Abstract
Fumagillin and its derivatives are therapeutically useful because they can decrease cancer progression. The specific molecular target of fumagillin is methionine aminopeptidase 2 (MetAP2), one of the two MetAPs present in the cytosol. MetAPs catalyze N-terminal methionine excision (NME), an essential pathway of cotranslational protein maturation. To date, it remains unclear the respective contribution of MetAP1 and MetAP2 to the NME process in vivo and why MetAP2 inhibition causes cell cycle arrest only in a subset of cells. Here, we performed a global characterization of the N-terminal methionine excision pathway and the inhibition of MetAP2 by fumagillin in a number of lines, including cancer cell lines. Large-scale N-terminus profiling in cells responsive and unresponsive to fumagillin treatment revealed that both MetAPs were required in vivo for M[VT]X-targets and, possibly, for lower-level M[G]X-targets. Interestingly, we found that the responsiveness of the cell lines to fumagillin was correlated with the ability of the cells to modulate their glutathione homeostasis. Indeed, alterations to glutathione status were observed in fumagillin-sensitive cells but not in cells unresponsive to this agent. Proteo-transcriptomic analyses revealed that both MetAP1 and MetAP2 accumulated in a cell-specific manner and that cell sensitivity to fumagillin was related to the levels of these MetAPs, particularly MetAP1. We suggest that MetAP1 levels could be routinely checked in several types of tumor and used as a prognostic marker for predicting the response to treatments inhibiting MetAP2.
Highlights
N-terminal methionine excision (NME) is an essential cotranslational pathway and is the first modification to which proteins are subjected, whilst still bound to the ribosome and before their synthesis has even been completed [for a reviews see 1, 2, 3]
We performed cell growth assays with various mammalian primary, immortalized or tumor cell lines, including endothelial, non-tumor and tumor-derived lines with and without fumagillin treatment, to determine the precise selectivity of the methionine aminopeptidase 2 (MetAP2) inhibition phenotype
We investigated the importance of NME for the control of cellular homeostasis, by performing experiments to determine whether the low levels of proliferation resulting from cytoplasmic NME inhibition could be corrected by adding N-acetylcysteine to the culture medium
Summary
N-terminal methionine excision (NME) is an essential cotranslational pathway and is the first modification to which proteins are subjected, whilst still bound to the ribosome and before their synthesis has even been completed [for a reviews see 1, 2, 3]. In all living organisms and cell compartments in which polypeptides are synthesized, proteins are always initially generated with a methionine as their first residue (iMet). This iMet is removed from most of the proteins accumulating at steady state. It has remained unclear for decades why up to two thirds of the proteins in any proteome undergo NME. Recent advances have provided strong support for the “protein stability” hypothesis, bridging the gap between NME and protein half-life [for reviews see 5, 6]. Through its global control of protein halflife, NME has been shown to fine tune global glutathione redox homeostasis in plants, yeast and Archaea [7]
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