Mechanism of RACK1-dependent ZAKα activation at stalled and collided ribosomes

Anna Constance Vind  ¹ , José Francisco Martínez  ¹ , Zhenzhen Wu  ¹ , Andrii Bugai  ² , Kelly Mordente  ¹ , Giancarlo Abis  ³ , Sébastien Chamois  ⁴ , Sofia Ramalho  ¹ , Catarina Pechincha  ¹ , Laura Ryder  ¹ , Qiuyan Chen  ¹ , Mads Rasmussen  ¹ , Xinyao Shi  ¹ , Dandan He  ¹ , Jesper Q Svejstrup  ¹ , Peter Haahr  ¹ , David Gatfield  ⁴ , Maria R Conte  ³ , Torben Heick Jensen  ² , Melanie Blasius  ¹ , Simon Bekker-Jensen  ⁵

• Affiliations
• PMID: 42214329
• DOI: 10.1016/j.molcel.2026.04.034
• Free article
• Abstract
• Despite a growing interest in the ribotoxic stress response (RSR), it remains unknown how the upstream p38- and JNK-activating MAP3 kinase ZAKα senses translational impairment. Combining AlphaFold3 prediction and RNA crosslinking and immunoprecipitation (CLIP), we uncover that ZAKα dynamically monitors the mRNA exit channel of elongating ribosomes. This is accomplished by ZAKα via direct interactions with the ribosomal proteins RACK1 and RPS27 as well as 18S rRNA helix-26. In this conformation, the RNA-binding S (sensing) and C-terminal domain of ZAKα span across the mRNA exit channel. Loss of ribosome processivity and mRNA stasis stabilizes the interaction allowing for kinase activation. Prolonged binding of ZAKα to stalled and collided ribosomes is associated with sequestration of the sterile alpha-motif (SAM) domain on RACK1, which allows for transient ZAKα dimerization, activation loop trans-autophosphorylation, and RSR activation. Our findings highlight how ZAKα senses both stalled and collided ribosomes in human cells through overlapping mechanisms.

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Angptl4 integrates dietary and microbial signals to disrupt gut barrier function in MASH

Damien Chua  ¹ , Zun Siong Low  ² , Joseph Han Sol Kim  ² , Yin Hao Lee  ^{3   4} , Rattanaporn Kiatbumrung  ⁵ , Pornjira Somnark  ⁵ , Min Xu  ⁶ , Yue Shi  ⁶ , Gourav Kaushal  ⁷ , Marcus Ivan Gerard Vos  ² , Aparna Mahadevan  ² , Natalie Hooi  ² , Mathan Raj  ⁸ , Ekaterina Sviriaeva  ² , Beiming Cui  ⁹ , Shaun Tan  ² , Kazuyuki Kasahara  ² , Chun Loong Ho  ⁹ , Walter Wahli  ^{2   10   11} , Kuo Chao Yew  ¹² , Sunny H Wong  ^{2   12} , Christine Cheung  ^{2   13} , Mintu Pal  ¹⁴ , Ru Zhang  ^{15   16   17} , Natthaya Chuaypen  ⁵ , Pisit Tangkijvanich  ⁵ , Hong Sheng Cheng  ¹⁸ , Liang Li  ¹⁹ , Nguan Soon Tan  ^{20   21}

Affiliations

• PMID: 42173835
• DOI: 10.1038/s41467-026-72575-6

Free article

Abstract

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a major contributor to liver morbidity, yet mechanisms linking gut barrier dysfunction to early progression remains poorly defined. We identify intestinal angiopoietin-like 4 (Angptl4) as a central integrator of dietary and microbial signals that governs barrier integrity and hepatic oxidative stress, key early MASLD features. Using intestinal-specific Angptl4 knockout mice, mechanistic in vitro systems, humanized microbiota models, and multi-cohort human studies, we show that intestinal Angptl4 expression is regulated by dietary fatty acids via PPARα signaling and microbiota-derived pattern-recognition pathways, including flagellin-activated-TLR5-EGR1 activation, alongside diet-associated shifts in TLR signaling. These signals destabilize epithelial barriers, amplifying gut-to-liver metabolic and microbial flux. In human cohorts, fecal Angptl4 increases with dysbiosis and metabolic dysfunction, capturing a gut barrier-related dimension distinct from endotoxemia or acute injury. Thus, intestinal Angptl4 emerges as a mechanistic hub linking diet, microbiota, and gut-liver dysfunction, supporting precision barrier-targeted strategies in MASLD.