Skip to main content

Regulation of Physiologic and Pathologic Exocytosis in Pancreatic Acinar Cells

No comments (yet) Start the discussion
(1)Department of Medicine, University of Toronto, Toronto, Ontario, Canada, M5S 1A8. (2)Department of Physiology, University of Toronto, Toronto, Ontario, Canada, M5S 1A8. (3)These two authors are equal contributors
herbert.gaisano@utoronto.ca

Entry Version: 

Version 1.0, July 27, 2012

Citation: 

Dolai, Subhankar, Liang, Tao, Cosen-Binker, Laura I., Lam, Patrick P.L., Gaisano, Herbert Y.(2012). Regulation of Physiologic and Pathologic Exocytosis in Pancreatic Acinar Cells. The Pancreapedia: Exocrine Pancreas Knowledge Base, DOI: 10.3998/panc.2012.12

Abstract: The pancreatic acinar cell is one of the best-studied cell models of regulated secretion. On activation by neural or hormonal secretagogues, pancreatic acinar cells secrete a variety of inactive digestive enzyme precursors from zymogen granules (ZGs) undergoing exocytosis at the apical pole of this polarized cell. The acinar cell is also an excellent model to study pathologic membrane fusion events which underlie clinical pancreatitis. This includes apical exocytotic blockade along with ectopic fusion events including formation of large cytoplasmic vacuoles and redirected exocytosis to the basolateral plasma membrane; in these compartments zymogens become prematurely activated to initiate pancreatic tissue injury. Over the past two decades, my laboratory has been exploring the central role of SNARE [Soluble N-ethylmaleimide-sensitive factor (NSF) Attachment Protein (SNAP) Receptors] proteins in regulating physiologic and pathologic fusion events in the pancreatic acinar cell. SNARE proteins on cognate vesicles (v-SNARE) and target membrane (t-SNARE) mediate membrane fusion by their highly interactive coiled domains called SNARE motifs that form a trans-complex facilitated by Sec1/Munc18 (SM) and other accessory proteins. This forces the secretory granule (ZG) to come in proximity to the target membrane (plasma membrane) by the zippering action of the trans-SNARE complex that culminates in membrane fusion. This review provides an overview on how these proteins mediate normal regulated exocytosis in the pancreatic acinar cell and pathologic fusion events underlying pancreatitis. 

Regulated secretion in pancreatic acinar cells

While all eukaryotic cells are capable of basal constitutive secretion, some specialized secretory cells like pancreatic acinar cells release their secretory products by agonist-evoked regulated exocytosis. The pancreatic acinar cell possesses one of the most robust protein synthetic machinery, synthesizing digestive proteases as inactive proenzymes that are sorted out from the trans-Golgi into condensing vacuoles (CVs), which then undergo additional maturation steps. These mature ZGs, which are among the largest secretory vesicles (~1 µm), accumulate at the apical pole of the acinar cell, occupying 10-30% of the total cell volume. These ZGs are in an aggregate “ready-to-release” state waiting for fusogenic Ca2+ to induce their exocytosis with the apical plasma membrane and release of their cargo into the ductal lumen. Stimulation by secretagogues such as acetylcholine and cholecystokinin (CCK) activate respective G protein–coupled plasma membrane receptors to trigger a cascade of cellular events leading to the generation of intracellular messengers, primarily diacylglycerol (DAG) which activates protein kinase C (PKC), and inositol trisphosphate (IP3) which releases Ca2+ from IP3-sensitive stores, although Ca2+ is also released from other  storage compartments, including those sensitive to nicotinic acidic adenine dinucleotide. As well, there is generation of cyclic adenosine monophosphate (cAMP) which activates protein kinase A (PKA) and sequential activation of Rho and Rab family of small G proteins and other protein kinases. The concerted actions of these signalling events on downstream substrate proteins, most importantly SNARE and associated proteins that constitute the exocytotic apparatus, culminating in exocytosis of ZGs. However, the apical plasma membrane constitutes less than 10% of the total cell surface area even under maximal physiologic stimulation, and thus primary exocytosis of ZGs with apical plasma membrane would not be sufficiently effective in exporting the very large amount of zymogens needed to be delivered into the duodenal lumen to efficiently digest the food continually being emptied from the stomach during a meal. Remarkably, pancreatic acinar cells are equipped to effect an orderly (within 10 minute) fusion of majority (>30%) of the ZGs within the apical pole, termed sequential exocytosis.  Sequential and compound exocytosis are not unique to acinar cells and are also observed to be even more efficient in other cell types such as eosinophils and mast cells, as such exocytotic efficiency are required to effect the allergic response. However, it seems unique to the acinar cells that the fusion pores between this extensive network of homotypically-fused ZGs remain open for very long periods (> 10 min), enabling  a very efficient emptying of zymogen cargo from the deepest lying ZGs in the apical pole. This provides an exquisitely regulated metered machinery that matches digestive enzyme output to the varying amounts of food being ingested.

