Send to

Choose Destination
J Biol Chem. 2014 Oct 3;289(40):28040-53. doi: 10.1074/jbc.M114.593913. Epub 2014 Aug 19.

Vesicle associated membrane protein 8 (VAMP8)-mediated zymogen granule exocytosis is dependent on endosomal trafficking via the constitutive-like secretory pathway.

Author information

From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706.
Institute of Molecular and Cellular Biology, National University of Singapore, Singapore 138673.
Departments of Medicine and Physiology, University of Toronto, Ontario M5S 1A8, Canada, and.
Department of Neurosurgery, Georgia Institute of Technology, Atlanta, Georgia 30322.
From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706,

Erratum in

  • J Biol Chem. 2014 Dec 19;289(51):35264. Giasano, Herbert Y [Corrected to Gaisano, Herbert Y].


Acinar cell zymogen granules (ZG) express 2 isoforms of the vesicle-associated membrane protein family (VAMP2 and -8) thought to regulate exocytosis. Expression of tetanus toxin to cleave VAMP2 in VAMP8 knock-out (-/-) acini confirmed that VAMP2 and -8 are the primary VAMPs for regulated exocytosis, each contributing ∼50% of the response. Analysis of VAMP8(-/-) acini indicated that although stimulated secretion was significantly reduced, a compensatory increase in constitutive secretion maintained total secretion equivalent to wild type (WT). Using a perifusion system to follow secretion over time revealed VAMP2 mediates an early rapid phase peaking and falling within 2-3 min, whereas VAMP8 controls a second prolonged phase that peaks at 4 min and slowly declines over 20 min to support the protracted secretory response. VAMP8(-/-) acini show increased expression of the endosomal proteins Ti-VAMP7 (2-fold) and Rab11a (4-fold) and their redistribution from endosomes to ZGs. Expression of GDP-trapped Rab11a-S25N inhibited secretion exclusively from the VAMP8 but not the VAMP2 pathway. VAMP8(-/-) acini also showed a >90% decrease in the early endosomal proteins Rab5/D52/EEA1, which control anterograde trafficking in the constitutive-like secretory pathway. In WT acini, short term (14-16 h) culture also results in a >90% decrease in Rab5/D52/EEA1 and a complete loss of the VAMP8 pathway, whereas VAMP2-secretion remains intact. Remarkably, rescue of Rab5/D52/EEA1 expression restored the VAMP8 pathway. Expressed D52 shows extensive colocalization with Rab11a and VAMP8 and partially copurifies with ZG fractions. These results indicate that robust trafficking within the constitutive-like secretory pathway is required for VAMP8- but not VAMP2-mediated ZG exocytosis.


Endosome; Exocytosis; Intracellular Trafficking; Pancreas; SNARE Proteins

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center