0:00
My name is Stefan Hallermann.
I'm a professor at the
Carl-Ludwig-Institute of Physiology
at the University of
Leipzig in Germany.
You've selected the Henry
Stewart talk about vesicular
release of transmitter
at active zones.
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To communicate with
each other, neurons
can use chemical
synaptic transmission.
The enlargement shows a
schematic illustration
of an electron microscopic image
of such a chemical synapse.
Upon the arrival of
an action potential
in the presynaptic terminal
illustrated by the red arrow,
voltage-dependent calcium channels
open, and the influx of calcium
triggers the fusion
of transmitter-filled
synaptic vesicles.
As a consequence, the transmitter
illustrated by red triangles
diffuses through the synaptic cleft
to the postsynaptic receptors,
which finally elicits an electrical
signal in the postsynaptic cell.
The enlargement shows the double
lipid membrane of the vesicle
and the presynaptic plasma membrane.
The SNARE proteins, synaptobrevin,
SNAP-25, and syntaxin,
are involved in the fusion of these
two double lipid membranes, which
finally elicits the release
of neurotransmitter.
The binding of calcium
to the vesicular protein,
synaptotagmin, is involved
in triggering this fusion.
As shown in the enlargement
of a synaptic vesicle,
the protein composition
of the vesicle
is already quite well understood.
In contrast, the organization of the
proteins at the presynaptic plasma
membrane that built the active
zone is less well understood.
This protein network
is also referred to
as the cytomatrix
at the active zone.
In the here shown example
of a central synapse,
the cytomatrix appears as a
triangular, grid-like array.
The shape of the cytomatrix can
be very different depending on
on the type of synapse, as
shown in the next slide.
