Cystic Fibrosis

Question 1

CF is caused by what?

Answer 1

Loss of function mutations in gene encoding CFTR protein

Question 2

What is the main problem in CF?

Answer 2

deficient epithelial anion (Cl-) permeability

Question 3

What are the organs affected?

Answer 3

Airways, Sweat Glands, Pancreas, Small intestine

Question 4

What mode of inheritance does CF show?

Answer 4

Autosomal recessive

Question 5

Symptoms

Answer 5

cough with mucous, wheezing and SOB, chest infections, bowel disturbances, weight loss or failure to thrive, salty tasting sweat, infertility

Question 6

CFTR is a member of what large family of membrane transport proteins?

Answer 6

ATP-Binding Cassette (ABC) transporters

Question 7

What does CFTR stand for?

Answer 7

Cystic Fibrosis Transmembrane Conductance Regulator

Question 8

What are the domains of CFTR?

Answer 8

2 NBDs, 2 MSDs, R domain

Question 9

Why is this a unique ABC protein?

Answer 9

Because the rest use ATP to power active transport, this one hydrolizes ATP

Question 10

Channel activity is regulated by what?

Answer 10

Phosphorylation of a cytoplasmic regulatory domain (R domain)

Question 11

What chromosome is CFTR gene located on?

Answer 11

Chromosome 7

Question 12

What is the anion transported mediated by?

Answer 12

cAMP- mediated

Question 13

What other anions does CFTR transport?

Answer 13

Cl-, HCO3-, gluthathione, I-, SCN- (thiocyanate)

Question 14

What does the absence of functional CFTR result in?

Answer 14

increased viscocity of secretions, ciliary dysfunciton, mucous dehydration, mucous impaction, failure of MCC, repeated infections, neutrophilic inflammatory response, tissue damage, resp insufficiency

Question 15

What is the most common mutation?

Answer 15

Phenylalanine 508 deletion

Question 16

Loss of CFTR activity linked to over-activity of what?

Answer 16

ENaC

Question 17

Class 1 CFTR mutation

Answer 17

No functional CFTR, nonsense frameshift

Question 18

Class 2 CFTR mutation

Answer 18

CFTR traficking defect, misense amino acid deletion, Phe508del

Question 19

Class 3 CFTR mutation

Answer 19

Defective channel regulation, amino acid change

Question 20

Class 4 CFTR mutation

Answer 20

Decreased channel conductance, amino acid change

Question 21

Class 5 CFTR mutation

Answer 21

Reduced synthesis of CFTR, splicing defect

Question 22

Class 6 CFTR mutation

Answer 22

Decreased CFTR stability, increased turnover, amino acid change

Question 23

most common deletion and what percentage of all mutations it accounts for

Answer 23

F508del, 70%

Question 24

What percentage of mutations not associate with disease

Answer 24

15%

Question 25

MCC in normal airways

Answer 25

PCL height maintained at 7 micometers via coordinated Na absorption via ENaC and Cl secretion via CFTR

Question 26

MCC in CF

Answer 26

no CFTR, unrestrained Na hyperabsorption occurs with loss of Cl secretion = decreased PCL and failure of MCC

Question 27

When excess PCL is present:

Answer 27

Na absorption via ENaC is dominant and Cl is abosrobed passivlet via paracellular pathway

Question 28

When PCL volume is low:

Answer 28

ENaC is inhibited which makes the apical membrane potential more negative, so generating a driving force for Cl- secretion, Na follows paracellularly

Question 29

Abnormal Ion transport in CF results in what?

Answer 29

mucostasis - due to increased ion absorption across large airways, thickened mucous, plaques and plugs which adhere to airways

Question 30

CFTR transports HCO3- as well as Cl, so influences:

Answer 30

local pH

Question 31

local pH can influence

Answer 31

local proteins and ion channels (ENaC)

Question 32

Normal ASL pH =

Answer 32

7.0

Question 33

what is pH mediated by?

Answer 33

CFTR HCO3- secretion

Question 34

Experiments with cell line Calu-3 revealed CFTR will:

Answer 34

trnasport Cl or bicarb depending on activity of basolateral membrane

Question 35

Whole animal studies showed:

Answer 35

increased bicarb secretion in response to cAMP and calcium-inducing agnosit

Question 36

CF newborns show _____ ASL pH, why?

