Dissection of three Ca2+-dependent steps leading to secretion in chromaffin cells from mouse adrenal slices.
In neurosecretory cells, intracellular Ca2+ ([Ca2+]i) not only acts as the trigger for secretion but also regulates earlier steps in the secretory pathway. Here, a novel approach was developed to control [Ca2+]i over a broad concentration range, which allowed the quantification of three distinct actions of [Ca2+]i on large dense-core vesicle (LDCV) fusion in chromaffin cells from mouse adrenal slices. Basal [Ca2+]i regulated the transfer of vesicles toward a slowly releasable state, whereas further maturation to the readily releasable state was Ca2+ independent. [Ca2+]i levels above 3 microM triggered exocytosis of all readily and slowly releasable vesicles in two parallel, kinetically distinct fusion reactions. In a molecular context, these results suggest that Ca2+ acts both before and after trans-SNARE complex formation to regulate fusion competence and fusion kinetics of LDCVs.
Voets
T
T
Department of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany. tvoets@gwdg.de
D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology / Q000528:radiation effects; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008959:Models, Neurological; D010782:Photolysis; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D050600:SNARE Proteins; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism; D033921:Vesicular Transport Proteins
D005456:Fluorescent Dyes; D008565:Membrane Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; C085112:2-nitrophenyl-EGTA; D004533:Egtazic Acid; D002118:Calcium