JNK activation induced by ribotoxic stress is initiated from 80S monosomes but not polysomes

Abstract

Translation is a costly, but inevitable, cell maintenance process. To reduce unnecessary ATP consumption in cells, a fine-tuning mechanism is needed for both ribosome biogenesis and translation. Previous studies have suggested that the ribosome functions as a hub for many cellular signals such as ribotoxic stress response, mammalian target of rapamycin (mTOR), and ribosomal S6 kinase (RSK) signaling. Therefore, we investigated the relationship between ribosomes and mitogen-activated protein kinase (MAPK) activation under ribotoxic stress conditions and found that the activation of c-Jun N-terminal kinases (JNKs) was suppressed by ribosomal protein knockdown but that of p38 was not. In addition, we found that JNK activation is driven by the association of inactive JNK in the 80S monosomes rather than the polysomes. Overall, these data suggest that the activation of JNKs by ribotoxic stress is attributable to 80S monosomes. These 80S monosomes are active ribosomes that are ready to initiate protein translation, rather than polysomes that are already acting ribosomes involved in translation elongation.

Ribosome Collisions Trigger General Stress Responses to Regulate Cell Fate

“…We also observed free and monosome-associated highly phosphorylated ZAK⍺ in cells stimulated with intermediatedose ANS (Figure 3E, intermediate ANS, fractions 1-4), consistent with a recent report that phosphorylation of ZAK⍺ reduces affinity for ribosomes (Vind et al, 2020). Given that SAPKs do not associate with polysomes (Kim et al, 2019), we propose that ZAK⍺ dissociates from colliding disomes when phosphorylated to activate downstream signaling.…”

Negative charge in the RACK1 loop broadens the translational capacity of the human ribosome

“…Furthermore, cells expressing either WT or S 278 E RACK1 exhibited a similar ribotoxic stress response (RSR) that is activated to varying extents by 60S- and 40S-targeting drugs, resulting in phosphorylation of stress kinases p38 and JNK ( Iordanov et al, 1997 ; Laskin et al, 2002 ; Vind et al, 2020 ; Wu et al, 2020 ). We find that the RSR is not activated in RACK1 knockout cells ( Figures 2B – 2D ), which is in line with studies in other cell types ( Kim et al, 2019 ) and demonstrates that RACK1 mediates these ribosome-centric stress signals. The RSR was restored in WT or S 278 E RACK1 rescue lines, and in line with prior studies, the most potent response was elicited by anisomycin and to a lesser extent by cycloheximide ( Figures 2B and 2C ).…”

Development of Carbazole Derivatives Compounds against Candida albicans: Candidates to Prevent Hyphal Formation via the Ras1-MAPK Pathway

“…The cytotoxicity of the carbazole derivatives was determined in HeLa cells. HeLa cells were maintained as previously described [ 27 , 28 ] in Dulbecco’s modified Eagle’s medium (DMEM, Invitrogen, Waltham, MA, USA) supplemented with 10% FBS (Invitrogen, Waltham, MA, USA) and grown at 37 °C in a humidified atmosphere of 5% CO 2 . Viability was measured using the MTS assay.…”