TY - JOUR A1 - Dames, Petra A1 - Zimmermann, Bernhard A1 - Schmidt, Ruth A1 - Rein, Julia A1 - Voss, Martin A1 - Schewe, Bettina A1 - Walz, Bernd A1 - Baumann, Otto T1 - cAMP regulates plasma membrane vacuolar-type H+-ATPase assembly and activity in blowfly salivary glands N2 - Reversible assembly of the V0V1 holoenzyme from V-0 and V-1 subcomplexes is a widely used mechanism for regulation of vacuolar-type H+-ATPases (V-ATPases) in animal cells. in the blowfly (Calliphora vicina) salivary gland, V- ATPase is located in the apical membrane of the secretory cells and energizes the secretion of a KCl-rich saliva in response to the hormone serotonin. We have examined whether the CAMP pathway, known to be activated by serotonin, controls V-ATPase assembly and activity. Fluorescence measurements of pH changes at the luminal surface of isolated glands demonstrate that CAMP, Sp-adenosine-3',5'-cyclic monophosphorothioate, or forskolin, similar to serotonin, cause V-ATPase-dependent luminal acidification. In addition, V-ATPase-dependent ATP hydrolysis increases upon treatment with these agents. Immunofluorescence microscopy and pelleting assays have demonstrated further that V, components become translocated from the cytoplasm to the apical membrane and V-ATPase holoenzymes are assembled at the apical membrane during conditions that increase intracellular cAMP. Because these actions occur without a change in cytosolic Ca2+, our findings suggest that the cAMP pathway mediates the reversible assembly and activation of V-ATPase molecules at the apical membrane upon hormonal stimulus Y1 - 2006 UR - http://www.pnas.org/ U6 - https://doi.org/10.1073/pnas.0600011103 SN - 0027-8424 ER - TY - JOUR A1 - Pitzen, Valentin A1 - Sander, Sophia A1 - Baumann, Otto A1 - Gräf, Ralph A1 - Meyer, Irene T1 - Cep192, a novel missing link between the centrosomal core and corona in Dictyostelium amoebae JF - Cells : open access journal N2 - The Dictyostelium centrosome is a nucleus-associated body with a diameter of approx. 500 nm. It contains no centrioles but consists of a cylindrical layered core structure surrounded by a microtubule-nucleating corona. At the onset of mitosis, the corona disassembles and the core structure duplicates through growth, splitting, and reorganization of the outer core layers. During the last decades our research group has characterized the majority of the 42 known centrosomal proteins. In this work we focus on the conserved, previously uncharacterized Cep192 protein. We use superresolution expansion microscopy (ExM) to show that Cep192 is a component of the outer core layers. Furthermore, ExM with centrosomal marker proteins nicely mirrored all ultrastructurally known centrosomal substructures. Furthermore, we improved the proximity-dependent biotin identification assay (BioID) by adapting the biotinylase BioID2 for expression in Dictyostelium and applying a knock-in strategy for the expression of BioID2-tagged centrosomal fusion proteins. Thus, we were able to identify various centrosomal Cep192 interaction partners, including CDK5RAP2, which was previously allocated to the inner corona structure, and several core components. Studies employing overexpression of GFP-Cep192 as well as depletion of endogenous Cep192 revealed that Cep192 is a key protein for the recruitment of corona components during centrosome biogenesis and is required to maintain a stable corona structure. KW - Cep192 KW - SPD-2 KW - centrosome KW - Dictyostelium KW - microtubule-organization KW - MTOC Y1 - 2021 U6 - https://doi.org/10.3390/cells10092384 SN - 2073-4409 VL - 10 IS - 9 PB - MDPI CY - Basel ER - TY - JOUR A1 - Heindorff, Kristoffer A1 - Blenau, Wolfgang A1 - Walz, Bernd A1 - Baumann, Otto T1 - Characterization of a Ca2+/calmodulin-dependent AC1 adenylyl cyclase in a non-neuronal tissue, the blowfly salivary gland JF - Cell calcium N2 - Crosstalk between intracellular signalling pathways is a functionally important and widespread phenomenon in cell physiology across phyla. In the salivary gland of the blowfly, serotonin induces fluid secretion via parallel activation of both the InsP(3)/Ca2+ and the cAMP/PKA signalling pathways, which interact on multiple levels. We have determined the molecular identity of a link between both pathways that mediates a Ca2+-dependent rise of intracellular cAMP. Whereas hydrolysis of cAMP via phosphodiesterases is largely independent of Ca2+, cAMP synthesis by adenylyl cyclases (AC) is potentiated in a Ca2+/calmodulin (Ca2+/CaM)-dependent