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BIOLOGYA Global Approach
Campbell • Reece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2015 Pearson Education Ltd
TENTH EDITION
Global Edition
Lecture Presentation by Nicole Tunbridge andKathleen Fitzpatrick
9Cellular Signaling
© 2015 Pearson Education Ltd
Cellular Messaging
a) Cells can signal to each other and interpret the signals they receive from other cells and the environment
b) Signals are most often chemicals
c) The same small set of cell signaling mechanisms shows up in diverse species and processes
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Figure 9.1a
Epinephrine
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Concept 9.1: External signals are converted to responses within the cell
a) Communication among microorganisms provides some insight into how cells send, receive, and respond to signals
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Local and Long-Distance Signaling
a) Cells in a multicellular organism communicate via signaling molecules
b) In local signaling, animal cells may communicate by direct contact
c) Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells
d) Signaling substances in the cytosol can pass freely between adjacent cells
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Figure 9.4Plasma membranes Cell wall
(a) Cell junctions
(b) Cell-cell recognition
Gap junctionsbetween animal cells
Plasmodesmatabetween plant cells
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a) In many other cases, animal cells communicate using secreted messenger molecules that travel only short distances
b) Growth factors, which stimulate nearby target cells to grow and divide, are one class of such local regulators in animals
c) This type of local signaling in animals is called paracrine signaling
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a) Synaptic signaling occurs in the animal nervous system when a neurotransmitter is released in response to an electric signal
b) Local signaling in plants is not well understood beyond communication between plasmodesmata
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a) In long-distance signaling, plants and animals use chemicals called hormones
b) Hormonal signaling in animals is called endocrine signaling; specialized cells release hormones, which travel to target cells via the circulatory system
c) The ability of a cell to respond to a signal depends on whether or not it has a receptor specific to that signal
© 2015 Pearson Education Ltd
Figure 9.5 Local signaling
Target cells
Secreting cell
Secretoryvesicles
Local regulator Target cell
(b) Synaptic signaling(a) Paracrine signaling
(c) Endocrine (hormonal) signaling
Electrical signal triggersrelease of neurotransmitter.
Neurotransmitterdiffuses acrosssynapse.
Long-distance signalingEndocrine cell Target cell
specificallybindshormone.
Hormonetravels inbloodstream.
Bloodvessel
© 2015 Pearson Education Ltd
Figure 9.5a
Local signaling
Target cells
Secreting cell
Secretoryvesicles
Local regulator(a) Paracrine signaling
© 2015 Pearson Education Ltd
Figure 9.5b
Target cell
(b) Synaptic signaling
Electrical signal triggersrelease of neurotransmitter.
Neurotransmitterdiffuses acrosssynapse.
Local signaling
© 2015 Pearson Education Ltd
Figure 9.5c
(c) Endocrine (hormonal) signaling
Long-distance signalingEndocrine cell Target cell
specificallybindshormone.
Hormonetravels inbloodstream.
Bloodvessel
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The Three Stages of Cell Signaling: A Preview
a) Earl W. Sutherland discovered how the hormone epinephrine acts on cells
b) Sutherland suggested that cells receiving signals went through three processes
a)Reception
b)Transduction
c)Response
© 2015 Pearson Education Ltd
a) In reception, the target cell detects a signaling molecule that binds to a receptor protein on the cell surface
b) In transduction, the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway; transduction often occurs in a series of steps
c) In response, the transduced signal triggers a specific response in the target cell
