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Peptidomic Analysis of HEK293T Cells: Effect of the Proteasome Inhibitor Epoxomicin on Intracellular Peptides

Peptidomic Analysis of HEK293T Cells: Effect of the Proteasome Inhibitor Epoxomicin on Intracellular Peptides

Lloyd D Fricker, Julia S Gelman, Leandro M Castro, Fabio C Gozzo, Emer S Ferro

J Proteome Res. 2012 Mar 2;11(3):1981-90.

PMID: 22304392

Abstract:

Peptides derived from cytosolic, mitochondrial, and nuclear proteins have been detected in extracts of animal tissues and cell lines. To test whether the proteasome is involved in their formation, HEK293T cells were treated with epoxomicin (0.2 or 2 μM) for 1 h and quantitative peptidomics analysis was performed. Altogether, 147 unique peptides were identified by mass spectrometry sequence analysis. Epoxomicin treatment decreased the levels of the majority of intracellular peptides, consistent with inhibition of the proteasome beta-2 and beta-5 subunits. Treatment with the higher concentration of epoxomicin elevated the levels of some peptides. Most of the elevated peptides resulted from cleavages at acidic residues, suggesting that epoxomicin increased the processing of proteins through the beta-1 subunit. Interestingly, some of the peptides that were elevated by the epoxomicin treatment had hydrophobic residues in P1 cleavage sites. Taken together, these findings suggest that, while the proteasome is the major source of intracellular peptides, other peptide-generating mechanisms exist. Because intracellular peptides are likely to perform intracellular functions, studies using proteasome inhibitors need to be interpreted with caution, as it is possible that the effects of these inhibitors are due to a change in the peptide levels rather than inhibition of protein degradation.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP134381218	Epoxomicin		134381-21-8	Price

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