manner. The existence of a Ca2+/CaM-dependent AC is supported by physiological data and a molecular approach. We have cloned Cv rutabaga cDNA, encoding the first blowfly AC, and confirmed its expression in the salivary gland via reverse transcription followed by polymerase chain reaction. The putative gene product of Cv rutabaga is a Ca2+/CaM-dependent type I AC and shows highest homology to Rutabaga from Drosophila. Thus, a Ca2+/CaM-dependent AC serves as a link between the InsP(3)/Ca2+ and the cAMP/PKA signalling pathways in the salivary gland of the blowfly and might be important for the amplification and optimization of the secretory response. KW - Adenylyl cyclase KW - Phosphodiesterase KW - Crosstalk KW - Ca2+ KW - cAMP KW - Intracellular signalling KW - Salivary gland KW - Calliphora vicina KW - Rutabaga Y1 - 2012 U6 - https://doi.org/10.1016/j.ceca.2012.04.016 SN - 0143-4160 VL - 52 IS - 2 SP - 103 EP - 112 PB - Churchill Livingstone CY - Edinburgh ER - TY - JOUR A1 - Baumann, Otto A1 - Arlt, Kathleen A1 - Römmling, Katja A1 - Goller, Helmut A1 - Walz, Bernd T1 - Characterization of an extremely motile cellular network in the rotifer Asplanchna : Structure, kinetics and the cytoskeleton Y1 - 2000 ER - TY - JOUR A1 - Baumann, Otto A1 - Arlt, Kathleen A1 - Römmling, Katja A1 - Goller, Helmut A1 - Walz, Bernd T1 - Characterization of an extremely motile cellular network in the rotifer Asplanchna spp. : structure, kinetics, and cytoskeleton Y1 - 2000 ER - TY - JOUR A1 - Krüger, Anne A1 - Batsios, Petros A1 - Baumann, Otto A1 - Luckert, Eva A1 - Schwarz, Heinz A1 - Stick, Reimer A1 - Meyer, Irene A1 - Gräf, Ralph T1 - Characterization of NE81, the first lamin-like nucleoskeleton protein in a unicellular organism JF - Molecular biology of the cell : the official publication of the American Society for Cell Biology N2 - Lamins build the nuclear lamina and are required for chromatin organization, gene expression, cell cycle progression, and mechanical stabilization. Despite these universal functions, lamins have so far been found only in metazoans. We have identified protein NE81 in Dictyostelium, which has properties that justify its denomination as a lamin-like protein in a lower eukaryote. This is based on its primary structure, subcellular localization, and regulation during mitosis, and its requirement of the C-terminal CaaX box as a posttranslational processing signal for proper localization. Our knockout and overexpression mutants revealed an important role for NE81 in nuclear integrity, chromatin organization, and mechanical stability of cells. All our results are in agreement with a role for NE81 in formation of a nuclear lamina. This function is corroborated by localization of Dictyostelium NE81 at the nuclear envelope in human cells. The discovery of a lamin-like protein in a unicellular organism is not only intriguing in light of evolution, it may also provide a simple experimental platform for studies of the molecular basis of laminopathies. Y1 - 2012 U6 - https://doi.org/10.1091/mbc.E11-07-0595 SN - 1059-1524 VL - 23 IS - 2 SP - 360 EP - 370 PB - American Society for Cell Biology CY - Bethesda ER - TY - JOUR A1 - Blankenburg, Stefanie A1 - Balfanz, Sabine A1 - Hayashi, Y. A1 - Shigenobu, S. A1 - Miura, T. A1 - Baumann, Otto A1 - Baumann, Arnd A1 - Blenau, Wolfgang T1 - Cockroach GABA(B) receptor subtypes: Molecular characterization, pharmacological properties and tissue distribution JF - Neuropharmacology N2 - gamma-aminobutyric acid (GABA) is the predominant inhibitory neurotransmitter in the central nervous system (CNS). Its effects are mediated by either ionotropic GABA(A) receptors or metabotropic GABA(B) receptors. GABA(B) receptors regulate, via Gi/o, G-proteins, ion channels, and adenylyl cyclases. In humans, GABA(B) receptor subtypes are involved in the etiology of neurologic and psychiatric disorders. In arthropods, however, these members of the G-protein-coupled receptor family are only inadequately characterized. Interestingly, physiological data have revealed important functions of GABA(B) receptors in the American cockroach, Periplaneta americana. We have cloned cDNAs coding for putative GABA(B) receptor subtypes 1 and 2 of P. americana (PeaGB1 and PeaGB2). When both receptor proteins are co-expressed in mammalian cells, activation of the receptor heteromer with GABA leads to a dose-dependent decrease in cAMP production. The pharmacological profile differs from that of mammalian and Drosophila GABA(B) receptors. Western blot analyses