@article{StuermerBaumannWalz1995, author = {St{\"u}rmer, Karoline and Baumann, Otto and Walz, Bernd}, title = {Actin-dependent light-induced translocation of mitochondria and ER cisternae in the photoreceptor cells of the locust schistocerca gregaria}, year = {1995}, language = {en} } @article{FechnerBaumannWalz2013, author = {Fechner, Lennart and Baumann, Otto and Walz, Bernd}, title = {Activation of the cyclic AMP pathway promotes serotonin-induced Ca2+ oscillations in salivary glands of the blowfly Calliphora vicina}, series = {Cell calcium}, volume = {53}, journal = {Cell calcium}, number = {2}, publisher = {Churchill Livingstone}, address = {Edinburgh}, issn = {0143-4160}, doi = {10.1016/j.ceca.2012.10.004}, pages = {94 -- 101}, year = {2013}, abstract = {Ca2+ and cAMP signalling pathways interact in a complex manner at multiple sites. This crosstalk fine-tunes the spatiotemporal patterns of Ca2+ and cAMP signals. In salivary glands of the blowfly Calliphora vicina fluid secretion is stimulated by serotonin (5-hydroxytryptamine, 5-HT) via activation of two different 5-HT receptors coupled to the InsP(3)/Ca2+ (Cv5-HT2 alpha) or the cAMP pathway (Cv5-HT7), respectively. We have shown recently in permeabilized gland cells that cAMP sensitizes InsP(3)-induced Ca2+ release to InsP(3). Here we study the effects of the CAMP signalling pathway on 5-HT-induced oscillations in transepithelial potential (TEP) and in intracellular [Ca2+]. We show: (1) Blocking the activation of the cAMP pathway by cinanserin suppresses the generation of TEP and Ca2+ oscillations, (2) application of 8-CPT-cAMP in the presence of cinanserin restores 5-HT-induced TEP and Ca2+ oscillations, (3) 8-CPT-cAMP sensitizes the InsP(3)/Ca2+ signalling pathway to 5-HT and the Cv5-HT2 alpha, receptor agonist 5-MeOT, (4) 8-CPT-cAMP induces Ca2+ oscillations in cells loaded with subthreshold concentrations of InsP(3), (5) inhibition of protein kinase A by H-89 abolishes 5-HT-induced TEP and Ca2+ spiking and mimics the effect of cinanserin. These results suggest that activation of the cyclic AMP pathway promotes the generation of 5-HT-induced Ca2+ oscillations in blowfly salivary glands.}, language = {en} } @article{WalzBaumannZimmermannetal.1995, author = {Walz, Bernd and Baumann, Otto and Zimmermann, Bernhard and Ciriacy-Wantrup, E.v.}, title = {Caffeine- and ryanodine-sensitive Ca2+-induced Ca2+ release from the endo plasmatic reticulum in honeybee photoreceptors}, year = {1995}, language = {en} } @article{VossFechnerWalzetal.2010, author = {Voss, Martin and Fechner, Lennart and Walz, Bernd and Baumann, Otto}, title = {Calcineurin activity augments cAMP/PKA-dependent activation of V-ATPase in blowfly salivary glands}, issn = {0363-6143}, doi = {10.1152/ajpcell.00328.2009}, year = {2010}, abstract = {We have examined the role of the Ca2+-dependent protein phosphatase 2B (calcineurin) in the regulation of the vacuolar H+-ATPase (V-ATPase) in blowfly salivary glands. In response to the neurohormone serotonin [5-hydroxytryptamine (5-HT)] and under the mediation of the cAMP/PKA signaling pathway, the secretory cells assemble and activate V-ATPase molecules at the apical membrane. We demonstrate that the inhibition of calcineurin activity by cyclosporin A, by FK- 506, or by prevention of the elevation of Ca2+ diminishes the 5-HT-induced assembly and activation of V-ATPase. The effect of calcineurin on V-ATPase is mediated by the cAMP/PKA signaling pathway, with calcineurin acting upstream of PKA, because 1) cyclosporin A does not influence the 8-(4-chlorophenylthio) adenosine-3',5'-cyclic monophosphate (8-CPT-cAMP)-induced activation of V-ATPase, and 2) the 5-HT-induced rise in cAMP is highly reduced in the presence of cyclosporin A. Moreover, a Ca2+ rise evoked by the sarco(endo) plasmic reticulum Ca2+-ATPase (SERCA) inhibitor cyclopiazonic acid leads to an increase in intracellular cAMP concentration and a calcineurin-mediated PKA- dependent activation of V-ATPase. We propose that calcineurin activity mediates cross talk between the inositol 1,4,5- trisphosphate/Ca2+ and the cAMP/PKA signaling pathways, thereby augmenting the 5-HT-induced rise in cAMP and thus the cAMP/PKA-mediated activation of V-ATPase.