Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
Chapter 11 Cell Communication
Overview: The Cellular Internet <ul><li>Cell-to-cell communication is essential for multicellular organisms </li></ul><ul>...
Fig. 11-1
Concept 11.1: External signals are converted to responses within the cell <ul><li>Microbes are a window on the role of cel...
Evolution of Cell Signaling <ul><li>A  signal transduction pathway  is a series of steps by which a signal on a cell’s sur...
Fig. 11-2 Receptor    factor a factor a   a Exchange of mating factors Yeast cell, mating type a Yeast cell, mating typ...
<ul><li>Pathway similarities suggest that ancestral signaling molecules evolved in prokaryotes and were modified later in ...
Fig. 11-3 Individual rod- shaped cells Spore-forming structure (fruiting body) Aggregation in process Fruiting bodies 0.5 ...
Local and Long-Distance Signaling <ul><li>Cells in a multicellular organism communicate by chemical messengers </li></ul><...
Fig. 11-4 Plasma membranes Gap junctions between animal cells (a) Cell junctions Plasmodesmata between plant cells (b) Cel...
<ul><li>In many other cases, animal cells communicate using  local regulators , messenger molecules that travel only short...
Fig. 11-5 Local signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular flui...
Fig. 11-5ab Local signaling Target cell Secretory vesicle Secreting cell Local regulator diffuses through extracellular fl...
Fig. 11-5c Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell ...
The Three Stages of Cell Signaling:  A Preview <ul><li>Earl W. Sutherland discovered how the hormone epinephrine acts on c...
Fig. 11-6-1 Reception 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM 1 Receptor
Fig. 11-6-2 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM Transduction 2 Relay molecules in a signal ...
Fig. 11-6-3 EXTRACELLULAR FLUID Plasma membrane CYTOPLASM Receptor Signaling molecule Relay molecules in a signal transduc...
Concept 11.2: Reception: A signal molecule binds to a receptor protein, causing it to change shape <ul><li>The binding bet...
Receptors in the Plasma Membrane <ul><li>Most water-soluble signal molecules bind to specific sites on receptor proteins i...
<ul><li>A  G protein-coupled receptor  is a plasma membrane receptor that works with the help of a  G protein </li></ul><u...
Fig. 11-7a Signaling-molecule binding site Segment that interacts with G proteins G protein-coupled receptor
Fig. 11-7b G protein-coupled receptor Plasma membrane Enzyme G protein (inactive) GDP CYTOPLASM Activated enzyme GTP Cellu...
<ul><li>Receptor tyrosine kinases  are membrane receptors that attach phosphates to tyrosines </li></ul><ul><li>A receptor...
Fig. 11-7c Signaling molecule (ligand) Ligand-binding site    Helix Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosine k...
<ul><li>A  ligand-gated ion channel  receptor acts as a gate when the receptor changes shape </li></ul><ul><li>When a sign...
Fig. 11-7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellul...
Intracellular Receptors <ul><li>Some receptor proteins are intracellular, found in the cytosol or nucleus of target cells ...
Fig. 11-8-1 Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM
Fig. 11-8-2 Receptor protein Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Hormone- receptor complex DNA NUCL...
Fig. 11-8-3 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA NUCL...
Fig. 11-8-4 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA mRNA...
Fig. 11-8-5 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA...
Concept 11.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cel...
Signal Transduction Pathways <ul><li>The molecules that relay a signal from receptor to response are mostly proteins </li>...
Protein Phosphorylation and Dephosphorylation <ul><li>In many pathways, the signal is transmitted by a cascade of protein ...
<ul><li>Protein phosphatases  remove the phosphates from proteins, a process called dephosphorylation </li></ul><ul><li>Th...
Fig. 11-9 Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive ...
Small Molecules and Ions as Second Messengers <ul><li>The extracellular signal molecule that binds to the receptor is a pa...
