Selected contribution: PKC activation inhibits Ca(2+) signaling in tracheal epithelial cells kept in simulated microgravity.
Microgravity has been shown to alter protein kinase C (PKC) activity; therefore, we investigated whether microgravity influences mechanically stimulated Ca(2+) signaling and ATP-induced Ca(2+) oscillations, both of which are modulated by PKC. Rabbit tracheal epithelial outgrowth cultures or suspended epithelial sheets were rotated in bioreactors to simulate microgravity. Mechanical stimulation of a single cell increased the cytosolic Ca(2+) concentration in 35-55 cells of both outgrowth cultures and epithelial sheets kept at unit gravity (G) or in simulated microgravity (smicroG). In outgrowth cultures, 12-O-tetradecanoylphorbol-13-acetate (TPA; 80 nM), a PKC activator, restricted Ca(2+) "waves" to about 10 cells in unit G and to significantly fewer cells in smicroG. TPA only slightly reduced the spread of Ca(2+) waves in epithelial sheets kept in smicroG but did not inhibit Ca(2+) waves of sheets kept in unit G. In both cell preparations from both conditions, TPA inhibited ATP-induced Ca(2+) oscillations; however, the effect was more pronounced in cells kept in smicroG. These results suggest that PKC activation is more robust in cells subjected to smicroG.
Department of Neurobiology, School of Medicine, University of California, Los Angeles 90095, USA.
J A
JA
Felix
E R
ER
Dirksen
M L
ML
Woodruff
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000502:physiology; D004847:Epithelial Cells / Q000201:enzymology / Q000648:ultrastructure; D010812:Physical Stimulation; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D020545:Respiratory Mucosa / Q000166:cytology / Q000201:enzymology / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014132:Trachea / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D014893:Weightlessness / Q000009:adverse effects*; D018474:Weightlessness Simulation
D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate