Transcript 11_Lecture_picture version

Chapter 11
Cell Communication
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cell communication processes share common
features that reflect a shared evolutionary history.
• The basics of cell communication are found in all
living things.
• Signals from other cells or the environment can be
stimulatory (turn on a gene or protein) or inhibitory
(turn off a gene or protein)
• Natural selection favors correct and appropriate
signal transduction processes.
• In single-celled organisms, signal transduction
pathways influence how the cell responds to its
environment.
Cell-to-cell communication is essential for ALL
organisms to detect changes in the
environment and respond appropriately.
1.
1. Signal (usually a molecule)
2.
2. Signal Receptor (protein)
Protein
activated or
inactivated
3.
4.
Gene expression
turned on or off
Group behaviors that
promotes individuals’ survival
are an adaptation favored by
natural selection
3. Signal Transduction (other
proteins/ molecules that convert
the signal into a response )
4. Cell Response (change in
gene expression and or protein
activity)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Quorum Sensing in Bacteria reveals the
evolutionary origins of cell communication
• Signaling molecule concentration allows bacteria
to detect population density
• Bacteria evolved the beginnings of multicellularity:
– self vs. other
Group behavior gene
expression turned on
Capsule protein
to form colony
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Bacterial Biofilm Formation involves cell signaling
1. Attachment: Motile bacteria swim towards surface rich with
nutrients. Turn on genes associated with forming a biofilm.
2. Growth: Bacteria in biofilm grow and divide.
3. Dispersal. Bacteria in center do not receive as much nutrition,
this turns on motility associated genes. Bactera disperse to
find a new nutrient source.
Essential knowledge: Cells communicate with each
other through direct contact with other cells or
from a distance via chemical signaling.
• Cell To Cell Contact: Using membrane bound
receptors
• Short (local signaling): Secreted molecules that
diffuse over short distances
• Long Distances: Secreted molecules that travel
throughout the body
Cell communication is essential for individual
cells support the function of the organism as
a whole.
In other words.. “All for one and one for all”
Stress
Epinephrine
Glycogen
Glucose
Cell to Cell Contact: used to distinguish “self”
from “other”
• Animal cells have MHC proteins on the surface
of the cell to distinguish “self” from “other”
• Antigen Presenting Cells present antigen to T
cells by cell-cell contact.
• Recognition of foreign antigen causes T cell to
signal to other immune cells to mature.
B Cells are antigen presenting cells to T helper cells
• B cells present
antigen to TH cell.
• If the T cell receptor
recognizes the
antigen it will release
lymphokines
• The B cell matures
into a plasma cell and
releases antibodies
into the blood plasma.
Cells communicate over short distances by using
local regulators that target cells in the vicinity of
the emitting cell.
Local signaling
• Neurotransmitters
released in the synapse
Electrical signal
Target cell
along nerve cell
triggers release of
neurotransmitter
Secreting
cell
Local regulator
diffuses through
extracellular fluid
(a) Paracrine signaling
Neurotransmitter
diffuses across
synapse
Secretory
vesicle
Target cell
is stimulated
(b) Synaptic signaling
Long-distance signaling
Signals released
by one cell type
can travel long
distances to target
cells of another
cell type.
Endocrine cell
Blood
vessel
Hormone travels
in bloodstream
to target cells
Target
cell
(c) Hormonal signaling
1. The endocrine hormones FSH and LH are
made by the pituitary gland in the brain.
2. These hormones coordinate the maturation
of ovules and and Endometrium
The Three Stages of Cell Signaling
– Reception
– Transduction
– Response
Animation: Overview of Cell Signaling
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-6-1
EXTRACELLULAR
FLUID
1 Reception
Receptor
Signaling
molecule
CYTOPLASM
Plasma membrane
Fig. 11-6-2
CYTOPLASM
EXTRACELLULAR
FLUID
Plasma membrane
1 Reception
2 Transduction
Receptor
Relay molecules in a signal transduction pathway
Signaling
molecule
Fig. 11-6-3
CYTOPLASM
EXTRACELLULAR
FLUID
Plasma membrane
1 Reception
2 Transduction
3 Response
Receptor
Activation
of cellular
response
Relay molecules in a signal transduction pathway
Signaling
molecule
Receptors can exist on the surface of the cell or in
the cytoplasm
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
EXTRACELLULAR
FLUID
Plasma
membrane
CYTOPLASM
1 Reception
Receptor
CYTOPLASM
DNA
Signaling
molecule
NUCLEUS
Signal transduction pathways link signal reception
with cellular response.
1. Signaling recognition: chemical messenger
(ligand) binds to receptor protein.
– Chemical messenger can be a peptide, small inorganic
molecule, or lipid hormone
– Receptor and ligand have complementary structures
and fit together like a lock and key. (Concepts from
enzymes such as affinity apply)
