Regulation of granule size in human and horse eosinophils by number of fusion events among unit granules.
Abstract: 1. We have investigated the granule size distributions in human and horse eosinophils by time-resolved patch-clamp capacitance measurements. 2. During exocytosis of single granules the electrical capacitance of the plasma membrane increases in discrete steps. The steps in horse cells are about six times larger than those in human cells in accordance with the difference in granule size. 3. In both species a multimodal capacitance step size distribution is observed with a first peak at 6-7 fF corresponding to granules with a diameter of about 450-500 nm and a surface area of about 0.7 microns2, which we call the unit granule. The other peaks in the distributions correspond to multiples of the surface area of these units. 4. These results show that the larger granules are formed by fusion of several unit granules and the final size of mature granules is determined by the number of units allowed to fuse with each other. Whereas in human eosinophils most granules consist of one or two units, most granules of horse eosinophils are formed by fusion of seven to fifteen units. 5. The intracellular fusion events associated with vesicular traffic are believed to occur constitutively. In contrast, our results indicate that a cellular mechanism exists which regulates the size of the mature granules by determining the number of units allowed to fuse with each other. In view of our recent report that granule-granule fusion can be activated by GTP gamma S, this regulation may possibly involve GTP-binding proteins.
Publication Date: 1995-02-15 PubMed ID: 7776232PubMed Central: PMC1157882DOI: 10.1113/jphysiol.1995.sp020578Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article explores how the granule size in human and horse eosinophils is determined by fusion events amongst unit granules. The study finds that the final size of mature granules is established by the number of unit granules permitted to merge, with a cellular mechanism existence that regulates this process potentially involving GTP-binding proteins.
Research Method
- The researchers used time-resolved patch-clamp capacitance measurements to study granule size distributions in human and horse eosinophils. This technique is a method of studying the activity of single or multiple ion channels in cells.
- They observed the process of exocytosis, where cells release certain molecules by enclosing them in vesicles and fusing the vesicle membrane with the plasma membrane. This process increases the electrical capacitance of the plasma membrane in discrete steps.
- The study noted different step sizes between horse cells and human cells, reflecting the difference in granule sizes between the two species.
Findings
- The research found a multimodal capacitance step size distribution in both species. The first peak at 6-7 femtofarads, corresponding to granules with a diameter of 450-500 nm and a surface area of 0.7 micrometers squared, was identified as the unit granule size.
- The larger granules were formed by the fusion of several unit-sized granules. The final mature granule size was determined by the number of unit granules that were allowed to fuse together.
- Horse eosinophils tend to have granules formed by the fusion of seven to fifteen unit granules while in human eosinophils, most granules consist of one or two unit granules.
Implications
- The findings suggest the existence of a cellular mechanism that regulates the size of the mature granule by determining how many unit granules can fuse with each other.
- Based on a recent report that granule-granule fusion can be activated by GTP gamma S, the regulation of granule size may involve GTP-binding proteins. If further research confirms this, it could provide new insights into the regulation and function of granule fusion in eosinophils.
Cite This Article
APA
Hartmann J, Scepek S, Lindau M.
(1995).
Regulation of granule size in human and horse eosinophils by number of fusion events among unit granules.
J Physiol, 483 ( Pt 1)(Pt 1), 201-209.
https://doi.org/10.1113/jphysiol.1995.sp020578 Publication
Researcher Affiliations
- Abteilung Molekulare Zellforschung, Max-Planck-Institut für medizinische Forschung, Heidelberg, Germany.
MeSH Terms
- Animals
- Cell Membrane / physiology
- Cytoplasmic Granules / physiology
- Cytoplasmic Granules / ultrastructure
- Electric Conductivity
- Eosinophils / physiology
- Eosinophils / ultrastructure
- Exocytosis / physiology
- GTP-Binding Proteins / physiology
- Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
- Horses / blood
- Humans
- Membrane Fusion / physiology
- Patch-Clamp Techniques
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This article includes 24 references
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Citations
This article has been cited 8 times.- Ming M, Schirra C, Becherer U, Stevens DR, Rettig J. Behavior and Properties of Mature Lytic Granules at the Immunological Synapse of Human Cytotoxic T Lymphocytes. PLoS One 2015;10(8):e0135994.
- Doyle AD, Jacobsen EA, Ochkur SI, McGarry MP, Shim KG, Nguyen DT, Protheroe C, Colbert D, Kloeber J, Neely J, Shim KP, Dyer KD, Rosenberg HF, Lee JJ, Lee NA. Expression of the secondary granule proteins major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX) is required for eosinophilopoiesis in mice. Blood 2013 Aug 1;122(5):781-90.
- Hammel I, Meilijson I. Function suggests nano-structure: electrophysiology supports that granule membranes play dice. J R Soc Interface 2012 Oct 7;9(75):2516-26.
- Hammel I, Lagunoff D, Galli SJ. Regulation of secretory granule size by the precise generation and fusion of unit granules. J Cell Mol Med 2010 Jul;14(7):1904-16.
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