Question

Fos, a component of the transcription factor AP-1, is activated during T-cell signaling by a process involving a GTP-binding protein called _____?

1) inositol trisphosphate
2) Ras
3) protein kinase C-theta
4) Lck
5) ZAP-70

Answer 1

Fos is activated by a GTP-binding protein called Ras during T-cell signaling. This process involves a phosphorylation cascade, initiated by signal transduction pathways that include activation of PKC and the MAP kinase, leading to changes in gene expression.option 2 is correct answer.

Step-by-step explanation:

Fos, a component of the transcription factor AP-1, is activated during T-cell signaling by a process involving a GTP-binding protein called Ras. The activation pathway begins when an effector signal molecule binds to its receptor, which in turn activates an enzyme known as phospholipase C.

This enzyme then catalyzes the formation of inositol triphosphate (IP3) and diacylglycerol (DAG), both serving as second messengers. IP3 causes the release of calcium ions (Ca2+) from the smooth endoplasmic reticulum into the cytoplasm, and along with DAG, activates Protein Kinase C (PKC). PKC operates through a phosphorylation cascade that ultimately regulates protein expression, cellular metabolism, particularly the MAP-kinase cascade, and cell division through FAS-RAS signaling.

Specifically, the Ras protein-mediated activation of this phosphorylation cascade leads to the MAP kinase, which then phosphorylates transcription factors affecting gene activity related to cell proliferation and differentiation.