10 - Signal Transduction I

10 - Signal Transduction I - Signal Transduction I In...

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In multicellular organism cells have to communicate to control metabolism, growth, differentiation etc. Signal Transduction I
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Single-cellular organisms communicate using molecules called pheromones No mating factor Mating factor
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Steps during cell signaling (1) Storage of signaling molecule (2) Release (3) Transport in EC space (4) Binding to receptor (usually on cell surface) (5-6) Change in cellular function (short- term and/or long-term) (7-8) Termination of the response Important principles: Target cell has to have specific receptor for signaling molecule. No receptor - no response There are many different receptors for the same signaling molecule Same receptors can cause different changes in different cells Signaling cell (produce signal molecule) – target cell (has receptor for signal molecule)
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Extracellular signaling molecules can act over short or long distances Recall cadherens and integrins?
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Chemistry of signal molecule (ligand ) can be very different Epinephrine (adrenaline) (A) (B) (C) Competitor molecules: agonists and antagonists acetylcholine Muscarine Agonists Atropin Antagonist Nicotine What are requirements for signaling molecules? Should it be small or big ? Hydrophilic or hydrophobic ? Free or bound to the cell surface ? Can it be protein? Gas molecule? Light?
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Each receptor is highly specific for its ligand: molecular complementarity (protein) Relatively small patches of amino acids are important for specific binding between ligand and receptor: These can be discovered through mutant analysis (though have to be careful when mutating receptor) 8
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Identification of receptors and ligands Situations possible: (1) known ligand, unknown receptor (2) known receptor, unknown ligand (3) unknown receptor, unknown ligand Receptors that do not have known ligands: orphan receptors Methods: Genomics : can identify receptors, but not ligands Affinity chromatography: can be difficult as there are small number of receptors per cell Expression assay : express receptors in the cell and test different substances for activation of cellular response Identification of the pathways that regulates sleep and feeding by small peptide orexin
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There is an easy way:
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This note was uploaded on 01/12/2012 for the course BI 9 taught by Professor Aravin during the Spring '10 term at Caltech.

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10 - Signal Transduction I - Signal Transduction I In...

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