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DRAK2 Negatively Regulates T Cell Receptor Signaling by Increasing the Threshold for T
Cell Activation
Shanty Wijaya
Mentor: Craig Walsh
T cells play a central role in controlling acquired immune response. Regulatory molecules expressed
in T cells participate in setting the threshold for T cell activation and limit the response via negative
feedback regulation; hence, these molecules maintain T cell homeostasis. DRAK2 (DAP-related
apoptotic kinase-2) is a regulatory molecule that is expressed in T cells and is found exclusively in
lymphoid tissue. Kinases are known to have essential roles in lymphocyte activation and apoptotic
signaling, however, the regulation of intracellular signaling pathways is still not completely known. T
cells from DRAK2-/- mice have been shown to exhibit an increase in sensitivity to T Cell Receptor
(TCR) signaling and receive a greater intensity of TCR signal, resulting in an enhanced calcium flux
(calcium is an essential signal for T cell development and activation). Based on this understanding
(via an in vivo model), we hypothesize that DRAK2 negatively regulates T cell receptor signaling by
directly modulating calcium mobilization. An alternative hypothesis is that DRAK2 alters the
development/homeostasis of T cell populations in vivo. To discriminate between these two models, I
sought to knock down the expression of DRAK2 in an established E61 Jurkat T cell line using an
RNAi approach. Calcium flux of DRAK2 knock-down E61 T cells and wild type E61 T cells were
then analyzed by calcium flux assays. Calcium flux in DRAK2 knock-down E61 T cells was expected
to be significantly higher than E61 wild type T cells, which would provide proof that DRAK2
directly modulates TCR signaling.