Chapter 11Chapter 11

Cell CommunicationCell Communication

LE 11-2Exchange ofmating factors

Mating

Receptor

a

factor

a

a factorYeast cell,mating type a

Yeast cell,mating type

a/

New a/ cell

Signal Transduction PathwaysSignal Transduction Pathways

Local signalingLocal signaling Cell junctionsCell junctions Cell-cell recognitionCell-cell recognition Local regulators – growth factorsLocal regulators – growth factors

Paracrine signalingParacrine signaling Synaptic signalingSynaptic signaling

Long-Distance signalingLong-Distance signaling Endocrine signaling - hormonesEndocrine signaling - hormones

LE 11-3a

Plasma membranes

Gap junctionsbetween animal cells

Cell junctions

Plasmodesmatabetween plant cells

LE 11-3b

Cell-cell recognition

LE 11-4a

Paracrine signaling

Local regulatordiffuses throughextracellular fluid

Secretoryvesicle

Secretingcell

Target cell

Local signaling

Electrical signalalong nerve celltriggers release ofneurotransmitter

Neurotransmitter diffuses across synapse

Synaptic signaling

Target cellis stimulated

LE 11-4b

Endocrine cell Bloodvessel

Long-distance signaling

Hormone travelsin bloodstreamto target cells

Hormonal signaling

Target cell

Three StagesThree Stages

ReceptionReception TransductionTransduction ResponseResponse

LE 11-5_1

EXTRACELLULARFLUID

Reception

Plasma membrane

Transduction

CYTOPLASM

Receptor

Signalmolecule

LE 11-5_2

EXTRACELLULARFLUID

Reception

Plasma membrane

Transduction

CYTOPLASM

Receptor

Signalmolecule

Relay molecules in a signal transductionpathway

LE 11-5_3

EXTRACELLULARFLUID

Reception

Plasma membrane

Transduction

CYTOPLASM

Receptor

Signalmolecule

Relay molecules in a signal transductionpathway

Response

Activationof cellularresponse

ReceptionReception

Receptor-Ligand interactionReceptor-Ligand interaction ReceptorsReceptors

Intracellular – testosteroneIntracellular – testosterone In plasma membrane – Figure 11.7In plasma membrane – Figure 11.7

G-protein linked receptorG-protein linked receptor Receptor tyrosine kinasesReceptor tyrosine kinases Ion channel receptors – ligand-gated ion channelIon channel receptors – ligand-gated ion channel

LE 11-6

EXTRACELLULARFLUID

Plasmamembrane

The steroidhormone testosteronepasses through theplasma membrane.

Testosterone bindsto a receptor proteinin the cytoplasm,activating it.

The hormone-receptor complexenters the nucleusand binds to specificgenes.

The bound proteinstimulates thetranscription ofthe gene into mRNA.

The mRNA istranslated into aspecific protein.

CYTOPLASM

NUCLEUS

DNA

Hormone(testosterone)

Receptorprotein

Hormone-receptorcomplex

mRNA

New protein

LE 11-7aa

Segment thatinteracts withG proteins

Signal-binding site

G-protein-linked receptor

LE 11-7ab

G-protein-linked receptor

GDP

CYTOPLASM

Plasmamembrane

G protein(inactive)

Enzyme GDP

GDPGTP

Activatedreceptor

GTP

Signal moleculeInactiveenzyme

Activatedenzyme

Cellular response

P i

LE 11-7b

Signalmolecule

Helix in themembrane

Signal-binding site

Tyr

Tyr

Tyr Tyr

Tyr

TyrTyrosines

Receptor tyrosinekinase proteins(inactive monomers)CYTOPLASM

Tyr

Tyr

Tyr Tyr

Tyr

Tyr Tyr

Tyr

Tyr Tyr

Tyr

Tyr

Tyr

Tyr

Tyr Tyr

Tyr

Tyr

Activated tyrosine-kinase regions(unphosphorylateddimer)

Signalmolecule

Dimer

Fully activated receptor tyrosine-kinase(phosphorylateddimer)

Tyr

Tyr

Tyr Tyr

Tyr

TyrPPP

PPPATP 6 ADP

Tyr

Tyr

Tyr Tyr

Tyr

TyrP

PP

PPP

Inactiverelay proteins

Cellularresponse 2

Cellularresponse 1

Activated relay proteins

6

LE 11-7c

Signalmolecule(ligand)

