3. The figure below represents a typical example of a Ras protein acting downstr
ID: 133680 • Letter: 3
Question
3. The figure below represents a typical example of a Ras protein acting downstream of a Receptor Tyrosine Kinase (RTK). You are studying a cancer cell line with a mutation that results in a constitutively active Ras protein. You treat these cancer cells with several different drug treatments, detailed below. NORMAL SIGNALING REQUIRES Ras AND TWO PROTEINS X AND Y signal molecule active Ras protein CYTOSOL GTP active signaling protein Y active signaling protein X active receptor tyrosine kinase SIGNALING tment will cell proliferation be reduced or will there be no change in For each drug trea proliferation. Circle on correct answer. (8 total points/ 2 pts each (a) addition of a drug that prevents protein X from activating Ras Reduced / no change (b) addition of a drug that reduced the affinity for protein Y and its target Reduced / no change (c) addition of a drug that blocks ligand binding receptor tyrosine kinase Reduced / no change (d) addition of a drug that interferes with the interaction of Ras and protein Y Reduced / no changeExplanation / Answer
RTKs are a very discrete type of cellular signalling cassette which regulate a series of intracellular (cytoplasmic as well as nuclear) signalling set of events. These events are generally governed by phosphorylation and activation or cleavage of biomolecule into biologically active form. Thus, interruption in any of these events can lead to direct damage to the signalling, which can either reduce, enhance or altogether stop the singalling events.
Thus, based upon this background, the answers can be found as below:
Answer a: Reduced (in the absence of any binding of ligand with receptor, no intracellular signalling will take place)
Answer b: No change (the affinity of the receptor for its ligand determines the strength of their binding on the extracellular surface, not the extent of intracellular signalling events)
Answer c: Reduced (Blocking of the ligand-binding site of the receptor prevents initiation of signalling events which promote the series of biological reactions)
Answer d: Reduced (since the interaction is intefered, not interrupted altogether, there would be decline in singalling)
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