CD69 down‐modulation and inhibition of thymic egress by short‐ and long‐term selective chemical agonism of sphingosine 1‐phosphate receptors

Abstract

Thymic development requires proliferation, selection, maturation and release of mature single-positive CD4 and CD8 T cells into the periphery. In mice, non-selective sphingosine-1 phosphate (S1P) receptor agonists, active on four of the five known S1P receptors, alter thymocyte phenotype and egress. Here, we show that down-modulation of CD69 occurs acutely and transiently at a discrete and late stage of medullary development after a single-dose administration of S1P 1 receptor-selective agonist, which induces long-term tonic receptor activation in the absence of receptor degradation. In addition, agonist acutely inhibited egress of mature thymocytes into peripheral lymphoid organs, suggesting that both the phenotype and migration of medullary thymocytes are regulated simultaneously and coordinately by agonism of S1P 1 alone. Long-term dosing shifted the early/late medullary thymocyte ratio with an expansion of the late medullary compartment, as mature CD69 -thymocytes were retained within the thymus. Therefore, chemical agonism of S1P 1 accelerates medullary phenotypic maturation and inhibits egress, leading to the expansion and accumulation of the recent thymocyte emigrant population in the medulla. However, chemical agonism fails to replicate the S1P 1 -null CD69 hi late medullary phenotype, suggesting that agonism and gene deletion operate by distinct mechanisms, and that functional receptor antagonism may not be required for lymphocyte sequestration.

Mapping Pathways Downstream of Sphingosine 1-Phosphate Subtype 1 by Differential Chemical Perturbation and Proteomics

“…beyond that stimulated by SEW2871 or S1P herein). Furthermore, it is interesting that receptor ubiquitination by AFD-R was readily detectable at a concentration as low as 0.5 nM, similar to the reported affinity of its chiral analog, FTY720-P, in activating recombinant systems (13), and within the reported EC 50 value for AFD-R in vivo actions on lymphocyte sequestration and CD69 thymocyte maturation, reported to be 0.7 nM (25).…”

Sphingosine 1-Phosphate Receptor 1 (S1P1) Upregulation and Amelioration of Experimental Autoimmune Encephalomyelitis by an S1P1 Antagonist

“…3B). S1P 1 agonists cause a loss of surface expression of CD69 on mature thymocytes (Alfonso et al, 2006). In contrast to the effects seen with agonists, continuous Ex26 treatment led to significant upregulation of CD69 (Fig.…”

Dynamic regulation of miRNA expression in ordered stages of cellular development

“…While this was interpreted as a facilitated commitment to the B lineage, the results of this study provide an alternative explanation. Disruption of CD69 signaling has been shown to negatively impact the egress of lymphocytes from lymphoid organs, including the thymus (Nakayama et al 2002;Alfonso et al 2006;Shiow et al 2006). Forced expression of miR-181a past the DP stage of thymocyte development would be expected to decrease CD69 levels on positively selected thymocytes, resulting in retention of these cells in the thymus and an apparent decrease in peripheral T cells.…”