© 2015 Pearson Education Ltd
Figure 9.6-1
CYTOPLASMPlasma membrane
EXTRACELLULARFLUID
Receptor
Signalingmolecule
Reception1
© 2015 Pearson Education Ltd
Figure 9.6-2
CYTOPLASMPlasma membrane
EXTRACELLULARFLUID
Receptor
Signalingmolecule
Reception1 Transduction2
Relay molecules
1 2 3
© 2015 Pearson Education Ltd
Figure 9.6-3
CYTOPLASMPlasma membrane
EXTRACELLULARFLUID
Receptor
Signalingmolecule
Reception1 Transduction2
Relay molecules
1 2 3
Response3
Activationof cellularresponse
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Animation: Overview of Cell Signaling
© 2015 Pearson Education Ltd
Concept 9.2: Reception: A signaling molecule binds to a receptor protein, causing it to change shape
a) The binding between a signal molecule (ligand) and receptor is highly specific
b) A shape change in a receptor is often the initial transduction of the signal
c) Most signal receptors are plasma membrane proteins
© 2015 Pearson Education Ltd
Receptors in the Plasma Membrane
a) G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors
b) Most water-soluble signal molecules bind to specific sites on receptor proteins that span the plasma membrane
© 2015 Pearson Education Ltd
Figure 9.7
Plasmamembrane
Cholesterol
Moleculemimickingligand
β2-adrenergicreceptors
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a) There are three main types of membrane receptors
a)G protein-coupled receptors
b)Receptor tyrosine kinases
c)Ion channel receptors
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a) G protein-coupled receptors (GPCRs) are cell surface transmembrane receptors that work with the help of a G protein
b) G proteins bind the energy-rich GTP
c) G proteins are all very similar in structure
d) GPCR systems are extremely widespread and diverse in their functions
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a) Receptor tyrosine kinases (RTKs) are membrane receptors that attach phosphates to tyrosines
b) A receptor tyrosine kinase can trigger multiple signal transduction pathways at once
c) Abnormal functioning of RTKs is associated with many types of cancers
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a) A ligand-gated ion channel receptor acts as a gate when the receptor changes shape
b) When a signal molecule binds as a ligand to the receptor, the gate allows specific ions, such as Na+ or Ca2
+, through a channel in the receptor
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Figure 9.8a
Signaling molecule binding site
Segment thatinteracts withG proteins
G protein-coupled receptor
© 2015 Pearson Education Ltd
Figure 9.8b
Activatedenzyme
EnzymeG protein(inactive)CYTOPLASM
G protein-coupledreceptor
Plasma membrane Activatedreceptor
Signalingmolecule
GDP
GTPGDP
GTPGDP
Inactiveenzyme
Cellularresponse
P i
GTP
GDP
1 2
43
© 2015 Pearson Education Ltd
Figure 9.8ba
EnzymeG protein(inactive)CYTOPLASM
G protein-coupledreceptor
Plasma membrane
GDP
Activatedreceptor
Signalingmolecule
Inactiveenzyme
GTP
GDP
GDP
GTP
1
2
© 2015 Pearson Education Ltd
Figure 9.8bb Activatedenzyme
Cellularresponse
3
GTP
GDP
P i
4
© 2015 Pearson Education Ltd
Figure 9.8c
Tyrosines
CYTOPLASMReceptor tyrosinekinase proteins(inactive monomers)
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Ligand-binding site helix in themembrane
Signaling molecule(ligand)
Signaling molecule
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Dimer
Activated relayproteins
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Inactiverelay proteins
Cellularresponse 1
Cellularresponse 2
PPP
PPP
PPP
PPP
Tyr
Tyr
Tyr
Fully activatedreceptor tyrosinekinase (phos-phorylated dimer)
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr 6 6 ADPATP
Activated tyrosinekinase regions(unphosphorylateddimer)
1 2
43
© 2015 Pearson Education Ltd
Figure 9.8ca
Tyrosines
CYTOPLASMReceptor tyrosinekinase proteins(inactive monomers)
Ligand-binding site helix in themembrane
Signaling molecule(ligand)
TyrTyr
Tyr
TyrTyr
Tyr
1
© 2015 Pearson Education Ltd
Figure 9.8cb
Signaling molecule
Dimer
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
2
