A highly Ca2+-sensitive pool of vesicles is regulated by protein kinase C in adrenal chromaffin cells.
We have used flash photolysis of caged Ca2+ and membrane capacitance measurements to probe exocytosis in chromaffin cells at low concentrations of intracellular Ca2+ ([Ca2+]i) (<10 microM). We observed a small pool of granules that is more sensitive to [Ca2+]i than the previously described "readily releasable pool." Upon activation of PKC, this "highly Ca2+-sensitive pool" is enhanced in size to a greater extent than the readily releasable pool but is eliminated upon expression of a C-terminal deletion mutant (Delta9) of synaptosome-associated protein of 25 kDa (SNAP-25). Thus, in chromaffin cells, PKC enhances exocytosis both by increasing the number of readily releasable vesicles and by shifting vesicles to a highly Ca2+-sensitive state, enabling exocytosis at sites relatively distant from Ca2+ channels.
Yang
Yan
Y
Departments of Biological Engineering, Electrical Engineering, and Physiology, and Dalton Cardiovascular Research Center, University of Missouri, Research Park Drive, Columbia, MO 65211, USA.
Udayasankar
Sangeetha
S
Dunning
James
J
Chen
Peng
P
Gillis
Kevin D
KD
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism*; D004789:Enzyme Activation; D005089:Exocytosis; D008565:Membrane Proteins / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology*; D022142:Secretory Vesicles / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015220:Calcium Channels; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050825:Synaptosomal-Associated Protein 25; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium