TY - JOUR A1 - Deng, Chunchu A1 - Reinhard, Sebastian A1 - Hennlein, Luisa A1 - Eilts, Janna A1 - Sachs, Stefan A1 - Doose, Sören A1 - Jablonka, Sibylle A1 - Sauer, Markus A1 - Moradi, Mehri A1 - Sendtner, Michael T1 - Impaired dynamic interaction of axonal endoplasmic reticulum and ribosomes contributes to defective stimulus-response in spinal muscular atrophy JF - Translational Neurodegeneration N2 - Background: Axonal degeneration and defects in neuromuscular neurotransmission represent a pathological hallmark in spinal muscular atrophy (SMA) and other forms of motoneuron disease. These pathological changes do not only base on altered axonal and presynaptic architecture, but also on alterations in dynamic movements of organelles and subcellular structures that are not necessarily reflected by static histopathological changes. The dynamic interplay between the axonal endoplasmic reticulum (ER) and ribosomes is essential for stimulus-induced local translation in motor axons and presynaptic terminals. However, it remains enigmatic whether the ER and ribosome crosstalk is impaired in the presynaptic compartment of motoneurons with Smn (survival of motor neuron) deficiency that could contribute to axonopathy and presynaptic dysfunction in SMA. Methods: Using super-resolution microscopy, proximity ligation assay (PLA) and live imaging of cultured motoneurons from a mouse model of SMA, we investigated the dynamics of the axonal ER and ribosome distribution and activation. Results: We observed that the dynamic remodeling of ER was impaired in axon terminals of Smn-deficient motoneurons. In addition, in axon terminals of Smn-deficient motoneurons, ribosomes failed to respond to the brain-derived neurotrophic factor stimulation, and did not undergo rapid association with the axonal ER in response to extracellular stimuli. Conclusions: These findings implicate impaired dynamic interplay between the ribosomes and ER in axon terminals of motoneurons as a contributor to the pathophysiology of SMA and possibly also other motoneuron diseases. KW - spinal muscular atrophy KW - BDNF stimulation KW - dynamics of ribosomal assembly KW - presynaptic ER dynamics Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300649 SN - 2047-9158 VL - 11 IS - 1 ER - TY - JOUR A1 - Ghanawi, Hanaa A1 - Hennlein, Luisa A1 - Zare, Abdolhossein A1 - Bader, Jakob A1 - Salehi, Saeede A1 - Hornburg, Daniel A1 - Ji, Changhe A1 - Sivadasan, Rajeeve A1 - Drepper, Carsten A1 - Meissner, Felix A1 - Mann, Matthias A1 - Jablonka, Sibylle A1 - Briese, Michael A1 - Sendtner, Michael T1 - Loss of full-length hnRNP R isoform impairs DNA damage response in motoneurons by inhibiting Yb1 recruitment to chromatin JF - Nucleic Acids Research N2 - Neurons critically rely on the functions of RNA-binding proteins to maintain their polarity and resistance to neurotoxic stress. HnRNP R has a diverse range of post-transcriptional regulatory functions and is important for neuronal development by regulating axon growth. Hnrnpr pre-mRNA undergoes alternative splicing giving rise to a full-length protein and a shorter isoform lacking its N-terminal acidic domain. To investigate functions selectively associated with the full-length hnRNP R isoform, we generated a Hnrnpr knockout mouse (Hnrnpr\(^{tm1a/tm1a}\)) in which expression of full-length hnRNP R was abolished while production of the truncated hnRNP R isoform was retained. Motoneurons cultured from Hnrnpr\(^{tm1a/tm1a}\) mice did not show any axonal growth defects but exhibited enhanced accumulation of double-strand breaks and an impaired DNA damage response upon exposure to genotoxic agents. Proteomic analysis of the hnRNP R interactome revealed the multifunctional protein Yb1 as a top interactor. Yb1-depleted motoneurons were defective in DNA damage repair. We show that Yb1 is recruited to chromatin upon DNA damage where it interacts with gamma-H2AX, a mechanism that is dependent on full-length hnRNP R. Our findings thus suggest a novel role of hnRNP R in maintaining genomic integrity and highlight the function of its N-terminal acidic domain in this context. KW - nuclear ribonucleoprotein-R KW - determining gene-product KW - actin messenger RNA KW - comet assay KW - genome wide KW - spinal cord KW - YB-1 KW - SMN KW - interacts KW - enrichment Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265687 