TY - JOUR A1 - Beck, Katherina A1 - Ehmann, Nadine A1 - Andlauer, Till F. M. A1 - Ljaschenko, Dmitrij A1 - Strecker, Katrin A1 - Fischer, Matthias A1 - Kittel, Robert J. A1 - Raabe, Thomas T1 - Loss of the Coffin-Lowry syndrome-associated gene RSK2 alters ERK activity, synaptic function and axonal transport in Drosophila motoneurons JF - Disease Models & Mechanisms N2 - 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. KW - mrsk2 KO mouse KW - S6KII RSK KW - transmission KW - neuromuscular junction KW - synapse KW - MAPK signaling KW - axonal transport KW - motoneuron KW - RSK KW - Drosophila KW - mechanisms KW - plasticity KW - protein kinase KW - signal transduction pathway KW - mitochondrial transport KW - glutamate receptor Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145185 VL - 8 ER - TY - JOUR A1 - Ljaschenko, Dmitrij A1 - Ehmann, Nadine A1 - Kittel, Robert J. T1 - Hebbian Plasticity Guides Maturation of Glutamate Receptor Fields In Vivo JF - Cell Reports N2 - Synaptic plasticity shapes the development of functional neural circuits and provides a basis for cellular models of learning and memory. Hebbian plasticity describes an activity-dependent change in synaptic strength that is input-specific and depends on correlated pre- and postsynaptic activity. Although it is recognized that synaptic activity and synapse development are intimately linked, our mechanistic understanding of the coupling is far from complete. Using Channelrhodopsin-2 to evoke activity in vivo, we investigated synaptic plasticity at the glutamatergic Drosophila neuromuscular junction. Remarkably, correlated pre- and postsynaptic stimulation increased postsynaptic sensitivity by promoting synapse- specific recruitment of GluR-IIA-type glutamate receptor subunits into postsynaptic receptor fields. Conversely, GluR-IIA was rapidly removed from synapses whose activity failed to evoke substantial postsynaptic depolarization. Uniting these results with developmental GluR-IIA dynamics provides a comprehensive physiological concept of how Hebbian plasticity guides synaptic maturation and sparse transmitter release controls the stabilization of the molecular composition of individual synapses. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-128804 VL - 3 IS - 5 ER - TY - JOUR A1 - Scholz, Nicole A1 - Gehring, Jennifer A1 - Guan, Chonglin A1 - Ljaschenko, Dmitrij A1 - Fischer, Robin A1 - Lakshmanan, Vetrivel A1 - Kittel, Robert J. A1 - Langenhan, Tobias T1 - The adhesion GPCR Latrophilin/CIRL shapes mechanosensation JF - Cell Reports N2 - G-protein-coupled receptors (GPCRs) are typically regarded as chemosensors that control cellular states in response to soluble extracellular cues. However, the modality of stimuli recognized through adhesion GPCR (aGPCR), the second largest class of the GPCR superfamily, is unresolved. Our study characterizes the Drosophila aGPCR Latrophilin/dCirl, a prototype member of this enigmatic receptor class. We show that dCirl shapes the perception of tactile, proprioceptive, and auditory stimuli through chordotonal neurons, the principal mechanosensors of Drosophila. dCirl sensitizes these neurons for the detection of mechanical stimulation by amplifying their input-output function. Our results indicate that aGPCR may generally process and modulate the perception of mechanical signals, linking these important stimuli to the sensory canon of the GPCR superfamily. KW - \(\alpha\)-latrotoxin KW - chordotonal organs KW - Johnstons organ KW - ligand CD55 KW - hearing KW - binding KW - shear stress KW - protein-coupled receptors KW - drosophila larvae KW - domain Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148626 VL - 11 ER -