TY - JOUR A1 - Michalke, Bernhard A1 - Venkataramani, Vivek T1 - Editorial to the special issue “Homeostasis: metals and cellular redox and immunity status” JF - International Journal of Molecular Sciences N2 - No abstract available KW - homeostasis Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-311061 SN - 1422-0067 VL - 24 IS - 5 ER - TY - JOUR A1 - Mrestani, Achmed A1 - Pauli, Martin A1 - Kollmannsberger, Philip A1 - Repp, Felix A1 - Kittel, Robert J. A1 - Eilers, Jens A1 - Doose, Sören A1 - Sauer, Markus A1 - Sirén, Anna-Leena A1 - Heckmann, Manfred A1 - Paul, Mila M. T1 - Active zone compaction correlates with presynaptic homeostatic potentiation JF - Cell Reports N2 - Neurotransmitter release is stabilized by homeostatic plasticity. Presynaptic homeostatic potentiation (PHP) operates on timescales ranging from minute- to life-long adaptations and likely involves reorganization of presynaptic active zones (AZs). At Drosophila melanogaster neuromuscular junctions, earlier work ascribed AZ enlargement by incorporating more Bruchpilot (Brp) scaffold protein a role in PHP. We use localization microscopy (direct stochastic optical reconstruction microscopy [dSTORM]) and hierarchical density-based spatial clustering of applications with noise (HDBSCAN) to study AZ plasticity during PHP at the synaptic mesoscale. We find compaction of individual AZs in acute philanthotoxin-induced and chronic genetically induced PHP but unchanged copy numbers of AZ proteins. Compaction even occurs at the level of Brp subclusters, which move toward AZ centers, and in Rab3 interacting molecule (RIM)-binding protein (RBP) subclusters. Furthermore, correlative confocal and dSTORM imaging reveals how AZ compaction in PHP translates into apparent increases in AZ area and Brp protein content, as implied earlier. KW - active zone KW - Bruchpilot KW - RIM-binding protein KW - compaction KW - homeostasis KW - presynaptic plasticity KW - super-resolution microscopy Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265497 VL - 37 IS - 1 ER - TY - THES A1 - Meduri, Rajyalakshmi T1 - Elucidation of an intricate surveillance network for cellular U snRNP homeostasis T1 - Identifizierung eines komplexen Überwachungssystems für die Aufrechterhaltung der zellulären U snRNP-Homöostase N2 - Spliceosomal U-rich small ribonucleoprotein particles (U snRNPs) are the major building blocks of the nuclear pre-mRNA splicing machinery. The core composition of U snRNPs includes the name giving U snRNA and a set of seven common (Sm) proteins termed Sm B/B’, D1, D2, D3, E, F and G. These Sm proteins are arranged in the form of a toroidal ring on the single stranded conserved sequence element in the snRNA to form the Sm core domain. Even though U snRNPs assemble spontaneously in vitro, their assembly in vivo requires an amazingly large number of trans-acting assembly factors united in the Protein Arginine Methyltransferase 5 (PRMT5) and the Survival Motor Neuron (SMN) complexes. The cytoplasmic assembly pathway of U snRNPs can be divided into the early and the late phase. The early phase is dominated by the assembly chaperone, pICln, a subunit of the PRMT5 complex. This factor binds to Sm proteins and delivers them in a pICln-bound form to the PRMT5 complex. The early assembly phase then segregates into two lines. In one assembly line, a stable hexameric ring intermediate (6S complex) composed of pICln and the five Sm proteins D1, D2, F, E and G, is formed. This intermediate forms at the PRMT5 complex but dissociates from the latter upon completion of its assembly. Within the 6S complex, these Sm proteins are pre-organized into respective spatial positions adopted in the assembled U snRNP. The other assembly line forms a protein trimer composed of pICln, Sm B/B’ and D3, which unlike the 6S complex is not released from the PRMT5 complex. As a consequence of their association with pICln, Sm proteins are kinetically trapped and fail to proceed in the assembly pathway. The late phase of the U snRNP formation is dominated by the SMN complex, which resolves this kinetic trap by dissociating pICln from the pre-organized Sm proteins and, subsequently catalyzes the loading of the Sm proteins on the U snRNA. Even though basic principles of U snRNP assembly have been understood in some detail, the question arises as to why cells employ sophisticated assembly machinery for the assembly despite the reaction occurring spontaneously in vitro. A few studies have shown that the system works towards rendering specificity to the assembly reaction. However, Sm proteins