with polyclonal antibodies have revealed the expression of PeaGB1 and PeaGB2 in the CNS of the American cockroach. In addition to the widespread distribution in the brain, PeaGB1 is expressed in salivary glands and male accessory glands. Notably, PeaGB1-like immunoreactivity has been detected in the GABAergic salivary neuron 2, suggesting that GABA(B) receptors act as autoreceptors in this neuron. KW - GABA(B) receptor KW - G-protein-coupled receptor KW - Periplaneta americana KW - Central nervous system KW - Adenylyl cyclase KW - Salivary gland Y1 - 2015 U6 - https://doi.org/10.1016/j.neuropharm.2014.08.022 SN - 0028-3908 SN - 1873-7064 VL - 88 SP - 134 EP - 144 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kuhnert, Oliver A1 - Baumann, Otto A1 - Meyer, Irene A1 - Gräf, Ralph T1 - CP55, a novel key component of centrosomal organization in dictyostelium JF - Cellular and molecular life sciences N2 - Dictyostelium centrosomes consist of a layered core structure surrounded by a microtubule-nucleating corona. At the G2/M transition, the corona dissociates and the core structure duplicates, yielding two spindle pole bodies. Finally, in telophase, the spindle poles mature into two new, complete centrosomes. CP55 was identified in a centrosomal proteome analysis. It is a component of the centrosomal core structure, and persists at the centrosome throughout the entire cell cycle. FRAP experiments revealed that during interphase the majority of centrosomal GFP-CP55 is immobile, which indicates a structural task of CP55 at the centrosome. The CP55null mutant is characterized by increased ploidy, a less structured, slightly enlarged corona, and by supernumerary, cytosolic MTOCs, containing only corona proteins and lacking a core structure. Live cell imaging showed that supernumerary MTOCs arise in telophase. Lack of CP55 also caused premature recruitment of the corona organizer CP148 to mitotic spindle poles, already in metaphase instead of telophase. Forces transmitted through astral microtubules may expel prematurely acquired or loosely attached corona fragments into the cytosol, where they act as independent MTOCs. CP55null cells were also impaired in growth, most probably due to difficulties in centrosome splitting during prophase. Furthermore, although they were still capable of phagocytosis, they appeared unable to utilize phagocytosed nutrients. This inability may be attributed to their partially disorganized Golgi apparatus. KW - Dictyostelium KW - Corona KW - Microtubules KW - Centrosome KW - Nucleus Y1 - 2012 U6 - https://doi.org/10.1007/s00018-012-1040-3 SN - 1420-682X VL - 69 IS - 21 SP - 3651 EP - 3664 PB - Springer CY - Basel ER - TY - JOUR A1 - Stuckas, Heiko A1 - Messerschmidt, Katrin A1 - Putzler, Sascha A1 - Baumann, Otto A1 - Schenk, Jörg A. A1 - Tiedemann, Ralph A1 - Micheel, Burkhard T1 - Detection and characterization of gamete-specific molecules in Mytilus edulis using selective antibody production N2 - The mussel Mytilus edulis can be used as model to study the molecular basis of reproductive isolation because this species maintains its species integrity, despite of hybridizing in zones of contact with the closely related species M. trossulus or M. galloprovincialis. This study uses selective antibody production by means of hybridoma technology to identify molecules which are involved in sperm function of M. edulis. Fragmented sperm were injected into mice and 25 hybridoma cell clones were established to obtain monoclonal antibodies (mAb). Five clones were identified producing mAb targeting molecules putatively involved in sperm function based on enzyme immunoassays, dot and Western blotting as well as immunostaining of tissue sections. Specific localization of these mAb targets on sperm and partly also in somatic tissue suggests that all five antibodies bind to different molecules. The targets of the mAb obtained from clone G26-AG8 were identified using mass spectrometry (nano-LC-ESI-MS/MS) as M6 and M7 lysin. These acrosomal proteins have egg vitelline lyses function and are highly similar (76%) which explains the cross reactivity of mAb G26- AG8. Furthermore, M7 lysin was recently shown to be under strong positive selection suggesting a role in interspecific reproductive isolation. This study shows that M6 and M7 lysin are not only found in the sperm acrosome but also in male somatic tissue of the mantle and the posterior adductor muscle, while being completely absent in females. The monoclonal antibody G26-AG8 described here will