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Chapter 11
Cell Communication
LE 11-2
Exchange of
mating factors
a factor
Receptor
a
a
Yeast cell, a factor
mating type a
Yeast cell,
mating type a
Mating
a
a
New a/a cell
a/a
Signal Transduction Pathways

Local signaling



Cell junctions
Cell-cell recognition
Local regulators – growth factors



Paracrine signaling
Synaptic signaling
Long-Distance signaling

Endocrine signaling - hormones
LE 11-3a
Plasma membranes
Gap junctions
between animal cells
Cell junctions
Plasmodesmata
between plant cells
LE 11-3b
Cell-cell recognition
LE 11-4a
Local signaling
Target cell
Secreting
cell
Local regulator
diffuses through
extracellular fluid
Paracrine signaling
Electrical signal
along nerve cell
triggers release of
neurotransmitter
Neurotransmitter
diffuses across
synapse
Secretory
vesicle
Target cell
is stimulated
Synaptic signaling
LE 11-4b
Long-distance signaling
Endocrine cell
Blood
vessel
Hormone travels
in bloodstream
to target cells
Target
cell
Hormonal signaling
Three Stages



Reception
Transduction
Response
LE 11-5_1
EXTRACELLULAR
FLUID
CYTOPLASM
Plasma membrane
Reception
Receptor
Signal
molecule
Transduction
LE 11-5_2
EXTRACELLULAR
FLUID
CYTOPLASM
Plasma membrane
Reception
Transduction
Receptor
Relay molecules in a signal transduction
pathway
Signal
molecule
LE 11-5_3
EXTRACELLULAR
FLUID
CYTOPLASM
Plasma membrane
Reception
Transduction
Response
Receptor
Activation
of cellular
response
Relay molecules in a signal transduction
pathway
Signal
molecule
Reception


Receptor-Ligand interaction
Receptors


Intracellular – testosterone
In plasma membrane – Figure 11.7



G-protein linked receptor
Receptor tyrosine kinases
Ion channel receptors – ligand-gated ion channel
LE 11-6
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
Hormonereceptor
complex
The steroid
hormone testosterone
passes through the
plasma membrane.
Testosterone binds
to a receptor protein
in the cytoplasm,
activating it.
The hormonereceptor complex
enters the nucleus
and binds to specific
genes.
DNA
The bound protein
stimulates the
transcription of
the gene into mRNA.
mRNA
NUCLEUS
New protein
The mRNA is
translated into a
specific protein.
CYTOPLASM
LE 11-7aa
Signal-binding site
Segment that
interacts with
G proteins
G-protein-linked receptor
LE 11-7ab
Plasma
membrane
G-protein-linked
receptor
Activated
receptor
Signal molecule
GDP
CYTOPLASM
Enzyme
G protein
(inactive)
GDP
GTP
Activated
enzyme
GTP
GDP
Pi
Cellular response
Inactive
enzyme
LE 11-7b
Signal
molecule
Signal-binding site
a Helix in the
membrane
Signal
molecule
Tyrosines
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Receptor tyrosine
kinase proteins
(inactive monomers)
CYTOPLASM
Dimer
Activated relay
proteins
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
6
ATP
Activated tyrosinekinase regions
(unphosphorylated
dimer)
6 ADP
P Tyr
P Tyr
P Tyr
Tyr
P
P
Tyr P
Tyr
Fully activated receptor
tyrosine-kinase
(phosphorylated
dimer)
P Tyr
P Tyr
P Tyr
P
Tyr P
Tyr P
Tyr
Inactive
relay proteins
Cellular
response 1
Cellular
response 2
LE 11-7c
Signal
molecule
(ligand)
Gate
closed
Ligand-gated
ion channel receptor
Ions
Plasma
membrane
Gate open
Cellular
response
Gate closed
Transduction





Cascades of molecular interactions
Signal transduction pathway
Protein phosphorylation and
dephosphorylation
Second messengers
Calcium ions and IP3
LE 11-8
Signal molecule
Receptor
Activated relay
molecule
Inactive
protein kinase
1
Active
protein
kinase
1
Inactive
protein kinase
2
ATP
ADP
Pi
P
Active
protein
kinase
2
PP
Inactive
protein kinase
3
ATP
ADP
Pi
Active
protein
kinase
3
PP
Inactive
protein
P
ATP
P
ADP
Pi
PP
Active
protein
Cellular
response
LE 11-9
Phosphodiesterase
Adenylyl cyclase
Pyrophosphate
P
ATP
H2O
Pi
Cyclic AMP
AMP
LE 11-10
First messenger
(signal molecule
such as epinephrine)
Adenylyl
cyclase
G protein
G-protein-linked
receptor
GTP
ATP
cAMP
Second
messenger
Protein
kinase A
Cellular responses
LE 11-11
EXTRACELLULAR
FLUID
Plasma
membrane
Ca2+
pump
ATP
Mitochondrion
Nucleus
CYTOSOL
Ca2+
pump
Endoplasmic
reticulum (ER)
ATP
Key
Ca2+
pump
High [Ca2+]
Low [Ca2+]
LE 11-12_1
EXTRACELLULAR Signal molecule
FLUID
(first messenger)
G protein
DAG
GTP
G-protein-linked
receptor
IP3-gated
calcium channel
Endoplasmic
Ca2+
reticulum (ER)
CYTOSOL
Phospholipase C
PIP2
IP3 (second
messenger)
LE 11-12_2
EXTRACELLULAR Signal molecule
FLUID
(first messenger)
G protein
DAG
GTP
G-protein-linked
receptor
Phospholipase C
IP3 (second
messenger)
IP3-gated
calcium channel
Endoplasmic
Ca2+
reticulum (ER)
CYTOSOL
PIP2
Ca2+
(second
messenger)
LE 11-12_3
EXTRACELLULAR Signal molecule
FLUID
(first messenger)
G protein
DAG
GTP
G-protein-linked
receptor
Phospholipase C
PIP2
IP3 (second
messenger)
IP3-gated
calcium channel
Endoplasmic
Ca2+
reticulum (ER)
CYTOSOL
Ca2+
(second
messenger)
Various
proteins
activated
Cellular
responses
The Response


Cytoplasmic and nuclear responses
Fine tuning




Signal amplification
Specificity
Efficiency
Termination
LE 11-13
Reception
Binding of epinephrine to G-protein-linked receptor (1 molecule)
Transduction
Inactive G protein
Active G protein (102 molecules)
Inactive adenylyl cyclase
Active adenylyl cyclase (102)
ATP
Cyclic AMP (104)
Inactive protein kinase A
Active protein kinase A (104)
Inactive phosphorylase kinase
Active phosphorylase kinase (105)
Inactive glycogen phosphorylase
Active glycogen phosphorylase (106)
Response
Glycogen
Glucose-1-phosphate
(108 molecules)
LE 11-14
Growth factor
Reception
Receptor
Phosphorylation
cascade
Transduction
CYTOPLASM
Inactive
transcription Active
transcription
factor
factor
P
Response
DNA
Gene
NUCLEUS
mRNA
LE 11-15
Signal
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
Activation
or inhibition
Response 4
Cell C. Cross-talk occurs
between two pathways
Response 5
Cell D. Different receptor
leads to a different response
LE 11-16
Signal
molecule
Plasma
membrane
Receptor
Three
different
protein
kinases
Scaffolding
protein