Chapter 15- Cell Communication

Part I- General signaling strategies

Part II- G protein signaling

Part III- Enzyme-linked cell surface receptors

Part IV- Proteolysis-dependent signaling pathways

Outline

A. Two cell types

Part I- General signaling strategies

B. A typical signaling pathwayC. Most signaling molecules are hydrophilic (water loving) D. Some signaling molecules are hydrophobic (water hating) E. A review of membranes (from chapter 10) F. Signaling over short or long distancesG. Autocrine signalingH. Cells respond to specific combinations of factorsI. Signaling through gap junctionsJ. Different cells respond differently to the same signal moleculesK. Nuclear receptors are ligand-activated gene regulatory proteins L. Three classes of cell-surface receptorsM. Common features of G protein-linked and enzyme-linked receptors

Part II- G protein signaling

B. Trimeric GTP-binding proteins (G proteins) relay the signal

A. G protein-linked receptors

C. Steps to activate a G protein

D. cAMP-mediated transduction

E. Examples of hormone-induced cell responses mediated by cAMP

F. Some examples of phospholipase C- cell responses-

G. Overview of phospholipase C-pathway

H. We can activate these pathways with drugs

I. Ca++ is a ubiquitous intracellular messenger

J. G-protein linked receptors required for vision and smell

K. How is a response desensitized?

L. Summary

PATHWAY 1 - cAMP

PATHWAY 2- Phospholipase C-

A. G protein-linked receptors

•______ membrane proteins•__% of C. nematode genes •~_____ G proteins used

for _____ in mice

•Activated by _____________________,____________ B. Trimeric GTP-binding

proteins (_______) relay the signal

Three subunits-

1. Inactive state- a subunit bound with ______

2. and subunits in one complex

INACTIVE G protein

Part II- G protein signaling

C. Steps to activate a G protein

1. Signal molecule binds ____________

2. G protein _________ with receptor

3. GDP is replaced by _____ on subunit

4. proteins dissociate from subunit

Part II- G protein signaling

5. subunit binds to and ______ a ____________

6. GTP on subunit is _________ to _____

7. subunit __________ with subunits

Part II- G protein signaling

D. cAMP-mediated transduction1. Signal molecule binds

_________

2. G protein interacts with receptor, ____ is replaced by ____, and dissociate from subunit

3. A subunit interacts with ___________________

4. ____ is converted to ______

G protein is termed “__” in this pathway

PATHWAY 1 - cAMPPart II- G protein signaling

What does cAMP look like??

2. Note that ________ binds both __ and __ carbons of dATP ribose, hence the name “________”

1. ___________ produces ____

3. cAMP ___________ breaks cAMP down to _______

This is the “Target” protein for the G- protein designated ___

PATHWAY 1 - cAMP Part II- G protein signaling

5. cAMP binds ____________________ (PKA)

•PKA action likely accounts for all ___________ effects•PKA is composed of _______________ subunits and _____ __________ subunits

6. Binding of cAMP causes active subunits to __________ and become “___________”

PATHWAY 1 - cAMP Part II- G protein signaling

7. Activated PKA is transported into ______________.

8. PKA_____________ CRE-binding protein (______).

9. CREB interacts with cofactor ____, which activates gene ____________.

PATHWAY 1 - cAMP Part II- G protein signaling

cAMP induction by serotonin

= High level cAMPRed

= Moderate level cAMPYellow

= Low level cAMPBlue

E. Examples of hormone-induced cell responses mediated by cAMP

Muscle ___________ ____________________

Heart __________ ____________________

Fat _____________ _________________

Ovary _________ __________

____________________

Target tissue Hormone Major response

PATHWAY 1 - cAMP Part II- G protein signaling

PATHWAY 2- Phospholipase C-F. Some examples of phospholipase C-

cell responses- Smooth muscle contraction, blood platelet aggregation, glycogen breakdown

PI4,5-bisphosphatea. ______

3. __activates phospholipase C-

4. phospholipase C-breaks down _____ ____________ into:

b. ___

a. ____

b. _____

Activates protein ________

Release of Ca++ from ___________ ____________

1. Signal molecule binds receptor

2. G protein interacts with receptor, GDP is replaced by GTP, and proteins dissociate from subunit

G protein is termed “__” in this pathway

Part II- G protein signaling

___ binds a IP3-gated __________ channel

G. Overview of phospholipase C-pathway ____activates protein kinase C (PKC)

PATHWAY 2- Phospholipase C- Part II- G protein signaling

H. We can activate these pathways with drugs

a. DAG

b. IP3 __________________ _____________________

PATHWAY 2- Phospholipase C-

______________Drug Effect

____________

__________________

Ca++ release via a non-G protein pathway: __________ interaction

Part II- G protein signaling

I. Ca++ is a ubiquitous intracellular messenger

a. Free Ca++ in cytoplasm is <____ M,

Example- Nerve cells- _____________, influx of Ca++, secretion of ____________________

Part II- G protein signaling

b. Extracellular is _____ M

c. Ca++-_______ pumps Ca++ out of cell and into ___

How is the Ca++ signal transduced??

Through ______________

1. Ca++ binds ___________

2. This complex binds ______________

3. CaM kinases ______________ other proteins

If knock out _____________ in mice-

Defect in ____________ where things are in _____

One CaM kinase is important in ____________Part II- G protein signaling

J. G-protein linked receptors required for ______ and _______

Humans- distinguish >__________ distinct smells

How?- by 1000s of __________ olfactory receptors (____)

1. ________ binds receptor2. _____________ activated3. ________ produced4. Gate opened5. ____ infux6. Initiate __________ to

brain

____________ also use G-proteins

Termed “____“

Part II- G protein signaling

operates through ______ production

K. How is a response _______________?

____, _____ or other G-linked receptor kinases (______) ______________the receptor

________ then binds the phosphorylated receptor

• GTP converted to ____ on subunit• IP3 __________________• Ca++ pumped ______• cAMP _____________

Mechanisms of inactivating responses

Part II- G protein signaling

L. SummaryG-protein linked receptors act through G proteins

Gs

Gq

__________________ _____

_______________ ____

______ _______

__________, __________

Golf ______________________ __________

Gt __________ ____________

_____ _________

___________

Target Enzyme

G protein Molecule made Target

PKC, PKA and CaM kinases all phosphorylate target proteins on________ or __________residues

Part II- G protein signaling