allow elucidating M7/M6 lysin function in somatic and gonad tissue of adult and developing animals. Y1 - 2009 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/37692 U6 - https://doi.org/10.1002/Mrd.20916 SN - 1040-452X ER - TY - JOUR A1 - Baumann, Otto A1 - Bauer, Alexandra T1 - Development of apical membrane organization and V-ATPase regulation in blowfly salivary glands JF - The journal of experimental biology N2 - Secretory cells in blowfly salivary gland are specialized via morphological and physiological attributes in order to serve their main function, i.e. the transport of solutes at a high rate in response to a hormonal stimulus, namely serotonin (5-HT). This study examines the way that 5-HT-insensitive precursor cells differentiate into morphologically complex 5-HT-responsive secretory cells. By means of immunofluorescence microscopy, immunoblotting and measurements of the transepithelial potential changes, we show the following. (1) The apical membrane of the secretory cells becomes organized into an elaborate system of canaliculi and is folded into pleats during the last pupal day and the first day of adulthood. (2) The structural reorganization of the apical membrane is accompanied by an enrichment of actin filaments and phosphorylated ERM protein (phospho-moesin) at this membrane domain and by the deployment of the membrane-integral part of vacuolar-type H+-ATPase (V-ATPase). These findings suggest a role for phospho-moesin, a linker between actin filaments and membrane components, in apical membrane morphogenesis. (3) The assembly and activation of V-ATPase can be induced immediately after eclosion by way of 8-CPT-cAMP, a membrane-permeant cAMP analogue. (4) 5-HT, however, produces the assembly and activation of V-ATPase only in flies aged for at least 2 h after eclosion, indicating that, at eclosion, the 5-HT receptor/adenylyl cyclase/cAMP signalling pathway is inoperative upstream of cAMP. (5) 5-HT activates both the Ca2+ signalling pathway and the cAMP signalling cascade in fully differentiated secretory cells. However, the functionality of these signalling cascades does not seem to be established in a tightly coordinated manner during cell differentation. KW - secretory cell KW - moesin KW - morphogenesis KW - serotonin KW - vacuolar ATPase KW - cAMP Y1 - 2013 U6 - https://doi.org/10.1242/jeb.077420 SN - 0022-0949 VL - 216 IS - 7 SP - 1225 EP - 1234 PB - Company of Biologists Limited CY - Cambridge ER - TY - JOUR A1 - Baumann, Otto A1 - Salvaterra, Paul M. A1 - Takeyasu, Kunio T1 - Developmental changes in beta-subunit composition of Na,K-ATPase in the Drosophila eye N2 - The Drosophila genome contains at least three loci for the Na,K-ATPase beta-subunit; however, only the protein products of nrv1 and nrv2 have been characterized hitherto. Here, we provide evidence that nrv3 also encodes for a functional Na,K-ATPase beta-subunit, as its protein product co-precipitates with the Na,K-ATPase alpha-subunit. Nrv3 expression in adult flies is restricted to the nervous system in which Nrv3 is enriched in selective types of sensory cells. Because Nrv3 expression is especially prominent in the compound eye, we have analyzed the subcellular and developmental distribution of Nrv3 within the visual cells and related this distribution to those of the alpha-subunit and of the beta-subunits Nrv1 and Nrv2. Prospective visual cells express Nrv2 in the third larval instar stage and during the first half of pupal development. During the last third of pupal life, Nrv3 gradually replaces Nrv2 as the Na,K-ATPase beta-subunit in the photoreceptor cells. Adult photoreceptors express Nrv3 as their major beta-subunit; the visual cells R1-R6 co-express Nrv2 at a low level, whereas R7 and R8 co-express Nrv1. Notably, beta-subunits do not co- distribute exactly with the alpha-subunit at some developmental stages, supporting the concept that the alpha-subunit and beta-subunit can exist in the plasma membrane without being engaged in alpha/beta heterodimers. The non-visual cells within the compound eye express almost exclusively Nrv2, which segregates together with the alpha-subunit to septate junctions throughout development. Y1 - 2010 UR - http://www.springerlink.com/content/100524 U6 - https://doi.org/10.1007/s00441-010-0948-x SN - 0302-766X ER - TY - JOUR A1 - Schulz, Irene A1 - Baumann, Otto A1 - Samereier, Matthias A1 - Zoglmeier, Christine A1 - Gräf, Ralph T1 - Dictyostelium Sun1 is a dynamic membrane protein of both nuclear membranes and required for