Cyclic AMP <ul><li>Cyclic AMP (cAMP)  is one of the most widely used second messengers </li></ul><ul><li>Adenylyl cyclase ...
Adenylyl cyclase Fig. 11-10 Pyrophosphate P P i ATP cAMP Phosphodiesterase AMP
<ul><li>Many signal molecules trigger formation of cAMP </li></ul><ul><li>Other components of cAMP pathways are G proteins...
First messenger Fig. 11-11 G protein Adenylyl cyclase GTP ATP cAMP Second messenger Protein kinase A G protein-coupled rec...
Calcium Ions and Inositol Triphosphate (IP 3 ) <ul><li>Calcium ions (Ca 2+ ) act as a second messenger in many pathways </...
EXTRACELLULAR FLUID Fig. 11-12 ATP Nucleus Mitochondrion Ca 2+  pump Plasma membrane CYTOSOL Ca 2+ pump Endoplasmic reticu...
<ul><li>A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol </li></ul><ul>...
Fig. 11-13-1 EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein GTP G protein-coupled receptor Phospholi...
Fig. 11-13-2 G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase...
Fig. 11-13-3 G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase...
Concept 11.4: Response: Cell signaling leads to regulation of transcription or cytoplasmic activities <ul><li>The cell’s r...
Nuclear and Cytoplasmic Responses <ul><li>Ultimately, a signal transduction pathway leads to regulation of one or more cel...
Fig. 11-14 Growth factor Receptor Phosphorylation cascade Reception Transduction Active transcription factor Response P In...
<ul><li>Other pathways regulate the  activity  of enzymes </li></ul>Copyright © 2008 Pearson Education, Inc., publishing a...
Fig. 11-15 Reception Transduction Response Binding of epinephrine to G protein-coupled receptor (1 molecule) Inactive G pr...
<ul><li>Signaling pathways can also affect the physical characteristics of a cell, for example, cell shape </li></ul>Copyr...
Fig. 11-16 RESULTS CONCLUSION Wild-type (shmoos) ∆ Fus3 ∆ formin Shmoo projection forming Formin P Actin subunit P P Formi...
Fig. 11-16a RESULTS Wild-type (shmoos) ∆ Fus3 ∆ formin
Fig. 11-16b CONCLUSION Mating factor G protein-coupled receptor GDP GTP Phosphory- lation cascade Shmoo projection forming...
Fine-Tuning of the Response <ul><li>Multistep pathways have two important benefits: </li></ul><ul><ul><li>Amplifying the s...
Signal Amplification <ul><li>Enzyme cascades amplify the cell’s response </li></ul><ul><li>At each step, the number of act...
The Specificity of Cell Signaling and Coordination of the Response <ul><li>Different kinds of cells have different collect...
Fig. 11-17 Signaling molecule Receptor Relay molecules Response 1 Cell A. Pathway leads to a single response. Response 2 R...
Fig. 11-17a Signaling molecule Receptor Relay molecules Response 1 Cell A. Pathway leads to a single response. Cell B. Pat...
Fig. 11-17b Response 4 Response 5 Activation or inhibition Cell C. Cross-talk occurs between two pathways. Cell D. Differe...
Signaling Efficiency: Scaffolding Proteins and Signaling Complexes <ul><li>Scaffolding proteins  are large relay proteins ...
Fig. 11-18 Signaling molecule Receptor Scaffolding protein Plasma membrane Three different protein kinases
Termination of the Signal <ul><li>Inactivation mechanisms are an essential aspect of cell signaling </li></ul><ul><li>When...
Concept 11.5: Apoptosis (programmed cell death) integrates multiple cell-signaling pathways <ul><li>Apoptosis  is programm...
Fig. 11-19 2 µm
Apoptosis in the Soil Worm  Caenorhabditis elegans <ul><li>Apoptosis is important in shaping an organism during embryonic ...
Fig. 11-20 Ced-9 protein (active) inhibits  Ced-4 activity Mitochondrion Receptor for death- signaling molecule Ced-4 Ced-...
