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2010 Fall Bio 317 Exam 3

B only egf engages proto oncogenes in its signaling

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Unformatted text preview: and Phospholipase C (PLC) pathways. b) Ras is multifunctional, stimulating multiple effector signaling pathways. c) Erk kinases have a wide variety of substrates, causing activation of enzymes and transcription factors. d) All of the above e) None of the above. 7) The following is NOT true about the Trk receptor: a) It binds to an NGF dimer, which stabilizes an active Trk dimer. b) Activation of the receptor involves a conformational change which results in activation of the receptor serine kinase. c) Phospho-tyrosine sites on Trk provide for docking of adaptors and signaling effectors. d) It stimulates PI 3-kinase for PIP3-mediated activation of protein kinase B (PKB). e) It inhibits a Bax-mediated apoptotic pathway. 8) The following is NOT true of the signaling pathways stimulated by NGF-Trk: a) Each of the steps in the Ras pathway leading to Erk kinase activation is a potential target (proto-oncogene) for mutational carcinogenesis leading to cancer. b) PIP3 acts as a nucleation site for the binding of the PH domains of PKD and PKB, bringing this kinase and substrate together for activation of PKB. c) Ras-GTP activates Raf by bringing Raf to the membrane where it can be phosphorylated and activated by an as yet unknown protein kinase. d) Phospholipase C-gamma binds to, is phosphorylated by and thereby activated by Trk to cause PIP2 breakdown. e) None of the above. 9) The following is true of Trk and/or EGFR endosomal signaling in PC12 cells: a) Both receptors are endocytosed through the classical clathrin-based mechanism. b) Endocytosis of both Trk and EGFRs causes rapid receptor degradation. c) Trk endosomes are longer-lasting, allowing for sustained signaling through the endosomal RapErk kinase pathway. d) Receptor signaling is enhanced immediately upon endocytosis, due to ligand- independent receptor activation in endosomes. e) All of the above. 10) The following is NOT true of retrograde axonal signaling by growth factors. a) Retrograde signaling by NGF is mediated by axonal transport of endosomes containing activa...
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