The SNARE Hypothesis for Membrane Fusion

Exocytosis as we know today comes from the convergence of insights from primitive yeast constitutive secretion to the most highly regulated mammalian neurotransmitter release, where molecules mediating membrane fusion called soluble NSF (N-ethyl maleimide sensitive factor) attachment protein receptor (SNARE) proteins were shown to be remarkably and evolutionarily conserved. This SNARE Hypothesis has continued to evolve over the past two decades as new molecules have been discovered along with better methods for spatio-temporal resolution of exocytosis. Since SNARE motifs of different SNARE proteins are highly conserved and can in fact undergo promiscuous assembly in vitro, the fidelity of the numerous membrane fusion events that exist in vivo in a cell requires strict compartmentalized targeting of the different SNARE isoforms. Distinct spatial pairing and assembly of v-SNAREs (vesicle-associated membrane protein or VAMPs) and t-SNAREs (Syntaxins (Syn) and synaptosomal associated protein (SNAP) of 25 kDa or SNAP-25) into fusion-competent trans-SNARE complexes are selectively activated by a host of regulatory proteins including large families of Sec1/Munc18 or SM proteins, calcium sensors and other proteins, many of which are coupled to second messengers such as Ca2+, cAMP and protein kinases (C and A) triggered by different agonists. The pancreatic acinar cell has been an ideal model to examine these tenets of the SNARE Hypothesis.

SNARE protein regulation of physiologic exocytosis in the acinar cell

 We first mapped out the cellular locations of the v-SNARE (VAMPs) and t-SNAREs (syntaxins (Syn) and SNAP-25) in the pancreatic acinar cell (Figure 1).

 

Figure 1. Distinct sets of cognate SM and SNARE proteins mediating apical and basolateral exocytoses, and ZG-ZG fusion. Respective SM proteins bind to syntaxins at the specific compartments at basal state (left). Upon stimulation (right), the SM proteins activate syntaxins into open conformation capable of binding the cognate VAMPs and SNAP-23 to form the distinct SNARE complexes that mediate the different exocytoses.