VL - 49 IS - 21 ER - TY - JOUR A1 - Ji, Changhe A1 - Bader, Jakob A1 - Ramanathan, Pradhipa A1 - Hennlein, Luisa A1 - Meissner, Felix A1 - Jablonka, Sibylle A1 - Mann, Matthias A1 - Fischer, Utz A1 - Sendtner, Michael A1 - Briese, Michael T1 - Interaction of 7SK with the Smn complex modulates snRNP production JF - Nature Communications N2 - Gene expression requires tight coordination of the molecular machineries that mediate transcription and splicing. While the interplay between transcription kinetics and spliceosome fidelity has been investigated before, less is known about mechanisms regulating the assembly of the spliceosomal machinery in response to transcription changes. Here, we report an association of the Smn complex, which mediates spliceosomal snRNP biogenesis, with the 7SK complex involved in transcriptional regulation. We found that Smn interacts with the 7SK core components Larp7 and Mepce and specifically associates with 7SK subcomplexes containing hnRNP R. The association between Smn and 7SK complexes is enhanced upon transcriptional inhibition leading to reduced production of snRNPs. Taken together, our findings reveal a functional association of Smn and 7SK complexes that is governed by global changes in transcription. Thus, in addition to its canonical nuclear role in transcriptional regulation, 7SK has cytosolic functions in fine-tuning spliceosome production according to transcriptional demand. KW - Molecular neuroscience KW - RNA KW - RNA splicing KW - Transcription Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259125 VL - 12 IS - 1 ER - TY - THES A1 - Hennlein, Luisa T1 - Plastin 3 rescues defective cell surface translocation and activation of TrkB in mouse models for spinal muscular atrophy T1 - Plastin 3 kompensiert die defekte Zelloberflächen-Translokation und Aktivierung von TrkB in Mausmodellen für spinale Muskelatrophie N2 - Spinal muscular atrophy (SMA) is a genetic pediatric condition that affects lower motoneurons leading to their degeneration and muscle weakness. It is caused by homozygous loss or mutations in the Survival Motor Neuron 1 (SMN1) gene; however, the pathomechanism leading to motoneuron degeneration is not fully resolved. Cultured embryonic SMA motoneurons display axon elongation and differentiation defects accompanied by collapsed growth cones with a disturbed actin cytoskeleton. Intriguingly, motoneurons cultured from mice deficient for the Tropomyosin-kinase receptor B (TrkB), exhibit similar pathological features. Thus, the question arises whether SMA motoneurons suffer from defective Brain-derived neurotrophic factor (BDNF)/TrkB signaling and whether there is a link to the disturbed actin cytoskeleton. In the recent years, modifier genes such as Plastin 3 (PLS3) were shown to beneficially interfere with SMA pathology. Nevertheless, the mechanism of how the actin-bundler PLS3 counteracts SMN deficiency is not well understood. In this study, we investigated TrkB localization and its activation in cultured SMA motoneurons and neuromuscular junctions (NMJs). While TrkB levels are only mildly affected locally in axon terminals, BDNF-mediated TrkB phosphorylation was massively disturbed. The activity-dependent TrkB translocation to the cell surface and its activation via BDNF were shown to be Pls3-dependent processes, that can be abolished by knockdown of Pls3. In contrast, PLS3 overexpression in SMA motoneurons rescued the defects on morphological and functional level. In particular, the relocation of TrkB to the cell surface after BDNF-induced internalization is disturbed in SMA, which is based on an actin-dependent TrkB translocation defect from intracellular stores. Lastly, AAV9-mediated PLS3 overexpression in vivo in neonatal SMA mice provided further evidence for the capacity of PLS3 to modulate actin dynamics necessary for accurate BDNF/TrkB signaling. In conclusion, we provide a novel role for PLS3 in mediating proper alignment of transmembrane proteins as prerequisite for their appropriate functioning. Hence, PLS3 is required for a key process indispensable for the development and function of motoneurons even beyond the context of SMA. N2 - Die spinale Muskelatrophie (SMA) ist eine Erkrankung der unteren Motoneurone, die zu deren Degeneration und Muskelschwund führt. Ausgelöst wird sie durch Verlust oder Mutation des Survival