}, language = {en} } @misc{SchmidtBaumannWalz2008, author = {Schmidt, Ruth and Baumann, Otto and Walz, Bernd}, title = {cAMP potentiates InsP3-induced Ca2+ release from the endoplasmic reticulum in blowfly salivary glands}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {842}, issn = {1866-8372}, doi = {10.25932/publishup-42977}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-429770}, pages = {13}, year = {2008}, abstract = {Background Serotonin induces fluid secretion from Calliphora salivary glands by the parallel activation of the InsP3/Ca2+ and cAMP signaling pathways. We investigated whether cAMP affects 5-HT-induced Ca2+ signaling and InsP3-induced Ca2+ release from the endoplasmic reticulum (ER). Results Increasing intracellular cAMP level by bath application of forskolin, IBMX or cAMP in the continuous presence of threshold 5-HT concentrations converted oscillatory [Ca2+]i changes into a sustained increase. Intraluminal Ca2+ measurements in the ER of ß-escin-permeabilized glands with mag-fura-2 revealed that cAMP augmented InsP3-induced Ca2+ release in a concentration-dependent manner. This indicated that cAMP sensitized the InsP3 receptor Ca2+ channel for InsP3. By using cAMP analogs that activated either protein kinase A (PKA) or Epac and the application of PKA-inhibitors, we found that cAMP-induced augmentation of InsP3-induced Ca2+ release was mediated by PKA not by Epac. Recordings of the transepithelial potential of the glands suggested that cAMP sensitized the InsP3/Ca2+ signaling pathway for 5-HT, because IBMX potentiated Ca2+-dependent Cl- transport activated by a threshold 5-HT concentration. Conclusion This report shows, for the first time for an insect system, that cAMP can potentiate InsP3-induced Ca2+ release from the ER in a PKA-dependent manner, and that this crosstalk between cAMP and InsP3/Ca2+ signaling pathways enhances transepithelial electrolyte transport.}, language = {en} } @article{DamesZimmermannSchmidtetal.2006, author = {Dames, Petra and Zimmermann, Bernhard and Schmidt, Ruth and Rein, Julia and Voss, Martin and Schewe, Bettina and Walz, Bernd and Baumann, Otto}, title = {cAMP regulates plasma membrane vacuolar-type H+-ATPase assembly and activity in blowfly salivary glands}, issn = {0027-8424}, doi = {10.1073/pnas.0600011103}, year = {2006}, abstract = {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}, language = {en} } @article{HeindorffBlenauWalzetal.2012, author = {Heindorff, Kristoffer and Blenau, Wolfgang and Walz, Bernd and Baumann, Otto}, title = {Characterization of a Ca2+/calmodulin-dependent AC1 adenylyl cyclase in a non-neuronal tissue, the blowfly salivary gland}, series = {Cell calcium}, volume = {52}, journal = {Cell calcium}, number = {2}, publisher = {Churchill Livingstone}, address = {Edinburgh}, issn = {0143-4160}, doi = {10.1016/j.ceca.2012.04.016}, pages = {103 -- 112}, year = {2012}, abstract = {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.}, language = {en} } @article{BaumannArltRoemmlingetal.2000, author = {Baumann, Otto and Arlt, Kathleen and R{\"o}mmling, Katja and Goller, Helmut and Walz, Bernd}, title = {Characterization of an extremely motile cellular network in the rotifer Asplanchna : Structure, kinetics and the cytoskeleton}, year = {2000}, language = {en} } @article{BaumannArltRoemmlingetal.2000, author = {Baumann, Otto and Arlt, Kathleen and R{\"o}mmling, Katja and Goller, Helmut and Walz, Bernd}, title = {Characterization of an extremely motile cellular network in the rotifer Asplanchna spp. : structure, kinetics, and