2. Binding causes change in receptor protein shape
3. Shape change initiates transduction of the signal.
Receptors in the Plasma Membrane
• Most water-soluble signal molecules bind to
receptor proteins in the plasma membrane
• There are three main types of membrane
receptors:
– G protein-coupled receptors
– Receptor tyrosine kinases
– Ion channel receptors
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-7b
G Protein Coupled Receptors
Plasma
membrane
G protein-coupled
receptor
Activated
receptor
Signaling molecule
GDP
CYTOPLASM
GDP
Enzyme
G protein
(inactive)
1
Activated
Adenylyl
Cyclase
GTP
2
GTP
GDP
Pi
ATP
Signal is
terminated
Cellular response
4
3
cAMP
Other Enzymes
Activated
Inactive
Adenylyl
Cyclase
Fig. 11-7c
Receptor Tyrosine Kinase
Ligand-binding site
Signaling
molecule (ligand)
Signaling
molecule
Tyrosines
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Receptor tyrosine
kinase proteins
CYTOPLASM
Dimer
1
2
Activated relay
proteins
Tyr
Tyr
Tyr
Tyr
P Tyr
P Tyr
Tyr
Tyr
P
6 ATP
Activated tyrosine
kinase regions
6 ADP
Tyr
Tyr
P Tyr
Tyr
P
Tyr
P Tyr
P Tyr
Tyr
P
P
P
P
Tyr P
Tyr
Fully activated receptor
tyrosine kinase
Inactive
relay proteins
3
4
Cellular
response 1
Cellular
response 2
Fig. 11-7d
Ligand-gated ion
channel receptors
Lingand binding causes channel to
change shape
1 Signaling
molecule
(ligand)
Gate
closed
Ligand-gated
ion channel receptor
2
Channel opening can allow specific
ions, such as Na+ or Ca2+, through
a channel in the receptor.
Ions
Plasma
membrane
Gate open
Cellular
response
3
Gate closed
Fig. 11-8-5
Intracellular Receptors
•Hydrophobic molecules
can diffuse directly
through the membrane
and bind to receptors in
the cytoplasm
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
Hormonereceptor
complex
DNA
•Activated hormonereceptor complex goes
to the nucleus and can
turn on specific genes
mRNA
NUCLEUS
CYTOPLASM
New protein
Signal transduction coverts the signal
to a cellular response
1. Signaling transduction cascades involve:
• Modifying Protein structure
• Generate second messenger
• Phosphorylation cascade
• Amplification of signal
Fig. 11-14
Signaling cascades involve:
•Generation of a Second Messenger
•Phosphorylation cascade
•Protein Modification
•Amplification
Growth factor
Reception
Receptor
Phosphorylation
cascade
Transduction
CYTOPLASM
Inactive
transcription
factor
Active
transcription
factor
P
Response
DNA
Gene
NUCLEUS
mRNA
Common Second Messengers
• Second Messenger: a small non protein
molecule that diffuses rapidly through the cell
during signal transduction.
– Cyclic AMP (cAMP)
– Inositol triphosphate (IP3)
– Calcium ion (Ca2+)
Fig. 11-11
First messenger
Adenylyl
cyclase
G protein
G protein-coupled
receptor
GTP
•Protein Modification
•Second Messenger
•Phosphorylation cascade
•Amplification
ATP
cAMP
Second
messenger
Protein
kinase A
Cellular responses
G protein-coupled receptor: found in the cell
membrane
• Ligand binding activates the G protein
• Signal Transduction occurs inside the cell
– The G protein activates Adenylyl Cyclase
– Adenylyl Cyclase makes a second messenger
Cyclic AMP
– Cyclic AMP activates Protein Kinase A
– Protien Kinase A activates a phosphorylation
cascade
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
•Protein Modification
•Second Messenger
•Phosphorylation cascade
•Amplification
Fig. 11-13-3
EXTRACELLULAR
FLUID
Signaling molecule
(first messenger)
G protein
DAG
GTP
G protein-coupled
receptor
Phospholipase C
PIP2
IP3
(second messenger)
IP3-gated
calcium channel
Endoplasmic
reticulum (ER)
CYTOSOL
Ca2+
Various
proteins
activated
Ca2+
(second messenger)
Cellular
responses
Fig. 11-9
Signaling molecule
Receptor
•Protein Modification
•Second Messenger
•Phosphorylation cascade
•Amplification
Activated relay
molecule
Inactive
Kinase 1
Active
Kinase 1
Inactive
Kinase 2
ATP
ADP
Pi
P
Active
Kinase 2
PP
Inactive
Kinase 3
ATP
ADP
Pi
P
Active
Kinase 3
PP
Inactive
protein
ATP
P
ADP
Pi
PP
Active
protein
Cellular
response
Definitions
•
Ligand: the chemical signal that binds to a receptor.
•
Receptor: a protein that can bind to the signal (in the case of a
molecule) or detect a signal in the case of light or other non-molecule
signals.
•
Kinase: an enzyme that attaches a phosphate to another protein
(usually activating it)
•
Phosphatase: an enzyme that removes phosphate from a protein
(usually inactivating it)
•
Second Messenger: a small non protein molecule that diffuses rapidly
through the cell during signal transduction. Examples include cAMP,
IP3, DAG, Ca2+
•
Reception: when the receptor binds to the signal, causing the receptor
to change shape.
•
Signal Transduction: converting a signal into a cellular response.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 11-10
In case you were curious… modification of ATP to
form cyclic AMP
Adenylyl cyclase
Phosphodiesterase
Pyrophosphate
P
ATP
Pi
cAMP
AMP
Cell Communication Review:
1.
What are the 4 basic parts/ requirements of cell signaling?
2.
Give/ describe an example of how bacteria detect and respond to their environment
using cell signaling.
3.
Why is cell signaling a universal characteristic of life (why is it necessary, what
advantages does it give)?
4.
What are the two basic cellular responses to a signal?
5.
What are the three types of cell to cell communication in multicellular organisms. Give
an example of each type.
6.
Describe the nature of a ligand-receptor interaction and state how such interactions
initiate a signal-transduction system.
7.
Explain how an original signal molecule can produce a cellular response when it may
not even enter the target cell.
8.
What are the four features of signal transduction cascade. Give an example of each
type from one of the types of signaling pathways discussed?
9.
Define the term second messenger; briefly describe the role of these molecules in
signaling pathways
10.
Explain why different types of cells may respond differently to the same signal
molecule. For example, Epinephrine causes relaxation of smooth muscle and
contraction of skeletal muscle.