Chapter8 Cell signaling o Cell signaling can affect virtually every aspect of cell structure and function t Activation of enzyme activity t Change in cytoskeletal organization t Change in ion permeability t Initiation of DNA synthesis t Activation or repression of gene expression Importance of Signal Transduction Development Apoptosis Transduction Cell Growth Immunology Metabolism
❖Cell signaling can affect virtually every aspect of cell structure and function: Activation of enzyme activity; Change in cytoskeletal organization; Change in ion permeability; Initiation of DNA synthesis; Activation or repression of gene expression. Chapter 8 Cell Signaling
1. Overview of intercellular signaling (c) Autocrine signaling (a) Endocrine signaling Key: Blood vessel o Extracellular signal Receptor ⊙ 9 Membrane-attached Hormone secretion signal into blood by endocrine gland Distant target cells Target sites on same cell (b)Paracrine signaling (d)Signaling by plasma membrane-attached proteins ⑧ Secretory cell Adjacent target cell Signaling cell Adjacent target cell General schemes of intercellular signaling
1. Overview of intercellular signaling General schemes of intercellular signaling
A. Some of the basic characteristics of cell signaling (1)Each cell is programmed to respond to specific combinations of extracellular signal molecules The cell integrates differentinformation and mounts an appropriate and comprehensive response. ☆ These signal molecules work in combinations to DIVIDE regulate the behavior of the cell E DIFFERENTIATE ☆ Cells respond to stimuli via cell signaling
(1) Each cell is programmed to respond to specific combinations of extracellular signal molecules The cell integrates different information and mounts an appropriate and comprehensive response. ❖These signal molecules work in combinations to regulate the behavior of the cell. ❖Cells respond to stimuli via cell signaling A. Some of the basic characteristics of cell signaling
Signal integration (A) (B) B B TP ATP ATP ATP ADP ADP DP ADP PrY e DOWNSTREAM SIGNALS DOWNSTREAM SIGNALS
(2) Signaling pathways consist of a series of steps Recognition of the EXTRACELLULAR SIGNAL MOLECULE stimulus by a specific RECEPTOR PROTEIN plasma membrane receptor 2. Transfer of a signal across the plasma membrane INTRACELLULAR SIGNALING PROTEINS3. Signal magnification: signal magnification Transmission of the signal to effector molecules within the cell, which causes a change in cellular TARGET PROTEINS activities metabolic gene regulatory cytoskeletal enzyme protein 4. Cessation of the cellular altered altered gene altered ce response due to metabolism expression shape or movement inactivation of the signal molecule
(2) Signaling pathways consist of a series of steps signal magnification 1. Recognition of the stimulus by a specific plasma membrane receptor. 2. Transfer of a signal across the plasma membrane. 3. Signal magnification: Transmission of the signal to effector molecules within the cell, which causes a change in cellular activities. 4. Cessation of the cellular response due to inactivation of the signal molecule
3)Four features of signal-transducing systems Part II Structure and Catalysis (a)Specificity (c) Desensitization/Adaptation Signal molecule fits Receptor activation triggers binding site on its a feedback circuit that shuts off the receptor or removes Receptor complementary receptor other signals do not fit. Receptor it from the cell surface Effect Response (b)Amplification (d)Integration when enzymes activate Signal When two signals have Signal 1 Signal 2 enzymes, the number of opposite effects on a affected molecules metabolic characteristic increases geometrically such as the concentration in an enzyme cascade. Enzyme 1 of a second messenger X, Receptor(Receptor or the membrane potential results from the integrated input from both receptors.↑ X]or TV↓ X]or v Net△ X]or v name 3313 Response
(3) Four features of signal-transducing systems
(4)Different cells can respond differently to the same extracellular signal molecule IC)skeletal muscle cell A heart muscle cell (B》 salivary gland cell receptor … secreTION acetylcholine DECREASED RATE AND CONTR FORCE OF CONTRACTION Various responses induced by neurotransmitter acetylcholine
(4) Different cells can respond differently to the same extracellular signal molecule Various responses induced by neurotramsmitter acetylcholine
(5)A cell can remember the effect of some signals, after the signal has disappeared.(Ca2+) Protein kinase activited by Cat to phosphorylate itself and other proteins, the autophosphorylation keeps the kinase active long after Cat levels return to normal Transient extracellular signals often induce much longer-term changes in cells during the development of a multicellular organism. They usually depend on self- activating memory mechanisms that operate further downstream in a signaling pathway, at the level of gene transcription
(5) A cell can remember the effect of some signals, after the signal has disappeared. (Ca2+) Protein kinase activited by Ca2+ to phosphorylate itself and other proteins, the autophosphorylation keeps the kinase active long after Ca2+ levels return to normal. Transient extracellular signals often induce much longer-term changes in cells during the development of a multicellular organism.They usually depend on selfactivating memory mechanisms that operate further downstream in a signaling pathway,at the level of gene transcription
B. Signal Molecules and Receptors (1)Signal molecules Some Signals to Which Cells Respond Antigens Cell surface glycoproteins/oligosaccharides Developmental signals Extracellular matrix components Growth factors Hormones Light Mechanical touch Neurotransmitters Odorants Pheromones Tastants
B. Signal Molecules and Receptors (1) Signal molecules:
(2) Receptors include two classes: A ION-CHANNEL-LINKED RECEPTOR CELL- SURFACE RECEPTORS plasma plasma membran cell-surface receptor 1B) G-PROTEIN-LINKED RECEPTOR hydrophilic signa molecule INTRACELLULAR RECEPTORS small hydrophobic ignal molecule activated zyme G protein IC) ENZYME-LINKED RECEPTORS carrier protein gnal molecule in form of a dimer nucleus intracellular receptor inactive catalytic active catalytic domain
(2) Receptors include two classes:
