Aj. Chu, DIFFERENTIAL REGULATIONS OF PHOSPHATIDYLCHOLINE BIOSYNTHESIS IN U937 CELLS BY INHIBITORS OF PROTEIN AND TYROSINE KINASES, International Journal of Biochemistry, 26(2), 1994, pp. 189-193
1. The differential effects of inhibitors of protein kinase (PK) or ty
rosine kinase (TK) on phosphatidylcholine (PC) biosynthesis in monocyt
e-like U937 cells were compared in pulse-chase studies in which the ce
lls prelabelled with [H-3]choline for 30 min were chased in the absenc
e or presence of kinase inhibitors. 2. PKA inhibitor (H-89) decreased
the label incorporation into PC, while PKA activator (8-BrcAMP) had no
effect. 3. PKC inhibitors (chelerythrine and hypericin) inhibited PC
biosynthesis; on the other hand, PKC activator (SC-10) was stimulatory
. 4. The inhibition of PC biosynthesis by H-89 and chelerythrine was a
ccompanied by the inactivation of CTP: cholinephosphate cytidylyltrans
ferase (CT). 5. In contrast, TK inhibitor (genistein) markedly stimula
ted CT and PC biosynthesis, while erbstatin and tyrphostin No. 25 show
ed no effect.