NatB-mediated protein N-α-terminal acetylation is a potential therapeutic target in hepatocellular carcinoma

Abstract

The identification of new targets for systemic therapy of hepatocellular carcinoma (HCC) is an urgent medical need. Recently, we showed that hNatB catalyzes the N-α-terminal acetylation of 15% of the human proteome and that this action is necessary for proper actin cytoskeleton structure and function. In tumors, cytoskeletal changes influence motility, invasion, survival, cell growth and tumor progression, making the cytoskeleton a very attractive antitumor target. Here, we show that hNatB subunits are upregulated in in over 59% HCC tumors compared to non-tumor tissue and that this upregulation is associated with microscopic vascular invasion. We found that hNatB silencing blocks proliferation and tumor formation in HCC cell lines in association with hampered DNA synthesis and impaired progression through the S and the G2/M phases. Growth inhibition is mediated by the degradation of two hNatB substrates, tropomyosin and CDK2, which occurs when these proteins lack N-α-terminal acetylation. In addition, hNatB inhibition disrupts the actin cytoskeleton, focal adhesions and tight/adherens junctions, abrogating two proliferative signaling pathways, Hippo/YAP and ERK1/2. Therefore, inhibition of NatB activity represents an interesting new approach to treating HCC by blocking cell proliferation and disrupting actin cytoskeleton function.

Molecular Basis for N-terminal Alpha-Synuclein Acetylation by Human NatB

“…These observations suggest that the proper function of actin and tropomyosin requires NTA by the intact NatB complex [42]. In humans, disruption of NatB (hNatB) by knockout leads to defects in proper actin cytoskeleton structure, cell cycle progression and cell proliferation [17,[43][44][45]. In addition, hNatB is upregulated in human hepatocellular carcinoma [43], where it has been suggested as a potential therapeutic target as silencing of this complex can block cell proliferation and tumor formation [45].…”

“…In humans, disruption of NatB (hNatB) by knockout leads to defects in proper actin cytoskeleton structure, cell cycle progression and cell proliferation [17,[43][44][45]. In addition, hNatB is upregulated in human hepatocellular carcinoma [43], where it has been suggested as a potential therapeutic target as silencing of this complex can block cell proliferation and tumor formation [45]. hNatB-mediated NTA of αsynuclein (αSyn) has been shown to increase αSyn stability and lipid binding, and to reduce aggregation capacity [10,[46][47][48][49][50][51][52][53].…”

“…However, hNAA20 and hNAA25 share only ~40% and ~20% sequence identity with the Candida albicans homologue [57], respectively. Moreover, nearly all biological studies of NatB have been conducted in Saccharomyces cerevisiae [58][59][60], Arabidopsis [61,62], mouse [63] and human [17,[43][44][45] as model organisms. As a result, the mode of human NatB-mediated catalysis and aSyn-specific NatB recognition remains unresolved.…”

NatB modulates Rb mutant cell death and tumor growth by regulating EGFR/MAPK signaling through the N-end rule pathways

“…The high sequence conservation of these EGFR signaling components suggest that the mechanisms we uncovered in Drosophila will likely be conserved in mammalian systems. Indeed, a recent study found that inhibition of NatB significantly decreased EGFinduced ERK activation in human liver cancer cells [38]. As mutation or overexpression of EGFR or Ras that deregulate EGFR signaling are quite common in human cancers and NatB subunits are significant unfavorable prognostic markers for human cancers [39][40][41], our results could potentially provide a new strategy to develop therapeutic interventions for these cancers.…”

A genome-wide screen identifies genes that suppress the accumulation of spontaneous mutations in young and aged yeast cells

“…NAT3 was identified in a screen for radiation sensitive mutants, and thereafter named RAD56 [63,64]. Importantly, its human homologue hNAT3 has been implicated in carcinogenesis [65,66]. Non-degradative protein N-acetylation occurs co-translationally and can modulate protein folding, protein localization and protein-protein interactions [67].…”