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  - Niemann, Axel
A1  - Huber, Nina
A1  - Wagner, Konstanze M.
A1  - Somandin, Christian
A1  - Horn, Michael
A1  - Lebrun-Julien, Frédéric
A1  - Angst, Brigitte
A1  - Pereira, Jorge A.
A1  - Halfter, Hartmut
A1  - Welzl, Hans
A1  - Feltri, M. Laura
A1  - Wrabetz, Lawrence
A1  - Young, Peter
A1  - Wessig, Carsten
A1  - Toyka, Klaus V.
A1  - Suter, Ueli
T1  - The Gdap1 knockout mouse mechanistically links redox control to Charcot–Marie–Tooth disease
JF  - Brain
N2  - The ganglioside-induced differentiation-associated protein 1 (GDAP1) is a mitochondrial fission factor and mutations in GDAP1 cause Charcot–Marie–Tooth disease. We found that Gdap1 knockout mice (\(Gdap1^{−/−}\)), mimicking genetic alterations of patients suffering from severe forms of Charcot–Marie–Tooth disease, develop an age-related, hypomyelinating peripheral neuropathy. Ablation of Gdap1 expression in Schwann cells recapitulates this phenotype. Additionally, intra-axonal mitochondria of peripheral neurons are larger in \(Gdap1^{−/−}\) mice and mitochondrial transport is impaired in cultured sensory neurons of \(Gdap1^{−/−}\) mice compared with controls. These changes in mitochondrial morphology and dynamics also influence mitochondrial biogenesis. We demonstrate that mitochondrial DNA biogenesis and content is increased in the peripheral nervous system but not in the central nervous system of \(Gdap1^{−/−}\) mice compared with control littermates. In search for a molecular mechanism we turned to the paralogue of GDAP1, GDAP1L1, which is mainly expressed in the unaffected central nervous system. GDAP1L1 responds to elevated levels of oxidized glutathione by translocating from the cytosol to mitochondria, where it inserts into the mitochondrial outer membrane. This translocation is necessary to substitute for loss of GDAP1 expression. Accordingly, more GDAP1L1 was associated with mitochondria in the spinal cord of aged \(Gdap1^{−/−}\) mice compared with controls. Our findings demonstrate that Charcot–Marie–Tooth disease caused by mutations in GDAP1 leads to mild, persistent oxidative stress in the peripheral nervous system, which can be compensated by GDAP1L1 in the unaffected central nervous system. We conclude that members of the GDAP1 family are responsive and protective against stress associated with increased levels of oxidized glutathione.
KW  - animal models
KW  - Charcot-Marie-Tooth disease
KW  - mitochondria
KW  - axonal transport
KW  - demyelinating disease
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-120731
VL  - 137
IS  - 3
ER  -