T-cells are activated when antigen-MHC complexes bind to the T-cell receptor on the cell membrane. This process activates second messengers that in turn activate protein kinase C (PKC), leading to induction of transcription factors and subsequent gene expression. Which of the following most likely represents the second messenger of this signal transduction?
A) calcium ions
B) cAMP
C) cGMP
D) diacylglycerol
E) interleukin-2 (IL-2)

Question

Quizplus · Accepted Answer

Diacylglycerol (DAG) is a second messenger that is produced in response to the binding of antigen-MHC complexes to the T-cell receptor. DAG activates protein kinase C (PKC), which in turn activates transcription factors and subsequent gene expression. The activation of the T-cell receptor results in activation of the phospholipase C-γ (PLC-γ) isoform of PLC. PLC-γ hydrolyzes membrane-associated phosphatidylinositol-4,5-bisphosphate (PIP₂) into inositol trisphosphate (IP₃) and diacylglycerol (DAG). IP₃ binds to a receptor on the ER membrane and triggers the release of stored calcium ion into the cytosol. The calcium ions and the DAG serve to act as second messengers in the activation of PKC.

T-Cells Are Activated When Antigen-MHC Complexes Bind to the T-Cell