centrosomal association with clustered centromeres N2 - Centrosomal attachment to nuclei is crucial for proper mitosis and nuclear positioning in various organisms, and generally involves Sun-family proteins located at the inner nuclear envelope. There is still no common scheme for the outer nuclear membrane proteins interacting with Sun I in centrosome/nucleus attachment. Here we propose a model in which Sun1 mediates a physical link between centrosomes and clustered centromeres through both nuclear membranes in Dictyostelium. For the first time we provide a detailed microscopic analysis of the centrosomal and nuclear envelope localization of endogenous Dictyostelium Sun1 during interphase and mitosis. By immunogold electron microscopy we show that Sun1 is a resident of both nuclear membranes. Disruption of Sun1 function by overexpression of full-length GFP-Sun1 or a GFP-Sun-domain deletion construct revealed not only the established function in centrosome/nucleus attachment and maintenance of ploidy, but also a requirement of Sun1 for the association of the centromere cluster with the centrosome. Live-cell imaging visualized the occurrence of mitotic defects, and demonstrated the requirement of microtubules for dynamic distance changes between centrosomes and nuclei. FRAP analysis revealed at least two populations of Sun1, with an immobile fraction associated with the centrosome, and a mobile fraction in the nuclear envelope. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/01719335 U6 - https://doi.org/10.1016/j.ejcb.2009.06.003 SN - 0171-9335 ER - TY - JOUR A1 - Dubreuil, R. R. A1 - Grushko, T. A1 - Baumann, Otto T1 - Differential effects of a labial mutation on the development, structure, and function of stomach acid-secreting cells in Drosophila larvae and adults Y1 - 2001 ER - TY - JOUR A1 - Baumann, Otto T1 - Disruption of actin filaments causes redistribution of ryanodine receptor Ca2+ channels in honeybee photoreceptor cells Y1 - 2001 ER - TY - JOUR A1 - Zimmermann, Bernhard A1 - Dames, Petra A1 - Walz, Bernd A1 - Baumann, Otto T1 - Distribution and serotonin-induced activation of vacuolar-type H+-ATPase in the salivary glands of the blowfly Calliphora vicina Y1 - 2003 ER - TY - JOUR A1 - Baumann, Otto T1 - Distribution of Na+, K+-ATPase in photoreceptor cells of insects. Y1 - 1997 ER - TY - JOUR A1 - Baumann, Otto T1 - Distribution of nonmuscle myosin-II in honeybee photoreceptor cells and its possible role in maintaining compound eye architecture Y1 - 2001 ER - TY - JOUR A1 - Baumann, Otto T1 - Distribution of ryanodine receptor Ca2+ channels in insect photoreceptor cells Y1 - 2000 ER - TY - JOUR A1 - Baumann, Otto A1 - Dames, Petra A1 - Kühnel, Dana A1 - Walz, Bernd T1 - Distribution of serotonergic and dopaminergic nerve fibers in the salivary gland complex of the cockroach Periplaneta americana Y1 - 2002 UR - http://www.biomedcentral.com/1472-6793/2/9 ER - TY - JOUR A1 - Baumann, Otto A1 - Kühnel, Dana A1 - Dames, Petra A1 - Walz, Bernd T1 - Dopaminergic and serotonergic innervation of cockroach salivary glands : distribution and morphology of synapses and release sites N2 - The paired salivary glands in the cockroach are composed of acini with ion-transporting peripheral P-cells and protein-secreting central C-cells, and a duct system for the modification of the primary saliva. Secretory activity is controlled by serotonergic and dopaminergic neurons, whose axons form a dense plexus on the glands. The spatial relationship of release sites for serotonin and dopamine to the various cell types was determined by anti-synapsin immunofluorescence confocal microscopy and electron microscopy. Every C-cell apparently has only serotonergic synapses on its surface. Serotonergic and dopaminergic fibres on the acini have their release zones at a distance of similar to0.5 mum from the P-cells. Nerves between acinar lobules may serve as neurohaemal organs and contain abundant dopaminergic and few serotonergic release sites. Some dopaminergic and serotonergic release sites reside in the duct epithelium, the former throughout the duct system, the latter only in segments next to acini. These findings are consistent with the view that C-cells respond exclusively to serotonin, P-cells to serotonin and dopamine, and most duct cells only to dopamine. Moreover, the data suggest that C-cells are stimulated by serotonin released close to their surface, whereas P-cells and most duct cells are exposed to serotonin/dopamine liberated at some distance Y1 - 2004 ER -