in their free form expose hydrophobic surfaces to the cytosolic solvent. Hence, I reasoned that the assembly machinery of snRNPs might also prevent Sm protein aggregation. In this thesis, I describe the work that leads to the discovery of a multi-layered regulatory network for Sm proteins involving post-transcriptional and post-translational surveillance mechanisms. Here, I show that the reduced level of SMN (a key assembly factor of the late phase) leads to the initial tailback of Sm proteins over pICln followed by the transcriptional down regulation of Sm protein encoding mRNAs. In contrast, depletion of pICln, a key factor of the early phase, results in the retention of Sm proteins on the ribosomes followed by their degradation via autophagy. Furthermore, I show that exceeding levels of Sm proteins over pICln caused by overexpression results in aggregation and mis-localization of Sm proteins. Thus, my findings uncover a complex regulatory network that helps to maintain the cellular U snRNP homeostasis by either preventing or clearing the unassembled Sm protein aggregates when they are not faithfully incorporated into the U snRNPs. N2 - Eukaryontische mRNA Moleküle werden häufig als Vorläufer (prä-mRNAs) hergestellt, und durch diverse Prozessierungschritte zur reifen Form umgewandelt. Ein wichtiger Schritt ist hierbei die Spleißreaktion, welche das Herausschneiden von Introns und die Ligation der Exons zur reifen mRNA katalysiert. Dieser Prozess wird durch das sog. Spleißosom ermöglicht, einer makromolekularen Maschinerie, deren wichtigste Bausteine Uridin-reiche kleine Ribonukleoproteinpartikel (U snRNPs) sind. Die spleißosomalen U snRNPs bestehen aus kleinen nicht-codierenden RNAs (U snRNA) sowie spezifischen und allgemeinen Proteinen. Während die spezifischen Proteine definierte Funktionen im Spleißprozess vermitteln, haben die allgemeinen Proteine, auch Sm Proteine genannt, primär strukturelle Funktion und vermitteln wichtige Schritte der U snRNP Biogenese. Jedes U snRNP Partikel enthält sieben Sm-Proteine (Sm B/B’, D1, D2, D3, E, F, G), die sich ringförmig an einen einzelsträngigen Bereich der U snRNPs anlagern und so eine toroidale Sm Corestruktur ausbilden. Obwohl die Zusammenlagerung dieses Sm Cores in vitro spontan erfolgt, werden hierfür in vivo trans-agierende Assemblierungsfaktoren benötigt. Diese agieren im Kontext zweier miteinander kooperierender Einheiten, die als PRMT5- und SMN-Komplex bezeichnet werden. Die initiale Phase wird vom Assemblierungs-Chaperon pICln dominiert, welches eine Untereinheit des PRMT5-Komplexes darstellt. Dieser Faktor stabilisiert die Sm-Proteine in höhergeordneten oligomeren Einheiten, die als Bausteine für die spätere Zusammenlagerungsreaktion dienen. pICln-assoziierte Sm-Proteine sind jedoch kinetisch gefangen und können daher nicht spontan auf die snRNA geladen werden. Diese Funktion übernimmt der SMN-Komplex, indem er die pICln-Sm Proteinkomplexe bindet und gleichzeitig pICln dissoziiert. Der SMN-Komplex fügt dann im letzten Schritt die Sm Proteine und die snRNA zum Sm Core zusammen. Es stellte sich die prinzipielle Frage, weshalb Zellen für die U snRNP Biogenese eine komplexe Maschinerie ermöglichen, wenn dieselbe Reaktion in vitro auch spontan erfolgen kann. Eine Hypothese, die dieser Arbeit zu Grunde lag, war, dass das PRMT5/SMN System in vivo notwendig ist, um die unspezifische Aggregation der hydrophoben Sm Proteine zu vermeiden und deren spezifische Zusammenlagerung mit den snRNAs zu ermöglichen. In der vorliegenden Arbeit werden Experimente geschildert, die diese Hypothese bestätigen und ein vielschichtiges regulatorisches post-transkriptionelles und post-translationales Netzwerk für die Sm-Proteine aufdeckten. Es wird gezeigt, dass eine verringerte Menge an SMN, dem Schlüsselfaktor der späten Zusammenlagerungs-Phase, zu einem anfänglichen Rückstau der Sm-Proteine an pICln zur Folge hat. Dieser Rückstau führt in einer späteren Phase zur Herunterregulierung der mRNAs, die für die Sm-Proteine codieren. Im Gegensatz dazu resultiert das Fehlen von pICln darin, dass die Sm-Proteine nicht in den Zusammenlagerungsweg eintreten können und statt dessen durch Autophagie degradiert werden. Wird die Degradation der Sm Proteine unterdrückt, komm es zu deren Delokalisation in der Zelle und Aggregation in unphysiologischen Strukturen. Die Daten offenbaren ein komplexes Regulationsnetzwerk, das die zelluläre U snRNP-Homöostase aufrechterhält und Zellen vor potentiell toxischer Proteinaggregation bewahrt. KW - U snRNPs KW - SMN KW - pICln KW - homeostasis Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143173 ER - TY - JOUR A1 - Klotz, Barbara A1 - Mentrup, Birgit A1 - Regensburger, Martina A1 - Zeck, Sabine A1 - Schneidereit, Jutta A1 - Schupp, Nicole A1 - Linden, Christian A1 - Merz, Cornelia A1 - Ebert, Regina A1 - Jakob, Franz T1 - 1,25-Dihydroxyvitamin D3 Treatment Delays Cellular Aging in Human Mesenchymal Stem Cells while Maintaining Their Multipotent Capacity JF - PLoS ONE N2 - 1,25-dihydroxyvitamin D3 (1,25D3) was reported to induce premature organismal aging in fibroblast growth factor-23 (Fgf23) and klotho deficient mice, which is of main interest as 1,25D3 supplementation of its precursor cholecalciferol is used in basic osteoporosis treatment. We wanted to know if 1,25D3 is able to modulate aging processes on a cellular level in human mesenchymal stem cells (hMSC). Effects of 100 nM 1,25D3 on hMSC were analyzed by cell proliferation and apoptosis assay, beta-galactosidase staining, VDR and surface marker immunocytochemistry, RT-PCR of 1,25D3-responsive, quiescence-and replicative senescence-associated genes. 1,25D3 treatment significantly inhibited hMSC proliferation and apoptosis after 72 h and delayed the development of replicative senescence in long-term cultures according to beta-galactosidase staining and P16 expression. Cell morphology changed from a fibroblast like appearance to broad and rounded shapes. Long term treatment did not induce lineage commitment in terms of osteogenic pathways but maintained their clonogenic capacity, their surface marker characteristics (expression of CD73, CD90, CD105) and their multipotency to develop towards the chondrogenic, adipogenic and osteogenic pathways. In conclusion, 1,25D3 delays replicative senescence in primary hMSC while the pro-aging effects seen in mouse models might mainly be due to elevated systemic phosphate levels, which propagate organismal aging. KW - perspectives KW - bone marrow KW - mutant mice KW - oxidative stress KW - transcription factors KW - vitamin-D-receptor KW - differentiation KW - tissue KW - 2',7'-dichlorofluorescin KW - homeostasis Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-133392 VL - 7 IS - 1 ER - TY - JOUR A1 - Palkovits, Miklós A1 - Šebeková, Katarína A1 - Klenovics, Kristina Simon A1 - Kebis, Anton A1 - Fazeli, Gholamreza A1 - Bahner, Udo A1 - Heidland, August T1 - Neuronal Activation in the Central Nervous System of Rats in the Initial Stage of Chronic Kidney Disease-Modulatory Effects of Losartan and Moxonidine JF - PLoS ONE N2 - The effect of mild chronic renal failure (CRF) induced by 4/6-nephrectomy (4/6NX) on central neuronal activations was investigated by c-Fos immunohistochemistry staining and compared to sham-operated rats. In the 4/6 NX rats also the effect of the angiotensin receptor blocker, losartan, and the central sympatholyticum moxonidine was studied for two months. In serial brain sections Fos-immunoreactive neurons were localized and classified semiquantitatively. In 37 brain areas/nuclei several neurons with different functional properties were strongly affected in 4/6NX. It elicited a moderate to high Fos-activity in areas responsible for the monoaminergic innervation of the cerebral cortex, the limbic system, the thalamus and hypothalamus (e.g. noradrenergic neurons of the locus coeruleus, serotonergic neurons in dorsal raphe, histaminergic neurons in the tuberomamillary nucleus). Other monoaminergic cell groups (A5 noradrenaline, C1 adrenaline, medullary raphe serotonin neurons) and neurons in the hypothalamic paraventricular nucleus (innervating the sympathetic preganglionic neurons and affecting the peripheral sympathetic outflow) did not show Fos-activity. Stress- and pain-sensitive cortical/subcortical areas, neurons in the limbic system, the hypothalamus and the circumventricular organs were also affected by 4/6NX. Administration of losartan and more strongly moxonidine modulated most effects and particularly inhibited Fos-activity in locus coeruleus neurons. In conclusion, 4/6NX elicits high activity in central sympathetic, stress- and pain-related brain areas as well as in the limbic system, which can be ameliorated by losartan and particularly by moxonidine. These changes indicate a high sensitivity of CNS in initial stages of CKD which could be causative in clinical disturbances. KW - brain natriuretic peptide KW - kidneys KW - cognitive impairment KW - central nervous system KW - chronic kidney disease KW - neurons KW - homeostasis KW - blood pressure Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130108 VL - 8 IS - 6 ER -