Chemical proteomic mapping and functional manipulation of extracellular proteinaceous cysteines

Project Summary Around 262,000 cysteine residues are intricately distributed throughout the human proteome. These cysteines play pivotal roles in influencing protein folding, stability, enzymatic functions, and the response to oxidative stress. Chemical probes designed to target cysteines are critical tools for investigating protein functionality and advancing drug development. Chemical proteomics, particularly cysteine-directed activity-based protein profiling (ABPP), has emerged as a fundamental technique for studying proteinaceous cysteines. ABPP employs a wide- spectrum cysteine-reactive probe to effectively pinpoint cysteine sites across a variety of proteins, enabling comprehensive functional exploration and facilitating ligand discovery. Traditionally, extracellular proteinaceous cysteines have been largely neglected in the field of chemical proteomics. It was also believed that these cysteines mainly formed disulfide bonds to stabilize protein structures. However, recent research has challenged this notion by revealing the dynamic nature of extracellular redox environments, which can significantly influence proteinaceous cysteine reactivity in the extracellular space. Consequently, a substantial knowledge gap remains in identifying extracellular proteins containing unmodified, reactive cysteines in specific biological contexts. To address this gap, this research program aims to establish an innovative chemical proteomic platform tailored for mapping extracellular proteinaceous cysteines across a wide range of biological scenarios. These scenarios include T cell activation, GGT5 genetic knockout, and various chemical treatments. Subsequently, we will investigate the potential druggability of these extracellular proteinaceous cysteines. Finally, utilizing the insights gained from targeting druggable extracellular proteinaceous cysteines, we aim to manipulate their functionality in pursuit of two key outcomes: inducing cell-cell interactions and promoting targeted protein degradation.