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Two modes of exocytosis at hippocampal synapses revealed by rate of FM1-43 efflux from individual vesicles.

Richards DA, Bai J, Chapman ER - J. Cell Biol. (2005)

Bottom Line: We have examined the kinetics by which FM1-43 escapes from individual synaptic vesicles during exocytosis at hippocampal boutons.These populations of destaining events are distinct in both brightness and kinetics, suggesting that they result from two distinct modes of exocytosis.Small amplitude events show tightly clustered rate constants of dye release, whereas larger events have a more scattered distribution.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Wisconsin-Madison, Madison, WI 53706, USA.

ABSTRACT
We have examined the kinetics by which FM1-43 escapes from individual synaptic vesicles during exocytosis at hippocampal boutons. Two populations of exocytic events were observed; small amplitude events that lose dye slowly, which made up more than half of all events, and faster, larger amplitude events with a fluorescence intensity equivalent to single stained synaptic vesicles. These populations of destaining events are distinct in both brightness and kinetics, suggesting that they result from two distinct modes of exocytosis. Small amplitude events show tightly clustered rate constants of dye release, whereas larger events have a more scattered distribution. Kinetic analysis of the association and dissociation of FM1-43 with membranes, in combination with a simple pore permeation model, indicates that the small, slowly destaining events may be mediated by a narrow approximately 1-nm fusion pore.

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The distribution of fluorescence steps reveals two populations of events. (A and B) Two separate sets (batches of cultures, four to six coverslips each) of pooled events analyzed for the extent of fluorescence decline in individual steps. A similar distribution is seen in each case. (C) The events of smaller amplitude (<14 units) are linear on a semi-log plot, indicating that they can be described by a single exponential distribution. Closed circles are data from A, open circles are data from B. (D) Larger amplitude events (>14 units) show a normal distribution with a peak around 16 units. Closed circles are data from A, open circles are data from B.
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fig3: The distribution of fluorescence steps reveals two populations of events. (A and B) Two separate sets (batches of cultures, four to six coverslips each) of pooled events analyzed for the extent of fluorescence decline in individual steps. A similar distribution is seen in each case. (C) The events of smaller amplitude (<14 units) are linear on a semi-log plot, indicating that they can be described by a single exponential distribution. Closed circles are data from A, open circles are data from B. (D) Larger amplitude events (>14 units) show a normal distribution with a peak around 16 units. Closed circles are data from A, open circles are data from B.

Mentions: To provide an illustration of the lack of variability between preparations, we plotted frequency histograms of step amplitudes from two separate batches of cultures in Fig. 3 (A and B). In each case there are many events declining exponentially in frequency as they increase in amplitude. In addition to these small events, there is an additional component of larger events with amplitudes corresponding to the estimated single vesicle fluorescence.


Two modes of exocytosis at hippocampal synapses revealed by rate of FM1-43 efflux from individual vesicles.

Richards DA, Bai J, Chapman ER - J. Cell Biol. (2005)

The distribution of fluorescence steps reveals two populations of events. (A and B) Two separate sets (batches of cultures, four to six coverslips each) of pooled events analyzed for the extent of fluorescence decline in individual steps. A similar distribution is seen in each case. (C) The events of smaller amplitude (<14 units) are linear on a semi-log plot, indicating that they can be described by a single exponential distribution. Closed circles are data from A, open circles are data from B. (D) Larger amplitude events (>14 units) show a normal distribution with a peak around 16 units. Closed circles are data from A, open circles are data from B.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171786&req=5

fig3: The distribution of fluorescence steps reveals two populations of events. (A and B) Two separate sets (batches of cultures, four to six coverslips each) of pooled events analyzed for the extent of fluorescence decline in individual steps. A similar distribution is seen in each case. (C) The events of smaller amplitude (<14 units) are linear on a semi-log plot, indicating that they can be described by a single exponential distribution. Closed circles are data from A, open circles are data from B. (D) Larger amplitude events (>14 units) show a normal distribution with a peak around 16 units. Closed circles are data from A, open circles are data from B.
Mentions: To provide an illustration of the lack of variability between preparations, we plotted frequency histograms of step amplitudes from two separate batches of cultures in Fig. 3 (A and B). In each case there are many events declining exponentially in frequency as they increase in amplitude. In addition to these small events, there is an additional component of larger events with amplitudes corresponding to the estimated single vesicle fluorescence.

Bottom Line: We have examined the kinetics by which FM1-43 escapes from individual synaptic vesicles during exocytosis at hippocampal boutons.These populations of destaining events are distinct in both brightness and kinetics, suggesting that they result from two distinct modes of exocytosis.Small amplitude events show tightly clustered rate constants of dye release, whereas larger events have a more scattered distribution.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Wisconsin-Madison, Madison, WI 53706, USA.

ABSTRACT
We have examined the kinetics by which FM1-43 escapes from individual synaptic vesicles during exocytosis at hippocampal boutons. Two populations of exocytic events were observed; small amplitude events that lose dye slowly, which made up more than half of all events, and faster, larger amplitude events with a fluorescence intensity equivalent to single stained synaptic vesicles. These populations of destaining events are distinct in both brightness and kinetics, suggesting that they result from two distinct modes of exocytosis. Small amplitude events show tightly clustered rate constants of dye release, whereas larger events have a more scattered distribution. Kinetic analysis of the association and dissociation of FM1-43 with membranes, in combination with a simple pore permeation model, indicates that the small, slowly destaining events may be mediated by a narrow approximately 1-nm fusion pore.

Show MeSH
Related in: MedlinePlus