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
© 2015 Pearson Education Ltd
Figure 9.8cc
3
Fully activatedreceptor tyrosinekinase (phos-phorylated dimer)
6 6 ADPATP
Activated tyrosinekinase regions(unphosphorylateddimer)
TyrTyr
Tyr
TyrTyr
Tyr
TyrTyr
Tyr
TyrTyr
Tyr
PPP
PPP
© 2015 Pearson Education Ltd
Figure 9.8cd
4
TyrTyr
Tyr
PPP
TyrTyr
Tyr
PPP
Activated relayproteins
Inactiverelay proteins
Cellularresponse 1
Cellularresponse 2
© 2015 Pearson Education Ltd
Figure 9.8d-1
1Ions
PlasmamembraneLigand-gated
ion channel receptor
GateclosedSignaling
molecule(ligand)
© 2015 Pearson Education Ltd
Figure 9.8d-2
1Ions
PlasmamembraneLigand-gated
ion channel receptor
GateclosedSignaling
molecule(ligand)
Gate open2
Cellularresponse
© 2015 Pearson Education Ltd
Figure 9.8d-3
1Ions
PlasmamembraneLigand-gated
ion channel receptor
GateclosedSignaling
molecule(ligand)
Gate open2
Cellularresponse
Gate closed3
© 2015 Pearson Education Ltd
Intracellular Receptors
a) Intracellular receptor proteins are found in the cytoplasm or nucleus of target cells
b) Small or hydrophobic chemical messengers can readily cross the membrane and activate receptors
c) Examples of hydrophobic messengers are the steroid and thyroid hormones of animals
d) An activated hormone-receptor complex can act as a transcription factor, turning on specific genes
© 2015 Pearson Education Ltd
Figure 9.9Hormone(aldosterone)
Receptorprotein
Plasmamembrane
Hormone-receptorcomplex
EXTRA-CELLULARFLUID
DNA
mRNA
NUCLEUS
Newprotein
CYTOPLASM
© 2015 Pearson Education Ltd
Figure 9.9a
Hormone(aldosterone)
Receptorprotein
PlasmamembraneHormone-receptorcomplex
EXTRA-CELLULARFLUID
NUCLEUS CYTOPLASM
© 2015 Pearson Education Ltd
Figure 9.9b
Hormone-receptorcomplex
DNA
mRNA
NUCLEUS
Newprotein
CYTOPLASM
Concept 9.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell
a) Signal transduction usually involves multiple steps
b) Multistep pathways can greatly amplify a signal
c) Multistep pathways provide more opportunities for coordination and regulation of the cellular response
© 2015 Pearson Education Ltd
© 2015 Pearson Education Ltd
Signal Transduction Pathways
a) The binding of a signaling molecule to a receptor triggers the first step in a chain of molecular interactions
b) Like falling dominoes, the receptor activates another protein, which activates another, and so on, until the protein producing the response is activated
c) At each step, the signal is transduced into a different form, usually a shape change in a protein
© 2015 Pearson Education Ltd
Protein Phosphorylation and Dephosphorylation
a) Phosphorylation and dephosphorylation of proteins is a widespread cellular mechanism for regulating protein activity
b)Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation
c) Many relay molecules in signal transduction pathways are protein kinases, creating a phosphorylation cascade
© 2015 Pearson Education Ltd
Figure 9.10
Signaling molecule
Activated relaymolecule
Receptor
Inactiveprotein kinase
1
Inactiveprotein kinase
2
Inactiveprotein kinase
3
Activeprotein kinase
1
Activeprotein kinase
2
Activeprotein kinase
3
Activeprotein
Inactiveprotein
Phosphorylation cascade
ATPADP
PP
ATPADP
P i
P
P
P i
ATPADP
PP
PPP i
P
Cellularresponse
© 2015 Pearson Education Ltd
Figure 9.10a
Signaling molecule
Activated relaymolecule
Receptor
Inactiveprotein kinase
1 Activeprotein kinase
1
© 2015 Pearson Education Ltd
Figure 9.10b
Inactiveprotein kinase
1
Inactiveprotein kinase
2
Inactiveprotein kinase
3
Activeprotein kinase
1
Activeprotein kinase
2
Activeprotein kinase
3
ATPADP
PPP i
ATPADP
PPP i
Phosphorylationcascade
P
P
© 2015 Pearson Education Ltd
Figure 9.10c
Inactiveprotein kinase
3 Activeprotein kinase
3
ATPADP
PPP i
P i
P
P
ATPADP
PP
Inactiveprotein
Activeprotein
Cellularresponse
© 2015 Pearson Education Ltd
a) Protein phosphatases rapidly remove the phosphates from proteins, a process called dephosphorylation
b) This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off or up or down, as required
© 2015 Pearson Education Ltd
Small Molecules and Ions as Second Messengers
a) Many signaling pathways involve second messengers
