Skip to main content
NCBI home page
Cytotechnology logoLink to Cytotechnology
. 2002 Nov;40(1-3):151–154. doi: 10.1023/A:1023988405518

Possible involvement of phospholipase C and protein kinase C in stimulatory actions of L-leucine and its keto acid, α-ketoisocaproic acid, on protein synthesis in RLC-16 hepatocytes

Kazumi Yagasaki 1,✉, Naoko Morisaki-Tsuji 1, Atsuhito Miura 1, Ryuhei Funabiki 1
PMCID: PMC3449520  PMID: 19003115

Abstract

Effects of leucine and related compounds on protein synthesis were studied in RLC-16 hepatocytes. The incorporation of [3H] tyrosine into cellular protein was measured as an indexof protein synthesis. In leucine-depleted RLC-16 cells, L-leucineand its keto acid, α-ketoisocaproic acid (KIC), stimulated protein synthesis, while D-leucine did not. Mepacrine, an inhibitor of both phospholipase A2 and C canceled stimulatory actions of L-leucine and KIC on protein synthesis, suggesting a possible involvement of either arachidonic acid metabolism by phospholipase A2, cyclooxygenase or lipoxygenase, or phosphatidylinositol degradation by phospholipase C in the stimulatory actions of L-leucine and KIC.Neither indomethacin, an inhibitor of cyclooxygenase, nor caffeic acid, an inhibitor of lipoxygenase, diminished their stimulatory actions, suggesting no involvement of arachidonic acid metabolism. Conversely, 1-O-hexadecyl-2-O-methylglycerol, an inhibitor of protein kinase C, significantly canceled the stimulatory actions of L-leucine and KIC on protein synthesis, suggesting an involvement of phosphatidylinositol degradation and activation of protein kinase C. These results strongly suggest that both L-leucine and KIC stimulate protein synthesis in RLC-16 cells via activation of phospholipase C and production of diacylglycerol and inositol triphosphate from phosphatidylinositol, which in turn activate protein kinase C.

Keywords: α-ketoisocaproic acid, L-leucine, phospholipase inhibitor, protein kinase C inhibitor, protein synthesis, RLC-16 hepatocyte

Full Text

The Full Text of this article is available as a PDF (64.2 KB).

References

  1. Crabb DW, Harris RA. Studies on the regulation of leucine catabolism in the liver. Stimulation by pyruvate and dichloroacetate. J Biol Chem. 1978;253:1481–1487. [PubMed] [Google Scholar]
  2. Fernandez L, Flores-Morales A, Lahuna O, Sliva D, Norstedt G, Haldosen LA, Mode A, Gustafsson JÅ. Desensitization of the growth hormone-induced Janus kinase 2 (Jak 2)/signal transducer and activator of transcription 5 (Stat5)-signaling pathway requires protein synthesis and phospholipase C. Endocrinology. 1998;139:1815–1824. doi: 10.1210/endo.139.4.5931. [DOI] [PubMed] [Google Scholar]
  3. Koshihara Y, Neichi T, Murota S, Lao A, Fujimoto Y, Tatsuno T. Selective inhibitor of 5-lipoxygenase by natural compounds isolated from Chinese plants, Artemisia rubripes Nakai. FEBS Lett. 1983;158:41–44. doi: 10.1016/0014-5793(83)80672-3. [DOI] [PubMed] [Google Scholar]
  4. Kramer IM, Van der Bend RL, Tool AT, Van Blitterswijk WJ, Roos D, Verhoeven AL. 1-O-hexadecyl-2-Omethylglycerol, a novel inhibitor of protein kinase C, inhibits the respiratory burst in human neutrophils. J Biol Chem. 1989;264:5876–5884. [PubMed] [Google Scholar]
  5. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951;193:265–275. [PubMed] [Google Scholar]
  6. Mayes PJ. Metabolism of Unsaturated Fatty Acids and Eicosanoids. In: Murray RK, Granner DK, Mayes PA, Rodwell VW, editors. Harper's Biochemistry. 25th ed. Stamford: Appleton & Lange; 2000. pp. 250–258. [Google Scholar]
  7. Mortimore GE, Pösö AR, Kadowaki M, Wert JJ., Jr Multiphasic control of hepatic protein degradation by regulatory amino acids. J Biol Chem. 1987;262:16322–16327. [PubMed] [Google Scholar]
  8. Patti M-E, Brambilla E, Luzi L, Landaker EJ, Kahn CR. Bidirectional modulation of insulin action by amino acids. J Clin Invest. 1998;101:1519–1529. doi: 10.1172/JCI1326. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Pösö AR, Wert JJ, Jr, Mortimore GE. Multifunctional control by amino acids of deprivation-induced proteolysis in liver. J Biol Chem. 1982;257:12114–12120. [PubMed] [Google Scholar]
  10. Premecz G, Markovits A, Bagi G, Farkas T, Foldes I. Phospholipase C and phospholipase A2 are involved in the antiviral activity of human interferon-α. FEBS Lett. 1989;249:257–260. doi: 10.1016/0014-5793(89)80635-0. [DOI] [PubMed] [Google Scholar]
  11. Rodemann HP, Goldberg AL. Arachidonic acid, prostaglandin E2 and F2α influence rates of protein turnover in skeletal and cardiac muscle. J Biol Chem. 1982;257:1632–1638. [PubMed] [Google Scholar]
  12. Takaoka T, Yasumoto S, Katsuta H. A simple method for the cultivation of rat liver cells. Japan J Exp Med. 1975;45:317–326. [PubMed] [Google Scholar]
  13. Tischler ME, Desautels M, Goldberg AL. Does leucine, leucyl-tRNA, or some metabolite of leucine regulate protein synthesis and degradation in skeletal and cardiac muscle? J Biol Chem. 1982;257:1613–1621. [PubMed] [Google Scholar]
  14. Yagasaki K, Saito K, Yamaguchi M, Funabiki R. Involvement of arachidonic acid metabolism in insulin-stimulated protein synthesis in cultured L6 myocytes. Agric Biol Chem. 1991;55:1449–1453. [Google Scholar]
  15. Yagasaki K, Kida Y, Miura Y, Funabiki R. Actions of Branched-chain Amino Acids on Protein Degradation in Cultured Muscle Cells. In: Kobayashi T, Kitagawa Y, Okumura K, editors. Animal Cell Technology: Basic & Applied Aspects. Dordrecht: Kluwer Academic Publishers; 1994. pp. 279–285. [Google Scholar]

Articles from Cytotechnology are provided here courtesy of Springer Science+Business Media B.V.

RESOURCES