26 signaling07aris

26 signaling07aris - Medical Cell and Tissue Biology BMS...

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Unformatted text preview: Medical Cell and Tissue Biology BMS 6110 John P. Aris, Ph.D. Rm B1-8, 392-1873, [email protected] Molecular Biology of the Cell, 4th Ed., Ch 15 Molecular Cell Biology, 5th Ed., Ch 13 Cell Signaling Cell Signaling Modes Autocrine See MBoC4 Fig 15-4 Paracrine Cell Signaling Modes Endocrine Signal usually carried in blood Cell adhesion protein signaling Cells Respond to Multiple Signals • Different signaling molecules bind to different receptors on and/or in a cell • Different signals work in combination to regulate cell survival, growth, behavior, and death • In the absence of signals, many cell types stop division and/or die MBoC4 Fig 15-8 Specificity: Signal - Receptor Interaction • Specific signal binds to specific receptor on/in target cell • Ligand - molecule (not a substrate) that binds a protein GH receptor in plasma membrane GH receptor dimer formation in plasma membrane MCB5 Fig 13-2 A Signal Can Elicit Multiple Responses Heart muscle, salivary gland cells, and skeletal muscle have receptors for acetylcholine, but exhibit different responses MBoC4 Fig 15-9 Steps in Cell Signaling 1. Synthesis of signaling molecule by signaling cell 2. Release of signaling molecule by signaling cell 3. Transport /diffusion of signaling molecule to target cell 4. Detection of signaling molecule by specific receptor protein (signaling molecule binds to a specific receptor and in most cases has no other function than to activate its receptor) 5. Change in cellular metabolism of target cell (alters cell function and/or development; most changes require activation of an intracellular signaling pathway) 6. Removal of signaling molecule and termination of cellular response (most signaling molecules have a short lifetime) Intracellular Receptors • Ligands - small and hydrophobic signaling molecules that diffuse across the plasma membrane • Bind to intracellular receptors in cytosol • Ligand-receptor complex is imported into the nucleus and binds to specific promoters to regulate gene expression (e.g., functions as a transcription factor) Nuclear Receptor Ligands MBoC4 Fig 15-12 Cell Surface Receptors • Ligands - hydrophilic, water-soluble molecules (e.g., peptide hormones), bind cell surface receptors in plasma membrane • Some hydrophobic signals also bind cell surface receptors Signal Transduction Signal transduction - steps in target cell that convert or “transduce” ligand binding into cellular response(s) Ligand binding to receptor is first step in signal transduction (receptor is located in plasma membrane) Intracellular signaling molecules transmit the signal to cell targets MBoC4 Fig 15-1 Membrane Cell-Surface Receptors Classes: 1. Ion channel-linked receptors 2. Receptors with intrinsic or associated enzymatic activity 3. G-protein coupled receptors Function: All transduce signals across the plasma membrane via changes in receptor protein conformation that lead to changes in receptor protein activity and/or receptor protein interactions. Ion Channel Receptors...
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26 signaling07aris - Medical Cell and Tissue Biology BMS...

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