b)Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion
c) Second messengers participate in pathways initiated by GPCRs and RTKs
d) Cyclic AMP and calcium ions are common second messengers
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Cyclic AMP
a) Cyclic AMP (cAMP) is one of the most widely used second messengers
b)Adenylyl cyclase, an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal
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Figure 9.11
ATP cAMP AMP
PhosphodiesteraseAdenylyl cyclase
Pyrophosphate H2O
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Figure 9.11a
ATP cAMP
Adenylyl cyclase
Pyrophosphate
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Figure 9.11b
cAMP AMP
H2O
Phosphodiesterase
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a) Many signal molecules trigger formation of cAMP
b) Other components of cAMP pathways are G proteins, G protein-coupled receptors, and protein kinases
c) cAMP usually activates protein kinase A, which phosphorylates various other proteins
d) Further regulation of cell metabolism is provided by G-protein systems that inhibit adenylyl cyclase
© 2015 Pearson Education Ltd
Figure 9.12
First messenger(signaling moleculesuch as epinephrine)
G protein
Adenylylcyclase
G protein-coupledreceptor
Secondmessenger
Cellular responses
Proteinkinase A
GTP
ATP
cAMP
© 2015 Pearson Education Ltd
a) Understanding of the role of cAMP in G protein signaling pathways helps explain how certain microbes cause disease
b) The cholera bacterium, Vibrio cholerae, produces a toxin that modifies a G protein so that it is stuck in its active form
c) This modified G protein continually makes cAMP, causing intestinal cells to secrete large amounts of salt into the intestines
d) Water follows by osmosis and an untreated person can soon die from loss of water and salt
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Calcium Ions and Inositol Triphosphate (IP3)
a) Calcium ions (Ca2+) act as a second messenger in
many pathways
b) Ca2+ can function as a second messenger because
its concentration in the cytosol is normally much lower than the concentration outside the cell
c) A small change in number of calcium ions thus represents a relatively large percentage change in calcium concentration
© 2015 Pearson Education Ltd
Figure 9.13
Endoplasmicreticulum (ER)
Plasmamembrane
Mitochondrion
ATP
ATP
ATPCYTOSOL
Nucleus
Ca2+
pump
EXTRACELLULARFLUID
Key High [Ca2+] Low [Ca2+]
© 2015 Pearson Education Ltd
a) A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol
b) Pathways leading to the release of calcium involve inositol triphosphate (IP3) and diacylglycerol (DAG) as additional second messengers
c) These two are produced by cleavage of a certain phospholipid in the plasma membrane
© 2015 Pearson Education Ltd
Figure 9.14-1
EXTRA-CELLULARFLUID
Signaling molecule(first messenger)
G protein
GTP
CYTOSOL G protein-coupledreceptor Phospholipase C
DAG
PIP2
IP3(second messenger)
IP3-gatedcalcium channel
Ca2+
Nucleus
Endoplasmicreticulum (ER)lumen
© 2015 Pearson Education Ltd
Figure 9.14-2
EXTRA-CELLULARFLUID
Signaling molecule(first messenger)
G protein
GTP
CYTOSOL G protein-coupledreceptor Phospholipase C
DAG
PIP2
IP3(second messenger)
IP3-gatedcalcium channel
Ca2+
Nucleus
Endoplasmicreticulum (ER)lumen
Ca2+
(secondmessenger)
© 2015 Pearson Education Ltd
Figure 9.14-3
EXTRA-CELLULARFLUID
Signaling molecule(first messenger)
G protein
GTP
CYTOSOL G protein-coupledreceptor Phospholipase C
DAG
PIP2
IP3(second messenger)
IP3-gatedcalcium channel
Ca2+
Nucleus
Endoplasmicreticulum (ER)lumen
Ca2+
(secondmessenger)
Variousproteinsactivated
Cellularresponses
© 2015 Pearson Education Ltd
Animation: Signal Transduction Pathways
Concept 9.4: Response: Cell signaling leads to regulation of transcription or cytoplasmic activities
a) The cell’s response to an extracellular signal is called the “output response”
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© 2015 Pearson Education Ltd
Nuclear and Cytoplasmic Responses
a) Ultimately, a signal transduction pathway leads to regulation of one or more cellular activities