Fig. 11-20a Ced-9 protein (active) inhibits  Ced-4 activity Mitochondrion Ced-4 Ced-3 Receptor for death- signaling molecu...
Fig. 11-20b (b) Death signal Death- signaling molecule Ced-9 (inactive) Cell forms blebs Active Ced-4 Active Ced-3 Activat...
Apoptotic Pathways and the Signals That Trigger Them <ul><li>Caspases are the main proteases (enzymes that cut up proteins...
<ul><li>Apoptosis evolved early in animal evolution and is essential for the development and maintenance of all animals </...
Fig. 11-21 Interdigital tissue 1 mm
Fig. 11-UN1 Reception Transduction Response Receptor Relay molecules Signaling molecule Activation of cellular response 1 ...
Fig. 11-UN2
You should now be able to: <ul><li>Describe the nature of a ligand-receptor interaction and state how such interactions in...
<ul><li>Define the term  second messenger ; briefly describe the role of these molecules in signaling pathways </li></ul><...
Upcoming SlideShare
Loading in …5
×

Chapter 11 Textbook Presentation

0 views

Published on

Published in: Education
  • Be the first to comment

Chapter 11 Textbook Presentation

  1. 1. Chapter 11 Cell Communication
  2. 2. Overview: The Cellular Internet <ul><li>Cell-to-cell communication is essential for multicellular organisms </li></ul><ul><li>Biologists have discovered some universal mechanisms of cellular regulation </li></ul><ul><li>The combined effects of multiple signals determine cell response </li></ul><ul><li>For example, the dilation of blood vessels is controlled by multiple molecules </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  3. 3. Fig. 11-1
  4. 4. Concept 11.1: External signals are converted to responses within the cell <ul><li>Microbes are a window on the role of cell signaling in the evolution of life </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  5. 5. Evolution of Cell Signaling <ul><li>A signal transduction pathway is a series of steps by which a signal on a cell’s surface is converted into a specific cellular response </li></ul><ul><li>Signal transduction pathways convert signals on a cell’s surface into cellular responses </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  6. 6. Fig. 11-2 Receptor  factor a factor a   a Exchange of mating factors Yeast cell, mating type a Yeast cell, mating type  Mating New a/  cell a/  1 2 3
  7. 7. <ul><li>Pathway similarities suggest that ancestral signaling molecules evolved in prokaryotes and were modified later in eukaryotes </li></ul><ul><li>The concentration of signaling molecules allows bacteria to detect population density </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  8. 8. Fig. 11-3 Individual rod- shaped cells Spore-forming structure (fruiting body) Aggregation in process Fruiting bodies 0.5 mm 1 3 2
  9. 9. Local and Long-Distance Signaling <ul><li>Cells in a multicellular organism communicate by chemical messengers </li></ul><ul><li>Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells </li></ul><ul><li>In local signaling, animal cells may communicate by direct contact, or cell-cell recognition </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  10. 10. Fig. 11-4 Plasma membranes Gap junctions between animal cells (a) Cell junctions Plasmodesmata between plant cells (b) Cell-cell recognition
  11. 11. <ul><li>In many other cases, animal cells communicate using local regulators , messenger molecules that travel only short distances </li></ul><ul><li>In long-distance signaling, plants and animals use chemicals called hormones </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  12. 12. Fig. 11-5 Local signaling Target cell Secreting cell Secretory vesicle Local regulator diffuses through extracellular fluid (a) Paracrine signaling (b) Synaptic signaling Target cell is stimulated Neurotransmitter diffuses across synapse Electrical signal along nerve cell triggers release of neurotransmitter Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling
  13. 13. Fig. 11-5ab Local signaling Target cell Secretory vesicle Secreting cell Local regulator diffuses through extracellular fluid (a) Paracrine signaling (b) Synaptic signaling Target cell is stimulated Neurotransmitter diffuses across synapse Electrical signal along nerve cell triggers release of neurotransmitter
  14. 14. Fig. 11-5c Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling
  15. 15. The Three Stages of Cell Signaling: A Preview <ul><li>Earl W. Sutherland discovered how the hormone epinephrine acts on cells </li></ul><ul><li>Sutherland suggested that cells receiving signals went through three processes: </li></ul><ul><ul><li>Reception </li></ul></ul><ul><ul><li>Transduction </li></ul></ul><ul><ul><li>Response </li></ul></ul>Animation: Overview of Cell Signaling Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  16. 16. Fig. 11-6-1 Reception 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM 1 Receptor
  17. 17. Fig. 11-6-2 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM Transduction 2 Relay molecules in a signal transduction pathway Reception 1 Receptor
  18. 18. Fig. 11-6-3 EXTRACELLULAR FLUID Plasma membrane CYTOPLASM Receptor Signaling molecule Relay molecules in a signal transduction pathway Activation of cellular response Transduction Response 2 3 Reception 1
  19. 19. Concept 11.2: Reception: A signal molecule binds to a receptor protein, causing it to change shape <ul><li>The binding between a signal molecule ( ligand ) and receptor is highly specific </li></ul><ul><li>A shape change in a receptor is often the initial transduction of the signal </li></ul><ul><li>Most signal receptors are plasma membrane proteins </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  20. 20. Receptors in the Plasma Membrane <ul><li>Most water-soluble signal molecules bind to specific sites on receptor proteins in the plasma membrane </li></ul><ul><li>There are three main types of membrane receptors: </li></ul><ul><ul><li>G protein-coupled receptors </li></ul></ul><ul><ul><li>Receptor tyrosine kinases </li></ul></ul><ul><ul><li>Ion channel receptors </li></ul></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  21. 21. <ul><li>A G protein-coupled receptor is a plasma membrane receptor that works with the help of a G protein </li></ul><ul><li>The G protein acts as an on/off switch: If GDP is bound to the G protein, the G protein is inactive </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  22. 22. Fig. 11-7a Signaling-molecule binding site Segment that interacts with G proteins G protein-coupled receptor
  23. 23. Fig. 11-7b G protein-coupled receptor Plasma membrane Enzyme G protein (inactive) GDP CYTOPLASM Activated enzyme GTP Cellular response GDP P i Activated receptor GDP GTP Signaling molecule Inactive enzyme 1 2 3 4
  24. 24. <ul><li>Receptor tyrosine kinases are membrane receptors that attach phosphates to tyrosines </li></ul><ul><li>A receptor tyrosine kinase can trigger multiple signal transduction pathways at once </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  25. 25. Fig. 11-7c Signaling molecule (ligand) Ligand-binding site  Helix Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosine kinase proteins CYTOPLASM Signaling molecule Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Dimer Activated relay proteins Tyr Tyr Tyr Tyr Tyr Tyr P P P P P P Cellular response 1 Cellular response 2 Inactive relay proteins Activated tyrosine kinase regions Fully activated receptor tyrosine kinase 6 6 ADP ATP Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr P P P P P P 1 2 3 4
  26. 26. <ul><li>A ligand-gated ion channel receptor acts as a gate when the receptor changes shape </li></ul><ul><li>When a signal molecule binds as a ligand to the receptor, the gate allows specific ions, such as Na + or Ca 2+ , through a channel in the receptor </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  27. 27. Fig. 11-7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellular response Gate closed 3 2 1
  28. 28. Intracellular Receptors <ul><li>Some receptor proteins are intracellular, found in the cytosol or nucleus of target cells </li></ul><ul><li>Small or hydrophobic chemical messengers can readily cross the membrane and activate receptors </li></ul><ul><li>Examples of hydrophobic messengers are the steroid and thyroid hormones of animals </li></ul><ul><li>An activated hormone-receptor complex can act as a transcription factor, turning on specific genes </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  29. 29. Fig. 11-8-1 Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM
  30. 30. Fig. 11-8-2 Receptor protein Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM
  31. 31. Fig. 11-8-3 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM
  32. 32. Fig. 11-8-4 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA mRNA NUCLEUS CYTOPLASM
  33. 33. Fig. 11-8-5 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS New protein CYTOPLASM
  34. 34. Concept 11.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell <ul><li>Signal transduction usually involves multiple steps </li></ul><ul><li>Multistep pathways can amplify a signal: A few molecules can produce a large cellular response </li></ul><ul><li>Multistep pathways provide more opportunities for coordination and regulation of the cellular response </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  35. 35. Signal Transduction Pathways <ul><li>The molecules that relay a signal from receptor to response are mostly proteins </li></ul><ul><li>Like falling dominoes, the receptor activates another protein, which activates another, and so on, until the protein producing the response is activated </li></ul><ul><li>At each step, the signal is transduced into a different form, usually a shape change in a protein </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  36. 36. Protein Phosphorylation and Dephosphorylation <ul><li>In many pathways, the signal is transmitted by a cascade of protein phosphorylations </li></ul><ul><li>Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  37. 37. <ul><li>Protein phosphatases remove the phosphates from proteins, a process called dephosphorylation </li></ul><ul><li>This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  38. 38. Fig. 11-9 Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 ATP ADP Active protein kinase 2 P P PP Inactive protein kinase 3 ATP ADP Active protein kinase 3 P P PP i ATP ADP P Active protein PP P i Inactive protein Cellular response Phosphorylation cascade i
  39. 39. Small Molecules and Ions as Second Messengers <ul><li>The extracellular signal molecule that binds to the receptor is a pathway’s “first messenger” </li></ul><ul><li>Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion </li></ul><ul><li>Second messengers participate in pathways initiated by G protein-coupled receptors and receptor tyrosine kinases </li></ul><ul><li>Cyclic AMP and calcium ions are common second messengers </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  40. 40. Cyclic AMP <ul><li>Cyclic AMP (cAMP) is one of the most widely used second messengers </li></ul><ul><li>Adenylyl cyclase , an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  41. 41. Adenylyl cyclase Fig. 11-10 Pyrophosphate P P i ATP cAMP Phosphodiesterase AMP
  42. 42. <ul><li>Many signal molecules trigger formation of cAMP </li></ul><ul><li>Other components of cAMP pathways are G proteins, G protein-coupled receptors, and protein kinases </li></ul><ul><li>cAMP usually activates protein kinase A, which phosphorylates various other proteins </li></ul><ul><li>Further regulation of cell metabolism is provided by G-protein systems that inhibit adenylyl cyclase </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  43. 43. First messenger Fig. 11-11 G protein Adenylyl cyclase GTP ATP cAMP Second messenger Protein kinase A G protein-coupled receptor Cellular responses
  44. 44. Calcium Ions and Inositol Triphosphate (IP 3 ) <ul><li>Calcium ions (Ca 2+ ) act as a second messenger in many pathways </li></ul><ul><li>Calcium is an important second messenger because cells can regulate its concentration </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  45. 45. EXTRACELLULAR FLUID Fig. 11-12 ATP Nucleus Mitochondrion Ca 2+ pump Plasma membrane CYTOSOL Ca 2+ pump Endoplasmic reticulum (ER) Ca 2+ pump ATP Key High [Ca 2+ ] Low [Ca 2+ ]
  46. 46. <ul><li>A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol </li></ul><ul><li>Pathways leading to the release of calcium involve inositol triphosphate (IP 3 ) and diacylglycerol (DAG) as additional second messengers </li></ul>Animation: Signal Transduction Pathways Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  47. 47. Fig. 11-13-1 EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein GTP G protein-coupled receptor Phospholipase C PIP 2 IP 3 DAG (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL
  48. 48. Fig. 11-13-2 G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase C PIP 2 DAG IP 3 (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL Ca 2+ (second messenger) GTP
  49. 49. Fig. 11-13-3 G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase C PIP 2 DAG IP 3 (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL Various proteins activated Cellular responses Ca 2+ (second messenger) GTP
  50. 50. Concept 11.4: Response: Cell signaling leads to regulation of transcription or cytoplasmic activities <ul><li>The cell’s response to an extracellular signal is sometimes called the “output response” </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  51. 51. Nuclear and Cytoplasmic Responses <ul><li>Ultimately, a signal transduction pathway leads to regulation of one or more cellular activities </li></ul><ul><li>The response may occur in the cytoplasm or may involve action in the nucleus </li></ul><ul><li>Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by turning genes on or off in the nucleus </li></ul><ul><li>The final activated molecule may function as a transcription factor </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  52. 52. Fig. 11-14 Growth factor Receptor Phosphorylation cascade Reception Transduction Active transcription factor Response P Inactive transcription factor CYTOPLASM DNA NUCLEUS mRNA Gene
  53. 53. <ul><li>Other pathways regulate the activity of enzymes </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  54. 54. Fig. 11-15 Reception Transduction Response Binding of epinephrine to G protein-coupled receptor (1 molecule) Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Active protein kinase A (10 4 ) Inactive phosphorylase kinase Active phosphorylase kinase (10 5 ) Inactive glycogen phosphorylase Active glycogen phosphorylase (10 6 ) Glycogen Glucose-1-phosphate (10 8 molecules)
  55. 55. <ul><li>Signaling pathways can also affect the physical characteristics of a cell, for example, cell shape </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  56. 56. Fig. 11-16 RESULTS CONCLUSION Wild-type (shmoos) ∆ Fus3 ∆ formin Shmoo projection forming Formin P Actin subunit P P Formin Formin Fus3 Phosphory- lation cascade GTP G protein-coupled receptor Mating factor GDP Fus3 Fus3 P Microfilament 1 2 3 4 5
  57. 57. Fig. 11-16a RESULTS Wild-type (shmoos) ∆ Fus3 ∆ formin
  58. 58. Fig. 11-16b CONCLUSION Mating factor G protein-coupled receptor GDP GTP Phosphory- lation cascade Shmoo projection forming Fus3 Fus3 Fus3 Formin Formin P P P Formin P Actin subunit Microfilament 1 2 3 4 5
  59. 59. Fine-Tuning of the Response <ul><li>Multistep pathways have two important benefits: </li></ul><ul><ul><li>Amplifying the signal (and thus the response) </li></ul></ul><ul><ul><li>Contributing to the specificity of the response </li></ul></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  60. 60. Signal Amplification <ul><li>Enzyme cascades amplify the cell’s response </li></ul><ul><li>At each step, the number of activated products is much greater than in the preceding step </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  61. 61. The Specificity of Cell Signaling and Coordination of the Response <ul><li>Different kinds of cells have different collections of proteins </li></ul><ul><li>These different proteins allow cells to detect and respond to different signals </li></ul><ul><li>Even the same signal can have different effects in cells with different proteins and pathways </li></ul><ul><li>Pathway branching and “cross-talk” further help the cell coordinate incoming signals </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  62. 62. Fig. 11-17 Signaling molecule Receptor Relay molecules Response 1 Cell A. Pathway leads to a single response. Response 2 Response 3 Cell B. Pathway branches, leading to two responses. Response 4 Response 5 Activation or inhibition Cell C. Cross-talk occurs between two pathways. Cell D. Different receptor leads to a different response.
  63. 63. Fig. 11-17a Signaling molecule Receptor Relay molecules Response 1 Cell A. Pathway leads to a single response. Cell B. Pathway branches, leading to two responses. Response 2 Response 3
  64. 64. Fig. 11-17b Response 4 Response 5 Activation or inhibition Cell C. Cross-talk occurs between two pathways. Cell D. Different receptor leads to a different response.
