Epithelial Chloride Channel 4 Flashcards
First CFTR KO mouse
1992 - Beverly Koller
3 groups
Gabriel et al 1993
CFTR and ORCCs distinct proteins in regulatory relationship
Gabriel 1993 findings - ORCCs and CFTR
KO mice lacking CF gene express ORCCs
PKA only activates ORCCS in CFTR expressing cells
CFTR involved in regulating ORCCs by PKA
1995 Jovov
CFTR and ORCCs
Explain Jovov 1995
CFTR and ORCC immunopurified from bovine trachea
planar lipid bilayers
nonfunctional mutant –> functional mutant
CFTR needed for OCC activation by ATP and PKA
Smith 1996
airway surface liquid bacteriacidal
pseudomonas aeruginosa bacteria killed in normal but thrive in CF airway
epithelial human b defensins
1 and 2
important natural bacteriacidal agents
HBD1 and 2 - Singh et al 1998 findings
present in normal and CF
HBD activity dependent on ionic strength of medium
If NaCl high then reduction in killing
singh et al 1998 lysosymes
in saliva - also affected by salts but not by non-ionic osmolytes
charge important
which HBD particularly affected by NaCl conc?
1
thiocyanate
sodium iodide transporter in basolateral membrane
exit via CFTR
important in bacteriacidal action
Conner et al 2006
thiocyanate (-ve)
duox enzyme thiocyanate –> hypothiocyanate
reduced SCN transport by CFTR impairs lypoxygenase mediated bacteriacidal action
thiocyanate or hypothiocyanate bacteriacidal?
hypothiocyanate
Type 1 CFTR defect and therapy
protein production
gentamicin - suppress premature termination of transcription
read through compounds
Type 2 CFTR defect and therapy
Processing
CFTR chaperones - stabilise protein structure/promote folding - expression in apical membrane
Type 3 CFTR defect and therapy
Regulation
CFTR activators : flavinoids, alkylxanthines prevent cAMP breakdown
MBP derivatives
what kind of defect is dF505?
type 2 - processing
type 4 defect and therapy
conduction
CFTR potentiators: VX 770
What is vx770?
Ivacaftor
MPB-07 - Becq 1999
measure Isc over time
apply cpt-cAMP increase in secretion
glibenclamide inhibits CFTR bring current down - normal
MPB-07 = increase in current, similar to levels with cAMP - activate CFTR
MPB-07 Iodine channels CFTR
iodine efflux only with MPB-07 not IBMX
getting deltaF508 to the membrane - chaperone aswell as an activator
Pedemonte 2005
amiloride then FSK - not much in deltaF508
lower temperature FSK has more effect
amiloride
KO sodium channels Enac
FSK
activates adenylate cyclase then cAMP
Van Groor et al 2009
rat thyroid cells
FSK not much effect
VX770 big effect on Isc - activity through CFTR
Van Groor et al 2009 dF508 and G551D
FSK does little
VX770 substantial increase in current in human bronchial epithelium
G551D at membrane, better even though not at membrane
Orkambi
Ivacaftor - VX770 Lumacaftor - VX809 licensed UK 2015 deltaF508 CFTR +/+ >£100, 000/year approved NHS in 2019
lumacaftor
CFTR chaperone and corrector
CF airway and ENaC
increased sodium conductance in apical membrane
CFTR inhibits Enac in airway
in CF –> airway surface dehydration water follows
CFTR and Enac in sweat duct
CFTR activate Enac in sweat duct
absence of CFTR in CF - salty sweat
last 4 amino acids at c terminus of CFTR
aspartic acid, threonine, arginine, leucine
what do 4 amino acids at c terminus of CFTR bind?
PDZ proteins
PDZ proteins
PSD-95, zo-1, Dlg
apical localisation of CFTR?
