Increased Cell Surface Free Thiols Identify Effector CD8+ T Cells Undergoing T Cell Receptor Stimulation

Abstract

Recognition of peptide Major Histocompatibility Complexes (MHC) by the T cell receptor causes rapid production of reactive oxygen intermediates (ROI) in naïve CD8+ T cells. Because ROI such as H2O2 are membrane permeable, mechanisms must exist to prevent overoxidation of surface proteins. In this study we used fluorescently labeled conjugates of maleimide to measure the level of cell surface free thiols (CSFT) during the development, activation and differentiation of CD8+ T cells. We found that during development CSFT were higher on CD8 SP compared to CD4 SP or CD4CD8 DP T cells. After activation CSFT became elevated prior to division but once proliferation started levels continued to rise. During acute viral infection CSFT levels were elevated on antigen-specific effector cells compared to memory cells. Additionally, the CSFT level was always higher on antigen-specific CD8+ T cells in lymphoid compared to nonlymphoid organs. During chronic viral infection, CSFT levels were elevated for extended periods on antigen-specific effector CD8+ T cells. Finally, CSFT levels on effector CD8+ T cells, regardless of infection, identified cells undergoing TCR stimulation. Taken together these data suggest that CD8+ T cells upregulate CSFT following receptor ligation and ROI production during infection to prevent overoxidation of surface proteins.

Proposed Neuroimmune Roles of Dimethyl Fumarate, Bupropion, S-Adenosylmethionine, and Vitamin D3 in Affording a Chronically Ill Patient Sustained Relief from Inflammation and Major Depression

“…Glutathione adds via conjugate, 1,4-addition, and coenzyme-A (CoA) reacts with fumarates only via acylation (or 1,2-addition), see reactions marked A and B, Figure 1 . Thereafter, fumarate-CoA-adducts form Krebs cycle metabolites in cells, however, formation and fate of conjugate 1,4-addition products of CoA with fumarates are unknown in animal biochemistry literature [ 30 , 31 ].…”

“…Upon combining with cytoplasmic Nrf2 protein, the glutathione-thiosuccinate-Nrf2 complex is expected to migrate into the nucleus, activate the antioxidant defense system genes, and generate antioxidants (glutathione, superoxide dismutase, and catalase) that quench free radicals, avert oxidative stress, subdue inflammation, and preclude NLRP3 inflammasome mediated pyroptosis [ 24 , 25 , 30 , 31 , 32 , 33 , 34 , 35 ].…”

CD44 Binding to Hyaluronic Acid Is Redox Regulated by a Labile Disulfide Bond in the Hyaluronic Acid Binding Site

“…There is evidence that post translational control of disulfide bond topology also plays a role in regulation of the immune system. Activation of T cells results in up regulation of thioredoxin-1 (Trx1), a ubiquitous thiol reductase enzyme [ 14 ], and results in increased thiols at the T cell surface [ 15 , 16 ], which can be inhibited with thiol reductase inhibitors [ 15 ]. Activated dendritic cells also secrete Trx1 [ 17 ] which can reduce disulfide bonds at the surface of both the dendritic cells and co cultured T cells [ 18 ].…”

Reduction of leucocyte cell surface disulfide bonds during immune activation is dynamic as revealed by a quantitative proteomics workflow (SH-IQ)

“…Therefore, controlling this modulation provides a potential means of therapeutic intervention of many diseases, such as those involving the immune system [ 13 ], haemostasis [ 12 ] and cancer [ 35 ]. An increase in free thiols on immune cells upon activation was first described 20 years ago by Lawrence et al [ 33 ] and was henceforth confirmed in various studies [ 36 – 38 ]. However, these studies are limited as they only provide global data and do not identify the modified proteins, nor do they provide a quantitative determination of the level of reduction of each protein.…”

“…Similar effects were observed by Lawrence et al [ 33 ] using PMA (independent of antigen presentation) to stimulate PBMCs and the ubiquitous thiol isomerase inhibitor bacitracin. Although it was previously shown that Trx1 and other oxidoreductases are upregulated and secreted from T cells upon activation [ 38 , 40 ], we provide the first global identification of the proteins containing labile disulfide bonds sensitive to oxidoreductases on the surface of T cells undergoing activation and expansion. The self-modulation of cell surface receptors by labile disulfide bond reduction is a concept analogous to the autocrine function of cytokines.…”