AbuArish_CPPS325_March14_2025_Lecture 4_Upload (1)

Question 1

What is the most common CF-causing mutation?

Answer 1

ΔF508-CFTR

This mutation impacts 80-90% of people with CF.

Question 2

What is the main consequence of the ΔF508-CFTR mutation?

Answer 2

Causes CFTR misfolding

Question 3

What percentage of ΔF508-CFTR is trafficked to the plasma membrane (PM)?

Answer 3

5%

Question 4

What happens to the majority of ΔF508-CFTR that is not trafficked to the PM?

Answer 4

Targeted for lysosomal degradation

Question 5

How does ΔF508-CFTR distribution differ from WT-CFTR?

Answer 5

ΔF508-CFTR is predominantly retained in the ER due to misfolding

Question 6

What effect do small molecule folding correctors have on ΔF508-CFTR?

Answer 6

They attempt to restore folding and trafficking

Question 7

What is the role of VX809 in CF therapy?

Answer 7

A small molecule folding corrector

Question 8

True or False: VX809 restores ΔF508-CFTR clustering.

Answer 8

False

Question 9

What is the impact of VX770 in combination with VX809?

Answer 9

Does not restore ΔF508-CFTR clustering

Question 10

What is the significance of lipid rafts in relation to CFTR?

Answer 10

CFTR must be incorporated inside lipid rafts for proper function

Question 11

What happens to ΔF508-CFTR in terms of lipid raft partitioning?

Answer 11

Partitions at least 2-fold less inside lipid rafts than WT-CFTR

Question 12

What are VX445 and VX661?

Answer 12

Small molecular folding correctors of CFTR

Question 13

What was the outcome of treatment with VX445 and VX661?

Answer 13

Restores ΔF508-CFTR clustering and reduces ER retention

Question 14

What is the effect of Trikafta (VX445 + VX661 + VX770) on ΔF508-CFTR?

Answer 14

Restores clustering at the PM by 70%

Question 15

What does the diffusion coefficient of CFTR inside microdomains indicate?

Answer 15

Confined mobility

Question 16

How does ΔF508-CFTR mobility inside lipid rafts compare to WT-CFTR?

Answer 16

ΔF508-CFTR is significantly faster, by at least 2-fold

Question 17

What is the impact of cell stress on ΔF508-CFTR?

Answer 17

Does not induce clustering or proper function

Question 18

What is the difference in cluster formation between WT-CFTR and ΔF508-CFTR?

Answer 18

WT-CFTR forms more clusters and higher fluorescence

Question 19

What does a fraction of 0.15 indicate regarding ΔF508-CFTR?

Answer 19

15% of total membrane CFTR is inside lipid rafts

Question 20

What is the mobility of F508-CFTR inside lipid rafts compared to WT-CFTR?

Answer 20

Diffuses significantly faster inside lipid rafts than WT-CFTR by several folds.

This indicates that the mutant CFTR experiences less confining lipid environment.

Question 21

What effect does cell stress have on F508-CFTR tethering inside ceramide-rich platforms?

Answer 21

Cell stress doesn’t induce F508-CFTR tethering inside ceramide-rich platforms.

Question 22

What do the folding correctors VX445 and VX661 restore in F508-CFTR?

Answer 22

They restore F508-CFTR confined mobility inside clusters and its incorporation inside ceramide-rich platforms after cell stress.

Question 23

What is the fraction of CFTR inside microdomains (lipid rafts) for WT-CFTR?

Answer 23

0.22 or 22% of total membrane.

Question 24

How does the partitioning of F508-CFTR compare to WT-CFTR inside lipid rafts?

Answer 24

F508-CFTR partitions at least 3-fold less inside lipid rafts than WT-CFTR.

Question 25

True or False: Cell stress with Thaps increases F508-CFTR recruitment inside ceramide platforms.

Answer 25

False.

Question 26

What does the small molecule folding correctors VX445 and VX661 do for S13F-CFTR?

Answer 26

They fully restore S13F-CFTR confined mobility inside clusters and its tethering inside ceramide-rich platforms after cell stress.

Question 27

What is the significance of the S13F mutation in CFTR?

Answer 27

The S13F mutation behaves like the F508-CFTR, suggesting it is a misfolding mutation.

Question 28

What is the interaction site for Filamin A in CFTR?

Answer 28

At aa-S13.

Question 29

What did co-immunoprecipitation experiments reveal about WT-CFTR and S13F-CFTR?

Answer 29

WT-CFTR interacts with Filamin A while S13F-CFTR doesn’t.

Question 30

What effect do VX445 and VX661 have on S13F-CFTR's interaction with Filamin A?

Answer 30

They restore the interaction for both S13F-CFTR and F508-CFTR.

Question 31

Fill in the blank: The diffusion coefficient of CFTR inside microdomains is referred to as _______.

Answer 31

confined mobility.

Question 32

What happens to the mobility of S13F-CFTR inside lipid rafts compared to WT-CFTR?

Answer 32

S13F-CFTR mobility inside rafts is significantly faster than WT-CFTR by 2-fold.

Question 33

How does cell stress affect S13F-CFTR tethering inside ceramide-rich platforms?

Answer 33

Cell stress doesn’t induce S13F-CFTR tethering inside ceramide-rich platforms.

Question 34

What is the impact of the S13F mutation on CFTR expression at the plasma membrane?

Answer 34

S13F-CFTR is retained in the ER with little to no expression at the plasma membrane.

Question 35

What conclusion can be drawn about the S13F mutation in comparison to the F508 mutation?

Answer 35

The S13F mutation is not as severe as the F508 mutation.

Question 36

What is the relationship between CFTR folding and lipid raft behaviors?

Answer 36

Successful folding of F508-CFTR restores lipid rafts behaviors.

Question 37

What is the main takeaway regarding the expression of F508-CFTR and its effect on cell lipid profile?

Answer 37

F508-CFTR expression changes the cell lipid profile, especially the composition of lipid rafts.

Question 38

What is the role of fluorescent cholera toxin B subunit (CTXB) in the study?

Answer 38

CTXB binds to GM1 in lipid rafts.