b) The response may occur in the cytoplasm or in the nucleus
c) Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by turning genes on or off in the nucleus
d) The final activated molecule in the signaling pathway may function as a transcription factor
© 2015 Pearson Education Ltd
Figure 9.15
Growth factorReceptor
Phospho-rylation
cascade
Reception
Transduction
CYTOPLASM
Inactivetranscriptionfactor
Activetranscriptionfactor
DNA
ResponseP
Gene
mRNANUCLEUS
© 2015 Pearson Education Ltd
Figure 9.15a
Growth factorReceptor
Phospho-rylation
cascade
Reception
Transduction
NUCLEUS
CYTOPLASM
Inactivetranscriptionfactor
© 2015 Pearson Education Ltd
Figure 9.15b
NUCLEUS
CYTOPLASM
Phospho-rylation
cascade Transduction
Inactivetranscriptionfactor
Activetranscriptionfactor Response
DNA
P
Gene
mRNA
© 2015 Pearson Education Ltd
a) Other pathways regulate the activity of enzymes rather than their synthesis
b) For example, a signal could cause opening or closing of an ion channel in the plasma membrane, or a change in cell metabolism
© 2015 Pearson Education Ltd
Figure 9.16
Reception Transduction
InactiveG protein
Active G protein (102 molecules)
Inactiveadenylyl cyclase
Active adenylyl cyclase (102)
ATP
Cyclic AMP (104)Inactiveprotein kinase A
Active protein kinase A (104)
Inactivephosphorylase kinase
Active phosphorylase kinase (105)
Active glycogen phosphorylase (106)
Inactiveglycogen phosphorylaseGlycogen
Response
Glucose 1-phosphate(108 molecules)
Binding of epinephrine to G protein-coupledreceptor(1 molecule)
© 2015 Pearson Education Ltd
Figure 9.16a
Reception
Glycogen
Response
Glucose 1-phosphate(108 molecules)
Binding of epinephrine to G protein-coupledreceptor(1 molecule)
© 2015 Pearson Education Ltd
Figure 9.16b
Transduction
InactiveG protein
Active G protein (102 molecules)
Inactiveadenylyl cyclase
Active adenylyl cyclase (102)
ATP
Cyclic AMP (104)Inactiveprotein kinase A
Active protein kinase A (104)
© 2015 Pearson Education Ltd
Figure 9.16c
Inactivephosphorylase kinase
Active phosphorylase kinase (105)
Active glycogen phosphorylase (106)
Inactiveglycogen phosphorylase
Cyclic AMP (104)Inactiveprotein kinase A
Active protein kinase A (104)
Transduction
© 2015 Pearson Education Ltd
a) Signaling pathways can also affect the overall behavior of a cell, for example, a signal could lead to cell division
© 2015 Pearson Education Ltd
Regulation of the Response
a) A response to a signal may not be simply “on” or “off”
b) There are four aspects of signal regulation to consider
a)Amplification of the signal (and thus the response)
b)Specificity of the response
c)Overall efficiency of response, enhanced by scaffolding proteins
d)Termination of the signal
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Signal Amplification
a) Enzyme cascades amplify the cell’s response to the signal
b) At each step, the number of activated products is much greater than in the preceding step
© 2015 Pearson Education Ltd
The Specificity of Cell Signaling and Coordination of the Response
a) Different kinds of cells have different collections of proteins
b) These different proteins allow cells to detect and respond to different signals
c) The same signal can have different effects in cells with different proteins and pathways
d) Pathway branching and “cross-talk” further help the cell coordinate incoming signals
© 2015 Pearson Education Ltd
Figure 9.17
Signalingmolecule
Receptor
Relaymole-cules
Response 1 Response 2 Response 3 Response 4 Response 5
Cell A: Pathway leadsto a single response.
Cell B: Pathway branches, leading totwo responses.
Cell C: Cross-talkoccurs between twopathways.
Cell D: Differentreceptor leads to a different response.
Activationor inhibition
© 2015 Pearson Education Ltd
Figure 9.17a
Signalingmolecule
Receptor
Relaymole-cules
Response 1 Response 2 Response 3
Cell A: Pathway leadsto a single response.
Cell B: Pathway branches, leading totwo responses.
© 2015 Pearson Education Ltd
Figure 9.17b
Response 4 Response 5
Cell C: Cross-talkoccurs between twopathways.
Cell D: Differentreceptor leads to a different response.