cytoskeleton}, year = {2000}, language = {en} } @article{ZimmermannDamesWalzetal.2003, author = {Zimmermann, Bernhard and Dames, Petra and Walz, Bernd and Baumann, Otto}, title = {Distribution and serotonin-induced activation of vacuolar-type H+-ATPase in the salivary glands of the blowfly Calliphora vicina}, year = {2003}, language = {en} } @article{BaumannDamesKuehneletal.2002, author = {Baumann, Otto and Dames, Petra and K{\"u}hnel, Dana and Walz, Bernd}, title = {Distribution of serotonergic and dopaminergic nerve fibers in the salivary gland complex of the cockroach Periplaneta americana}, year = {2002}, language = {en} } @article{BaumannKuehnelDamesetal.2004, author = {Baumann, Otto and K{\"u}hnel, Dana and Dames, Petra and Walz, Bernd}, title = {Dopaminergic and serotonergic innervation of cockroach salivary glands : distribution and morphology of synapses and release sites}, year = {2004}, abstract = {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}, language = {en} } @article{ReinZimmermannHilleetal.2006, author = {Rein, Julia and Zimmermann, Bernhard and Hille, Carsten and Lang, Ingo and Walz, Bernd and Baumann, Otto}, title = {Fluorescence measurements of serotonin-induced V-ATPase-dependent pH changes at the luminal surface in salivary glands of the blowfly Calliphora vicina}, issn = {0022-0949}, doi = {10.1242/Jeb.02187}, year = {2006}, abstract = {Secretion in blowfly salivary glands is induced by the neurohormone serotonin and powered by a vacuolar-type H+- ATPase (V-ATPase) located in the apical membrane of the secretory cells. We have established a microfluorometric method for analysing pH changes at the luminal surface of the secretory epithelial cells by using the fluorescent dye 5-N- hexadecanoyl-aminofluorescein (HAF). After injection of HAF into the lumen of the tubular salivary gland, the fatty acyl chain of the dye molecule partitions into the outer leaflet of the plasma membrane and its pH-sensitive fluorescent moiety is exposed at the cell surface. Confocal imaging has confirmed that HAF distributes over the entire apical membrane of the secretory cells and remains restricted to this membrane domain. Ratiometric analysis of HAF fluorescence demonstrates that serotonin leads to a reversible dose-dependent acidification at the luminal surface. Inhibition by concanamycin A confirms that the serotonin-induced acidification at the luminal surface is due to H+ transport across the apical membrane via V-ATPase. Measurements with pH-sensitive microelectrodes corroborate a serotonin-induced luminal acidification and demonstrate that luminal pH decreases by about 0.4 pH units at saturating serotonin concentrations. We conclude that ratiometric measurements of HAF fluorescence provide an elegant method for monitoring V-ATPase-dependent H+ transport in the blowfly salivary gland in vivo and for analysing the spatiotemporal pattern of pH changes at the luminal surface}, language = {en} } @misc{ReinVossBlenauetal.2008, author = {Rein, Julia and Voss, Martin and Blenau, Wolfgang and Walz, Bernd and Baumann, Otto}, title = {Hormone-induced assembly and activation of V-ATPase in blowfly salivary glands is mediated by protein kinase A}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-46126}, year = {2008}, abstract = {The vacuolar H+-ATPase (V-ATPase) in the apical membrane of blowfly (Calliphora vicina) salivary gland cells energizes the secretion of a KCl-rich saliva in response to the neurohormone serotonin (5-HT). We have shown previously that exposure to 5-HT induces a cAMP-mediated reversible assembly of V-0 and V-1 subcomplexes to V-ATPase holoenzymes and increases V-ATPase-driven proton transport. Here, we analyze whether the effect of cAMP on V-ATPase is mediated by protein kinase A (PKA) or exchange protein directly activated by cAMP (Epac), the cAMP target proteins that are present within the