@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{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}
}