CTFR in human disease

Question 1

Cystic Fibrosis

Answer 1

A genetic disorder caused by a bacterial infection leading to the build up of mucus in the lungs resulting in difficulty breathing

Question 2

Cystic Fibrosis Transmembrane conductance Regulator (CFTR)

Answer 2

Chloride channel on apical surface (side facing lumen) of epithelial cells

Question 3

Function of CFTR

Answer 3

Regulates the flow of ions and therefore fluid

Question 4

Mutations in CFTR gene

Answer 4

Mutations associated with cystic fibrosis

Question 5

Most common mutation

Answer 5

(delta)F508

Question 6

Why is Cystic Fibrosis lungs susceptible to infection?

Answer 6

Due to loss of CFTR function, the composition of the airway surface liquid (ASL) in the lung is altered

Question 7

Features of CF lung

Answer 7

Dehydrated ASL

Increased salt concentration

Question 8

Mucociliary clearance

Answer 8

Airways are lined by ciliated epithelial cells and mucus.

Bacteria are trapped by the mucus, and cilia beat the mucus and bacteria out

Question 9

Effects of Dehydrated ASL

Answer 9

Mucociliary clearance cannot function properly

Question 10

Effects of increased salt concentration in ASL

Answer 10

Anti-microbial peptides produced by endothelial cells are inhibited

Anti-microbial peptides inhibit bacterial membranes

Question 11

Pseudomonas aeruginosa

Answer 11

This bacteria dominates the respiratory infections in patients with CF

Gram-negative opportunistic (takes advantage of patients weakened immune system) pathogen

Question 12

Virulence factors of Pseudomonas that contribute to CF infection

Answer 12

Converts to mucoid phenotype

P. aeruginosa is associated with the overproduction of alginate

This influences biofilm formation and antibiotic tolerance and interaction with immune cells

P. aeruginosa is capable of inhibiting mucociliary clearance by reducing the beating frequency of cilia by production of pyocyanin.
Pyocyanin depletes ATP levels.

Question 13

CFTR and P. aeruginosa

Answer 13

CFTR is a receptor for P. aeruginosa.

When CFTR is reduced clearance of Pseudomonas is impaired

CFTR is not used to establish the infection, it is used as a pattern recognition receptor to trigger an immune response

Question 14

CFTR immune response

Answer 14

1. P. aeruginosa binds to CFTR
   2 a. Release of IL-1beta from epithelial cells
   3 a. Inflammatory response
   2 b. Recruitment of CFTR to lipid rafts
   3 b i . Nuclear translocation of NF-kB
   4 b i . Co-ordination of inflammatory response to control infection
   3 b ii. Endocytosis of bacteria by epithelial cells
   4 b ii. Desquamation of epithelial cells with subsequent clearance

the a. pathway doesnt happen without CFTR

Question 15

CFTR to lipid rafts

Answer 15

Lipid rafts formed in plasma membrane with P. aeruginosa attached to CFTR

Question 16

CFTR binding to LPS of P. aeruginosa

Answer 16

Pseudomonas has a LPS that allows for interaction with CFTR.

Mutants of Pseudomonas shortened LPS are not internalised

Exogenous LPS cannot be internalised