Evaluation of possible mechanisms of phorbol ester stimulation of phosphatidylcholine synthesis in HeLa cells

H. W. Cook, D. E. Vance

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

Phorbol esters, including 12-O-tetradecanoylphorbol-13-acetate (TPA) and 12,13-dibutyrylphorbol acetate, markedly stimulate the synthesis of phosphatidylcholine (PC) and the activity of CTP:phosphocholine cytidyltransferase (CT) in cultured HeLa cells. Two possible mechanisms whereby the phorbol esters stimulated PC biosynthesis were investigated. One consideration was that phorbol esters may induce the release of fatty acyl chains from endogenous complex lipids; increased fatty acids or fatty acyl-CoAs could cause the translocation of CT from cytosol to microsomes and thereby increase the activity of the rate-limiting enzyme in PC synthesis. In HeLa cells prelabeled with [3H]oleate or [3H]arachidonate, phorbol ester treatment increased the redistribution of arachidonate in phospholipids and neutral lipids and release of label to the medium, but there was little effect on the cellular fatty acid pools with either of the labeled fatty acids or of the phorbol esters. A second possibility was that protein kinase C (PKC), a receptor for phorbol esters, might be involved in activation of CT activity. TPA stimulated the phosphorylation of cytosolic proteins of HeLa cells more than 2-fold during a 10- or 60-min incubation with 32P(i). However, an approximate 6-fold purified preparation of PKC from rat brain did not stimulate the activity of partially purified (12- to 15-fold) CT; a slight inhibition, dependent on ATP but independent of Ca2+ and diolein, was observed. Our results suggest that intracellular release of free fatty acids or direct phosphorylation of CT by PKC probably do not account for the observed levels of stimulation by phorbol esters. Other possible mechanisms are discussed.

Original languageEnglish
Pages (from-to)145-151
Number of pages7
JournalCanadian Journal of Biochemistry and Cell Biology
Volume63
Issue number2
DOIs
Publication statusPublished - 1985
Externally publishedYes

ASJC Scopus Subject Areas

  • General Medicine

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't

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Cook, H. W., & Vance, D. E. (1985). Evaluation of possible mechanisms of phorbol ester stimulation of phosphatidylcholine synthesis in HeLa cells. Canadian Journal of Biochemistry and Cell Biology, 63(2), 145-151. https://doi.org/10.1139/o85-021