Brain-wide measurement of protein turnover with high spatial and temporal resolution

Cellular functions are regulated by synthesizing and degrading proteins on time scales ranging from minutes to weeks. Protein turnover varies across proteins, cellular compartments, cell types, and tissues. In the brain, circuit-specific protein turnover is thought to underlie synaptic plasticity, but current methods to track protein turnover lack cellular or subcellular resolution. We describe a pulse–chase method (DELTA) to measure protein turnover with high spatial and temporal resolution throughout the body. DELTA relies on the rapid covalent capture by HaloTag of fluorescent ligands optimized for bioavailability in vivo , overcoming the unique challenges associated with labeling in the brain. We found that the nuclear protein MeCP2 showed brain-region- and cell-type-specific turnover, and the synaptic protein PSD95 was destabilized in specific brain regions following behavioral enrichment. A new variant of expansion microscopy enabled turnover measurements at individual synapses. DELTA will enable studies of adaptive and maladaptive plasticity in brain-wide neural circuits. ### Competing Interest Statement The authors have declared no competing interest.