T cells with defective TCR signaling are discovered, and found to have an inactivating mutation in a key TCR signaling protein. Using an antibody that recognizes the phosphorylated (activated) form of the Erk Map-kinase, stimulated T cells are permeabilized, stained with this antibody, and analyzed on the flow cytometer. These data are shown in Figure Q21). Figure Q21) Additional experiments examining Ca²⁺ influx into T cells following TCR stimulation show a normal response in the mutant T cells. One likely candidate gene that could be mutated in the defective cells is:

Question

Quizplus · Accepted Answer

The Erk Map-kinase is downstream of RasGRP in the TCR signaling pathway. Therefore, a mutation in RasGRP would prevent Erk phosphorylation and activation, as seen in the defective T cells. PLC-γ, ITK, Calcineurin, and WASp are not directly involved in the RasGRP/Erk signaling pathway. The normal response of Ca2+ influx also suggests that the defect lies downstream of PLC-γ activation.

T Cells with Defective TCR Signaling Are Discovered, and Found γ\gammaγ

T Cells with Defective TCR Signaling Are Discovered, and Found $\gamma$