Chapter 16 lecture - Cell Communication Signal Transduction...

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1 Cell Communication Signal Transduction - conversion of one type of signal to another can consider it from a couple of view points: • chemical to electrical • electrical to chemical • chemical to chemical or from: • inside to outside • outside to inside ions What turns ON must turn OFF! Affector(s) Effector(s) Receptors feedback (+’ve or -’ve) extracellular_sig.jpg Affector(s) Effector(s) Receptors the combination dictates final effect including cell identity, survival, fitness
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2 General forms of “between cell” signaling in body include: + a fifth one not mentioned - “autocrine” self-regulation, feedback to self long & short range, very rapid, accurate long range (whole body) chemical signal short range chemical signal short range chemical signal Very short range - intimate contact required Signal transduction: conversion of an extracellular signal to intracellular effects ± cascade can include chemical second messenger cascades ± protein-protein interactions (kinases and phosphatases) ± information processing ± effector function effect multiple cell processes ligand
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3 Signaling Cascades: provide 1. Transduction of first signal (can change physical properties of stimulus - elect to chem, light to chemical sound to chemical) 2. Relay information into cell - (different types of molecules and signals) 3. Amplification of signal: (multiple steps allow increase gain of signal - or can decrease gain of signal in some cases) 4. Distribution of signal - (to various organelles, compartments or systems in cell). Multiple steps provide plenty of opportunity to MODULATE signal - crosstalk between signaling pathways. ligand –receptor: major determinant of initial response Integration of signals Many “RELAY” signaling molecules act as molecular switches: - RAPID changes in On & OFF states - e.g. phosphorylation rapid switch - KINASE : produces a phosphorylation event &/or a cascade of signals into cell. - PHOSPHATASES attentuate signal by removing phosphate groups
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4 GEF s Guanine Exchange Factors GAPs - Guanine Activating Proteins GTPases • molecular switches • self-regulating • ON vs OFF states also regulated externally • GEFs = guanine exchange factor • GAPs = guanine activating protein TWO general types of GTPases 1. Trimeric G-proteins - 2. Monomeric GTPases - (Ras, Rac, Rho Cdc42) αβγ Ligand (signaing molecule) Receptor Type 1 Receptor Type 2 Effector Group 1 Effector Group 2 Effector Group3 Response 1 Response 2 Response 3 A response to a given ligand depends on 1. Receptor-ligand interaction 2. Repertoire of downstream effectors Examples of all three cases exist in nature
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5 Heart & salivary glands: Similar Receptors BUT Different effectors = different response skeletal muscle: Different receptor Different effectors [changes ion flow to convert chemical signal to electrical to contraction) e.g. Acetycholine = ACh ligand –receptor: determines initial response Downstream effectors dictate a cell’s response pattern Receptors: location is dictated by nature of ligand - i.e. can ligand cross membrane barrier?
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This note was uploaded on 04/02/2008 for the course BIO 2600 taught by Professor Vanburkem during the Winter '08 term at Wayne State University.

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Chapter 16 lecture - Cell Communication Signal Transduction...

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