We found three exocytotic syntaxin isoforms in different exocytotic compartments: syntaxin 2 (Syn-2) on the apical plasma membrane, syntaxin 3 (Syn-3) on ZG membrane, and syntaxin 4 (Syn-4) on the basolateral membrane. A smaller SNAP-25 isoform, SNAP-23, was the dominant SNAP-25 isoform present in ZGs and the entire acinar plasma membrane. Although VAMP-2 and VAMP-3 were both present in acini, VAMP-2 was the dominant form for regulated exocytosis, while VAMP-3 may play a role in constitutive secretion. Different strategies were used to assess the exocytotic functions of these SNARE proteins. The first strategy was by employing botulinum neurotoxins or BoNTs, including tetanus neurotoxin or TeNT, which have been long known to block neurosecretion; and the discovery that exocytotic blockade was by proteolytic cleavage of SNARE proteins was instrumental in catapulting the field forward. However, unlike neurons, pancreatic acinar cells do not have plasma membrane receptors to internalize BoNTs. Thus, cell permealization strategies (ie. streptolysin O) were employed to internalized the BoNTs, which allowed us and others to show that TeNT and BoNT/C1 selectively cleaved pancreatic acinar VAMP-2 and syntaxins (Syn-2 and Syn-3 only), respectively, blocking Ca2+-evoked enzyme release. Of note, our initial observation in 1994 showed that in spite of the complete proteolysis of VAMP-2 by TeNT, there was only a 30% inhibition of enzyme secretion. It was 15 years later when we discovered that another VAMP, VAMP-8, when genetically-deleted, abrogated the majority of regulated apical exocytosis. This was primarily by VAMP-8’s role in mediating ZG-ZG fusion, shown by epifluorescence and confocal imaging of the fluorescent dye FM1-43, and with higher spatial resolution employing multi-photon microscopy. Thus, primary exocytosis of ZGs with apical plasma membrane is mediated by VAMP-2 per se. Interestingly, the VAMP-8-deleted mice showed no symptoms of malabsorption suggesting that the remaining zymogens secreted by the restricted primary exocytosis into the gut were sufficient for digestion. The exocytosis role of SNAP-23, which was resistant to BoNTs, was shown by adenovirus expression of dominant-negative carboxyl-terminal deleted SNAP-23. The current thinking of the SNARE Hypothesis indicates a critical role for SM proteins (6) to bind and activate syntaxins to bind cognate SNAREs proteins to form fusion-competent SM/trans-SNARE complexes. SM (nSec1/Munc18)  proteins are a group of hydrophilic 60–70-kDa polypeptides, first identified as UNC-18 in C. elegans and Sec1 in yeast. The mammalian homologue neuronal Munc18-1 (also known as Munc18a, nSec1 or RbSec1) was first identified and found to bind syntaxin-1A, then later shown to activate syntaxin-1A to bind cognate SNAREs proteins to form fusion-competent SM/trans-SNARE complexes. Neuronal Munc18a is not present in acinar cells, whereas Munc18b and Munc18c are. Using immunoprecipitation assays on physiologic CCK- and carbachol-stimulated pancreatic acini, distinct quaternary SM/SNARE complexes were captured, including Munc18b binding to the trans-SNARE complex – Syn-2/VAMP-2/SNAP-23 we postulate to mediate primary exocytosis of ZGs with apical plasma membrane, and Munc18b binding to the trans-SNARE complex – Syn-3/VAMP-8/SNAP-23 we postulate to mediate sequential ZG-ZG fusion.

While the basic tenets of the different above-mentioned exocytotic processes mediated by distinct SM/SNARE complexes in the pancreatic acinar cell seem to mimic the well-studied synaptic vesicle exocytosis in the neuron, the pancreatic acinar cell does exhibit some distinct features. Unlike neurons and other secretory cells, it seems that most of the acinar ZGs do not completely collapse into the plasma membrane during exocytosis; thus the complete disassembly and recycling of SNARE complexes postulated to occur in neuro-exocytosis may not be completely mimicked in the acinar cell. Future work will also be needed to elucidate how this architecture of intact ZGs is maintained during exocytosis. Furthermore, in the acinar cell, the fusion pores between the sequentially-fused ZGs remain open for great lengths of time and then close after partial emptying of the zymogen cargo. The partially emptied ZGs then reload with zymogens to get ready for the next round of exocytosis. Much work will also be needed to elucidate the molecular machinery that maintains the fusion pores to remain open for such extended periods.

Other proteins in regulated apical exocytosis.

Complexins (complexins 1 and 2), Synaptotagmins (Syts) and cysteine string protein (CSP)-α have been recently described to be accessory SNARE-interacting effectors of neural exocytosis. Complexins preferentially bind to assembled SNARE complexes and act both as clamp and an activator of SNAREs by pulling the complex closer to the membrane, leading to a “super-primed” state ready for immediate fusion. It is believed that the Ca2+ sensing Syts finally triggers fusion. Ca2+ binding to Syts promote their oligomerization and binding to the SNARE complex, allowing the formation of a quaternary SNARE-synaptotagmin-Ca2+-phospholipid complex and thus promote membrane fusion. CSPα is a synaptic vesicle protein which forms a complex with heat shock protein cognate 70 (Hsc70) and complexin in neurons. These proteins are all present in the pancreatic acinar cell. In pancreatic acinar cells, complexin 2 is in the apical pole and CSP-α is on the ZG, the latter further shown to interacted with VAMP-8 and Hsc70. Recently, several isoforms of Syt (Syt 1, 3, 6 and 7) were also found in pancreatic acini, with Syt 1 found in the ZGs and apical membrane, and Syt 3 found in both acinar membrane and microsomes. It is possible that some of these proteins, particularly Syts and complexins, may act as either fusion clamps and/or calcium sensors capable of responding to the different Ca2+ release events, including apical oscillatory Ca2+ spikes versus global Ca2+ rise, mediating physiologic (above) and pathologic (below) exocytoses, respectively.

