Localized cytosolic alkalization and its functional impact in ciliary cells.
Using confocal microscopy we demonstrate that ciliary cells from airway epithelium maintain two qualitatively distinct cytosolic regions in terms of pH regulation. While the bulk of the cytosol is stringently buffered and is virtually insensitive to changes in extracellular pH (pHo), the values of cytosolic pH in the vicinity of the ciliary membrane is largely determined by pHo. Variation of pHo from 6.2 up to 8.5 failed to affect ciliary beat frequency (CBF). Application of NH(4)Cl induced profound localized alkalization near cilia, which did not depress ciliary activity, but resulted in strong and prolonged enhancement of CBF. Calmodulin and protein kinase A (PKA) functionality was essential for the alkalization-induced CBF enhancement. We suggest that the ability of airway epithelium to sustain unusually strong but localized cytosolic alkalization near cilia facilitates CBF enhancement through altering the binding constants of Ca2+ to calmodulin and promotion of Ca2+-calmodulin complex formation. The NH4Cl-induced elevations in cytosolic pH and Ca2+ concentration act synergistically to activate calmodulin-dependent processes, cAMP pathway, and, thereby, stimulate CBF.
Lemberskiy-Kuzin
Liubov
L
Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
Fainshtein
Michal
M
Fridman
Polina
P
Passwell
Elena
E
Braiman
Alex
A
Priel
Zvi
Z
D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002147:Calmodulin / Q000378:metabolism; D002478:Cells, Cultured; D002923:Cilia / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D018613:Microscopy, Confocal; D011817:Rabbits; D020545:Respiratory Mucosa / Q000166:cytology; D013552:Swine
D002147:Calmodulin; D000643:Ammonium Chloride; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium