a) What purpose does this forward reaction serve in that pathway? b) Does the reverse reaction participate directly in this pathway? c) Which signalling pathway in the above diagram relies on phosphorylation/dephosphorylation as part of its transduction cascade? Circle the correct answer. mTOR pathway Hippo pathway Both pathways Neither pathway
Below are two cell signalling pathways that work together to regulate cell growth, proliferation and ultimately the size of organs in O.Extremus. In other closely related organisms, dysfunction of these pathways has been associated with tumor growth.
mTOR pathway: 1. Growth factors bind and stimulate the receptors.
2. Receptors can activate the phosphatidylinositol 3 kinase (PI3K) – Akt signaling pathway.
3. The activated Akt, a serine threonine kinase, inhibits theTSC1–TSC2 complex, allowing Rheb to activate mTORC1.
4. In parallel, amino acids activate the mTORC1 pathway through a mechanism requiring the Rag– Ragulator complex.
Hippo pathway: 1. The binding of the ligand activates the receptors which activate Mst and Lats.
2. YAP activity is modulated by phosphorylation of Mst and Lats. YAP upregulates miR-29, which in turn downregulates PTEN, an inhibitor of PI(3)K and Akt. So, the two pathways crosstalk and coordinate cell number and growth.
a) What purpose does this forward reaction serve in that pathway?
b) Does the reverse reaction participate directly in this pathway?
c) Which signalling pathway in the above diagram relies on phosphorylation/dephosphorylation as part of its transduction cascade? Circle the correct answer.
mTOR pathway Hippo pathway Both pathways Neither pathway
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