Purinergic signaling underlies CFTR control of human airway epithelial cell volume.
BACKGROUND
Loss of cystic fibrosis transmembrane conductance regulator (CFTR) function in cystic fibrosis (CF) causes dysregulation of multiple ion channels, water channels, and acid-base transporters in epithelia. As such, we hypothesized that dysregulation of many critical ion channels and transporters may cause defects in human airway epithelial cell volume regulation.


METHODS
Cell volume, regulatory volume decrease, and its regulation was assessed in real-time via Coulter Counter Multisizer III-driven electronic cell sizing in non-CF, CF, and CFTR-complemented CF human airway epithelial cells. SPQ halide fluorescence assay of hypotonicity-induced chloride efflux provided indirect validation of the cell volume assays.


RESULTS
CFTR, via autocrine ATP signaling, governs human airway epithelial cell volume regulation. Non-CF cells and wild-type (WT)-CFTR-transfected CF cells had normal regulatory volume decrease (RVD) responses that were attenuated by blockade of autocrine and paracrine purinergic signaling. In contrast, parental IB3-1 CF cells or IB3-1 cells expressing CFTR mutants (DeltaF508, G551D, and S1455X) failed to RVD. CF cell RVD was rescued by agonists to P2Y G protein-coupled receptors and, more robustly, by agonists to P2X purinergic receptor channels.


CONCLUSIONS
Loss of CFTR and CFTR-driven autocrine ATP signaling may underlie defective cell volume regulation and dysregulated ion, water, and acid-base transport in CF airway epithelia.
Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL 35294-0005, USA.
Gavin M
GM
Braunstein
Akos
A
Zsembery
Torry A
TA
Tucker
Erik M
EM
Schwiebert
D000255:Adenosine Triphosphate / Q000378:metabolism; D019898:Autocrine Communication / Q000502:physiology; D001980:Bronchi / Q000166:cytology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism; D003550:Cystic Fibrosis / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D014882:Water-Electrolyte Balance / Q000502:physiology*
C505032:CFTR protein, human; D002712:Chlorides; D007038:Hypotonic Solutions; D007552:Isotonic Solutions; D018048:Receptors, Purinergic P2; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate; D002118:Calcium