Only a fraction of quantal content is released during exocytosis as revealed by electrochemical cytometry of secretory vesicles

Donna M. Omiatek, Yan Dong, Michael L. Heien, Andrew G. Ewing

Research output: Contribution to journalArticlepeer-review

103 Scopus citations

Abstract

[Figure presented] The primary method for neuronal communication involves the release of chemical messengers that are packaged intracellularly in vesicles. Although experiments measuring release at single cells have classically been thought to assess the entire content of vesicles, there is evidence in the literature that suggests that the total transmitter stored in vesicles is not expelled during exocytosis. In this work, we introduce a novel technology using a microfluidic-based platform to electrochemically probe individual PC12 cell vesicles isolated from the cell environment. We measure the total vesicular content using methodology that circumvents the biophysical processes of the cell associated with exocytosis. Direct comparisons of amperometric data from release experiments at single PC12 cells versus our cell-free model reveal that on average vesicles release only 40% of their total transmitter load. The data support the intriguing hypothesis that the average vesicle does not open all the way during the normal exocytosis process, resulting in incomplete distention of the vesicular contents. In addition, we have shown that vesicular catecholamine levels can be altered with pharmacological manipulation and variances observed from these treatments can be resolved at the single vesicle level in a high-throughput manner, a process that we have termed electrochemical cytometry. Upon establishing that release in exocytotic processes proceeds in an incomplete manner, we related electrochemical data quantified from both single cell release experiments and electrochemical cytometry of vesicles to vesicular volume from electron microscopy measurements to investigate the location of intravesicular catecholamine stores retained postfusion.

Original languageEnglish (US)
Pages (from-to)234-245
Number of pages12
JournalACS Chemical Neuroscience
Volume1
Issue number3
DOIs
StatePublished - Mar 17 2010
Externally publishedYes

Keywords

  • Amperometry
  • Catecholamine
  • Electrochemical cytometry
  • Exocytosis
  • Partial release
  • Vesicle

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Cognitive Neuroscience
  • Cell Biology

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