Cell Signaling 2015

Topics: Signal transduction, Cell signaling, Hormone Pages: 20 (883 words) Published: April 21, 2015
Cell Communication/Signaling
Examples:
1) “Change the voltage across your membrane.”
2) “Increase/Decrease enzymatic activity.”
3) “Make fuel available to other cells”
4) “Change gene expression and make new proteins.”
5) “Change shape.”
6) “Copy genetic material and divide.”
7) “Die.”
Adapted from Prof. Dunlap

Response
time
milliseconds
secs – mins
hrs/
days

John Locke (1632-1704)
Essay concerning human understanding
“Did we but know the
mechanical affections of the
particles of rhubarb,
hemlock, opium and a
manywe should be able to
tell beforehand that rhubarb
will purge, hemlock kill and
opium make a man sleepy”
Rang (2006) British Journal of Pharmacology 147, S9–S16

Local signaling
Electrical signal
along nerve cell
triggers release of
neurotransmitter.

Target cell

Secreting
cell

Neurotransmitter
diffuses across
synapse.

Secretory
vesicle

Local regulator
diffuses through
extracellular fluid.
(a) Paracrine signaling
Paracrine:
Secreting cell acts on nearby target cells.
Particularly important in development.

Target cell
is stimulated.
(b) Synaptic signaling
Synaptic:
Nervous system communication – trigger
physiological/behavioral changes

1. “Change the voltage across the membrane.”
• Cell signalling pathway
Ligand-gated ion channel
• Response time
milliseconds
• Example
Acetylcholine causes a muscle
cell to become more positive (& then
contract).

Adapted from Prof. Dunlap

Long-distance signaling
Endocrine cell

Blood
vessel

Hormone travels
in bloodstream.
Target cell
specifically
binds
hormone.

(c) Endocrine (hormonal) signaling

Cells release hormones into the
general circulation trigger physiological changes

Hydrophobic
signaling molecule

Hormone
(testosterone)

EXTRACELLULAR
FLUID

Plasma
membrane

Receptor
protein

Hormonereceptor
complex

Examples:
Testosterone,
other steroid
hormones
Receptors act as
ligand-activated
transcription factors

Relatively slow
response that
involves changes in
gene expression-

DNA
mRNA

NUCLEUS

CYTOPLASM

New protein

Example –
build muscle
protein

Hydrophilic signaling
molecule

Three phases of cell signalling

EXTRACELLULAR
FLUID
1 Reception

CYTOPLASM
Plasma membrane
2 Transduction

3 Response

Receptor

Relay molecules in a signal transduction
pathway
Signaling
molecule

Activation
of cellular
response

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

G protein-coupled
receptor

CYTOPLASM
1

Plasma
membrane

Activated
receptor

Signaling
molecule

Inactive
enzyme

GTP
GDP

GDP

Enzyme

G protein
(inactive)

2

GDP

GTP

Activated
enzyme

GTP

GDP
Pi

3

Cellular response

4
Lectures by
Erin Barley
Kathleen Fitzpatrick

© 2011 Pearson Education, Inc.

Figure 11.12

First messenger
(signaling molecule
such as epinephrine)
Adenylyl
cyclase

G protein

G protein-coupled
receptor

GTP
ATP
cAMP

Second
messenger
Protein
kinase A

Cellular responses

Second Messengers : cAMP
(formation)

Adenylyl cyclase
Pyrophosphate
P
ATP

Pi
cAMP

Figure 11.11b

Second Messengers : cAMP
(breakdown)

Phosphodiesterase
H2 O

cAMP

H2O

AMP

Fig. 11-13-3

Second Messengers Inositol phosphate (IP3)
EXTRACELLULAR
FLUID

Signaling molecule
(first messenger)
G protein
DAG
GTP

G protein-coupled
receptor

PIP2

Phospholipase C

IP3
(second messenger)

IP3-gated
calcium channel

Endoplasmic
reticulum (ER)

CYTOSOL

Ca

Various
proteins
activated

2+

Ca2+
(second
messenger
)

Cellular
responses

Figure 11.10

Signaling molecule

Receptor

Activated relay
molecule

Inactive
protein kinase
1

Inactive
protein kinase
2

ATP

PP

Inactive...
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