salivary glands. Immunofluorescence microscopy shows that PKA activators, but not Epac activators, induce the translocation of V1 components from the cytoplasm to the apical membrane, indicative of an assembly of V-ATPase holoenzymes. Measurements of transepithelial voltage changes and microfluorometric pH measurements at the luminal surface of cells in isolated glands demonstrate further that PKA-activating cAMP analogs increase cation transport to the gland lumen and induce a V-ATPase-dependent luminal acidification, whereas activators of Epac do not. Inhibitors of PKA block the 5-HT-induced V-1 translocation to the apical membrane and the increase in proton transport. We conclude that cAMP exerts its effects on V-ATPase via PKA.}, language = {en} } @article{RoeserJordanBalfanzetal.2012, author = {R{\"o}ser, Claudia and Jordan, Nadine and Balfanz, Sabine and Baumann, Arnd and Walz, Bernd and Baumann, Otto and Blenau, Wolfgang}, title = {Molecular and pharmacological characterization of serotonin 5-HT2 alpha and 5-HT7 receptors in the salivary glands of the blowfly calliphora vicina}, series = {PLoS one}, volume = {7}, journal = {PLoS one}, number = {11}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0049459}, pages = {13}, year = {2012}, abstract = {Secretion in blowfly (Calliphora vicina) salivary glands is stimulated by the biogenic amine serotonin (5-hydroxytryptamine, 5-HT), which activates both inositol 1,4,5-trisphosphate (InsP(3))/Ca2+ and cyclic adenosine 3',5'-monophosphate (cAMP) signalling pathways in the secretory cells. In order to characterize the signal-inducing 5-HT receptors, we cloned two cDNAs (Cv5-ht2 alpha, Cv5-ht7) that share high similarity with mammalian 5-HT2 and 5-HT7 receptor genes, respectively. RT-PCR demonstrated that both receptors are expressed in the salivary glands and brain. Stimulation of Cv5-ht2 alpha-transfected mammalian cells with 5-HT elevates cytosolic [Ca2+] in a dose-dependent manner (EC50 = 24 nM). In Cv5-ht7-transfected cells, 5-HT produces a dose-dependent increase in [cAMP](i) (EC50 = 4 nM). We studied the pharmacological profile for both receptors. Substances that appear to act as specific ligands of either Cv5-HT2 alpha or Cv5-HT7 in the heterologous expression system were also tested in intact blowfly salivary gland preparations. We observed that 5-methoxytryptamine (100 nM) activates only the Cv(5)-HT2 alpha receptor, 5-carboxamidotryptamine (300 nM) activates only the Cv5-HT7 receptor, and clozapine (1 mu M) antagonizes the effects of 5-HT via Cv5-HT7 in blowfly salivary glands, providing means for the selective activation of each of the two 5-HT receptor subtypes. This study represents the first comprehensive molecular and pharmacological characterization of two 5-HT receptors in the blowfly and permits the analysis of the physiological role of these receptors, even when co-expressed in cells, and of the modes of interaction between the Ca2+- and cAMP-signalling cascades. Citation: Roser C, Jordan N, Balfanz S, Baumann A, Walz B, et al. (2012) Molecular and Pharmacological Characterization of Serotonin 5-HT2a and 5-HT7 Receptors in the Salivary Glands of the Blowfly Calliphora vicina.}, language = {en} } @article{DamesSchmidtWalzetal.2004, author = {Dames, Petra and Schmidt, R. and Walz, Bernd and Baumann, Otto}, title = {Regulation of vacuolar-type H+-ATPase (vATPase) in blowfly salivary glands}, issn = {0171-9335}, year = {2004}, language = {en} } @misc{BlenauRotteWitteetal.2009, author = {Blenau, Wolfgang and Rotte, Cathleen and Witte, Jeannine and Baumann, Otto and Walz, Bernd}, title = {Source, topography and excitatory effects of GABAergic innervation in cockroach salivary glands}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-44353}, year = {2009}, abstract = {Cockroach salivary glands are innervated by dopaminergic and serotonergic neurons. Both transmitters