CPPS FINAL EXAM Practice Questions WITH CORRECT ANSWERS Graded A+ | 2023/2024

CPPS FINAL EXAM Practice Questions WITH CORRECT ANSWERS Graded A+ | 2023/2024. What is the importance of RBD in Raf activation? - Correct Answer-It is the N-terminal regulatory domain of the Raf protein. The RBD needs to interact with RasGTP to enable activaiton of Raf. Interaction of RBD with RasGTP at the membrane destabilizes Raf interaction with 14-3-3. This allows for PP2A to dephosphorylate Raf phosphoserines (the locks on the inactive state). What is RBD? - Correct Answer-Ras Binding Domain. It is the Raf N-terminal domain of the Raf protein. How is Raf maintained in an inactivate state? - Correct Answer-Scaffold protein 14-3-3 is bound to two phosphoserine in the N terminus on the Raf protein and locks it in the inactive form. What is the function of serine/threonine phosphatase PP2A in the activation of Raf? - Correct Answer-Once RBD has bound RasGTP the interaction between Ras and 14-3-3 destabilizes. PP2A comes and dephosphorylates the phosphoserines on the Ras. Allowing for other phosphorylations on Raf activating it and causing dimerization. How does Raf associate with RasGTP to become activated? - Correct Answer-RBD binds to the activated Ras (RasGTP) and causes the destabilization of the inhibitory protein 14-3-3 which allows the PP2A to dephosphorylate Raf and allow for other phosphorylations on Raf that result in activation and dimerization. How does Ras activation lead to Raf dimerization in the Raf/MEK/ERK pathway? - Correct Answer-Ras forms nanoclusters when activated and promotes Raf dimerization in the Raf/MEK/ERK pathway. Monomeric Raf is autoinhibited in cytosol. RBD domain of Raf binding to Ras is a high affinity interaction and releases autoinhibition. Ras-RBD interaction leads to Raf activation through side-by-side dimerization. What is Raf? - Correct Answer-Raf (Ras-associating factor) is a MAPKKK = Mitogen activated protein kinase-kinase-kinase. It is a serine/threonine kinase. What does activated Ras do? - Correct Answer-Activated Ras recruits MAPKKK (Raf) to the cell membrane and induces a conformational change in MAPKKK that activates its ser/thr kinase activity. What is another term for MAPKK? - Correct Answer-MEK How is MAPKK activated by MAPKKK? - Correct Answer-MAPKK binds to the cterminal catalytic domain of Raf (MAPKKK). It is phosphorylated on two serine residues = activation. What does activated Raf/MAPKKK do? - Correct Answer-Phosphorylates MAP kinasekinase at two serine residues to activate it. What is MAPKK? - Correct Answer-Is a dual specificity kinase: Has both ser/thr and tyrosine kinase catalytic domains. What is the substrate of MAPKK? - Correct Answer-MAPK is the only substrate of MAPKK. It is a tightly regulated response. What is the function of MAPKK? - Correct Answer-MAPKK/MEK catalyzes a phosphorylation event on threonine and one on tyrosine to make MAP-kinase (MAPK) fully active. How is MAPK activated? - Correct Answer-Only when both threonine and tyrosine are phosphorylated by MEK/MAPKK. It dimerizes. What is the pathway of Ras activation to activated MAPK? - Correct Answer-RTK-(SH2- SH3)-SOS-Ras-(RBD-Raf/MAPKKK)-MAPKK/MEK-MAPK What are the six steps of Ras activation to activated MAPK? - Correct Answer-1. Ras activated by exchange of GDP for GTP 2. Active Ras recruits, binds, and activates Raf 3. GTP hydrolysis leads to dissociation of Ras from Raf 4. Raf activates MEK 5. MEK activates MAPK 6. Dimeric form of active MAPK translocates to nucleus; activates many transcription factors. What is the function of MAPK? - Correct Answer-Activates many transcription factors. It induces transcription of c-fos by modifying two transcription factors (TCF and SRF). What is TCF? - Correct Answer-A transcription factor. Ternary Complex factor. It resides in the nucleus. What is the function of TCF? - Correct Answer-TCF is a transcription factor activated by phosphorylation by MAPK. It binds enhancer element SRE regulating c-fos and other transcriptional events What is SRF? - Correct Answer-Serum response element. SRF is a transcription factor. What is the function of SRF? - Correct Answer-MAPK phosphorylates and activates the kinase p90Rsk (in cytosol) which translocates to the nucleus and phosphorylates nuclear SRF (transcription factor). This increases the binding rate and affinity of SRF binding to SRE = increased transcriptional frequency. What is the pathway of regulation of transcription activated by MAPK? - Correct Answer-MAPK phosphorylates p90Rsk which phosphorylates SRF and MAPK also phosphorylates TCF which both are trasncription factors that bind to the SRE enhancer element to regulate c-fos and other target gene transcriptional events. What is the function of SRE? - Correct Answer-Enhancer element that regulates cFos and other target gene transcriptional events. When transcription factors bind it induces transcription. What is SRE? - Correct Answer-Serum response elements. They allow for activated transcription following growth factor (mitogen) stimulation. They are found in genes involved in cellular proliferation. What is c-fos? - Correct Answer-An early response gene/transcription factor that is regulated by the RTK/Ras pathway. c-fos is an SRE. It is required for the induction of delayed response genes including cyclin D What regulates c-fos? - Correct