Ca2+ and protein kinase C activation of mucin granule exocytosis in permeabilized SPOC1 cells.
Mucin secretion by airway goblet cells is under the control of apical P2Y2, phospholipase C-coupled purinergic receptors. In SPOC1 cells, the mobilization of intracellular Ca2+ by ionomycin or the activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) stimulates mucin secretion in a fully additive fashion [L. H. Abdullah, J. D. Conway, J. A. Cohn, and C. W. Davis. Am. J. Physiol. 273 (Lung Cell. Mol. Physiol. 17): L201-L210, 1997]. This apparent independence between PKC and Ca2+ in the stimulation of mucin secretion was tested in streptolysin O-permeabilized SPOC1 cells. These cells were fully competent to secrete mucin when Ca2+ was elevated from 100 nM to 3.1 microM for 2 min following permeabilization; the Ca2+ EC50 was 2.29 +/- 0.07 microM. Permeabilized SPOC1 cells were exposed to PMA or 4alpha-phorbol at Ca2+ activities ranging from 10 nM to 10 microM. PMA, but not 4alpha-phorbol, increased mucin release at all Ca2+ activities tested: at 10 nM Ca2+ mucin release was 2.1-fold greater than control and at 4.7 microM Ca2+ mucin release was maximal (3.6-fold increase). PMA stimulated 27% more mucin release at 4.7 microM than at 10 nM Ca2+. Hence, SPOC1 cells possess Ca2+-insensitive, PKC-dependent, and Ca2+-dependent PKC-potentiated pathways for mucin granule exocytosis.
Scott
C E
CE
Cystic Fibrosis/Pulmonary Research and Treatment Center and the Department of Physiology, University of North Carolina, Chapel Hill, North Carolina 27599-7248, USA.
Abdullah
L H
LH
Davis
C W
CW
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D003594:Cytoplasmic Granules / Q000502:physiology*; D004789:Enzyme Activation; D005089:Exocytosis; D007700:Kinetics; D009077:Mucins / Q000378:metabolism*; D009092:Mucous Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D010704:Phorbols / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D013301:Streptolysins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014132:Trachea; D014544:Uridine Triphosphate / Q000494:pharmacology
D001426:Bacterial Proteins; D009077:Mucins; D010704:Phorbols; D013301:Streptolysins; C025964:streptolysin O; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D014544:Uridine Triphosphate; C033085:phorbol