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.
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Yagasaki, K., Morisaki-Tsuji, N., Miura, A. et al. 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. Cytotechnology 40, 151–154 (2002). https://doi.org/10.1023/A:1023988405518
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DOI: https://doi.org/10.1023/A:1023988405518