Highlights d Chemical proteomics identifies cysteine reactivity changes in activated T cells d Chemical proteomics maps ligandable cysteines in diverse immune-relevant proteins d Cysteine-directed electrophilic compounds suppress T cells by distinct mechanisms d Electrophile-cysteine interactions promote the degradation of immune proteins

A decline in stem cell function impairs tissue regeneration during aging, but the role of the stem cell supporting niche in aging is not well understood. The small intestine is maintained by actively cycling intestinal stem cells (ISCs) that are regulated by the Paneth cell niche 1,2. Here we show that the regenerative potential of human and mouse intestinal epithelium diminishes with age due to defects in both stem cells and their niche. The functional decline was caused by decrease in stemness maintaining Wnt signalling due to production of an extracellular Wnt-inhibitor, Notum, in aged Paneth cells. Mechanistically, high mTORC1 activity in old Paneth cells inhibits PPARa activity 3 and lowered PPARa increased Notum expression. Genetic targeting of Notum or Wnt-supplementation restored function of old intestinal organoids. Moreover, pharmacological inhibition of Notum in mice enhanced the regenerative capacity of old stem cells and promoted recovery from chemotherapy induced damage. Our results reveal an unappreciated role for the stem cell niche in aging and demonstrate that targeting of Notum can promote regeneration of old tissues. Tissue turnover and regenerative capacity decrease upon aging in many tissue types 4-6. The intestinal epithelium is one of the fastest renewing tissues in the human body and has been reported to regenerate without loss of self-renewal in long term in vitro organoid culture 7. However,

The transcription factor NRF2 is a master regulator of the cellular antioxidant response and is often genetically activated in Non-Small Cell Lung Cancers (NSCLCs) by, for instance, mutations in the interacting protein KEAP1. While direct pharmacological inhibition of NRF2 has proven challenging, its aberrant activation rewires biochemical networks in cancer cells that may create special vulnerabilities. Here, we use chemical proteomics to map druggable proteins that are selectively expressed in KEAP1-mutant NSCLC cells. Principal among these was NR0B1, an atypical orphan nuclear receptor that we show engages in a multimeric protein complex to regulate the transcriptional output of KEAP1-mutant NSCLC cells. We further identify small molecules that covalently target a conserved cysteine within the NR0B1 protein interaction domain and demonstrate that these compounds disrupt NR0B1 complexes and impair the anchorage-independent growth of KEAP1-mutant cancer cells. Our findings designate NR0B1 as a druggable, transcriptional regulator that supports NRF2-dependent lung cancers.

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Highlights d We identified ALDH1A family inhibitors (ALDH1Ai) that target CD133 + ovarian CSCs d ALDH1Ai triggers calcium-dependent cell-programmed necrosis d ALDH1Ai induces mitochondrial uncoupling proteins affecting cellular metabolism d ADH1Ai overcomes chemotherapy resistance to increase tumor eradication