Dual-Mechanism ERK1/2 Inhibitors Exploit a Distinct Binding Mode to Block Phosphorylation and Nuclear Accumulation of ERK1/2

Abstract

The RAS-regulated RAF-MEK1/2-ERK1/2 signaling pathway is frequently deregulated in cancer due to activating mutations of growth factor receptors, RAS or BRAF. Both RAF and MEK1/2 inhibitors are clinically approved and various ERK1/2 inhibitors (ERKi) are currently undergoing clinical trials. To date, ERKi display two distinct mechanisms of action (MoA): catalytic ERKi solely inhibit ERK1/2 catalytic activity, whereas dual mechanism ERKi additionally prevents the activating phosphorylation of ERK1/2 at its T-E-Y motif by MEK1/2. These differences may impart significant differences in biological activity because T-E-Y phosphorylation is the signal for nuclear entry of ERK1/2, allowing them to access many key transcription factor targets.Here, we characterized the MoA of five ERKi and examined their functional consequences in terms of ERK1/2 signaling, gene expression, and antiproliferative efficacy. We demonstrate that catalytic ERKi promote a striking nuclear accumulation of p-ERK1/2 in KRAS-mutant cell lines. In contrast, dualmechanism ERKi exploits a distinct binding mode to block ERK1/2 phosphorylation by MEK1/2, exhibit superior potency, and prevent the nuclear accumulation of ERK1/2. Consequently, dual-mechanism ERKi exhibit more durable pathway inhibition and enhanced suppression of ERK1/2-dependent gene expression compared with catalytic ERKi, resulting in increased efficacy across BRAF-and RAS-mutant cell lines.

Interference with ERK-dimerization at the nucleocytosolic interface targets pathological ERK1/2 signaling without cardiotoxic side-effects

“…Thus, ERK T188 -phosphorylation and subsequent nuclear ERK localization/accumulation are key determinants of gene expression and ERK-mediated pathological cardiomyocyte hypertrophy. Selective interference with ERK T188 -phosphorylation or ERK dimerization, in contrast to global ERK1/2 kinase inhibition and presumably also ERK kinase inhibitors 51 , offers the possibility to preserve beneficial cytosolic, and to specifically interfere with maladaptive nuclear ERK1/2 signaling in cardiomyocytes. The strong effect of EDI on gene regulation and thus cardiac remodeling as well as cancer cell proliferation may be due to direct or indirect activation of nuclear transcription factors by ERK1/2, but also kinase-independent ERK1/2 effects such as a direct binding of ERK to oligonucleotides, as shown for ERK2, activated ERK2, and ERK2 T188D (ref.…”

ASTX029, a Novel Dual-mechanism ERK Inhibitor, Modulates Both the Phosphorylation and Catalytic Activity of ERK

“…We and others have suggested that the differing abilities of ERK inhibitors to prevent the phosphorylation of ERK is related to their binding modes (28,30). The mechanism by which this distinctive ERK-binding mode leads to a decrease in the phosphorylation of ERK has not previously been defined.…”

“…Mol Cancer Ther; 20 (10) October 2021 that GDC-0994, an ERK inhibitor that binds within the ERK active site, but does not extend into the secondary pocket (21,28), did not robustly prevent the phosphorylation of ERK by MEK. As expected, the MEK inhibitor, trametinib, bound directly to MEK while inhibiting the phosphorylation of ERK.…”

“…The first inhibit the kinase activity of ERK alone and have been termed "catalytic ERK inhibitors" (21,22). In addition to inhibiting the kinase activity of ERK, the second class or "dual-mechanism ERK inhibitors" also prevent the phosphorylation of ERK itself (23,28,29). These dual-mechanism inhibitors alter the conformation of the glycine-rich loop of ERK, resulting in decreased phosphorylation of the activation loop and stabilization of ERK in its catalytically inactive form (26,30).…”

Ribosomal protein L22-like1 (RPL22L1) mediates sorafenib sensitivity via ERK in hepatocellular carcinoma

“…We confirmed ERKi (SCH772984 and Ulixertinib) achieved synergistic efficacy with sorafenib in RPL22L1-overexpressed cells. The two ERKi display distinct mechanism of action, with Ulixertinib (Catalytic ERKi) solely preventing ERK1/2 catalytic activity while SCH772984 (Dual mechanism ERKi) extra blocking p-ERK1/2 at T-E-Y motif by MEK1/2 [ 34 ]. This probably explained the discrepancy in p-ERK level between the two ERKi.…”