| First Author | Reginald K | Year | 2015 |
| Journal | J Immunol | Volume | 195 |
| Issue | 11 | Pages | 5472-81 |
| PubMed ID | 26512138 | Mgi Jnum | J:239190 |
| Mgi Id | MGI:5825414 | Doi | 10.4049/jimmunol.1501300 |
| Citation | Reginald K, et al. (2015) Revisiting the Timing of Action of the PAG Adaptor Using Quantitative Proteomics Analysis of Primary T Cells. J Immunol 195(11):5472-81 |
| abstractText | The protein tyrosine kinase LCK plays a key role in TCR signaling, and its activity is dynamically controlled by the tyrosine kinase C-terminal Src kinase (CSK) and the tyrosine phosphatase CD45. CSK is brought in contiguity to LCK via binding to a transmembrane adaptor known as phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG). The lack of a blatant phenotype in PAG-deficient mice has impeded our understanding of the mechanisms through which PAG exerts its negative-regulatory role in TCR signaling. We used quantitative mass spectrometry and both thymocytes and CD4(+) T cells from mice in which a tag for affinity purification was knocked in the gene coding for PAG to determine the composition and dynamics of the multiprotein complexes that are found around PAG over 5 min of activation. Most of the high-confidence interactions that we observed were previously unknown. Using phosphoproteomic analysis, PAG showed low levels of tyrosine phosphorylation in resting primary mouse CD4(+) T cells; the levels of tyrosine phosphorylation increased and reached a maximum 2 min after stimulation. Analysis of the dynamics of association of the protein tyrosine phosphatase PTPN22 and lipid phosphatase SHIP-1 with PAG following T cell activation suggests that both cooperate with CSK to terminate T cell activation. Our findings provide a model of the role for PAG in mouse primary CD4(+) T cells that is consistent with recent phosphoproteomic studies of the Jurkat T cell line but difficult to reconcile with former biochemical studies indicating that PAG is constitutively phosphorylated in resting T cells and rapidly dephosphorylated once the TCR is engaged. |