Answer-Is regulated by MAPK. How is the RTK-Ras-Raf-MAPK pathway terminated? - Correct Answer-RTK signalling is downregulated by: - Protein phosphatatses - PTP1B, SHP1/2 and DEP1 - Activated MAPK/ERK1/2 is part of negative feedbac loop. It can phosphorylate SOS which decreases SOS' affinity for GRb-2 - Endocytosis, RTK ubiquination What is Her2/neu/ErbB-2? - Correct Answer-RTK of EGF class. What is EGF? - Correct Answer-Epidermal growth factor. It stimulates proliferation of many cell types. Is Her-2/neu/ErbB-2 an oncogene? - Correct Answer-Yes. It has the potential to mutate and contribute to uninhibited proliferation and can induce cell transformation. It is frequently amplified/over-expressed in human tumours of epithelial origin. What happens when Her2/neu/ErbB-2(GF) is mutated? - Correct Answer-Mutations within the TM region can cause constitutive dimerization in an activated state and this, in the case of the ErbB2 receptor can induce cell transformation. It is an oncogene. Frequently amplified/over-expressed in human tumours of epithelial origin. What is the amplification or overexpression of Her-2 recognized as? - Correct AnswerAmplification of Her-2 is a recognized prognostic marker that is associated with poor survival for patients with node-positive breast cancer. Why is mutation not necessary, but overexpression of Her-2 sufficient to become tumourigenic? - Correct Answer-If there is overexpression than it leads to ligand independent activation What is Herceptin? - Correct Answer-Designer Cancer therapy. Humanized monoclonal antibody. What is another name for Herceptin? - Correct Answer-Trastuzumab. mab because it is a humanized monoclonal antibody. How is Herceptin administered? - Correct Answer-Herceptin is given IV. Is Herceptin only used for breast cancer? - Correct Answer-No. It is also in trial for late stage pancreatic cancers that over-express Her2/neu/ErbB. It is given in combination with the chemotherapeutic drug Gemzar. How does Herceptin function? - Correct Answer-It binds to Her-2 and blocks its activation. How can mutated Ras result in cancer? - Correct Answer-Mutated Ras can make Ras insentitive to GAP binding, so GTP can't be hydrolyzed to GDP. This results in permanent activation. Resulting in unihibited cellular proliferation. What types of cancer is Ras mutation associated with? - Correct Answer-Of the 30% of human tumours that have Ras mutation, pancreatic cancer has the most common incidence (90%), followed by colon (50%), thyroid (50%), lung (30%), ovarian (15%), bladder (6%), breast, skin, liver, kidney and some leukemias. How does Herceptin act on mutated Ras that causes cancer? - Correct AnswerWhat is the function of farnesyl isoprenoid? - Correct Answer-It is an unusual lipid that is involved in attachment of Ras proteins to the membrane. Farensyl isoprenoid is a posttranslational modification done to Ras proteins to enable them to attach to the membrane. What is farnesyl transferase? - Correct Answer-FTase. It is the enzyme responsible for the post translational modification attachment of farenesyl isoprenoid to Ras. What is farnesylation? - Correct Answer-Protein prenylation. It is critcal for Ras localization to Inner Membrane. Why is farnesyl transferase a target for anticancer chemotherapeutic agents? - Correct Answer-It is the enzyme that attaches farnesyl isoprenoid to Ras, which is the lipid that attaches Ras to the membrane. So the rational is that if you inhibit the enzyme that allows for Ras to associate with the membrane then this will block signalling associated with abnormal cell division. What is another target therapy, other than Her2 inhibition? - Correct Answer-FTase inhibitors. It also blocks cellular proliferation. What is Lonafarnib and Tipifarnib? - Correct Answer-They are farnesyl transferase inhibitors. What is Rigosertib? - Correct Answer-It is a drug that prevents Raf/Ras interactions to block the MARK signalling pathway to inhibit tumourigenic proliferation. What is the function of Rigosertib? - Correct Answer-It is a small molecule that binds to the RBD N terminal of Raf and prevents its association with Ras. What are three therapeutic targets in the RTK/MAPK pathway? - Correct Answer-HER2 - Herceptin binds to the RTK and prevents cellular proliferation FTase Inhibitors - Lonafarnib/Tipifarnib inhibits Ras from binding to the inner membrane and prevents proliferation RBD of Raf - Rigosertib is a molecule that binds the N terminal and prevents RAS from binding to the RBD of Raf. How is PI3-K activated? - Correct Answer-They are activated by binding to specific phospho-tyrosines on activated RTKs. What is the ultimate goal of PI3-K? - Correct Answer-It initiates the activation of a major intracellular signalling pathway that promotes cell survival. PI3-K is responsible for the activation of Akt. What does PI stand for? - Correct Answer-Phosphatidylinositol What is Atk also known as? - Correct Answer-Protein Kinase B. PKB What are the components of PI3-K? - Correct Answer-There are 2 subunits; a regulatory subunit (p85, with SH2 domain) and a catalytic subunit (p110). What is the characteristics of p85 subunit of PI3-K? - Correct Answer-There are two SH2 domains, an N-terminal and a C-terminal domain that recognize phosphorylated tyrosine motifs. There is consesnus. What is Akt? - Correct Answer-It is a serine/threonine kinase