Author/Editor		Dolenšek, Jurij; Skelin, Maša; Rupnik, Marjan
Title		Calcium dependencies of regulated exocytosis in different endocrine cells
Type		članek
Vol. and No.		Letnik 60, št. Suppl. 1
Publication year		2011
Volume		str. S29-S38
ISSN		0862-8408 - Physiological research / Academia Scientiarum Bohemoslovaca
Language		eng
Abstract		Exocytotic machinery in neuronal and endocrine tissues is sensitive to changesin intracellular Ca2+ concentration. Endocrine cell models, that are most frequently used to study the mechanisms of regulated exocytosis, are pancreatic beta cells, adrenal chromaffin cells and pituitary cells. To reliably study the Ca2+ sensitivity in endocrine cells, accurate and fast determination of Ca2+ dependence in each tested cell is required. With slow photo-release it is possible to induce ramp-like increase in intracellular Ca2+ concentration ([Ca2+]i) that leads to a robust exocytotic activity. Slow increases in the [Ca2+]i revealed exocytotic phases with different Ca2+ sensitivities that have been largely masked in step-like flash photo-release experiments. Strikingly, in the cells of the three described model endocrine tissues (beta, chromaffin and melanotroph cells), distinct Ca2+ sensitivity ćclassesć of secretory vesicles have been observed: a highly Ca2+-sensitive, amedium Ca2+-sensitive and a low Ca2+- sensitive kinetic phase of secretory vesicle exocytosis. We discuss that a physiological modulation of a cellular activity, e.g. by activating cAMP/PKA transduction pathway, can switch the secretory vesicles between Ca2+ sensitivity classes. This significantly alterslate steps in the secretory release of hormones even without utilizationof an additional Ca2+ sensor protein.
Keywords		Calcium sensitivity Exocytosis Insulin-secreting cells Chromaffin cells Melanotrophs