L8 - Why is cell signaling interesting and important? 1....

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Unformatted text preview: Why is cell signaling interesting and important? 1. Cell signaling tells cells when to divide, when to stop dividing, and how much to grow. 2. Cancer is caused by defects in cell signaling 3. Differentiation into different cell types is induced by signaling 4. Communication between nerve cells is regulated by signaling 5. Most drugs modulate the activity of signaling Signals are received by receptor proteins . There are two kinds of receptors General Principles of Cell Communication Ligands act at very low concentration <10-8 M and bind receptors with high affinity An example of a generic signaling pathway Contact-dependent- Cells are in direct contact. Endocrine signaling Secreted signal to cells widely distributed throughout the organism. Synaptic signaling- Secreted signal to synapses. Paracrine signaling- Secreted signal to neighboring cells. Autocrine signaling - Secreted signal in which identical cells signal to each other and themselves. Different kinds of signaling: Different kinds of signaling: Important during development and during immune responses Most often, signaling molecules are secreted and can act locally (paracrine) on cells of a different type.or on distant targets Different kinds of signaling: Specialized signaling in the nervous system Super fast 100 meters/sec, millisecond across the synaptic cleft Specialized signaling in the endocrine system Relies on diffusion and blood flow Adapted to coordinate cell behavior in large multicellular organisims Different kinds of signaling: Autocrine: signaling when identical cells produce the same signal which binds back onto receptor of the same and neighboring cell. Be clear about difference between paracrine and autocrine Basic Principles: Molecules with a short half-life allow more rapid and transient changes in concentration in response to signaling The relative rates of change in intracellular concentration of molecules with different lives (indicatd in blue) Red is molecule with rapid turnover Basic Principles: Molecules with a short half-life allow more rapid and transient changes in concentration in response to signaling Example: Two intracellular signaling molecules X and Y, maintained at 1000 molecules/cell. Molecule Y is synthesized and degraded at 100 molecules/sec with each molecule lasting an average of 10 sec. 100 mol/s X 10s=1000 mol Molecule X has a rate 10X slower--that is to say it is synthesized and degraded at 10 molecules/sec with each molecules lasting an average of 100 sec. 10 mol/s X 100s=1000 mol A signal amplifies the rate of synthesis of Y and X 10- fold. After 1 sec , Y will have 900 more molecules in the cell (100mol/s X 10 (amplify =1000)-100mol degraded in 1 sec=900 X will have only 90 more molecules (10mol/sec X 10 (amplify = 100)-10mole degraded in 1 sec=90 Take home message: turnover rate (both synthesis and destruction) determines promptness of response to an extracellular signal Basic Principles: Many signaling pathways can respond...
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This note was uploaded on 03/28/2010 for the course MCD BIO 110 taught by Professor Hinck during the Fall '09 term at UCSC.

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L8 - Why is cell signaling interesting and important? 1....

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