complexin binds to the H3 domain of syntaxin 1

S10.5

DIRECT BINDING

133 ATSUKO

HONDA,

Department

HIDE0

OF SYNAPTOTAGMIN

SAISU, TERUO ABE

of Cellular Neurobiology,

Synaptotagmin

Brain Research Institute,

proteins

When

tubulin

immobilized

the fusion

I, Nilgata 95 l-8585

Asahimachi

significant

To determine

on Cal-

of glutathione

was Incubated

Purified tubulins

in the bound material

nitrocellulosefilters

vesicle protein

protem

on glutathione-Sepharose

was dependent

were incubated

,S-transferase

with the soluble

(GST)-the

fraction

lacking MAPS and tau proteins

which of the two tubulin subunits

cytoplasmic

bmds tagmin, purified tubulins

with a Triton X-100 extract of brain membranes.

SYNAPHINiCOMPLEXIN

ABE.

Department

HIDE0

(also called complexin)

SNAP-25

and VAMP (synaptobrevm) release

IS

However,

Brain Research Institute,

a cytosolic

Synaphin

for transmitter

l3-Tubulin but not rr-tubulin

domain was comparable

were inhibited

a- and l&SNAP

SNAP-25

protem associated

GST-syntaxm

This synergistic

wrth that to GST-entire

GST-entire

cytoplasmic

synaphin

binding to syntaxin

effect on syntaxin

Conversely,

binding between synaphin

Asahimachi

I, Niigata 95 l-8585

without

IA is sufficient VAMP

and VAhlP-2

of VAMP-2 portion

syntaxin. is required

We have exammed binding of

remains unclear

cytoplasmic

portion

of the 7s complex thought to be involved in the final phase of synaptic

135

showed

1

we have shown that the protein

IA in the presence

These results indicate that the H3 domain of svntaxm enhanced

on to

X-100 extract

with the 7s complex containing synaptotagmin.

its exact role in the release mechanisms

1 to immobilized

synaphin by

OF SYNT4XrN

Niigata University,

Using the squid presynapticterminal.

binding to GST-H3 synaphin

blotted

SAISU, TORU ISHlZlJKA

of Cellular Neurobiology,

histidine-tagged

BlNDS TO THE H3 DOMAIN

of tagmin

were only maJor The binding also bound to GST-tagmin

tagmin and tubulins were coimmunoprecipitated from theTriton against tubulin These results indicate that tagmm directly binds to l.-tubulin

antibody

134

portion

of rat brain. tubulins

tagmin binding. Furthermore,

with a monoclonal

TERUO

is a synaptic

Niigata University.

thought to be a major Caz+ sensor in transmitter release \~a its interaction with syntaxin and SNAP-25 Moreover, it binds other proteins including neurexins and the clathrrn .AP-2. We have found tagmm binds to the cytoskelrtal suggesting that the protein is also involved in other presynapticfunctions protein

I (tagmm)

TO TUBULIN

and SNAP-25

of syntaxin

Synaphin

I A Both bindmgs

the H3 domain was incapable of bindmg for synaphin

bmdmg to syntaxm

binding

suggests that svnaphin

but not

facilitates the formation

vesicle fusion with the presynaptic

TEMPOLARY-DISTINCT INDUCTION OF INITIAL AND LATE PHASES POTENTIATION IN BULLFROG SYMPATHETIC GANGLIA

VAMP-2

was enhanced by synaphin membrane

OF LONG-TERM

K. Fujita, H. Tokuno & K. Kuba’ First Dept. ofPhysiology’

Nagoya Univ. Sch. Med., Nagoya 466-8550. Japan

Fast excitatory postsynaptic potentials (fEPSP) were recorded by an intracellular recording technique in a low Ca:‘. high Mg” solution. The quanta1 content and size of fEPSP were analyzed by a failure or variance method. A short tetanus (50 pulses) of 50 Hz to the preganglionic nerve produced the enhancement of the amplitude and quanta1 content of fEPSP lasting for one to one and half hours. A longer tetanus (50 Hz) of 100 pulses induced two distinct phases of long-term potentiation (LTP). Following the initial potentiation of tEPSP and the subsequent period of no potentiation for 20 to 30 min, the amplitude of fEPSP increased again. This late phase of LTP was accompanied by increases in both quanta1 content and size, and lasted for more than 8 hours. Tetanus of 300 pulses at 50 Hz consistently caused both the initial and late phases of LTP, which were interrupted by a period of no potentiation. Thus, the initial phase of LTP are predominantly induced by an increase in transmitter release from the presynaptic nerve terminals, while the late phase is caused by both the pre- and post-synaptic mechanisms. The initial phase of LTP could be caused by the activation of Ca/calmodulin-dependent protein kinase II and subsequent protein phosphorylation (Minota et al., 1991, J. Physiol 435. 421-438) while the late phase appears to be produced a much slower process, such as protein synthesis