The crucial role of chromogranins in storage and exocytosis revealed using chromaffin cells from chromogranin A null mouse.
Chromogranins (Cgs) are the major soluble proteins of dense-core secretory vesicles. Chromaffin cells from Chga null mice [chromogranin A knock-out (CgA-KO)] exhibited approximately 30% reduction in the content and in the release of catecholamines compared with wild type. This was because of a lower secretion per single exocytotic event, rather than to a lower frequency of exocytotic events. Cell incubation with L-DOPA produced an increase in the vesicular amine content of wild-type, but not CgA-KO vesicles. In contrast, intracellular electrochemistry showed that L-DOPA produced a significantly larger increase in cytosolic amines in CgA-KO cells than in the wild type. These data indicate that the mechanisms for vesicular accumulation in CgA-KO cells were fully saturated. Patch-amperometry recordings showed a delayed initiation of the amperometric signal after vesicle fusion, whereas no changes were observed in vesicle size or fusion pore kinetics despite the smaller amine content. We conclude that intravesicular proteins are highly efficient systems directly implicated in transmitter accumulation and in the control of neurosecretion.
Montesinos
Monica S
MS
Unit of Pharmacology, Medical School, University of La Laguna, 38071 Tenerife, Spain.
Machado
J David
JD
Camacho
Marcial
M
Diaz
Jesica
J
Morales
Yezer G
YG
Alvarez de la Rosa
Diego
D
Carmona
Emilia
E
Castañeyra
Agustin
A
Viveros
O Humberto
OH
O'Connor
Daniel T
DT
Mahata
Sushil K
SK
Borges
Ricardo
R
D000311:Adrenal Glands / Q000166:cytology; D000818:Animals; D002395:Catecholamines / Q000378:metabolism; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000502:physiology*; D053379:Chromogranin A / Q000172:deficiency; D002864:Chromogranins / Q000502:physiology*; D015259:Dopamine Agents / Q000494:pharmacology; D004563:Electrochemistry / Q000379:methods; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D007980:Levodopa / Q000494:pharmacology; D008561:Membrane Fusion / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011336:Probability; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D002395:Catecholamines; D053379:Chromogranin A; D002864:Chromogranins; D015259:Dopamine Agents; D007980:Levodopa; D014446:Tyrosine 3-Monooxygenase