Following TCR stimulation, the small GTPase Ras is activated. Ras activation is induced by the Ras GTP-exchange factor (GEF), RasGRP. Both Ras and RasGRP are constitutively expressed in resting T cells. The reason Ras activation is only induced following TCR stimulation is:

Question

Quizplus · Accepted Answer

RasGRP recruitment to the plasma membrane requires TCR stimulation. Unlike the other options, this choice correctly explains why Ras activation is only induced following TCR stimulation. While both Ras and RasGRP are constitutively expressed in resting T cells, RasGRP must be recruited to the plasma membrane in order to activate Ras. This recruitment is dependent on TCR stimulation, as it involves the binding of RasGRP to the phosphorylated cytoplasmic tail of the TCR complex.

Following TCR Stimulation, the Small GTPase Ras Is Activated