Accumulating evidence suggests that proteins tethered to the plasma membrane through glycosylphosphatidylinositol (GPI) anchors share common biological properties. In the present study we demonstrate that GPI-anchored proteins regulate T cell growth. Specifically, anti-TCR-induced proliferation was profoundly inhibited by co-immobilized mAb specific for Thy-1, CD48 and Ly6A/E. However, neither IL-2 production nor the effector function of cytotoxic T lymphocytes was impaired in these circumstances. Analysis of the IL-2 receptor (IL-2R) signaling pathway revealed that the association of IL-2R β and γ chains with the Janus kinases, JAK1 and JAK3, was not perturbed in the presence of mAb specific for GPI-linked proteins. However, in these conditions, IL-2-mediated recruitment of IL-2Rα, β and γ chains, resulting in the formation of the high-affinity hetero-trimeric IL-2R, was inhibited. The resulting phosphorylation of JAK1 and JAK3, indicative of their activation states, was correspondingly reduced. These results characterize a novel state of T cell physiology in which effector function is maintained, in the absence of clonal expansion. A physiological role for GPI-anchored proteins in the maintenance of cellular homeostasis and function is discussed.
- Glycosylphosphatidylinositol-anchored proteins
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