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Increases in cytosolic Ca²⁺ induce dynamin- and calcineurin-dependent internalisation of CFTR

Lookup NU author(s): Waseema Patel, Dr Michael Gray

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-regulated, apical anion channel that regulates ion and fluid transport in many epithelia including the airways. We have previously shown that cigarette smoke (CS) exposure to airway epithelia causes a reduction in plasma membrane CFTR expression which correlated with a decrease in airway surface hydration. The effect of CS on CFTR was dependent on an increase in cytosolic Ca²⁺. However, the underlying mechanism for this Ca²⁺-dependent, internalisation of CFTR is unknown. To gain a better understanding of the effect of Ca²⁺ on CFTR, we performed whole cell current recordings to study the temporal effect of raising cytosolic Ca²⁺ on CFTR function. We show that an increase in cytosolic Ca²⁺ induced a time-dependent reduction in whole cell CFTR conductance, which was paralleled by a loss of cell surface CFTR expression, as measured by confocal and widefield fluorescence microscopy. The decrease in CFTR conductance and cell surface expression were both dynamin-dependent. Single channel reconstitution studies showed that raising cytosolic Ca²⁺ per se had no direct effect on CFTR. In fact, the loss of CFTR plasma membrane activity correlated with activation of calcineurin, a Ca²⁺-dependent phosphatase, suggesting that dephosphorylation of CFTR was linked to the loss of surface expression. In support of this, the calcineurin inhibitor, cyclosporin A, prevented the Ca²⁺-induced decrease in cell surface CFTR. These results provide a hitherto unrecognised role for cytosolic Ca²⁺ in modulating the residency of CFTR at the plasma membrane through a dynamin- and calcineurin-dependent mechanism.

Publication metadata

Author(s): Patel W, Moore PJ, Sassano MF, Lopes-Pacheco M, Aleksandrov AA, Amaral MD, Tarran R, Gray MA

Publication type: Article

Publication status: Published

Journal: Cellular and Molecular Life Sciences

Year: 2019

Volume: 76

Issue: 5

Pages: 977-994

Print publication date: 01/03/2019

Online publication date: 13/12/2018

Acceptance date: 04/12/2018

Date deposited: 18/12/2018

ISSN (print): 1420-682X

ISSN (electronic): 1420-9071

Publisher: Springer

URL: https://doi.org/10.1007/s00018-018-2989-3

DOI: 10.1007/s00018-018-2989-3

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