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.
Felix
J A
JA
Department of Neurobiology, School of Medicine, University of California, Los Angeles 90095, USA.
Dirksen
E R
ER
Woodruff
M L
ML
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