Activationor inhibition
© 2015 Pearson Education Ltd
Signaling Efficiency: Scaffolding Proteins and Signaling Complexes
a) Scaffolding proteins are large relay proteins to which other relay proteins are attached
b) Scaffolding proteins can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway
c) In some cases, scaffolding proteins may also help activate some of the relay proteins
© 2015 Pearson Education Ltd
Figure 9.18
Signalingmolecule
Receptor
Scaffoldingprotein
Plasmamembrane
Threedifferentproteinkinases
© 2015 Pearson Education Ltd
Termination of the Signal
a) Inactivation mechanisms are an essential aspect of cell signaling
b) If ligand concentration falls, fewer receptors will be bound
c) Unbound receptors revert to an inactive state
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Concept 9.5: Apoptosis integrates multiple cell-signaling pathways
a) Cells that are infected or damaged or have reached the end of their functional lives often undergo “programmed cell death”
b)Apoptosis is the best understood type
c) Components of the cell are chopped up and packaged into vesicles that are digested by scavenger cells
d) Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells
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Figure 9.19
2 µm
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Apoptosis in the Soil Worm Caenorhabditis elegans
a) In worms and other organisms, apoptosis is triggered by signals that activate a cascade of “suicide” proteins in the cells programmed to die
b) When the death signal is received, an apoptosis inhibiting protein (Ced-9) is inactivated, triggering a cascade of caspase proteins that promote apoptosis
c) The chief caspase in the nematode is called Ced-3
© 2015 Pearson Education Ltd
Figure 9.20
Ced-9 protein (active)inhibits Ced-4 activity
Mitochondrion
Receptorfor death-signalingmolecule
(a) No death signal (b) Death signal
Ced-4 Ced-3
Inactive proteins
Death-signalingmolecule
Ced-9 (inactive)
ActiveCed-4
ActiveCed-3
Cellformsblebs
Otherproteases
NucleasesActivationcascade
© 2015 Pearson Education Ltd
Figure 9.20a
Ced-9 protein (active)inhibits Ced-4 activity
Mitochondrion
Receptorfor death-signalingmolecule
(a) No death signal
Ced-4 Ced-3
Inactive proteins
© 2015 Pearson Education Ltd
Figure 9.20b
(b) Death signal
Death-signalingmolecule
Ced-9 (inactive)
ActiveCed-4
ActiveCed-3
Cellformsblebs
OtherproteasesNucleases
Activationcascade
© 2015 Pearson Education Ltd
Apoptotic Pathways and the Signals That Trigger Them
a) In humans and other mammals, several different pathways, including about 15 caspases, can carry out apoptosis
b) Apoptosis can be triggered by signals from outside the cell or inside it
c) Internal signals can result from irreparable DNA damage or excessive protein misfolding
© 2015 Pearson Education Ltd
a) Apoptosis evolved early in animal evolution and is essential for the development and maintenance of all animals
b) For example, apoptosis is a normal part of development of hands and feet in humans (and paws in other mammals)
c) Apoptosis may be involved in some diseases (for example, Parkinson’s and Alzheimer’s); interference with apoptosis may contribute to some cancers
© 2015 Pearson Education Ltd
Figure 9.21
Interdigitaltissue 1 mm
Cellsundergoingapoptosis
Spacebetweendigits
© 2015 Pearson Education Ltd
Figure 9.21a
Interdigitaltissue1 mm
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Figure 9.21b
1 mm
Cellsundergoingapoptosis
© 2015 Pearson Education Ltd
Figure 9.21c
Spacebetweendigits1 mm
© 2015 Pearson Education Ltd
Figure 9.UN01a
Matingfactor
Mating factoractivatesreceptor.
GDPG protein binds GTPand becomes activated.
GTP
Fus3 Fus3P
Phosphoryl- ation cascade
Phosphorylation cascadeactivates Fus3, which movesto plasma membrane.
Formin ForminP
Fus3 phos-phorylatesformin,activating it.
Formin initiates growth ofmicrofilaments that formthe shmoo projections.
Microfilament
P
P
Fus3Actinsubunit
Formin
Shmoo projectionformingG protein-coupled
receptor
1
2
5
4
3
© 2015 Pearson Education Ltd
Figure 9.UN01aa
Matingfactor
Mating factoractivatesreceptor.
GDPG protein binds GTPand becomes activated.
GTP
Fus3 Fus3P
Phosphoryl- ation cascade
Phosphorylation cascadeactivates Fus3, which movesto plasma membrane.
G protein-coupledreceptor
1
2
3
© 2015 Pearson Education Ltd
Figure 9.UN01ab
Formin ForminP
Fus3 phos-phorylatesformin,activating it.
Formin initiates growth ofmicrofilaments that formthe shmoo projections.
Microfilament
P
P
Fus3Actinsubunit
Formin
Shmoo projectionforming
4
5
© 2015 Pearson Education Ltd
Figure 9.UN01b
Wild type
© 2015 Pearson Education Ltd
Figure 9.UN01c
Fus3
© 2015 Pearson Education Ltd
Figure 9.UN01d
formin
© 2015 Pearson Education Ltd
Figure 9.UN02
Reception Transduction Response
Relay molecules
Signalingmolecule
Receptor
Activationof cellularresponse
1 2 3
1 2 3
© 2015 Pearson Education Ltd
Figure 9.UN03