The role of JAK1 and JAK3 in CD8+ effector T cells

Student thesis: Doctoral ThesisDoctor of Philosophy


The aim of this project was to explore the role of the tyrosine kinases JAK1 and JAK3 in cytokine signalling, focusing on interleukin-2 signalling in CD8+ effector T lymphocytes. Initial experiments compared the effects of the pan JAK1/JAK3 inhibitor tofacitinib, the selective JAK1 inhibitor GSK186, and the selective JAK3 inhibitor GSK192 on IL-2 control of effector CD8+ cytotoxic T cells (CTL). On the basis of these preliminary data, a detailed analysis of the effect of tofacitinib on effector CD8+ T lymphocytes was performed.

Phosphorylation events regulated by tofacitinib were identified using mass spectrometry analysis of SILAC (stable isotope labelling with amino acids in cell culture) labelled CTL. Tofacitinib regulated a selective number of phosphorylation sites, with less than 1.2% of the CTL phosphoproteome significantly regulated by tofacitinib treatment following 4hrs tofacitinib treatment. Proteins with downregulated phosphorylation sites were enriched in functions related to the Jak-STAT signalling, regulation of gene expression, and MAPK signalling cascades. Proteins with upregulated phosphorylations were also enriched in functions related to regulation of gene transcription.

The proteome of tofacitinib treated CTL was defined by label free mass spectrometry. Approximately 4.5% of the CTL proteome was significantly regulated following 24 hours tofacitinib treatment, suggesting tofacitinib regulates the expression of a selective subset of proteins. Tofacitinib treatment resulted in the downregulation of proteins involved in ribosome biosynthesis, steroid biosynthesis, regulation of transcription and the cell cycle; and the upregulation of proteins with hydrolase activity, and with roles in the lysosome and extracellular exosomes. The phosphoproteomic and proteomic data demonstrates that JAK kinase dependent IL-2 signalling regulates essential processes in CTL by controlling a selective number of phosphorylation events and proteins. Validation of proteins identified as regulated following tofacitinib treatment identified new targets of IL-2 signalling in CTL, including the transcription factor NFIL3. NFIL3 was shown to be upregulated in CD8+ T lymphocytes following stimulation with IL-2 and regulated perforin and CD62L expression, suggesting a role in the regulation of CTL effector function.
Date of Award2016
Original languageEnglish
SupervisorDoreen Cantrell (Supervisor)


  • IL-2 signalling
  • CD8 T cells
  • jak kinases
  • tofacitinib
  • NFIL3

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