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The EMBO journal1993; 12(5); 1811-1817; doi: 10.1002/j.1460-2075.1993.tb05829.x

Focal exocytosis by eosinophils–compound exocytosis and cumulative fusion.

Abstract: We have investigated the granule fusion events during exocytosis in horse eosinophils by time-resolved patch-clamp capacitance measurements. Stimulation with intracellular GTP gamma S leads to a stepwise capacitance increase by 4.0 +/- 0.9 pF. At GTP gamma S concentrations < 20 microM the step size distribution is in agreement with the granule size distribution in resting cells. Above 80 microM the number of steps is reduced and very large steps occur. The total capacitance increase, however, is unaffected. These results show that at high GTP gamma S concentrations granule--granule fusion occurs inside the cell forming large compound granules, which then fuse with the plasma membrane (compound exocytosis). The electrical equivalent circuit of the cell during degranulation indicates the formation of a degranulation sac by cumulative fusion events. Fusion of the first granule with the plasma membrane induces fusion of further granules with this granule directing the release of all the granular material to the first fusion pore. The physiological function of eosinophils is the killing of parasites. Compound exocytosis and cumulative fusion enable the cells to focus the release of cytotoxic proteins to well defined target regions and prevent uncontrolled diffusion of this material, which would damage intact host cells.
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Publication Date: 1993-05-01 PubMed ID: 8491174PubMed Central: PMC413400DOI: 10.1002/j.1460-2075.1993.tb05829.xGoogle Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article focuses on the process and role of exocytosis in horse eosinophils, a type of white blood cell. The find suggests that high concentrations of GTP gamma S invoke a form of granule fusion within the cell, leading to formation of large compound granules that merge with the plasma membrane in a process known as ‘compound exocytosis’. This focused release of cytotoxic proteins helps in combating parasites.

Investigation of Granule Fusion Events

  • The research was aimed to understand granule fusion events during exocytosis in horse eosinophils. The process was observed using time-resolved patch-clamp capacitance measurements.
  • Stimulation of eosinophils with intracellular GTP gamma S caused a stepwise increase in capacitance by approximately 4.0 ± 0.9 pF.
  • When GTP gamma S concentrations were less than 20 microM, the step size distribution corresponded with the granule size distribution in resting cells.

Granule Fusion in High GTP gamma S Concentrations

  • In situations where GTP gamma S concentrations exceeded 80 microM, the number of steps were reduced, while very large steps occurred.
  • Interestingly, the total capacitance increase remained unaffected in such conditions.
  • This observation indicated that higher GTP gamma S concentrations resulted in granule-granule fusion occurring within the cell, leading to the formation of large compound granules.
  • These large compound granules were then observed to fuse with the plasma membrane, a process termed ‘compound exocytosis’.

Formation of Degranulation Sac & Role of Eosinophils

  • The experiment further revealed that the cell’s electrical equivalent circuit during degranulation indicated the formation of a degranulation sac through cumulative fusion events.
  • This sequence suggests that the initial fusion of the first granule with the plasma membrane triggers the fusion of additional granules with the initial granule.
  • This mechanism leads to the release of all granular material to the first fusion pore.
  • Functionally, eosinophils are implicated in the elimination of parasites. Through compound exocytosis and cumulative fusion processes, these cells can focus the release of cytotoxic proteins in specific target areas.
  • This targeted release prevents unintentional diffusion of cytotoxic materials that could potentially harm intact host cells.

Cite This Article

APA
Scepek S, Lindau M. (1993). Focal exocytosis by eosinophils–compound exocytosis and cumulative fusion. EMBO J, 12(5), 1811-1817. https://doi.org/10.1002/j.1460-2075.1993.tb05829.x

Publication

The EMBO journal
ISSN: 0261-4189
NlmUniqueID: 8208664
Country: England
Language: English
Volume: 12
Issue: 5
Pages: 1811-1817

Researcher Affiliations

Scepek, S
  • Abteilung Molekulare Zellforschung, Max-Planck-Institut für medzinische Forschung, Heidelberg, Germany.
Lindau, M

    MeSH Terms

    • Animals
    • Cell Membrane / metabolism
    • Cytoplasmic Granules / metabolism
    • Eosinophils / cytology
    • Eosinophils / metabolism
    • Eosinophils / physiology
    • Exocytosis
    • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
    • Horses
    • In Vitro Techniques
    • Membrane Fusion
    • Membrane Potentials

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    Citations

    This article has been cited 37 times.
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