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Pharmacology II > GPCR > Flashcards

GPCR Flashcards

1
Q

Improperly folded proteins have the following effects (5)

A 
Aggregation-prone
Bind chaperones
Non-functional (improper interactions or non-productive interactions)
Targeted to degradation
Resource Drain : energy and material
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2
Q

What is the ER signal sequence?

A

Protein sequence on the N-terminal that allows ER import

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3
Q

How does the GPCR have so many loops inside the membrane?

A

multiple stop and start sequences

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4
Q

General role of molecular chaperones

A

Assist proteins during their maturation

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5
Q

What do the molecular chaperones bind to on the protein so assure proper maturation?

A

Hydrophobic segments that could potentially bind to these same segments on other proteins

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6
Q

If hydrophobic segments from different proteins bind, what does this cause?

A

aggregation

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7
Q

3 functions of chaperones

A

General folding helpers
Formation of disulfide bridges
Enzymes of the quality control cycle

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8
Q

Example of a chaperone that helps folding, what does it do?

A

BiP : prevents premature and incorrect folding of segments that arrive in ER lumen

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9
Q

Example of chaperone that helps the formation of disulfide bridges

A

Protein Disulfide Isomerase (PDI)

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10
Q

Two enzymes of the quality control cycle? what do they do?

A

Calnexin (membrane)
Calreticulin (soluble)

They bind to glucosylated oligosaccharides of incompletely folded proteins and prevent aggregation until PDI arrives

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11
Q

What is glycosylation?

A

Addition of oligosaccharides

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12
Q

The addition of oligosaccharides (glycosylation) serves as what?
The presence of sugars is used to monitor the _____ state of a protein

A

a tag to mark the state of protein folding

folded

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13
Q

What enzyme does glycosylation?

A

Oligosaccharyl transferase

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14
Q

Quality control cycle:

What happens after addition of sugars? This leaves what as a substrate? What chaperone acts on that substrate?

A

Trimming in the ER (removal of 2-3 outer chain glucose)
Leaves one glucose
Calnexin acts on glucose

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15
Q

Quality control cycle:

After action of calnexin on the single glucose substrate, which enzyme comes into play and what is their role?

A

Glucosidase

Removes remaining glucose and allows the protein to continue folding

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16
Q

Quality control cycle:

What happens if the protein is incompletely folded after already going through a quality control cycle?

A

A single terminal glucose is readded by glucosyl transferase and a calnexin is regenerated. This is repeated until protein is properly folded.

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17
Q

4 modifications to create a functional receptor

A

Glycosylation
Palmitoylation
Disulfide bridges
Dimerization

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18
Q

Which chaperone is important for dimerization of GPCR?

A

Dimer-probing chaperone

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19
Q

Where does dimerization of GPCR happen?

A

Membrane of ER

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20
Q

What happens to unfolded and monomeric GPCRs?

A

Degraded by ER-associated degradation pathway

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21
Q

After GPCR dimerization at ER, GPCRs are matured in the ____

A

Golgi

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22
Q

After maturation of GPCR at Golgi, GPCR homodimers go to the ____________ where they interact with ______

A

plasma membrane

heterotrimeric G protein

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23
Q

5 GPCR dimerization functions

A 
Ontogeny
Ligand-promoted regulation
Pharmacological diversity
Signal transduction
Internalization
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24
Q

3 ER retention motifs?

A

KDEL
KKXX
RXR

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25
Q

which proteins have KDEL motif?

A

ER luminal chaperone proteins (BiP + PDI)

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26
Q

with proteins have KKXX motif?

A

type I integral membrane proteins

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27
Q

Role of KDEL and KKXX motifs?

A

Recycling proteins from Golgi back to ER

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28
Q

RXR motif found where?

A

several GPCRs

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29
Q

Role of RXR motif?

A

Precludes exit of proteins from the ER

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30
Q

Two proteins involved in trafficking

A

SNARE proteins

Rab GTPases

31
Q

Role of SNAREs?

A

Recognition and catalyze fusion of transport vesicles with target membrane

32
Q

Role of Rab GTPases?

A

Regulate docking and tethering of the transport vesicle to the target membrane.

33
Q

Rabs in GDP-bound state are ____ and at ______

A

inactive

cytosol

34
Q

Rabs in GTP-bound state are _____ and at _____

A

active

membrane of an organelle or transport vesicle

35
Q

True or False

Each different Rab protein controls a different transport pathway between the ER and plasma membrane

A

True, different proteins control different pathways

36
Q

True or False :

Each Rab protein has a specific SNARE protein that will target them

A

True

37
Q

GPCRs can ______ or bind to ______

A

dimerize

G protein

38
Q

GPCR’s final destination is the ________

A

plasma membrane

39
Q

3 steps in signal transduction regulation

A

Desensitization
Sequestration
Recycling/Downregulation

40
Q

What is desensitization and why does it happen?