SNARE proteins mediate pathologic basolateral exocytosis underlying pancreatitis

The basolateral plasma membrane accounts for 90% of the acinar cell surface area where little or no exocytosis occurs normally. However, the basolateral plasma membrane of the pancreatic acinar cell contains a complete set of t-SNARE proteins (Syn-4, SNAP-23) and cognate SM protein Munc18c indicating that this plasma membrane domain has the membrane fusion machinery for exocytosis to potentially occur. An early morphological study showed that supraphysiological CCK or cholinergic stimulation caused apical exocytotic blockade and induced ectopic exocytosis at the lateral plasma membrane, releasing enzymes into the interstitial space, which when activated led to cellular destruction ie. interstitial pancreatitis. This report was largely ignored until more recently when we elucidated the exocytotic machinery mediating this pathologic fusion event, thus re-establishing the thinking that this is a major event contributing to pancreatitis. Employing FM1-43 fluorescence imaging, basolateral exocytosis was observed in dispersed rat pancreatic acini after supramaximal CCK or carbachol stimulation; and more remarkably, also after treatment with clinically-relevant concentrations of alcohol and putative alcohol metabolites followed by physiologic CCK or carbachol stimulation, thus simulating alcoholic pancreatitis. We recently reported an improved exocytosis imaging technique (Figure 2) whereby adenoviral expressed pH-sensitive fluorophore, syncollin-pHlourin, targeted to ZGs, fluoresced upon exocytosis observed by spinning disc microscopy, enabling high spatial resolution and real time visualization of both apical and basolateral exocytoses. In these reports, electron microscopic analysis of pancreatic tissues of rodents subjected to similar supramaximal stimulation showed aberrant exocytosis occurring at the lateral plasma membrane and consequential interstitial pancreatitis. We found SM protein Munc18c on the basolateral plasma membrane, which on supramaximal stimulation resulted in specific PKC-α phosphorylation of Munc18c, inducing its assembly and activation of trans-SNARE complex Syn-4/VAMP-8/SNAP-23, which we postulated to be the putative SM/SNARE complex mediating pathologic basolateral exocytosis. PKC phosphorylation of Munc18c activates Syn-4 into open conformation conducive to forming SNARE complexes with SNAP-23 and VAMP8, thus rendering the basolateral plasma membrane receptive to exocytosis with approaching VAMP8 containing ZGs. Activation of Munc18c reduces its affinity to open conformation Syn-4.

Figure 2. Imaging of apical and basolateral exocytosis by recording syncollin-pHlourin fluorescence hotspots using spinning disk confocal microscopy. Shown are DIC images with superimposed syncollin-pHluorin green images (scale bar=10 µm) of rat pancreatic acini. Two concentric circles are drawn. Inner dashed circle encompasses the ZG poles surrounding the apical lumen; exocytosis in this region we consider as apical exocytosis. Outer solid circle encompasses from the acinar basal plasma membrane up to the borders of the ZG poles; exocytosis in this region we consider as basal exocytosis. Note in A, in a rat pancreatic acinius stimulated with 200 pM CCK-8, syncollin-pHluorin green fluorescent hotspots were confined to the apical region (inner dashed circle) with arrowhead indicating the apical lumen. The fluorescent hotspots in the deeper regions of the apical pole (arrows) indicate sequential exocytosis with these deep-lying ZGs. In B, an acinus pretreated with 3 mM acetaldehyde (an alcohol metabolite) then stimulated with 200 pM CCK-8, caused a redirection of much of the apical exocytosis (arrowhead pointing to apical lumen) to the basolateral region. The arrow indicates a green hotspot at the junction of basal and lateral plasma membrane region. Many of the hotspots are outside the inner dashed circle and distant from the apical lumen and apical poles. These data are similar to those recently reported by us in ref. 9.

Interestingly, in a human case of quiescent chronic alcoholic pancreatitis, this resulted in Munc18c becoming displaced into the cytosol of residual intact acinar cells, suggesting that this might be a possible contributing mechanism predisposing to recurrent pancreatitis often observed in these patients. Whereas ZGs are sparse in the vicinity of the basolateral surface, we found that upon supramaximal carbachol or alcohol (or alcohol metabolite) plus submaximal agonist stimulation of pancreatic acini, VAMP-8-labeled ZGs were redirected to approach the basolateral membrane. Furthermore, employing VAMP-8 null mouse dispersed pancreatic acini, basolateral exocytosis was indeed completely prevented. Remarkably, induction of acute pancreatitis by in vivo supramaximal carbachol or alcohol plus submaximal carbachol stimulation did not result in pancreatitis in VAMP-8 null mice. To translate these findings to clinical pancreatitis, we fed mice with an alcohol diet and then stimulated with postprandial carbachol stimulation, which caused pancreatitis in wild type mice, but not in the VAMP-8 null mice. Likewise, the alcohol diet redirected CCK-mediated exocytosis to the basolateral membrane causing alcoholic pancreatitis. 

