Following TCR Stimulation, the Small GTPase Ras Is Activated

question 34

Multiple Choice

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:

• A) RasGRP undergoes a Ca²⁺-dependent conformational change required for its activity.
• B) RasGRP requires tyrosine phosphorylation for its activity.
• C) RasGRP is ubiquitinated and degraded in the absence of TCR stimulation.
• D) RasGRP recruitment to the plasma membrane requires TCR stimulation.
• E) Ras is only recruited to the activated TCR following assembly of the LAT:Gads:SLP-76 complex.

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