Final answer:
Rab-GTP is involved in intracellular membrane transport and vesicle trafficking, and when activated, it contributes to signal transduction and membrane traffic regulation. In the context of cancer, defective GTPase activity of proteins like RAS, which is similar to Rab, can lead to sustained signaling cascades, causing uncontrolled cell proliferation.
Step-by-step explanation:
The function associated with Rab-GTP is closely tied to the regulation of intracellular membrane transport and vesicle trafficking. Members of the Rab protein family, such as Rab11a, bind GTP to switch to an active state and interact with various effector proteins, including motor proteins, tethering proteins, and kinases. For instance, Phosphol 4-kinase Beta forms a complex with Rab11a-GTP, reflecting Rab's role in signal transduction and membrane traffic regulation.
In the context of cell signaling and cancer, the RAS protein, which is another small G-protein like Rab, is associated with cell growth and differentiation processes. When mutations occur that impair the GTPase activity of RAS, it leads to the inability to hydrolyze GTP into GDP. This continuous activation of RAS promotes uncontrolled cell growth and proliferation, a hallmark of cancer. Normally, the GTPase activity of RAS ends the signaling cascade, but when inhibited, downstream events like the MAPK kinase cascade remain active, potentially leading to cancerous states.