Formation of large cytoplasmic vacuoles

The current dogma over the past two decades postulated that the dominant key early cellular event leading to pancreatitis is the formation of large cytoplasmic vacuoles where hydrolytic lysosomal enzymes and zymogens become co-localized to cause premature activation of zymogens causing intracellular digestion leading to cell injury. The molecular and cellular mechanisms underlying the formation of these large vacuoles are only now becoming clearer. Studies on in vitro model of acute pancreatitis in dispersed acini or in vivo studies on cerulein/L-arginine model of acute pancreatitis reveal perturbation in endocytosis and autophagy underlying the process of vacuole formation and intracellular trypsinogen activation. The ability of cathepsin B inhibitor to inhibit trypsinogen activity in the endocytic vacuole, taken along with the evidence that autophagosomes/autolysosomes accumulate in acute pancreatitis suggest that vacuolar trypsinogen could be delivered to hydrolase-containing vesicles or lysosomes by endocytosis or autophagy. Of note, almost nothing is known about the precise molecules mediating these pathologic vesicular transport and fusion processes. Studies from different groups investigating other cell types have proposed the involvement of SNARE proteins in the fusion of endocytic and autophagic vacuoles with lysosomes (13,37). Syntaxin 7 is thought to be the SNARE protein required for both homotypic late endosome fusion and heterotypic fusion with lysosomes. The other SNARE proteins in this process were identified using antibody inhibition of cell-free assays, which are Vti1b, syntaxin 8, VAMP-7 and VAMP-8. These reports taken together lead us to postulate that these pathologic processes underlying pancreatitis may involve these candidate membrane fusion molecules rather than those we have described above for apical and basolateral exocytoses. Much further work from our laboratory and others will be required to pursue these possibilities. 

Future Directions

From this brief review, much is known about the different fusion molecules mediating physiologic and pathologic exocytosis in the pancreatic acinar cell, which we summarized in Table 1. Many of these exocytotic processes have been found to mimic neuronal exocytotic machinery. However, the pancreatic acinar cell exhibits a number of distinct features in physiologic exocytosis such as long fusion pore openings, and in pathologic exocytosis such as the formation of large cytoplasmic vacuoles, whose molecular bases are unknown. From the future work directed at defining the molecular mechanisms underlying these unique features in exocytosis, one may be able to identify strategies to increase the efficiency of secretion of residual pancreatic acinar cells to treat diseases of exocrine insufficiency, or block the pathologic exocytosis that could prevent progression to severe pancreatitis.

* (Note: Please see the pdf version of the review for a clearer version of Table.1)

Acknowledgement

This work was supported by a grant from the Canadian Institute of Health Research (CIHR), Grant no. CIHR MOP 119352. SD is funded by postdoctoral fellowships from CIHR and  Canadian Association of Gastroenterology, and the Banting and Best Diabetes Centre of the University of Toronto. 