Answer 36

reduced (more acidic) - because dysregulation of CFTR causes abnormal acid base balance

Question 37

Changes in pH affect airway clearance:

Answer 37

transient acidification of normal ASL increases trate of absorption while alkalinization leads to a slowing of absorption and restores ASL heigh

Question 38

What serine protease with trypsin like activity is involved in ENaC activation and is inactive below pH 7

Answer 38

Prostasin

Question 39

SPLUNC1 is another regluator of ENaC activity , and does ??? in acidic CF airways

Answer 39

unable to inhbit ENaC, so promoted Na hyperabsorption

Question 40

prior to secretion how are mucin molecules packaged

Answer 40

as small granules with electric charges masked by calcium

Question 41

when mucin released in neutral environment what happens?

Answer 41

bicarb complexes with calcium, negative charges revealed, repel each other and sliperiness and lubrication is possible

Question 42

IN CF airways, reduced biarb transport impais:

Answer 42

expansion of mucin

Question 43

are proteins required to cleave mucins

Answer 43

yes

Question 44

In CF is there long sticky strands of mucins that remain attached? Why?

Answer 44

yes, due to pH sensitivity of cleavage proteins

Question 45

Bacterial killing is highly dependent on

Answer 45

pH

Question 46

Does CFTR transport glutathione?

Answer 46

Yes

Question 47

excessive inflammatory response in absence of infection is common

Answer 47

Yes

Question 48

cytokine response?

Answer 48

IL-8 leads to neutropgil recruitment to airways, damage lung tissue

Question 49

CFTR deficient cells exhibit

Answer 49

innate pro-inflammatory state

Question 50

high concentration of what inflammaotry mediators?

Answer 50

IL-6,8,1B and decreased IL-10 (antiinflammatory)

Question 51

excessive activation of transcirption factors such as

Answer 51

NF kappa B and AP-1

Question 52

CF neutrophils have...

Answer 52

reduced phagocytic capability

Question 53

upon death, CF neutrophils release

Answer 53

increased DNA and oxidases

Question 54

therapeutic strategies in CF 1

Answer 54

broad based inflammatory modulators: corticosteroids, Ibuprofen

Question 55

therapeutic strategies in CF 2

Answer 55

antibacterials with antiinflammatory properties: azuthromycin

Question 56

therapeutic strategies in CF 3

Answer 56

modulators of intracellular signaling: interferon gamma

Question 57

therapeutic strategies in CF 4

Answer 57

inhibitors of neutropgil influex: anti IL8

Question 58

therapeutic strategies in CF 5

Answer 58

inhibitors of neutrophil products: dornase-alfa

Question 59

therapeutic strategies in CF 6

Answer 59

anto oxidants - N acteyl cysteine

Question 60

therapeutic strategies in CF 7

Answer 60

anti proteases - alpha 1 protease inhbitor

Question 61

therapeutic strategies in CF 8

Answer 61

hyperosmolar agents, hypetonic saline, mannitol

Question 62

therapeutic strategies in CF 9

Answer 62

CFTR potentiators - improve Cl transport through CFTR, Halydeco

Question 63

therapeutic strategies in CF 10

Answer 63

CFTR correctors, resuce trafficking deffect - Lumacaftor

Question 64

therapeutic strategies in CF 11

Answer 64

Gene therapy - ineffective

Question 65

what do CFTR potentiators do?

Answer 65

increase acitivty of defective CFTR at cell surace by acting on gating defects or conductance defects

Question 66

What do CFTR correctors do?

Answer 66

overcome defective protein processinf that normally results in production of misfolded protein

Question 67

Potentiator: Kalydeco

Answer 67

good for class 3 mutations, increases open probability of channel, reduced sweat Cl, increase FEV1 weight gain, improve QOL

Question 68

Corrector: Lumacaftor

Answer 68

Class 2 mutations, molecular chaperone for protein folding, only modest effects on sweat Cl, no improvement in clinical outcomes

Question 69

Production correctors..

Answer 69

read through agents, promote readthrough of premature temrination codons in mRNA, which result in truncated protein - supress normal proofreading function of ribosome result in full length protein despite PTC, generating more CFTR - for class 1 mutations - still experimental