Which one of the following accurately depicts the correct order of events in a TCR signal transduction pathway?
A)TCR → Lck → Zap-70 → LAT → Grb-2 → SOS → Ras → Erk → Fos
B)TCR → Lck → Zap-70 → LAT → SOS → Grb-2 → Ras → Erk → Fos
C)TCR → Lck → ITK → LAT → Grb-2 → SOS → Ras → Erk → Fos
D)TCR → Lck → Zap-70 → LAT → SOS → Grb-2 → Ras → Erk → Jun
E)TCR → Lck → Zap-70 → LAT → PLCƴ → DAG → calcium release

Question

Quizplus · Accepted Answer

Activated Zap-70 phosphorylates the transmembrane adapter protein LAT at tyrosine residues, which serve as docking sites for SH2 domains of other proteins. In one pathway, the SH2 domain of Grb-2 binds to phosphorylated LAT. Grb-2 is then able to recruit Sos to the membrane. Sos catalyzes GDP/GTP exchange on Ras, a G protein that is active when guanosine triphosphate (GTP) is bound and inactive when guanosine diphosphate (GDP) is bound. Active Ras functions as an allosteric activator of mitogen-activated protein kinases (MAPK), leading to downstream activation of Erk through phosphorylation. Activated Erk stimulates the transcription of Fos (through intermediate activation of a protein called Elk). In a second pathway, PLCƴ binds directly to activated LAT and is then phosphorylated by Zap-70. Activated PLCƴ leads to the cleavage of PIP2 to IP₃ and DAG. Although DAG activates protein kinase C (PKC), it is IP3 that causes a release of calcium into the cytosol.

Which One of the Following Accurately Depicts the Correct Order