  65. 65. Signaling Efficiency: Scaffolding Proteins and Signaling Complexes <ul><li>Scaffolding proteins are large relay proteins to which other relay proteins are attached </li></ul><ul><li>Scaffolding proteins can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  66. 66. Fig. 11-18 Signaling molecule Receptor Scaffolding protein Plasma membrane Three different protein kinases
  67. 67. Termination of the Signal <ul><li>Inactivation mechanisms are an essential aspect of cell signaling </li></ul><ul><li>When signal molecules leave the receptor, the receptor reverts to its inactive state </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  68. 68. Concept 11.5: Apoptosis (programmed cell death) integrates multiple cell-signaling pathways <ul><li>Apoptosis is programmed or controlled cell suicide </li></ul><ul><li>A cell is chopped and packaged into vesicles that are digested by scavenger cells </li></ul><ul><li>Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  69. 69. Fig. 11-19 2 µm
  70. 70. Apoptosis in the Soil Worm Caenorhabditis elegans <ul><li>Apoptosis is important in shaping an organism during embryonic development </li></ul><ul><li>The role of apoptosis in embryonic development was first studied in Caenorhabditis elegans </li></ul><ul><li>In C. elegans , apoptosis results when specific proteins that “accelerate” apoptosis override those that “put the brakes” on apoptosis </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  71. 71. Fig. 11-20 Ced-9 protein (active) inhibits Ced-4 activity Mitochondrion Receptor for death- signaling molecule Ced-4 Ced-3 Inactive proteins (a) No death signal Ced-9 (inactive) Cell forms blebs Death- signaling molecule Other proteases Active Ced-4 Active Ced-3 Nucleases Activation cascade (b) Death signal
  72. 72. Fig. 11-20a Ced-9 protein (active) inhibits Ced-4 activity Mitochondrion Ced-4 Ced-3 Receptor for death- signaling molecule Inactive proteins (a) No death signal
  73. 73. Fig. 11-20b (b) Death signal Death- signaling molecule Ced-9 (inactive) Cell forms blebs Active Ced-4 Active Ced-3 Activation cascade Other proteases Nucleases
  74. 74. Apoptotic Pathways and the Signals That Trigger Them <ul><li>Caspases are the main proteases (enzymes that cut up proteins) that carry out apoptosis </li></ul><ul><li>Apoptosis can be triggered by: </li></ul><ul><ul><li>An extracellular death-signaling ligand </li></ul></ul><ul><ul><li>DNA damage in the nucleus </li></ul></ul><ul><ul><li>Protein misfolding in the endoplasmic reticulum </li></ul></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  75. 75. <ul><li>Apoptosis evolved early in animal evolution and is essential for the development and maintenance of all animals </li></ul><ul><li>Apoptosis may be involved in some diseases (for example, Parkinson’s and Alzheimer’s); interference with apoptosis may contribute to some cancers </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  76. 76. Fig. 11-21 Interdigital tissue 1 mm
  77. 77. Fig. 11-UN1 Reception Transduction Response Receptor Relay molecules Signaling molecule Activation of cellular response 1 2 3
  78. 78. Fig. 11-UN2
  79. 79. You should now be able to: <ul><li>Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal-transduction system </li></ul><ul><li>Compare and contrast G protein-coupled receptors, tyrosine kinase receptors, and ligand-gated ion channels </li></ul><ul><li>List two advantages of a multistep pathway in the transduction stage of cell signaling </li></ul><ul><li>Explain how an original signal molecule can produce a cellular response when it may not even enter the target cell </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
  80. 80. <ul><li>Define the term second messenger ; briefly describe the role of these molecules in signaling pathways </li></ul><ul><li>Explain why different types of cells may respond differently to the same signal molecule </li></ul><ul><li>Describe the role of apoptosis in normal development and degenerative disease in vertebrates </li></ul>Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

×