An activity-guided map of electrophile-cysteine interactions in primary human immune cells

Abstract

Electrophilic compounds originating from nature or chemical synthesis have profound effects on immune cells. These compounds are thought to act by cysteine modification to alter the functions of immune-relevant proteins; however, our understanding of electrophile-sensitive cysteines in the human immune proteome remains limited. Here, we present a global map of cysteines in primary human T cells that are susceptible to covalent modification by electrophilic small molecules. More than 3000 covalently liganded cysteines were found on functionally and structurally diverse proteins, including many that play fundamental roles in immunology. We further show that electrophilic compounds can impair T cell activation by distinct mechanisms involving direct functional perturbation and/or ligand-induced degradation of proteins. Our findings reveal a rich content of ligandable cysteines in human T cells, underscoring the potential of electrophilic small molecules as a fertile source for chemical probes and ultimately therapeutics that modulate immunological processes and their associated disorders.

Histidine-specific bioconjugationviavisible-light-promoted thioacetal activation

“…Post-translational modifications (PTMs) of proteins enables a marked increase in protein functional diversity 1 for manipulation of protein structure and function 2 . Various chemical tools have been developed to assess modified sites of proteins, exploring many important information about protein interactions and/or enzymatic mechanism in drug development, molecular biology and medicine [3][4][5][6] . However, most of labeling strategies are limited to the functionalization of nucleophilic residues, namely cysteine, lysine and tyrosine [7][8][9][10][11][12][13] .…”

A Chemical Proteomic Probe for the Mitochondrial Pyruvate Carrier Complex

“…As part of a broader research program aimed at characterizing the protein targets of electrophilic compounds in primary human T cells [1] using a mass spectrometry (MS)based chemical proteomic method that quantifies cysteine reactivity on a global scale, [2] we discovered herein an alphachloroacetamide (aCA) YY4 (1; Figure 1 A) that strongly engages cysteine-54 (C54) in subunit 2 of the mitochondrial pyruvate carrier (MPC2) (Figure 2 A,B). This interaction was of interest because, to our knowledge, covalent, irreversible ligands have not been described for MPC2.…”

“…Additionally, C54 of MPC2 was not sensitive to structurally related aCA compounds (for example, EV-93 (3); Figures 1 A and 2 A, B; Supporting Information, Table 1) or broadly reactive electrophilic fragments (Supporting Information, Figure S1). [1] The restricted structure-activity relationship (SAR) displayed by C54 in MPC2 was suggestive of residence in a defined small molecule-binding pocket. Motivated by the important role of the MPC in human metabolism, [3] combined with the dearth of assays available to evaluate endogenous MPC activity and pharmacological inhibition in cells, [4] we set out to further investigate the YY4-MPC2 interaction.…”