TY - JOUR A1 - Schmitt, Dominique A1 - Funk, Natalia A1 - Blum, Robert A1 - Asan, Esther A1 - Andersen, Lill A1 - Rülicke, Thomas A1 - Sendtner, Michael A1 - Buchner, Erich T1 - Initial characterization of a Syap1 knock-out mouse and distribution of Syap1 in mouse brain and cultured motoneurons JF - Histochemistry and Cell Biology N2 - Synapse-associated protein 1 (Syap1/BSTA) is the mammalian homologue of Sap47 (synapse-associated protein of 47 kDa) in Drosophila. Sap47 null mutant larvae show reduced short-term synaptic plasticity and a defect in associative behavioral plasticity. In cultured adipocytes, Syap1 functions as part of a complex that phosphorylates protein kinase B alpha/Akt1 (Akt1) at Ser\(^{473}\) and promotes differentiation. The role of Syap1 in the vertebrate nervous system is unknown. Here, we generated a Syap1 knock-out mouse and show that lack of Syap1 is compatible with viability and fertility. Adult knock-out mice show no overt defects in brain morphology. In wild-type brain, Syap1 is found widely distributed in synaptic neuropil, notably in regions rich in glutamatergic synapses, but also in perinuclear structures associated with the Golgi apparatus of specific groups of neuronal cell bodies. In cultured motoneurons, Syap1 is located in axons and growth cones and is enriched in a perinuclear region partially overlapping with Golgi markers. We studied in detail the influence of Syap1 knockdown and knockout on structure and development of these cells. Importantly, Syap1 knockout does not affect motoneuron survival or axon growth. Unexpectedly, neither knockdown nor knockout of Syap1 in cultured motoneurons is associated with reduced Ser\(^{473}\) or Thr\(^{308}\) phosphorylation of Akt. Our findings demonstrate a widespread expression of Syap1 in the mouse central nervous system with regionally specific distribution patterns as illustrated in particular for olfactory bulb, hippocampus, and cerebellum. KW - Protein kinase B KW - Spinal Muscular-arthropy KW - Rictor-mTOR complex KW - Neurotrophic factors KW - Plasma-membrane KW - Axon growth KW - SAP47 gene KW - Phosphorylation KW - Drosophilia KW - Cells KW - BSTA KW - Viability KW - Brain KW - Syap1 localization KW - Glutamatergic synapses KW - PKB/Akt phosphorylation Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187258 VL - 146 IS - 4 ER - TY - JOUR A1 - Maass, Anne A1 - Düzel, Sandra A1 - Brigadski, Tanja A1 - Goerke, Monique A1 - Becke, Andreas A1 - Sobieray, Uwe A1 - Neumann, Katja A1 - Lövdén, Martin A1 - Lindenberger, Ulman A1 - Bäckman, Lars A1 - Braun-Dullaeus, Rüdiger A1 - Ahrens, Dörte A1 - Heinze, Hans-Jochen A1 - Müller, Notger G. A1 - Lessmann, Volkmar A1 - Sendtner, Michael A1 - Düzel, Emrah T1 - Relationships of peripheral IGF-1, VEGF and BDNF levels to exercise-related changes in memory, hippocampal perfusion and volumes in older adults JF - NeuroImage N2 - Animal models point towards a key role of brain-derived neurotrophic factor (BDNF), insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) in mediating exercise-induced structural and functional changes in the hippocampus. Recently, also platelet derived growth factor-C (PDGF-C) has been shown to promote blood vessel growth and neuronal survival. Moreover, reductions of these neurotrophic and angiogenic factors in old age have been related to hippocampal atrophy, decreased vascularization and cognitive decline. In a 3-month aerobic exercise study, forty healthy older humans (60 to 77 years) were pseudo-randomly assigned to either an aerobic exercise group (indoor treadmill, n = 21) or to a control group (indoor progressive-muscle relaxation/stretching, n = 19). As reported recently, we found evidence for fitness-related perfusion changes of the aged human hippocampus that were closely linked to changes in episodic memory function. Here, we test whether peripheral levels of BDNF, IGF-I, VEGF or PDGF-C are related to changes in hippocampal blood flow, volume and memory performance. Growth factor levels were not significantly affected by exercise, and their changes were not related to changes in fitness or perfusion. However, changes in IGF-I levels were positively correlated with hippocampal volume changes (derived by manual volumetry and voxel-based morphometry) and late verbal recall performance, a relationship that seemed to be independent of fitness, perfusion or their changes over time. These preliminary findings link IGF-I levels to hippocampal volume changes and putatively hippocampus-dependent memory changes that seem to occur over time independently of exercise. We discuss methodological shortcomings of our study and potential differences in the temporal dynamics of how IGF-1, VEGF and BDNF may be affected by exercise and to what extent these differences may have led to the negative findings reported here. KW - Exercise KW - Neurotrophic factors KW - Hippocampus KW - Vascular plasticity KW - Aging Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189219 VL - 131 ER - TY - JOUR A1 - Simon, Christian M. A1 - Rauskolb, Stefanie A1 - Gunnersen, Jennifer M. A1 - Holtmann, Bettina A1 - Drepper, Carsten A1 - Dombert, Benjamin A1 - Braga, Massimiliano A1 - Wiese, Stefan A1 - Jablonka, Sibylle A1 - Pühringer, Dirk A1 - Zielasek, Jürgen A1 - Hoeflich, Andreas A1 - Silani, Vincenzo A1 - Wolf, Eckhard A1 - Kneitz, Susanne A1 - Sommer, Claudia A1 - Toyka, Klaus V. A1 - Sendtner, Michael T1 - Dysregulated IGFBP5 expression causes axon degeneration and motoneuron loss in diabetic neuropathy JF - Acta Neuropathologica N2 - Diabetic neuropathy (DNP), afflicting sensory and motor nerve fibers, is a major complication in diabetes.The underlying cellular mechanisms of axon degeneration are poorly understood. IGFBP5, an inhibitory binding protein for insulin-like growth factor 1 (IGF1) is highly up-regulated in nerve biopsies of patients with DNP. We investigated the pathogenic relevance of this finding in transgenic mice overexpressing IGFBP5 in motor axons and sensory nerve fibers. These mice develop motor axonopathy and sensory deficits similar to those seen in DNP. Motor axon degeneration was also observed in mice in which the IGF1 receptor(IGF1R) was conditionally depleted in motoneurons, indicating that reduced activity of IGF1 on IGF1R in motoneurons is responsible for the observed effect. These data provide evidence that elevated expression of IGFBP5 in diabetic nerves reduces the availability of IGF1 for IGF1R on motor axons, thus leading to progressive neurodegeneration. Inhibition of IGFBP5 could thus offer novel treatment strategies for DNP. KW - Motor nerve biopsy KW - Diabetic polyneuropathy KW - Neuropathy KW - Neurotrophic factors KW - Axonal degeneration Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-154569 VL - 130 SP - 373 EP - 387 ER -