (C) 1
997 by The American Society of Hematology.