14898
2015
eng
29
9
article
1
2017-05-22
--
--
Bruchpilot and Synaptotagmin collaborate to drive rapid glutamate release and active zone differentiation
The active zone (AZ) protein Bruchpilot (Brp) is essential for rapid glutamate release at Drosophila melanogaster neuromuscular junctions (NMJs). Quantal time course and measurements of action potential-waveform suggest that presynaptic fusion mechanisms are altered in brp null mutants (brp\(^{69}\)). This could account for their increased evoked excitatory postsynaptic current (EPSC) delay and rise time (by about 1 ms). To test the mechanism of release protraction at brp\(^{69}\) AZs, we performed knock-down of Synaptotagmin-1 (Syt) via RNAi (syt\(^{KD}\)) in wildtype (wt), brp\(^{69}\) and rab3 null mutants (rab3\(^{rup}\)), where Brp is concentrated at a small number of AZs. At wt and rab3\(^{rup}\) synapses, syt\(^{KD}\) lowered EPSC amplitude while increasing rise time and delay, consistent with the role of Syt as a release sensor. In contrast, syt\(^{KD}\) did not alter EPSC amplitude at brp\(^{69}\) synapses, but shortened delay and rise time. In fact, following syt\(^{KD}\), these kinetic properties were strikingly similar in wt and brp\(^{69}\), which supports the notion that Syt protracts release at brp\(^{69}\) synapses. To gain insight into this surprising role of Syt at brp\(^{69}\) AZs, we analyzed the structural and functional differentiation of synaptic boutons at the NMJ. At tonic type Ib motor neurons, distal boutons contain more AZs, more Brp proteins per AZ and show elevated and accelerated glutamate release compared to proximal boutons. The functional differentiation between proximal and distal boutons is Brp-dependent and reduced after syt\(^{KD}\). Notably, syt\(^{KD}\) boutons are smaller, contain fewer Brp positive AZs and these are of similar number in proximal and distal boutons. In addition, super-resolution imaging via dSTORM revealed that syt\(^{KD}\) increases the number and alters the spatial distribution of Brp molecules at AZs, while the gradient of Brp proteins per AZ is diminished. In summary, these data demonstrate that normal structural and functional differentiation of Drosophila AZs requires concerted action of Brp and Syt.
Frontiers in Cellular Neuroscience
10.3389/fncel.2015.00029
urn:nbn:de:bvb:20-opus-148988
Frontiers in Cellular Neuroscience 9:29 (2015). DOI: 10.3389/fncel.2015.00029
CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International
Mila M. Paul
Martin Pauli
Nadine Ehmann
Stefan Hallermann
Markus Sauer
Robert J. Kittel
Manfred Heckmann
eng
uncontrolled
neuromuscular junction
eng
uncontrolled
Bruchpilot
eng
uncontrolled
synaptic delay
eng
uncontrolled
dSTORM
eng
uncontrolled
synaptotagmin
eng
uncontrolled
presynaptic differentiation
eng
uncontrolled
neurotransmitter release
eng
uncontrolled
active zone
eng
uncontrolled
synaptic transmission
eng
uncontrolled
fluorescent probes
Medizin und Gesundheit
open_access
Physiologisches Institut
Theodor-Boveri-Institut für Biowissenschaften
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/14898/052_Paul_Frontiers_in_Cellular_Neuroscience.pdf
14518
2015
eng
1389-1400
8
article
1
2017-03-02
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Loss of the Coffin-Lowry syndrome-associated gene RSK2 alters ERK activity, synaptic function and axonal transport in Drosophila motoneurons
Plastic changes in synaptic properties are considered as fundamental for adaptive behaviors. Extracellular-signal-regulated kinase (ERK)-mediated signaling has been implicated in regulation of synaptic plasticity. Ribosomal S6 kinase 2 (RSK2) acts as a regulator and downstream effector of ERK. In the brain, RSK2 is predominantly expressed in regions required for learning and memory. Loss-of-function mutations in human RSK2 cause Coffin-Lowry syndrome, which is characterized by severe mental retardation and low IQ scores in affected males. Knockout of RSK2 in mice or the RSK ortholog in Drosophila results in a variety of learning and memory defects. However, overall brain structure in these animals is not affected, leaving open the question of the pathophysiological consequences. Using the fly neuromuscular system as a model for excitatory glutamatergic synapses, we show that removal of RSK function causes distinct defects in motoneurons and at the neuromuscular junction. Based on histochemical and electrophysiological analyses, we conclude that RSK is required for normal synaptic morphology and function. Furthermore, loss of RSK function interferes with ERK signaling at different levels. Elevated ERK activity was evident in the somata of motoneurons, whereas decreased ERK activity was observed in axons and the presynapse. In addition, we uncovered a novel function of RSK in anterograde axonal transport. Our results emphasize the importance of fine-tuning ERK activity in neuronal processes underlying higher brain functions. In this context, RSK acts as a modulator of ERK signaling.
