Abstract
Leucine (Leu) is a multifunctional essential amino acid that plays crucial role in various cellular processes. However, the integral effect of Leu on the hepatic proteome remains largely unknown. Here, we for the first time applied an isobaric tags for relative and absolute quantification (iTRAQ)-based comparative proteomics strategy to investigate the proteome alteration induced by Leu deprivation in human hepatocellular carcinoma (HepG2) cells. A total of 4,111 proteins were quantified; 43 proteins were further identified as differentially expressed proteins between the normal and Leu deprivation groups. Bioinformatics analysis showed that the differentially expressed proteins were involved in various metabolic processes, including amino acid and lipid metabolism, as well as degradation of ethanol. Interestingly, several proteins involved in the fatty acid β-oxidation pathway, including ACSL1, ACADS, and ACOX1, were up-regulated by Leu deprivation. In addition, Leu deprivation led to the reduction of cellular triglycerides in HepG2 cells. These results reveal that the fatty acid β-oxidation pathway is activated by Leu deprivation in HepG2 cells, and provide new insights into the regulatory function of Leu in multiple cellular processes, especially fatty acid metabolism.
Highlights
They found that Gln altered the expressions of crucial apoptotic process related proteins including MAP3K7, Aven, Atg[5], and stathmin, giving multiple hypotheses regarding to the anti-apoptosis capacities of Gln
Our bioinformatics analysis suggested that Leu deprivation regulated the expressions of proteins that are involved in several crucial biological processes such as amino acid metabolism and lipid metabolism
Due to the large variation between different isobaric tags for relative and absolute quantification (iTRAQ) runs (Supplementary Fig. S2), and to identify more proteins that were potentially regulated by Leu deprivation, we used a less stringent strategy with the criteria of unique peptide >1, P-value < 0.05, fold change >2 in any one set of the two iTRAQ experiments
Summary
They found that Gln altered the expressions of crucial apoptotic process related proteins including MAP3K7, Aven, Atg[5], and stathmin, giving multiple hypotheses regarding to the anti-apoptosis capacities of Gln. Xin and colleagues[15] investigated the effects of Met restriction on the proteome of gastric cancer cells SGC7901 by culturing cells in normal and Met-deprived homocysteine-supplemented media. Xin and colleagues[15] investigated the effects of Met restriction on the proteome of gastric cancer cells SGC7901 by culturing cells in normal and Met-deprived homocysteine-supplemented media They identified a total of ten proteins, which are related to cell cycle arrest and apoptosis, that were differentially regulated by Met restriction. The present study suggests a potential regulatory role of Leu on fatty acid metabolism in HepG2 cells
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