elicit saliva secretion. We studied the distribution pattern of neurons containing gamma-aminobutyric acid ( GABA) and their physiological role. Immunofluorescence revealed a GABA-immunoreactive axon that originates within the subesophageal ganglion at the salivary neuron 2 (SN2) and this extends within the salivary duct nerve towards the salivary gland. GABA-positive fibers form a network on most acinar lobules and a dense plexus in the interior of a minor fraction of acinar lobules. Co-staining with anti-synapsin revealed that some putative GABAergic terminals seem to make pre-synaptic contacts with GABA-negative release sites. Many putative GABAergic release sites are at some distance from other synapses and at distance from the acinar tissue. Intracellular recordings from isolated salivary glands have revealed that GABA does not affect the basolateral membrane potential of the acinar cells directly. When applied during salivary duct nerve stimulation, GABA enhances the electrical response of the acinar cells and increases the rates of fluid and protein secretion. The effect on electrical cell responses is mimicked by the GABA(B) receptor agonists baclofen and SKF97541, and blocked by the GABAB receptor antagonists CGP52432 and CGP54626. These findings indicate that GABA has a modulatory role in the control of salivation, acting presynaptically on serotonergic and/or dopaminergic neurotransmission.}, language = {en} } @article{VossSchmidtWalzetal.2009, author = {Voss, Martin and Schmidt, Ruth and Walz, Bernd and Baumann, Otto}, title = {Stimulus-induced translocation of the protein kinase A catalytic subunit to the apical membrane in blowfly salivary glands}, issn = {0302-766X}, doi = {10.1007/s00441-008-0673-x}, year = {2009}, abstract = {Secretion in blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT), which activates the InsP(3)/Ca2+ pathway and the cAMP/protein kinase A (PKA) pathway in the secretory cells. The latter signaling cascade induces the activation of a vacuolar H+-ATPase on the apical membrane. Here, we have determined the distribution of PKA by using antibodies against the PKA regulatory subunit-II (PKA-RII) and the PKA catalytic subunit (PKA-C) of Drosophila. PKA is present in high concentrations within the secretory cells. PKA-RII and PKA-C co-distribute in non-stimulated glands, being enriched in the basal portion of the secretory cells. Exposure to 8-CPT-cAMP or 5-HT induces the translocation of PKA-C to the apical membrane, whereas the PKA-RII distribution remains unchanged. The recruitment of PKA-C to the apical membrane corroborates our hypothesis that vacuolar H+-ATPase, which is enriched in this membrane domain, is a target protein for PKA.}, language = {en} } @article{WalzBaumann1995, author = {Walz, Bernd and Baumann, Otto}, title = {Structure and cellular physiology of Ca2+ stores in invertebrate photoreceptors}, year = {1995}, language = {en} } @article{WalzBaumannKrachetal.2006, author = {Walz, Bernd and Baumann, Otto and Krach, Christian and Baumann, Arnd and Blenau, Wolfgang}, title = {The aminergic control of cockroach salivary glands}, year = {2006}, abstract = {The acinar salivary glands of cockroaches receive a dual innervation from the subesophageal ganglion and the stomatogastric nervous system. Acinar cells are surrounded by a plexus of dopaminergic and serotonergic varicose fibers. In addition, seroton-ergic terminals lie deep in the extracellulor spaces between acinar cells. Excitation-secretion coupling in cockroach salivary glands is stimulated by both dopamine and serotonin. These monoamines cause increases in the intracellular concentrations of cAMP and Ca2+. Stimulation of the glands by serotonin results in the production of a protein-rich saliva, whereas stimulation by dopamine results in saliva that is protein-free. Thus, two elementary secretary processes, namely electrolyte/water