Gateclosed Ions

Ligand-gatedion channel receptor

Plasmamembrane

Gate closed

Gate open

Cellularresponse

TransductionTransduction

Cascades of molecular interactionsCascades of molecular interactions Signal transduction pathwaySignal transduction pathway Protein phosphorylation and Protein phosphorylation and

dephosphorylationdephosphorylation Second messengersSecond messengers Calcium ions and IPCalcium ions and IP33

LE 11-8

Signal molecule

Activated relaymolecule

Receptor

Inactiveprotein kinase

1 Activeprotein kinase

1

Inactiveprotein kinase

2 Activeprotein kinase

2

Inactiveprotein kinase

3 Activeprotein kinase

3

ADP

Inactiveprotein

Activeprotein

Cellularresponse

Phosphorylation cascade

ATP

PPP i

ADPATP

PPP i

ADPATP

PPP i

P

P

P

LE 11-9

ATP Cyclic AMP AMP

Adenylyl cyclase

PyrophosphateP P i

Phosphodiesterase

H2O

LE 11-10

cAMP

ATPSecondmessenger

First messenger(signal moleculesuch as epinephrine)

G-protein-linkedreceptor

G protein

Adenylylcyclase

Proteinkinase A

Cellular responses

GTP

LE 11-11

ATP

EXTRACELLULARFLUID

ATP

Mitochondrion

Ca2+

pump

Plasmamembrane

CYTOSOL

Endoplasmicreticulum (ER)

Ca2+

pump

Ca2+

pump

High [Ca2+]Key

Nucleus

Low [Ca2+]

LE 11-12_1

CYTOSOL

Ca2+Endoplasmicreticulum (ER)

IP3-gatedcalcium channel

IP3 (secondmessenger)

DAG

PIP2G-protein-linkedreceptor Phospholipase C

G protein

Signal molecule(first messenger)

EXTRACELLULARFLUID

GTP

LE 11-12_2

CYTOSOL

Ca2+Endoplasmicreticulum (ER)

IP3-gatedcalcium channel

IP3 (secondmessenger)

DAG

PIP2G-protein-linkedreceptor Phospholipase C

G protein

Signal molecule(first messenger)

EXTRACELLULARFLUID

GTP

Ca2+ (secondmessenger)

LE 11-12_3

CYTOSOL

Ca2+Endoplasmicreticulum (ER)

IP3-gatedcalcium channel

IP3 (secondmessenger)

DAG

PIP2G-protein-linkedreceptor Phospholipase C

G protein

Signal molecule(first messenger)

EXTRACELLULARFLUID

GTP

Ca2+ (secondmessenger)

Variousproteinsactivated

Cellularre-sponses

The ResponseThe Response

Cytoplasmic and nuclear responsesCytoplasmic and nuclear responses Fine tuningFine tuning

Signal amplificationSignal amplification SpecificitySpecificity EfficiencyEfficiency TerminationTermination

LE 11-13

Binding of epinephrine to G-protein-linked receptor (1 molecule)

Reception

Transduction

Inactive G protein

Active G protein (102 molecules)

Inactive adenylyl cyclase

Active adenylyl cyclase (102)

ATP

Cyclic AMP (104)

Inactive protein kinase A

Inactive phosphorylase kinase

Active protein kinase A (104)

Active phosphorylase kinase (105)

Active glycogen phosphorylase (106)

Inactive glycogen phosphorylase

Glycogen

Response

Glucose-1-phosphate(108 molecules)

LE 11-14

ReceptionGrowth factor

Receptor

Phosphorylationcascade

Transduction

CYTOPLASM

Inactivetranscriptionfactor

Activetranscriptionfactor

PResponse

Gene

mRNA

DNA

NUCLEUS

LE 11-15Signalmolecule

Receptor

Relaymolecules

Response 1 Response 2 Response 3

Cell B. Pathway branches,leading to two responses

Cell A. Pathway leads to a single response

Cell C. Cross-talk occursbetween two pathways

Response 4 Response 5

Activationor inhibition

Cell D. Different receptorleads to a different response

LE 11-16

Signalmolecule

Plasmamembrane

Receptor

Scaffoldingprotein

Threedifferentproteinkinases