Disease Models & Mechanisms
10.1242/dmm.021246
urn:nbn:de:bvb:20-opus-145185
Disease Models & Mechanisms (2015) 8, 1389-1400. DOI: 10.1242/dmm.021246
Katherina Beck
Nadine Ehmann
Till F. M. Andlauer
Dmitrij Ljaschenko
Katrin Strecker
Matthias Fischer
Robert J. Kittel
Thomas Raabe
eng
uncontrolled
mrsk2 KO mouse
eng
uncontrolled
S6KII RSK
eng
uncontrolled
transmission
eng
uncontrolled
neuromuscular junction
eng
uncontrolled
synapse
eng
uncontrolled
MAPK signaling
eng
uncontrolled
axonal transport
eng
uncontrolled
motoneuron
eng
uncontrolled
RSK
eng
uncontrolled
Drosophila
eng
uncontrolled
mechanisms
eng
uncontrolled
plasticity
eng
uncontrolled
protein kinase
eng
uncontrolled
signal transduction pathway
eng
uncontrolled
mitochondrial transport
eng
uncontrolled
glutamate receptor
Medizin und Gesundheit
open_access
Physiologisches Institut
Institut für Medizinische Strahlenkunde und Zellforschung
Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie
Rudolf-Virchow-Zentrum
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/14518/095_Beck_Disease_Models_Mechanisms.pdf
14899
2015
eng
7
9
article
1
2017-05-22
--
--
Super-resolution microscopy of the synaptic active zone
Brain function relies on accurate information transfer at chemical synapses. At the presynaptic active zone (AZ) a variety of specialized proteins are assembled to complex architectures, which set the basis for speed, precision and plasticity of synaptic transmission. Calcium channels are pivotal for the initiation of excitation-secretion coupling and, correspondingly, capture a central position at the AZ. Combining quantitative functional studies with modeling approaches has provided predictions of channel properties, numbers and even positions on the nanometer scale. However, elucidating the nanoscopic organization of the surrounding protein network requires direct ultrastructural access. Without this information, knowledge of molecular synaptic structure-function relationships remains incomplete. Recently, super-resolution microscopy (SRM) techniques have begun to enter the neurosciences. These approaches combine high spatial resolution with the molecular specificity of fluorescence microscopy. Here, we discuss how SRM can be used to obtain information on the organization of AZ proteins
Frontiers in Cellular Neuroscience
10.3389/fncel.2015.00007
urn:nbn:de:bvb:20-opus-148997
Frontiers in Cellular Neuroscience 9:7 (2015). DOI: 10.3389/fncel.2015.00007
CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International
Nadine Ehmann
Markus Sauer
Robert J. Kittel
eng
uncontrolled
excitation-secretion coupling
eng
uncontrolled
Ca\(^{2+}\) channels
eng
uncontrolled
structure-function relationships
eng
uncontrolled
super-resolution microscopy
eng
uncontrolled
active zone
eng
uncontrolled
presynaptic calcium
eng
uncontrolled
neurotransmitter release
Medizin und Gesundheit
open_access
Physiologisches Institut
Theodor-Boveri-Institut für Biowissenschaften
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/14899/053_Ehmann_Frontiers_in_Cellular_Neuroscience.pdf