References

  1. Advani RJ, Yang B, Prekeris R, Lee KC, Klumperman J, and Scheller RH. VAMP-7 mediates vesicular transport from endosomes to lysosomes. J Cell Biol 146: 765-776, 1999.  PMID 10459012
  2. Antonin W, Holroyd C, Fasshauer D, Pabst S, Von Mollard GF, and Jahn R. A SNARE complex mediating fusion of late endosomes defines conserved properties of SNARE structure and function. EMBO J 19: 6453-6464, 2000.  PMID 11101518
  3. Beaudoin AR and Grondin G. Secretory pathways in animal cells: with emphasis on pancreatic acinar cells. J Electron Microsc Tech 17: 51-69, 1991.  PMID 1993938
  4. Behrendorff N, Dolai S, Hong W, Gaisano HY, and Thorn P. Vesicle-associated membrane protein 8 (VAMP8) is a SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) selectively required for sequential granule-to-granule fusion. J Biol Chem 286: 29627-29634, 2011.  PMID 21733851
  5. Brenner S. The genetics of Caenorhabditis elegans. Genetics 77: 71-94, 1974.  PMID 4366476
  6. Carr CM and Rizo J. At the junction of SNARE and SM protein function. Curr Opin Cell Biol 22: 488-495, 2010.  PMID 20471239
  7. Cosen-Binker LI, Binker MG, Wang CC, Hong W, and Gaisano HY. VAMP8 is the v-SNARE that mediates basolateral exocytosis in a mouse model of alcoholic pancreatitis. J Clin Invest 118: 2535-2551, 2008.  PMID 18535671
  8. Cosen-Binker LI, Lam PP, Binker MG, and Gaisano HY. Alcohol-induced protein kinase Calpha phosphorylation of Munc18c in carbachol-stimulated acini causes basolateral exocytosis. Gastroenterology 132: 1527-1545, 2007.  PMID 17408632
  9. Dolai S, Liang T, Lam PP, Fernandez NA, Chidambaram S, and Gaisano HY. Effects of Ethanol Metabolites on Exocytosis of Pancreatic Acinar Cells in Rats. Gastroenterology, 2012.  PMID 22710192
  10. Falkowski MA, Thomas DD, and Groblewski GE. Complexin 2 modulates vesicle-associated membrane protein (VAMP) 2-regulated zymogen granule exocytosis in pancreatic acini. J Biol Chem 285: 35558-35566, 2010.  PMID 20829354
  11. Falkowski MA, Thomas DD, Messenger SW, Martin TF, and Groblewski GE. Expression, localization, and functional role for synaptotagmins in pancreatic acinar cells. Am J Physiol Gastrointest Liver Physiol 301: G306-316, 2011.  PMID 21636530
  12. Fernandez NA, Liang T, and Gaisano HY. Live pancreatic acinar imaging of exocytosis using syncollin-pHluorin. Am J Physiol Cell Physiol 300: C1513-1523, 2011.  PMID 21307342
  13. Furuta N, Fujita N, Noda T, Yoshimori T, and Amano A. Combinational soluble N-ethylmaleimide-sensitive factor attachment protein receptor proteins VAMP8 and Vti1b mediate fusion of antimicrobial and canonical autophagosomes with lysosomes. Mol Biol Cell 21: 1001-1010, 2010.  PMID 20089838
  14. Gaisano HY, Ghai M, Malkus PN, Sheu L, Bouquillon A, Bennett MK, and Trimble WS. Distinct cellular locations of the syntaxin family of proteins in rat pancreatic acinar cells. Mol Biol Cell 7: 2019-2027, 1996.  PMID 8970162
  15. Gaisano HY and Gorelick FS. New insights into the mechanisms of pancreatitis. Gastroenterology 136: 2040-2044, 2009.  PMID 19379751
  16. Gaisano HY, Huang X, Sheu L, Ghai M, Newgard CB, Trinh KY, and Trimble WS. Snare protein expression and adenoviral transfection of amphicrine AR42J. Biochem Biophys Res Commun 260: 781-784, 1999.  PMID 10403842
  17. Gaisano HY, Lutz MP, Leser J, Sheu L, Lynch G, Tang L, Tamori Y, Trimble WS, and Salapatek AM. Supramaximal cholecystokinin displaces Munc18c from the pancreatic acinar basal surface, redirecting apical exocytosis to the basal membrane. J Clin Invest 108: 1597-1611, 2001.  PMID 11733555
  18. Gaisano HY, Sheu L, Foskett JK, and Trimble WS. Tetanus toxin light chain cleaves a vesicle-associated membrane protein (VAMP) isoform 2 in rat pancreatic zymogen granules and inhibits enzyme secretion. J Biol Chem 269: 17062-17066, 1994.  PMID 7516331
