The control of cytoskeletal actin and exocytosis in intact and permeabilized adrenal chromaffin cells: role of calcium and protein kinase C.
The control of cytoskeletal actin and exocytosis was examined in intact and digitonin-permeabilized chromaffin cells. Cytoskeletal actin was assayed by determining the actin content of Triton-insoluble cytoskeletons. The secretagogues nicotine, high K+ and Ba2+ resulted in a rapid reduction in the amount of actin associated with the cytoskeleton. The effect of nicotine but not high K+ on cytoskeletal actin was independent of external Ca2+ and the reduction in cytoskeletal actin was mimicked by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate suggesting a role for protein kinase C. In digitonin-permeabilized cells micromolar calcium produced both catecholamine secretion and a reduction in cytoskeletal actin. The reduction in cytoskeletal actin was transient. Secretion was enhanced by the GTP analogue guanosine 5'-(3-O-thio)triphosphate and the analogue also reduced cytoskeletal actin at low calcium levels. The effects of guanosine 5'-(3-O-thio)triphosphate were inhibited by the phospholipase C inhibitor neomycin and were mimicked by 12-O-tetradecanoylphorbol-13-acetate. An additional GTP analogue, guanyl-5'-yl imidodiphosphate, had no effect on cytoskeletal actin. These results provide further evidence for a requirement for reorganisation of cortical actin in the secretory processes and suggest that the reduction in actin associated with the cytoskeleton may be mediated by protein kinase C and/or calcium in intact and permeabilized chromaffin cells.
Burgoyne
R D
RD
Physiological Laboratory, University of Liverpool, U.K.
Morgan
A
A
O'Sullivan
A J
AJ
D000199:Actins / Q000378:metabolism*; D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002463:Cell Membrane Permeability; D003599:Cytoskeleton / Q000378:metabolism; D004072:Digitonin; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D009355:Neomycin / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D000199:Actins; D013873:Thionucleotides; D001464:Barium; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009538:Nicotine; D006160:Guanosine Triphosphate; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D009355:Neomycin; D004072:Digitonin; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium; D002118:Calcium