Motor Neuron 1 Gens. Kultivierte embryonale Motoneurone von SMA Mäusen zeigen eine veränderte zelluläre Differenzierung, sowie kollabierte Wachstumskegel und ein gestörtes Aktin Zytoskelett. Interessanterweise zeigen Motoneurone mit einem Verlust des Tropomyosinrezeptorkinase B (TrkB) die gleichen zellulären Dysregulationen. Daher stellte sich die Frage, ob SMA Motoneurone eine Störung der Brain-derived neurotrophic factor (BDNF)/TrkB Signalkaskade entwickeln, die auf einem gestörten Aktin Zytoskelett beruht. Studien der letzten Jahre haben gezeigt, dass modifizierende Gene wie Plastin 3 (PLS3) eine schützende Wirkung auf die SMA Pathophysiologie haben. Allerdings ist der genaue Mechanismus, inwieweit PLS3 F-Aktin-gesteuerte Prozesse reguliert nicht gut verstanden. In dieser Studie haben wir die Lokalisierung und Aktivierbarkeit von TrkB in Motoneuronen und Endplatten von SMA Mäusen untersucht. Obwohl die Lokalisierung von TrkB nur wenig verändert ist, war die Aktivierung von TrkB via BDNF in den Axonterminalen stark beeinträchtigt. Außerdem stellten sich die aktivitätsabhängige TrkB Translokation zur Plasmamembran, als auch dessen BNDF-induzierte Phosphorylierung als Pls3-abhängige Prozesse heraus, die durch Pls3 Knockdown inhibiert werden konnten. Im Gegensatz dazu, bewirkt die PLS3 Überexpression in SMA Motoneuronen eine Wiederherstellung der morphologischen und funktionellen Defekte. Vor allem die gestörte Re-Lokalisierung von TrkB an die Zellmembran nach BDNF-Stimulation, welches auf einer defekten Translokation aus intrazellulären Speichern basiert, konnte durch PLS3 Überexpression verbessert wird. Des Weiteren brachte die Viren-basierte PLS3 Überexpression in SMA Mäusen weitere Beweise für die Fähigkeit von PLS3, die Aktin Dynamik zu regulieren. Zusammenfassend zeigen die Daten eine neue Rolle von PLS3 für die korrekte Anordnung von Transmembranproteinen, als Grundvoraussetzung für deren Funktionalität. Somit wird PLS3 für Schlüsselprozesse benötigt, die für die Entwicklung und Funktion von Motoneuronen, auch über den Kontext von SMA hinaus, unverzichtbar sind. KW - Spinale Muskelatrophie KW - Brain-derived neurotrophic factor KW - Rezeptor-Tyrosinkinasen KW - Motoneuron-Krankheit KW - Zellskelett KW - Plastin 3 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-298793 PB - Journal of Cell Biology ER - TY - JOUR A1 - Tejero, Rocio A1 - Alsakkal, Mohammad A1 - Hennlein, Luisa A1 - Lopez-Cabello, Ana M. A1 - Jablonka, Sibylle A1 - Tabares, Lucia T1 - Nifedipine ameliorates cellular differentiation defects of Smn-deficient motor neurons and enhances neuromuscular transmission in SMA mice JF - International Journal of Molecular Sciences N2 - In spinal muscular atrophy (SMA), mutations in or loss of the Survival Motor Neuron 1 (SMN1) gene reduce full-length SMN protein levels, which leads to the degeneration of a percentage of motor neurons. In mouse models of SMA, the development and maintenance of spinal motor neurons and the neuromuscular junction (NMJ) function are altered. Since nifedipine is known to be neuroprotective and increases neurotransmission in nerve terminals, we investigated its effects on cultured spinal cord motor neurons and motor nerve terminals of control and SMA mice. We found that application of nifedipine increased the frequency of spontaneous Ca\(^{2+}\) transients, growth cone size, cluster-like formations of Cav2.2 channels, and it normalized axon extension in SMA neurons in culture. At the NMJ, nifedipine significantly increased evoked and spontaneous release at low-frequency stimulation in both genotypes. High-strength stimulation revealed that nifedipine increased the size of the readily releasable pool (RRP) of vesicles in control but not SMA mice. These findings provide experimental evidence about the ability of nifedipine to prevent the appearance of developmental defects in SMA embryonic motor neurons in culture and reveal to which extent nifedipine could still increase neurotransmission at the NMJ in SMA mice under different functional demands. KW - spinal muscular atrophy KW - motor neurons KW - synaptic transmission KW - neuromuscular junction KW - calcium channels KW - nifedipine KW - growth cone KW - axons KW - synaptic vesicles KW - postsynaptic potentials Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313636 SN - 1422-0067 VL - 24 IS - 8 ER -