AJP - Cell Physiology, Vol 251, Issue 6 883-C886, Copyright © 1986 by American Physiological Society
Kinase A does not activate phosphatidylinositol phosphorylation in rat lymphocyte membranes
A. Coco and I. G. Macara
The interaction of the dissociated catalytic subunit of adenosine
3',5'-cyclic monophosphate-dependent protein kinase (kinase A) and
phosphatidylinositol metabolism has been studied in rat spleen lymphocyte
membranes. As reported previously (Sarkadi et al., FEBS Lett. 152: 195-198,
1983) addition of kinase A increased by about twofold the phosphorylation
of phosphatidylinositol in lymphocyte membranes at low ATP concentrations.
However, we have found that this increase is an artifact of the assay
conditions, and that the increase is a consequence of an inhibition of
membrane adenosine triphosphatase activity by the protein kinase A. When
lipid phosphorylation was measured under initial rate conditions, at high
ATP concentrations, the increase was abolished. No effect of kinase A was
observed on initial rates of the synthesis or hydrolysis of
phosphatidylinositol phosphate. No phosphatidylinositol bisphosphate was
produced in the membranes under any of the assay conditions used.
