1305_1967129_BIS104_2017_Lecture+12_Liu.pdf

1305_1967129_BIS104_2017_Lecture+12_Liu.pdf -...

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VI: Cell Signaling 1. Introduction Signals, receptors Intracellular signaling molecules and secondary messengers Effectors 2. G proteins 3. Receptors I: G protein coupled receptors (GPCRs) 4. Receptors II: Protein kinase (enzyme) coupled receptors 5. MAP kinase cascades
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Signal amplification during transduction o A few signal/ligand molecules o Activate a few receptors o Receptors activate the next signaling molecule, repeatedly o Downstream enzymes work continuously o Generate many molecules of secondary messengers o More molecules/enzymes activated o Even more products produced
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Signaling molecules relay, amplify, integrate and distribute the incoming signal in order to effectively alter cell behavior, either rapidly or slowly Fast vs. slow responses
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2. G-proteins Monomeric (small) G proteins (GTPase) o Discovered as a proto oncogene product o Ras family: Rat sarcoma o A signaling protein in the membrane o The Q61K mutation makes it in GTP locked state constitutively active: cancer causing
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Conformation difference between Ras- GDP and Ras- GTP
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Heterotrimeric G proteins o G α : GTPase o G β interact with G α‐ GDP, but not G α‐ GTP o G α and G
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