Lecture 18 study guide

Question 1

What is the largest family of cell receptors?

Answer 1

1. GCPRs

Question 2

GCPR characteristics

Answer 2

• 7 transmembrane domains and binds to a GTPase
• When activated, binds to a gamma, alpha, and beta subunit that have different downstream effectors
• Acts as a GEF
• Subfamilies include Rhodopsin

Question 3

RTK

Answer 3

• Dimerizes
• Phosphorylates itself in order to recruit signaling proteins to relay targets downstream
• Subfamilies include insulin receptors
• Largest class is Eph receptors
• Uses an adaptor protein to bind to Ras-GEF

Question 4

Notch

Answer 4

• Attaches to a ligand presented on the surface of another cell
• Cleaved tail acts as a transcription factor
• Requires direct cell to cell contact
• Functions in development of multicellular organisms

Question 5

The alpha subunit of a g-protein acts as a?

Answer 5

GTPase

Question 6

G protein effectors act as a?

Answer 6

GAP

Question 7

True or False: G proteins and their effectors are attached to the lipid membrane (lipid linked)?

Answer 7

True

Question 8

True or False: the alpha subunit of the G protein is bound to GTP upon association with a GCPR.

Answer 8

False

Question 9

What is the function of adenylyl cyclase?

Answer 9

increase of cAMP levels by breaking down ATP

Question 10

What is the role of GCPR in regulating adenylyl cyclase?

Answer 10

can regulate or inhibit adenylyl cyclase activity depending on the signaling molecules

Question 11

What protein complex associated with GCPRs activate potassium channels?

Answer 11

G beta-gamma complex

Question 12

Where are the following Ptdlns found in the cell?
a. PI-3P
b. PI-4P
c. PI-4,5P
d. PI-3,5P

Answer 12

a. endosomes
b. golgi
c. plasma membrane
d. lysosomes

Question 13

What are the two parts of a Ptdlns?

Answer 13

Diacylglycerol (a double lipid tail) and an inositol (sugar) head.

Question 14

What do the numbers in question 10 stand for? (What does the 3 and 5 in PI-3,5 mean?)

Answer 14

Which OH (position) is phosphorylated.

Question 15

What is the function of PI-3P

Answer 15

Recruits endosomal proteins such as ESCRT proteins and participates in endosomal trafficking.

Question 16

What is the main purpose of Ptdins binding domains? (besides binding to Ptdins)

Answer 16

Localize protein to the specific membrane. FYVE domain is an example of a Ptdln binding domain which localizes a protein to that membrane.

Question 17

What protein activates PIs by breaking them into their two parts?

Answer 17

Phospholipase C

Question 18

Which two molecules must bind to PKC to activate it?

Answer 18

Diacylglycerol and Ca2+

Question 19

Ca2+ functions as what in cell signaling?

Answer 19

Second Messenger

Question 20

What protein recognizes a rise in Ca2+ levels and activates downstream targets? Give an example of these targets that are involved in memory formation?

Answer 20

Calmodulin, CaM-Kinases (Calmodulin dependent kinases)

Question 21

True or False: intramolecular Ca2+ levels are very high.

Answer 21

False: they are very low. This keeps the cell sensitive to any change in calcium levels which allows it to be a ubiquitous second messenger.

Question 22

What kind of protein is rhodopsin

Answer 22

A light sensitive GCPR

Question 23

PDE acts to keep cytosolic cGMP levels high or low?

Answer 23

Low. It converts cGMP to GMP

Question 24

Open Na+/Ca2+ ion channels require high or low levels of cGMP?

Answer 24

High

Question 25

Retinal is the cofactor found in rhodopsin. In active rhodopsin is retinal trans or cis?

Answer 25

Trans

Question 26

What is the role of phosphorylation of rhodopsin?

Answer 26

Phosphorylation of rhodopsin works to decrease its activity. This allows our cells to adapt to changes in light levels.

Question 27

What happens to rhodopsin in the presence of very high light?

Answer 27

Arrestin binds inactivating rhodopsin

Question 28

What is the role of Eph Receptors?

Answer 28

Regulates cell adhesion and migration

Question 29

A RTK is found that contains a fibronectin-like domain. What subfamily is this receptor likely from?

Answer 29

Eph receptors

Question 30

A RTK is found that contains a cysteine rich domain and three intramolecular disulfide bridges. What subfamily is this receptor likely from?

Answer 30

EGF receptors

Question 31

What is the role of EGF? Where are the receptors for this signal located?

Answer 31

a potent promoter of cell survival, growth and proliferation - almost all human cells respond to EGF (they express the EGF receptor)

Question 32

How are RTKs phosphorylated?

Answer 32

They dimerize and phosphorylate each other

Question 33

What protein involved in the RTK signaling pathway activates MAP kinase scaffold proteins?

Answer 33

Ras GTPase

Question 34

What are the two main consequences of the MAP kinase pathway?

Answer 34

1. Changes in protein activity and 2. gene expression

Question 35

In the MAP kinase pathway, which protein is specifically activated first?

Answer 35

MAP Kinase Kinase Kinase