SL+D103+lecture+13+Signaling+IV

SL+D103+lecture+13+Signaling+IV - D103: Cell Biology Dr....

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D103: Cell Biology Dr. Shin Lin
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Lecture 13 Signaling IV
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D103 Fall 2011 - lecture 13 - Second Messengers Page 3 Recommended Reading: MBOC 5e, pages 904 - 921 Release of Ca 2+ in starfish oocytes following fertilization Production of cAMP in response to serotonin signaling in a neuron (SEE LATER SLIDE FOR DETAILS) Second Messengers (e.g., Ca++ and cAMP )
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D103 Fall 2011 - lecture 13 - Second Messengers Page 4 The first "messenger" is the ligand that binds to a receptor (although the ligand is never referred to as the "first messenger"). Examples of ligands include serotonin (binding to a GPCR), growth factor (binding to a growth factor cell surface tyrosine kinase receptor). The term "second messenger" refers to signaling molecules that continue to transmit the initial signaling response inside the cell . (e.g. above, the second messengers are Ca 2+ , IP 3 , DAG ). Not all components of a signaling pathway inside the cell are referred to as " second messengers” (e.g. PKC is not a second messenger). This term is usually used to refer to small molecules that can diffuse rapidly and whose concentration changes rapidly following receipt of a signal . What is a Second Messenger ( 2 o M ) ? 2 o M 2 o M 2 o M SEE LATER SLIDE FOR DETAILS
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D103 Fall 2011 - lecture 13 - Second Messengers Page 5 Second messengers are small molecules that carry signals inside cells . Second messenger molecules are chemically diverse - e.g. inorganic ion (Ca 2+ ) cyclic nucleotides (cyclic adenosine monophosphate (cAMP), and cGMP) lipids (diacylglycerol (a.k.a. DAG)) gas (nitric oxide (NO)) Some molecules are hydrophilic (e.g. cAMP, Ca 2+ ) while others are hydrophobic (DAG). Different second messengers function in discrete sub-cellular compartments e.g. Ca 2+ in cytosol or diacylglycerol ( DAG ) in lipid bilayer . Rate of diffusion of second messenger varies - e.g. Ca 2+ - low (!); cGMP/cAMP - high. Messages are encoded by the change in concentration of the second messenger ( rise or fall ). Second messengers convey signals by binding to , and altering the conformation and behavior of, selected signaling molecules and effector proteins . Steady-state concentration of a second messenger is determined by the sum of its rate of synthesis and degradation by specific enzymes (sometimes these are the direct targets of the G-protein). The enzymes (or channels) that modulate intracellular levels of second messengers can switch on and off rapidly , leading to change in concentration of a second messenger on a milli-second (ms -1 ) time scale . Components of intracellular signal transduction - Second Messengers
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Page 6 There are four major target proteins for activated trimeric G-proteins adenylyl cyclase (see NEXT SLIDE ) phospholipase C cGMP phosphodiesterase K + ion channel The first three target proteins function by directly affecting levels of a second messenger . REVIEW: Targets for activated trimeric G-proteins
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This note was uploaded on 12/13/2011 for the course BIOSCI d103 taught by Professor Staff during the Fall '11 term at UC Irvine.

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SL+D103+lecture+13+Signaling+IV - D103: Cell Biology Dr....

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