cell communication.ppt

8/14/2019 cell communication.ppt

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Cell

CommunicationModules 21 and 22


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Todays Agenda

n 25 minute lecture on Cell communication

n LISTEN only

n Small group work to fill in notes and ask questions

n Class discussion and Review

n Concept Map

n In class quiz


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Cell Communication

Signal: agent whichinfluences a property of

the cell

Receptor: protein whichrecognizes signal and

begin the cellular

response

Why do cells need torespond to signals??

Glucose as a signal in yeast


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How are signals transferred?

1.Direct Intercellular Signaling: via cell junctions from

cytosol to cytosol. Ex. Gap junctions

2.Contact-dependent Signaling: signal molecule is

membrane-bound

3.Autocrine Signaling: cell secretes molecules that bind to

its OWN surface and neighboring cells of same type

4.Paracrine Signaling: secreted signal affects only target

cells in close proximity. Ex. Synapses

5.Endocrine Signaling: long distance via vascular system.

Hormones


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signaling

1.Receptor Activation

signal binds to receptor

2.Signal Transduction

activated receptor stimulates sequence ofreactions: signal transduction pathway

3.Cellular Response

Can: alter activity of enzymes, alter proteinstructure and function, or change gene expression

by regulating transcription factors


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How to ligands Bind?Specific, reversible, rapidly: ligand-receptor complex


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Cell Surface Receptors

Receptors found in Plasma Membrane

3 categories

1.Ligand-gated ion channels

2.Enzyme-Linked receptors

3.G-protein coupled receptors (GPCR)


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Ligand-Gated Ion Channels

Animal, Plant and fungal cells

Ligand Binds-receptor channel opens to allowflow of ions through membrane

Important in nervous system

Can allow Ca+ into cytosol-important for signaltransduction

EX. Acetylcholine Na+ channel


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nzyme- n ereceptors

Found in all living species Extracelluar domain: binds to signal and causes

conformational change

Intracellular domain: catalytic function

Most function as protein kinases

phosphorylate AAs of proteins

EX. Tyrosine Kinase: phosphorylate tyrosine thuschanging structure of protein. Most abundant type

Can mediate direct effects on cytoskeleton


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animation of

RTKs
http://www.wiley.com/college/fob/quiz/quiz21/21-15.htmlhttp://www.wiley.com/college/fob/quiz/quiz21/21-15.htmlhttp://www.wiley.com/college/fob/quiz/quiz21/21-15.htmlhttp://www.wiley.com/college/fob/quiz/quiz21/21-15.html


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Receptor T i


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Receptor TyrosineKinases receptor tyrosine kinase

recognize various signaling molecules includinghormones called growth factors

stimulate cell growth or division. Ex.Epidermal Growth Factor (EGF)

Receptor Activation results in

1.relay proteins activate protein kinasecascade

2.PKC phosphorylates transcription factors

3.activated transcription factors stimulate gene
http://www.dnatube.com/video/539/Receptor-Tyrosine-Kinase-Activation-and-Signallinghttp://www.dnatube.com/video/539/Receptor-Tyrosine-Kinase-Activation-and-Signallinghttp://www.dnatube.com/video/539/Receptor-Tyrosine-Kinase-Activation-and-Signalling


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GPCR

n GPCR animation
https://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttps://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.html


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31

cell response toEpinephrine- results

in glycogen

breakdown and

prevention of

glycogen synthesisresulting in more

glucose for use by

muscles- FIGHT or

FLIGHT

nG-Protein animation

Ad t f AMP
http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__second_messenger__camp.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__second_messenger__camp.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__second_messenger__camp.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__second_messenger__camp.html


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n 1. Signal amplification

n Binding of signal to single receptor can cause the synthesis of

many cAMP that activate PKA, each PKA can phosphorylatemany proteins

n 2. Speed

n In one experiment a substantial amount of cAMP was madewithin 20 seconds after addition of signal

Advantages of cAMP


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Intracellular Receptors

receptors found INSIDE the cell

cytoplasm or inside organelles (ex.aldosterone)

receptors for steroid hormones: estrogen andandrogens

Intracellular receptors
https://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__intracellular_receptor_model.htmlhttps://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__intracellular_receptor_model.html


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Cross talk between


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Cross-talk between

receptors

The receptor types are capable of activatingeach other via signal transduction pathways.

GPCR can activate receptor tyrosine kinasesand begin the MAP kinase cascade

http://www.cellsignal.com/reference/pathway/MAPK_G_Protein.html

Applications of Concept:

activation of glycine receptor
http://www.cellsignal.com/reference/pathway/MAPK_G_Protein.htmlhttp://www.cellsignal.com/reference/pathway/MAPK_G_Protein.htmlhttp://www.nature.com/principles/content/ne0000/ne0000/ne0000/ne0000/1256387/PLS_AnimSystem_nchembio.552.pdf%23toolbar=0/http://www.nature.com/principles/content/ne0000/ne0000/ne0000/ne0000/1256387/PLS_AnimSystem_nchembio.552.pdf%23toolbar=0/http://www.cellsignal.com/reference/pathway/MAPK_G_Protein.htmlhttp://www.cellsignal.com/reference/pathway/MAPK_G_Protein.html


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Group work


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Group workn How does the cell communicate? How does distance

determine method? provide an example

n Explain what a ligand is and how it binds to a receptor?

n What types of cell surface receptors are there? How do

they differ? How are they similar?

n What is a kinase? A phosphatase? What role do they play

in cell communication?

n Describe how each receptor type works to mediate a cell

response

n What are second messengers? Why are they used, what

are their advantages?


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Post Lecture Quiz

n module 22 quiz
http://www.nature.com/principles/ebooks/biol1115-1116-general-biology-1-17691792/17694926/4http://www.nature.com/principles/ebooks/biol1115-1116-general-biology-1-17691792/17694926/4

cell communication.ppt

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