A

Removal of receptor so it cannot accept more hormone/signal

41
Q

What happens in the desensitization step of signal transduction regulation?

A

Phosphorylation of receptor by GRK2
Arrestin recruitment
Clathrin recruitment and coats plasma membrane
Dynamin surrounds neck of vesicle and pinches it off

42
Q

Sequestration : two classes of GPCRs?

A

Class A

Class B

43
Q

Sequestration : what does the Class A GPCR do?

A

Removal of arrestin and hormone so the receptor can be reused

44
Q

Sequestration : what does the Class B GPCR do?

A

Slow recycling?

Degradation

45
Q

Recycling/Downregulation : what is the mechanism?

A

Dephosphorylation of receptor by PP2A

Removal from it’s ligand

46
Q

True or False :

Receptor localization is static

A

False

47
Q

The vesicle that gets pinched off to eventually get recycled is called the ________

A

early endosome

48
Q

Clathrin-coated pits internalization:

What are to components involved in the coat nucleation and assembly?

A 
AP-2
AP180
Clathrin
Synaptotagmin
PIP2
Cargo
49
Q

Clathrin-coated pits internalization:

What are the components involved in the coated pit maturation?

A

Dynamin
Endophilin
Amphiphysin
Actin

50
Q

Clathrin-coated pits internalization:

What are the components involved in Fission of the vesicle?

A

Dynamin

Endophilin

51
Q

Clathrin-coated pits internalization:

What are the componentsa involved in uncoating?

A

Hsc70
Auxilin
Synaptojanin
Stoned B

52
Q

Do early endosomes have lower or higher pH and why?

A

Lower so it can release the receptor and ligand

53
Q

What are the markers in the early endosome?

A

EEA-1 proteins

rab5-GDP

54
Q

Role of recycling endosomes?

A

Return the receptor to the cell surface by binding to the plasma membrane

55
Q

Marker for recycling endosome?

A

Rab4-GDP

56
Q

Late endosomes : low or high pH

A

Low

57
Q

Markers for late endosomes

A

rab7-GDP
LBPA
MPR+

58
Q

Can late endosomes digest all materials? If not, what do they do? What is the marker for this?

A

No
Fusion to lysosome
LAMPs

59
Q

Enzymes in the lysosome

A 
Acid hydrolases
Lipases
Carbohydrases
Proteases
Nucleases
Phosphoric acid monoesters
60
Q

Markers for the lysosome

A

LAMP+
Acid hydrolases
MPR negative

61
Q

Why would a receptor have to be degraded rather than recycled? (3)

A

If it requires cleavage during activation
If it is bound to irreversible ligands
Proteins that are not recycled back to plasma membrane, coming from the endocytic pathway

62
Q

If there is accumulation of proteins in the cytosol, what does this affect?

A

Transport to ER

63
Q

If there is accumulation of protein in the rough ER, what does this affect?

A

Budding of vesicles from rough ER

64
Q

If there is accumulation of protein in the ER-to-Golgi transport vesicles, what does this affect?

A

Fusion of transport vesicles with Golgi

65
Q

If there is accumulation of protein in the Golgi, what does this affect?

A

Transport from Golgi to secretory vesicles

66
Q

If there is accumulation of protein in the secretory vesicles, what does this affect?

A

Transport from the secretory vesicles to the cell surface

67
Q

What are the two fates of misfolded proteins?

A

Ubiquitination and degradation by proteasome

Molecular chaperones remodel the protein

68
Q

Which diseases cause misfolding? (4)

A

CF
Marfan Syndrome
Nephrogenic Diabetes Insipidus
Alpha-1-Antitrypsin Deficiency

69
Q

Which diseases cause retention in the ER?

A

CF
Nephrogenic Diabetes Insipidus
Alpha-1-Antitrypsin Deficiency

70
Q

Which disease cause aggregation in the brain after protein release?

A

Creutzfeldt-Jakob Disease

Alzheimer’s

71
Q

Phamacological chaperones role?

A

Stabilize protein conformation so it can redirected to the plasma membrane rather then to the proteasome/lysosome for degradation

72
Q

Lack of proper folding results in what? (3)

A

Aggregation
Intracellular retention of proteins that shouldn’t be there
Destruction of proteins that should be expressed

73
Q

Mistrafficking provokes ______ and ______ of essential proteins

A

Intracellular retention

Degradation

Pharmacology II (21 decks)

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