Brief encounters and lasting impressions-How target protein half-life affects reactive metabolite signaling

Cellular stress signaling conveys vital messages to the cell's machinery to respond dynamically to internal and external environmental cues. One prevailing hypothesis for such signaling is to bring about crucial downstream functional changes in the cell's ability to withstand intra- and extra-cellular stress, as exemplified by the NRF2-ARE pathway. Reactive electrophilic metabolites (REMs)-exemplified by the lipid-derived electrophile, 4-hydroxynonenal-are often generated from membrane lipids or respiratory metabolites in inflammatory and stress signaling contexts. REMs harbor an innate ability to irreversibly bind protein-cysteines and form DNA and RNA adducts. Our work has led us to propose a new hypothesis regarding the role of locale-specific REM build-up in stress signaling; whereby, they can label both the majority stable protein residents in a given locale and the minority guests transiently existing within a subcellular compartment at a kinetically significant rate to trigger a 'gain of function' signaling cascade. Much like the NRF2 signaling pathway, such downstream signaling messages could assist the cell's ability to survive against microenvironment-specific stress and adapt on demand. As REMs accumulate in several disease-specific cells, especially age-related disorders such as cancer and neurodegeneration, understanding the functional signal propagation mechanisms shaped by specific REMs engaging with specific biomolecular targets will prove vital for future therapeutic interventions with enhanced precision and context.