Identification and Quantification of Glutathionylated Cysteines under Ischemic Stress

Chemoproteomic strategy identified p120-catenin glutathionylation regulates E-cadherin degradation and cell migration

Identification of cysteines with high oxidation susceptibility is important for understanding redox-mediated biological processes. In this report, we report a chemical proteomic strategy that finds cysteines with high susceptibility to S-glutathionylation. Our proteomic strategy, named clickable glutathione-based isotope-coded affinity tag (G-ICAT), identified 1,518 glutathionylated cysteines while determining their relative levels of glutathionylated and reduced forms upon adding hydrogen peroxide. Among identified cysteines, we demonstrated that CTNND1 (p120) C692 has high susceptibility to glutathionylation. Also, p120 wild type (WT), compared to C692S, induces its dissociation from E-cadherin under oxidative stress, such as glucose depletion. p120 and E-cadherin dissociation correlated with E-cadherin destabilization via its proteasomal degradation. Lastly, we showed that p120 WT, compared to C692S, increases migration and invasion of MCF7 cells under glucose depletion, supporting a model that p120 C692 glutathionylation increases cell migration and invasion by destabilization of E-cadherin, a core player in cell-cell adhesion.

Clickable Glutathione-Based Identification of Cysteine Glutathionylation

Clickable glutathione is a glutathione-derived chemical probe designed to identify and analyze protein S-glutathionylation, a major cysteine oxidation in redox signaling. An engineered glutathione synthetase mutant (GS M4) is used to synthesize clickable glutathione in cells or in vitro, which affords utility via click chemistry to detect, identify, and quantify glutathionylation on individual or global proteins in biochemical and mass spectrometric analyses. The clickable glutathione approach is valuable for the unequivocal identification of glutathionylated cysteines, among many reversible cysteine oxoforms, via the direct enrichment and detection of glutathionylated proteins or peptides. Clickable glutathione, in combination with GS M4, has demonstrated utility in the mass-spectrometry-based discovery and profiling of new proteins and cysteines for glutathionylation in cell lines in response to physiologic and oxidative stress. The approach is versatile and applicable to validating the glutathionylation of proteins and cysteines in other biochemical analysis beside mass spectrometry. Here, we describe the applications of clickable glutathione and provide detailed protocols for the identification, profiling, and detection of glutathionylated proteins and cysteines. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Identification of glutathionylated cysteine in individual proteins in vitro Basic Protocol 2: Proteomic identification and quantification of glutathionylation Basic Protocol 3: Biochemical validation of glutathionylation in cells.

Desmin Reorganization by Stimuli Inducing Oxidative Stress and Electrophiles: Role of Its Single Cysteine Residue

The type III intermediate filament proteins vimentin and GFAP are modulated by oxidants and electrophiles, mainly through perturbation of their single cysteine residues. Desmin, the type III intermediate filament protein specific to muscle cells, is critical for muscle homeostasis, playing a key role in sarcomere organization and mitochondrial function. Here, we have studied the impact of oxidants and cysteine-reactive agents on desmin behavior. Our results show that several reactive species and drugs induce covalent modifications of desmin in vitro, of which its single cysteine residue, C333, is an important target. Moreover, stimuli eliciting oxidative stress or lipoxidation, including H2O2, 15-deoxy-prostaglandin J2, and CoCl2-elicited chemical hypoxia, provoke desmin disorganization in H9c2 rat cardiomyoblasts transfected with wild-type desmin, which is partially attenuated in cells expressing a C333S mutant. Notably, in cells lacking other cytoplasmic intermediate filaments, network formation by desmin C333S appears less efficient than that of desmin wt, especially when these proteins are expressed as fluorescent fusion constructs. Nevertheless, in these cells, the desmin C333S organization is also protected from disruption by oxidants. Taken together, our results indicate that desmin is a target for oxidative and electrophilic stress, which elicit desmin remodeling conditioned by the presence of its single cysteine residue.

Emerging chemistry and biology in protein glutathionylation

Protein S-glutathionylation serves a regulatory role in proteins and modulates distinct biological processes implicated in health and diseases. Despite challenges in analyzing the dynamic and reversible nature of S-glutathionylation, recent chemical and biological methods have significantly advanced the field of S-glutathionylation, culminating in selective identification and detection, structural motif analysis, and functional studies of S-glutathionylation. This review will highlight emerging studies of protein glutathionylation, beginning by introducing biochemical tools that enable mass spectrometric identification and live-cell imaging of S-glutathionylation. Next, it will spotlight recent examples of S-glutathionylation regulating physiology and inflammation. Lastly, we will feature two emerging lines of glutathionylation research in cryptic cysteine glutathionylation and protein C-glutathionylation.

Human Umbilical Vein Endothelial Cells Survive on the Ischemic TCA Cycle under Lethal Ischemic Conditions

It is generally believed that vascular endothelial cells (VECs) rely on glycolysis instead of the tricarboxylic acid (TCA) cycle under both normoxic and hypoxic conditions. However, the metabolic pattern of human umbilical vein endothelial cells (HUVECs) under extreme ischemia (hypoxia and nutrient deprivation) needs to be elucidated. We initiated a lethal ischemic model of HUVECs, performed proteomics and bioinformatics, and verified the metabolic pattern shift of HUVECs. Ischemic HUVECs displayed extensive aerobic respiration, including upregulation of the TCA cycle and mitochondrial respiratory chain in mitochondria and downregulation of glycolysis in cytoplasm. The TCA cycle was enhanced while the cell viability was decreased through the citrate synthase pathway when substrates of the TCA cycle (acetate and/or pyruvate) were added and vice versa when inhibitors of the TCA cycle (palmitoyl-CoA and/or avidin) were applied. The inconsistency of the TCA cycle level and cell viability suggested that the extensive TCA cycle can keep cells alive yet generate toxic substances that reduce cell viability. The data revealed that HUVECs depend on “ischemic TCA cycle” instead of glycolysis to keep cells alive under lethal ischemic conditions, but consideration must be given to relieve cell injury.