TCR-stimulated changes in cell surface CD46 expression generate type 1 regulatory T cells

Abstract

A lack of regulatory T cell function is a critical factor in the pathogenesis of autoimmune diseases, such as multiple sclerosis (MS). Ligation of the complement regulatory protein CD46 facilitates the differentiation of T helper 1 (T1) effector cells into interleukin-10 (IL-10)-secreting type 1 regulatory T cells (Tr1 cells), and this pathway is defective in MS patients. Cleavage of the ectodomain of CD46, which contains three N-glycosylation sites and multiple O-glycosylation sites, enables CD46 to activate T cells. We found that stimulation of the T cell receptor (TCR)-CD3 complex was associated with a reduction in the apparent molecular mass of CD46 in a manner that depended on O-glycosylation. CD3-stimulated changes in CD46 O-glycosylation status reduced CD46 processing and subsequent T cell signaling. During T cell activation, CD46 was recruited to the immune synapse in a manner that required its serine-, threonine-, and proline-rich (STP) region, which is rich in O-glycosylation sites. Recruitment of CD46 to the immune synapse switched T cells from producing the inflammatory cytokine interferon-γ (IFN-γ) to producing IL-10. Furthermore, CD4 T cells isolated from MS patients did not exhibit a CD3-stimulated reduction in the mass of CD46 and thus showed increased amounts of cell surface CD46. Together, these data suggest a possible mechanism underlying the regulatory function of CD46 on T cells. Our findings may explain why this pathway is defective in patients with MS and provide insights into MS pathogenesis that could help to design future immunotherapies.

The anthelmintic drug praziquantel promotes human Tr1 differentiation

“…We next assessed whether PZQ modulated cell activation by measuring the expression of the activation markers CD25, CD69 and PD‐1, and of CD46 after either 1 or 5 days of activation (Supplementary figure 2, Figure ). As expected, CD46 costimulation led to a strong decrease in CD46 surface expression due to the shedding of its ectodomain . Addition of PZQ had no significant effect on the expression of CD46 and did not significantly modulate the induction of CD69, CD25 and PD‐1.…”

“…As expected, CD46 costimulation led to a strong decrease in CD46 surface expression due to the shedding of its ectodomain. 17,18 Addition of PZQ had no significant effect on the expression of CD46 and did not significantly modulate the induction of CD69, CD25 and PD-1. PZQ has been shown to act as an adjuvant for vaccination, correlating with an increase in IL-17 and IFNc production by murine CD8 + T cells.…”

“…For detection of IFNγ, IL‐17, GM‐CSF and IL‐10 capture ELISAs were performed on day 5 supernatants, in duplicates. IL‐10 and IFNγ secretion was determined by ELISA specific for human IL‐10 (BD Pharmingen, Oxford, UK) and IFNγ (Thermo‐Fisher, Paisley, UK) as previously published . ELISAs for IL‐17 and GMCSF were purchased from BioLegend (ELISA MAX Deluxe, London, UK) and were performed according to the manufacturer's instructions.…”

The Role of Membrane Bound Complement Regulatory Proteins in Tumor Development and Cancer Immunotherapy

“…In terms of the regulation of CD46, it has been shown that CD46 is highly glycosylated, and that CD3 stimulation alters the O-glycosylation of CD46 in activated T-cells, resulting in decreased CD46 processing and T-cell singling, which ultimately leads to a T-reg phenotype characterized by the dominance of IL-10. Nuclear factor κB (NF-κB) has also been shown to regulate CD46 expression, where activation of NF-κB is critical for CD46 expression (65).…”

Current perspectives in assessing humoral immunity after measles vaccination

“…Ongoing functional studies in human cells expressing/overexpressing different CD46 isoforms demonstrate clear difference in MV infection/replication and innate immune pathway activation depending on the prevalence of specific CD46 isoforms ( Haralambieva and Poland , unpublished data). Lastly, the presence/absence of STP exons (associated also with difference in the O-glycosylation) in the extracellular portion of CD46 can result in altered processing, altered CD46 shedding/cleavage by metalloproteinases, altered downregulation and cell surface expression, and profound differences in T cell function and TCR signaling [139, 140].…”