  19. Gaisano HY, Sheu L, Grondin G, Ghai M, Bouquillon A, Lowe A, Beaudoin A, and Trimble WS. The vesicle-associated membrane protein family of proteins in rat pancreatic and parotid acinar cells. Gastroenterology 111: 1661-1669, 1996.  PMID 8942747
  20. Gaisano HY, Sheu L, and Whitcomb D. Alcoholic chronic pancreatitis involves displacement of Munc18c from the pancreatic acinar basal membrane surface. Pancreas 28: 395-400, 2004.  PMID 15097857
  21. Gaisano HY, Sheu L, Wong PP, Klip A, and Trimble WS. SNAP-23 is located in the basolateral plasma membrane of rat pancreatic acinar cells. FEBS Lett 414: 298-302, 1997.  PMID 9315706
  22. Galione A, Evans AM, Ma J, Parrington J, Arredouani A, Cheng X, and Zhu MX. The acid test: the discovery of two-pore channels (TPCs) as NAADP-gated endolysosomal Ca(2+) release channels. Pflugers Arch 458: 869-876, 2009.  PMID 19475418
  23. Hansen NJ, Antonin W, and Edwardson JM. Identification of SNAREs involved in regulated exocytosis in the pancreatic acinar cell. J Biol Chem 274: 22871-22876, 1999.  PMID 10428873
  24. Hartwig W, Jimenez RE, Werner J, Lewandrowski KB, Warshaw AL, and Fernandez-del Castillo C. Interstitial trypsinogen release and its relevance to the transformation of mild into necrotizing pancreatitis in rats. Gastroenterology 117: 717-725, 1999.  PMID 10464149
  25.  Hashimoto D, Ohmuraya M, Hirota M, Yamamoto A, Suyama K, Ida S, Okumura Y, Takahashi E, Kido H, Araki K, Baba H, Mizushima N, and Yamamura K. Involvement of autophagy in trypsinogen activation within the pancreatic acinar cells. J Cell Biol 181: 1065-1072, 2008.  PMID 18591426
  26. Hata Y, Slaughter CA, and Sudhof TC. Synaptic vesicle fusion complex contains unc-18 homologue bound to syntaxin. Nature 366: 347-351, 1993.  PMID 8247129
  27. Huang X, Sheu L, Tamori Y, Trimble WS, and Gaisano HY. Cholecystokinin-regulated exocytosis in rat pancreatic acinar cells is inhibited by a C-terminus truncated mutant of SNAP-23. Pancreas 23: 125-133, 2001.  PMID 11484914
  28. Lam PP, Cosen Binker LI, Lugea A, Pandol SJ, and Gaisano HY. Alcohol redirects CCK-mediated apical exocytosis to the acinar basolateral membrane in alcoholic pancreatitis. Traffic 8: 605-617, 2007. PMID 17451559
  29. Li C, Chen X, and Williams JA. Regulation of CCK-induced amylase release by PKC-delta in rat pancreatic acinar cells. Am J Physiol Gastrointest Liver Physiol 287: G764-771, 2004. PMID 15217780
  30. Mareninova OA, Hermann K, French SW, O’Konski MS, Pandol SJ, Webster P, Erickson AH, Katunuma N, Gorelick FS, Gukovsky I, and Gukovskaya AS. Impaired autophagic flux mediates acinar cell vacuole formation and trypsinogen activation in rodent models of acute pancreatitis. J Clin Invest 119: 3340-3355, 2009. PMID 19805911
  31. Maximov A, Tang J, Yang X, Pang ZP, and Sudhof TC. Complexin controls the force transfer from SNARE complexes to membranes in fusion. Science 323: 516-521, 2009. PMID 19164751
  32. Nemoto T, Kimura R, Ito K, Tachikawa A, Miyashita Y, Iino M, and Kasai H. Sequential-replenishment mechanism of exocytosis in pancreatic acini. Nat Cell Biol 3: 253-258, 2001. PMID 11231574
  33. Niederau C and Grendell JH. Intracellular vacuoles in experimental acute pancreatitis in rats and mice are an acidified compartment. J Clin Invest 81: 229-236, 1988. PMID 3335639
  34. Novick P, Field C, and Schekman R. Identification of 23 complementation groups required for post-translational events in the yeast secretory pathway. Cell 21: 205-215, 1980. PMID 6996832
  35. Palade G. Intracellular aspects of the process of protein synthesis. Science 189: 347-358, 1975. PMID 1096303
  36. Petersen OH, Gerasimenko OV, Tepikin AV, and Gerasimenko JV. Aberrant Ca(2+) signalling through acidic calcium stores in pancreatic acinar cells. Cell Calcium 50: 193-199, 2011. PMID 21435718
