T. Nordstrom et al., KINASE-C ACTIVATION ACCELERATES PROTON EXTRUSION BY VACUOLAR-TYPE H-ATPASES IN MURINE PERITONEAL-MACROPHAGES(), FEBS letters, 350(1), 1994, pp. 82-86
The role of protein kinase C in the regulation of vacuolar-type H+-ATP
ase (V-ATPase) activity was studied in thioglycolate-elicited mouse pe
ritoneal macrophages. Acid-loaded macrophages suspended in a Na+- and
HCO3--free K+-medium containing Zn2+, a H+-conductance blocker, exhibi
ted an initial intracellular pH recovery rate of 0.33 +/- 0.04 pH/min
(n = 9). Pretreatment with 12-O-tetradecanoyl phorbol 13-acetate (TPA)
or mezerein for as little as 3 min induced a marked (82%) increase in
the initial pH recovery rate. Stimulation was prevented by the V-ATPa
se inhibitor, bafilomycin A(l) (200 nM) indicating that the effect of
the protein kinase C agonists was via augmentation of proton pump acti
vity. The protein kinase C inhibitor, staurosporine (100 nM) completel
y blocked the stimulatory effects of TPA and mezerein, suggesting invo
lvement of protein kinase C. In keeping with this notion, the inactive
analogue of TPA, 4-phorbol didecanoate did not stimulate recovery fro
m an acid load. Extracellular pH determinations revealed that the obse
rved increase in cytosolic pH recovery rate by the protein kinase C ag
onists was due to increased extrusion of protons from the cells, likel
y through V-ATPases located in the plasma membrane. Considered togethe
r, these data demonstrate regulation of plasmalemmal V-ATPase-mediated
proton extrusion by protein kinase C.