secretion and protein secretion, are triggered by different aminergic transmitters. Because of its simplicity and experimental accessibility, cockroach salivary glands have been used extensively as a model system to study the cellular actions of biogenic amines and to examine the pharmacological properties of biogenic amine receptors. In this review, we summarize current knowledge concerning the aminergic control of cockroach salivary glands and discuss our efforts to characterize Periplaneta biogenic amine receptors molecularly}, language = {en} } @misc{BaumannWalz2012, author = {Baumann, Otto and Walz, Bernd}, title = {The blowfly salivary gland - A model system for analyzing the regulation of plasma membrane V-ATPase}, series = {Journal of insect physiology}, volume = {58}, journal = {Journal of insect physiology}, number = {4}, publisher = {Elsevier}, address = {Oxford}, issn = {0022-1910}, doi = {10.1016/j.jinsphys.2011.11.015}, pages = {450 -- 458}, year = {2012}, abstract = {Vacuolar H+-ATPases (V-ATPases) are heteromultimeric proteins that use the energy of ATP hydrolysis for the electrogenic transport of protons across membranes. They are common to all eukaryotic cells and are located in the plasma membrane or in membranes of acid organelles. In many insect epithelia, V-ATPase molecules reside in large numbers in the apical plasma membrane and create an electrochemical proton gradient that is used for the acidification or alkalinization of the extracellular space, the secretion or reabsorption of ions and fluids, the import of nutrients, and diverse other cellular activities. Here, we summarize our results on the functions and regulation of V-ATPase in the tubular salivary gland of the blowfly Calliphora vicina. In this gland, V-ATPase activity energizes the secretion of a KCl-rich saliva in response to the neurohormone serotonin (5-HT). Because of particular morphological and physiological features, the blowfly salivary glands are a superior and exemplary system for the analysis of the intracellular signaling pathways and mechanisms that modulate V-ATPase activity and solute transport in an insect epithelium.}, language = {en} } @article{BaumannWalz2001, author = {Baumann, Otto and Walz, Bernd}, title = {The endoplasmic reticulum of animal cells and its organization into structural and functional domains}, year = {2001}, language = {en} } @misc{VossBlenauWalzetal.2009, author = {Voss, Martin and Blenau, Wolfgang and Walz, Bernd and Baumann, Otto}, title = {V-ATPase deactivation in blowfly salivary glands is mediated by protein phosphatase 2C}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-44360}, year = {2009}, abstract = {The activity of vacuolar H+-ATPase (V-ATPase) in the apical membrane of blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT). 5-HT induces, via protein kinase A, the phosphorylation of V-ATPase subunit C and the assembly of V-ATPase holoenzymes. The protein phosphatase responsible for the dephosphorylation of subunit C and V-ATPase inactivation is not as yet known. We show here that inhibitors of protein phosphatases PP1 and PP2A (tautomycin, ocadaic acid) and PP2B (cyclosporin A, FK-506) do not prevent V-ATPase deactivation and dephosphorylation of subunit C. A decrease in the intracellular Mg2+ level caused by loading secretory cells with EDTA-AM leads to the activation of proton pumping in the absence of 5-HT, prolongs the 5-HT-induced response in proton pumping, and inhibits the dephosphorylation of subunit C. Thus, the deactivation of V-ATPase is most probably mediated by a protein phosphatase that is insensitive to okadaic acid and that requires Mg2+, namely, a member of the PP2C protein family. By molecular biological techniques, we demonstrate the expression of at least two PP2C protein family members in blowfly salivary glands. © 2009 Wiley Periodicals, Inc.}, language = {en} }