  37. Pryor PR, Mullock BM, Bright NA, Lindsay MR, Gray SR, Richardson SC, Stewart A, James DE, Piper RC, and Luzio JP. Combinatorial SNARE complexes with VAMP7 or VAMP8 define different late endocytic fusion events. EMBO Rep 5: 590-595, 2004. PMID 15133481
  38. Rizo J and Rosenmund C. Synaptic vesicle fusion. Nat Struct Mol Biol 15: 665-674, 2008. PMID 18618940
  39. Rothman JE. Lasker Basic Medical Research Award. The machinery and principles of vesicle transport in the cell. Nat Med 8: 1059-1062, 2002. PMID 12357232
  40. Sabbatini ME, Bi Y, Ji B, Ernst SA, and Williams JA. CCK activates RhoA and Rac1 differentially through Galpha13 and Galphaq in mouse pancreatic acini. Am J Physiol Cell Physiol 298: C592-601, 2010. PMID 19940064
  41. Saluja AK, Donovan EA, Yamanaka K, Yamaguchi Y, Hofbauer B, and Steer ML. Cerulein-induced in vitro activation of trypsinogen in rat pancreatic acini is mediated by cathepsin B. Gastroenterology 113: 304-310, 1997. PMID 9207291
  42. Scheele G, Adler G, and Kern H. Exocytosis occurs at the lateral plasma membrane of the pancreatic acinar cell during supramaximal secretagogue stimulation. Gastroenterology 92: 345-353, 1987. PMID 3792771
  43. Sherwood MW, Prior IA, Voronina SG, Barrow SL, Woodsmith JD, Gerasimenko OV, Petersen OH, and Tepikin AV. Activation of trypsinogen in large endocytic vacuoles of pancreatic acinar cells. Proc Natl Acad Sci U S A 104: 5674-5679, 2007. PMID 17363470
  44. Sudhof TC and Rizo J. Synaptic vesicle exocytosis. Cold Spring Harb Perspect Biol 3, 2011. PMID 22026965
  45. Sudhof TC and Rothman JE. Membrane fusion: grappling with SNARE and SM proteins. Science 323: 474-477, 2009. PMID 19164740
  46. Thorn P, Fogarty KE, and Parker I. Zymogen granule exocytosis is characterized by long fusion pore openings and preservation of vesicle lipid identity. Proc Natl Acad Sci U S A 101: 6774-6779, 2004. PMID 15090649
  47. Wade N, Bryant NJ, Connolly LM, Simpson RJ, Luzio JP, Piper RC, and James DE. Syntaxin 7 complexes with mouse Vps10p tail interactor 1b, syntaxin 6, vesicle-associated membrane protein (VAMP)8, and VAMP7 in b16 melanoma cells. J Biol Chem 276: 19820-19827, 2001. PMID 11278762
  48. Ward DM, Pevsner J, Scullion MA, Vaughn M, and Kaplan J. Syntaxin 7 and VAMP-7 are soluble N-ethylmaleimide-sensitive factor attachment protein receptors required for late endosome-lysosome and homotypic lysosome fusion in alveolar macrophages. Mol Biol Cell 11: 2327-2333, 2000. PMID 10888671
  49. Watanabe O, Baccino FM, Steer ML, and Meldolesi J. Supramaximal caerulein stimulation and ultrastructure of rat pancreatic acinar cell: early morphological changes during development of experimental pancreatitis. Am J Physiol 246: G457-467, 1984. PMID 6720895
  50. Weng N, Baumler MD, Thomas DD, Falkowski MA, Swayne LA, Braun JE, and Groblewski GE. Functional role of J domain of cysteine string protein in Ca2+-dependent secretion from acinar cells. Am J Physiol Gastrointest Liver Physiol 296: G1030-1039, 2009. PMID 19282376
  51. Williams JA. Receptor-mediated signal transduction pathways and the regulation of pancreatic acinar cell function. Curr Opin Gastroenterol 24: 573-579, 2008. PMID 19122497
  52. Williams JA, Chen X, and Sabbatini ME. Small G proteins as key regulators of pancreatic digestive enzyme secretion. Am J Physiol Endocrinol Metab 296: E405-414, 2009. PMID 19088252
  53. Yamasaki M, Masgrau R, Morgan AJ, Churchill GC, Patel S, Ashcroft SJ, and Galione A. Organelle selection determines agonist-specific Ca2+ signals in pancreatic acinar and beta cells. J Biol Chem 279: 7234-7240, 2004. PMID 14660554
AttachmentSize
Regulation of Physiologic and Pathophysiologic Exocytosis430.83 KB