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Cell Calcium. 2014 Jun;55(6):369-75. doi: 10.1016/j.ceca.2014.03.003. Epub 2014 Mar 28.

Ca²⁺-regulated secretory granule exocytosis in pancreatic and parotid acinar cells.

Author information

1
Department of Nutritional Sciences, Graduate Program in Biochemical and Molecular Nutrition, University of Wisconsin, Madison, WI 53706, United States.
2
Department of Nutritional Sciences, Graduate Program in Biochemical and Molecular Nutrition, University of Wisconsin, Madison, WI 53706, United States. Electronic address: groby@nutrisci.wisc.edu.

Abstract

Protein secretion from acinar cells of the pancreas and parotid glands is controlled by G-protein coupled receptor activation and generation of the cellular messengers Ca(2+), diacylglycerol and cAMP. Secretory granule (SG) exocytosis shares some common characteristics with nerve, neuroendocrine and endocrine cells which are regulated mainly by elevated cell Ca(2+). However, in addition to diverse signaling pathways, acinar cells have large ∼1 μm diameter SGs (∼30 fold larger diameter than synaptic vesicles), respond to stimulation at slower rates (seconds versus milliseconds), demonstrate significant constitutive secretion, and in isolated acini, undergo sequential compound SG-SG exocytosis at the apical membrane. Exocytosis proceeds as an initial rapid phase that peaks and declines over 3 min followed by a prolonged phase that decays to near basal levels over 20-30 min. Studies indicate the early phase is triggered by Ca(2+) and involves the SG proteins VAMP2 (vesicle associated membrane protein2), Ca(2+)-sensing protein synatotagmin 1 (syt1) and the accessory protein complexin 2. The molecular details for regulation of VAMP8-mediated SG exocytosis and the prolonged phase of secretion are still emerging. Here we review the known regulatory molecules that impact the sequential exocytic process of SG tethering, docking, priming and fusion in acinar cells.

KEYWORDS:

Acinar exocytosis; Ca(2+); Complexin; Docking; Fusion; Membrane trafficking; Pancreatic parotid acinar secretion; SNARE; Secretory granules; Synaptotagmin; Tethering; Zymogen granules; cAMP

PMID:
24742357
PMCID:
PMC4058401
DOI:
10.1016/j.ceca.2014.03.003
[Indexed for MEDLINE]
Free PMC Article

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