1
|
Hammel I, Meilijson I. The econobiology of pancreatic acinar cells granule inventory and the stealthy nano-machine behind it. Acta Histochem 2016; 118:194-202. [PMID: 26702787 DOI: 10.1016/j.acthis.2015.11.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 11/22/2015] [Accepted: 11/23/2015] [Indexed: 02/07/2023]
Abstract
The pancreatic gland secretes most of the enzymes and many other macromolecules needed for food digestion in the gastrointestinal tract. These molecules play an important role in digestion, host defense and lubrication. The secretion of pancreatic proteins ensures the availability of the correct mix of proteins when needed. This review describes model systems available for the study of the econobiology of secretory granule content. The secretory pancreatic molecules are stored in large dense-core secretory granules that may undergo either constitutive or evoked secretion, and constitute the granule inventory of the cell. It is proposed that the Golgi complex functions as a distribution center for secretory proteins in pancreatic acinar cells, packing the newly formed secretory molecules into maturing secretory granules, also known functionally as condensing vacuoles. Mathematical modelling brings forward a process underlying granule inventory maintenance at various physiological states of condensation and aggregation by homotypic fusion. These models suggest unique but simple mechanisms accountable for inventory buildup and size, as well as for the distribution of secretory molecules into different secretory pathways in pancreatic acinar cells.
Collapse
|
2
|
Hammel I, Meilijson I. Function Suggests Nano-Structure: Quantitative Structural Support for SNARE-Mediated Pore Formation. Neurotox Res 2015; 29:1-9. [PMID: 26407673 DOI: 10.1007/s12640-015-9559-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/22/2015] [Accepted: 08/24/2015] [Indexed: 10/23/2022]
Abstract
Granule secretory content is released in either basal or calcium-activated complete exocytosis mode. A vital element in these processes is the establishment of a fusion pore between the granule membrane and the plasma membrane, initiated by the formation of a circular rosette docking arrangement of SNARE protein complexes. The controversially disputed number of SNARE complexes needed for granule priming leading to the formation of the fusion pore, is granule-size dependent and varies between secretion modes. Resorting to a statistical mechanics approach that views SNARE complexes and Ca(2+) ions as interacting particles, we have developed a relationship that links secretion rate to SNARE rosette size, Ca(2+) concentration and Ca(2+) ion cooperativity. Data are presented and discussed which suggest this SNARE-dependent generalization of existing narrow-range biophysical models that correlate secretion rate with Ca(2+) concentration and maximal Ca(2+) ion cooperativity. Evidence from dozens of examples in the literature advocate for this relation, which holds through the entire biological range. The coalescence of so many areas of diverse research methodologies has greatly augmented our understanding of so many different sequences of granule life cycle. Accordingly, these new tools may become valuable in a variety of electrophysiological experiments.
Collapse
Affiliation(s)
- Ilan Hammel
- Department of Pathology, Sackler Faculty of Medicine, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Isaac Meilijson
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Mathematical Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
| |
Collapse
|
3
|
Azouz NP, Zur N, Efergan A, Ohbayashi N, Fukuda M, Amihai D, Hammel I, Rothenberg ME, Sagi-Eisenberg R. Rab5 Is a Novel Regulator of Mast Cell Secretory Granules: Impact on Size, Cargo, and Exocytosis. THE JOURNAL OF IMMUNOLOGY 2014; 192:4043-53. [DOI: 10.4049/jimmunol.1302196] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
4
|
Hammel I, Meilijson I. The stealthy nano-machine behind mast cell granule size distribution. Mol Immunol 2014; 63:45-54. [PMID: 24629227 DOI: 10.1016/j.molimm.2014.02.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Revised: 01/15/2014] [Accepted: 02/01/2014] [Indexed: 02/01/2023]
Abstract
The classical model of mast cell secretory granule formation suggests that newly synthesized secretory mediators, transported from the rough endoplasmic reticulum to the Golgi complex, undergo post-transitional modification and are packaged for secretion by condensation within membrane-bound granules of unit size. These unit granules may fuse with other granules to form larger granules that reside in the cytoplasm until secreted. A novel stochastic model for mast cell granule growth and elimination (G&E) as well as inventory management is presented. Resorting to a statistical mechanics approach in which SNAP (Soluble NSF Attachment Protein) REceptor (SNARE) components are viewed as interacting particles, the G&E model provides a simple 'nano-machine' of SNARE self-aggregation that can perform granule growth and secretion. Granule stock is maintained as a buffer to meet uncertainty in demand by the extracellular environment and to serve as source of supply during the lead time to produce granules of adaptive content. Experimental work, mathematical calculations, statistical modeling and a rationale for the emergence of nearly last-in, first out inventory management, are discussed.
Collapse
Affiliation(s)
- Ilan Hammel
- Sackler Faculty of Medicine, Department of Pathology, Tel Aviv University, Tel Aviv 6997801, Israel.
| | - Isaac Meilijson
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Mathematical Sciences, Department of Statistics and Operations Research, Tel Aviv University, Tel Aviv 6997801, Israel.
| |
Collapse
|
5
|
Křepelová-DROR M, Hammel I, Meilijson I. Statistical analysis of the quantal basis of secretory granule formation. Microsc Res Tech 2013; 77:1-10. [DOI: 10.1002/jemt.22305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 10/09/2013] [Accepted: 10/14/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Marika Křepelová-DROR
- Department of Econometrics; Faculty of Informatics and Statistics, University of Economics; Nám. W. Churchilla 4, 13067 Praha 3 Czech Republic
| | - Ilan Hammel
- Department of Pathology; Sackler Faculty of Medicine; Tel Aviv University. Tel Aviv 6997801; Israel
| | - Isaac Meilijson
- School of Mathematical Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University; Tel Aviv 6997801 Israel
| |
Collapse
|
6
|
Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
Collapse
Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| |
Collapse
|