+ Site Statistics
+ Search Articles
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ PDF Full Text
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn

+ Translate
+ Recently Requested

Multi-ion block and blocker permeation in a CFTR channel pore mutant

Multi-ion block and blocker permeation in a CFTR channel pore mutant

Biophysical Journal 86(1): 283a

Open channel block of CFTR Cl- channels expressed in mammalian cell lines by impermeant Pt(NO2)42- ions was studied using inside-out patch clamp recording. Block of wild type CFTR by intracellular Pt(NO2)42- was of modest affinity (Kdapprx556muM), voltage dependent, kinetically fast, and weakened by extracellular Cl- ions. A mutation in the pore region that alters anion selectivity, F337A, but not another mutation at the same site that has no effect on selectivity (F337Y), had a complex effect on channel block by Pt(NO2)42-. Relative to wild type, block of F337A-CFTR was weakened at depolarized voltages but strengthened at hyperpolarized voltages. Current in the presence of Pt(NO2)42- increased at very negative voltages in F337A but not wild type or F337Y, apparently due to relief of block by permeation of Pt(NO2)42- ions to the extracellular solution. This "punchthrough" was prevented by extracellular Cl- ions, reminiscent of a "lock-in" effect. Relief of block in F337A by Pt(NO2)42- permeation was only observed for blocker concentrations above 300 muM; as a result, block at very negative voltages showed an anomalous concentration dependence, with an increase in blocker concentration causing a significant weakening of block and an increase in Cl- current. We interpret this effect as reflecting concentration-dependent permeability of Pt(NO2)42- in F337A, an apparent manifestation of an anomalous mole fraction effect. We suggest that the F337A mutation allows intracellular Pt(NO2)42- to enter deeply into the CFTR pore where it interacts with multiple binding sites, and that simultaneous binding of multiple Pt(NO2)42- ions within the pore promotes their permeation to the extracellular solution.

(PDF emailed within 1 workday: $29.90)

Accession: 035349263

Download citation: RISBibTeXText

Related references

Novel pore-lining residues in CFTR that govern permeation and open-channel block. Neuron 13(3): 623-634, 1994

Mutation-induced blocker permeability and multiion block of the CFTR chloride channel pore. Journal of General Physiology 122(6): 673-687, 2003

Interaction between permeation and gating studied in pore-domain mutant in CFTR. Biophysical Journal 74(2 PART 2): A396, 1998

Evidence for a superficial external blocker binding site in CFTR channel pore. Biophysical Journal 86(1): 332a, 2004

State-dependent blocker interactions with the CFTR chloride channel: implications for gating the pore. Pflugers Archiv 466(12): 2243-2255, 2015

Coupling of permeation and gating in an NMDA-channel pore mutant. Neuron. 18(1): 167-177, 1997

The single pore residue Asp542 determines Ca2+ permeation and Mg2+ block of the epithelial Ca2+ channel. Journal of Biological Chemistry 276(2): 1020-1025, 2000

Point mutations in the pore region directly or indirectly affect glibenclamide block of the CFTR chloride channel. Pflugers Archiv 443(5-6): 739-747, 2002

Voltage-dependent flickery block of an open cystic fibrosis transmembrane conductance regulator (CFTR) channel pore. Journal of Physiology (Cambridge) 532(2): 435-448, 2001

CFTR potentiators partially restore channel function to A561E-CFTR, a cystic fibrosis mutant with a similar mechanism of dysfunction as F508del-CFTR. British Journal of Pharmacology 171(19): 4490-4503, 2015

Multi-Ion mechanism for ion permeation and block in the cystic fibrosis transmembrane conductance regulator chloride channel. Journal of General Physiology 110(4): 365-377, 1997

Inhibition of protein kinase CK2 closes the CFTR Cl channel, but has no effect on the cystic fibrosis mutant deltaF508-CFTR. Cellular Physiology and Biochemistry 24(5-6): 347-360, 2010

A specific two-pore domain potassium channel blocker defines the structure of the TASK-1 open pore. Journal of Biological Chemistry 286(16): 13977-13984, 2011