Abstract
Differential contributions of the glycosylphosphatidylinositol (GPI)-anchor and GPI-anchored proteins (GPI-AP) to signalling remain poorly understood. Here we show that GPI-AP deficient murine clones produce on average 18 and 181-fold more IL-2 mRNA and protein, respectively, upon T cell receptor (TCR) stimulation, in a cell-intrinsic fashion. This phenotype is formally attributed to a mutation within the transferase complex that predicates the initial step in GPI-anchor biosynthesis. Conditional disruption of the transferase complex enabled the generation of primary GPI-AP deficient CD4+ T cells, which produce on average 10- and 23-fold more IL-2 mRNA and protein, respectively, upon TCR stimulation. Conditional disruption of the transamidase complex yields GPI-sufficient, GPI-AP deficient primary CD4+ T cells. TCR stimulation of these cells yields levels of IL-2 mRNA and protein ranging from 1 - 3 and 3-fold, respectively, of controls. These results provide the first evidence of a profound impact of GPI in the regulation of TCR signalling.
Highlights
We show that GPI-anchored proteins (GPI-AP) deficient murine clones produce on average 18 and 181-fold more IL-2 mRNA and protein, respectively, upon T cell receptor (TCR) stimulation, in a cell-intrinsic fashion
Conditional disruption of the transferase complex enabled the generation of primary GPI-AP deficient CD4+ T cells, which produce on average 10- and 23-fold more IL-2 mRNA and protein, respectively, upon TCR stimulation
The initial observation supporting a role for GPI-AP in the regulation of T cell activation and growth was established in GPI-AP deficient variants of the IL-2-dependent, CD4−, I-Ab restricted, OVA143-157 specific, T cell clone 2.10 [18]
Summary
While this glycolipid structure has a highly conserved core sequence, the diversity among GPI-anchored proteins (GPI-AP) is consistent with their distinct functions which include transmembrane (TM) signalling, intracellular targeting, cellular adhesion and embryonic development [1] [2]. GPI-AP mediated TM signalling is predicated by their coordinated interaction with partnering molecules that couple to intracellular second messenger generating systems. While all GPI-AP share common attributes mediated by GPI, including intracellular trafficking, sorting, transport to plasma membrane [11] and dynamics at the cell surface [12] due to targeting to ordered lipid microdomains [13], there is a paucity of evidence that GPI per se directly impacts cell physiology. A recent paper has established a role for GPI in underpinning an inflammatory response in the generation of a distinct form of paroxysmal nocturnal hemoglobinuria [14]
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