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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.
Three-dimensional organization of endoplasmatic reticulum in the ventral photoreceptors of Limulus
(1994)
The phosphoinositide signaling cascade is involved in photoreception in the leech Hirudo medicinalis
(2000)
The effects of serotonin and dopamine on salivary secretion by isolated cockroach salivary glands
(1996)
The acinar salivary glands of the cockroach, Periplaneta americana, are innervated by dopaminergic and serotonergic nerve fibers. Serotonin stimulates the secretion of protein-rich saliva, whereas dopamine causes the production of protein-free saliva. This suggests that dopamine acts selectively on ion-transporting peripheral cells within the acini and the duct cells, and that serotonin acts on the protein-producing central cells of the acini. We have investigated the pharmacology of the dopamine-induced secretory activity of the salivary gland of Periplaneta americana by testing several dopamine receptor agonists and antagonists. The effects of dopamine can be mimicked by the non-selective dopamine receptor agonist 6,7-ADTN and, less effectively, by the vertebrate D1 receptor-selective agonist chloro-APB. The vertebrate D1 receptor-selective agonist SKF 38393 and vertebrate D2 receptor-selective agonist R(-)- TNPA were ineffective. R(+)-Lisuride induces a secretory response with a slower onset and a lower maximal response compared with dopamine-induced secretion. However, lisuride-stimulated glands continue secreting saliva, even after lisuride-washout. Dopamine-induced secretions can be blocked by the vertebrate dopamine receptor antagonists cis(Z)- flupenthixol, chlorpromazine, and S(+)-butaclamol. Our pharmacological data do not unequivocally indicate whether the dopamine receptors on the Periplaneta salivary glands belong to the D1 or D2 subfamily of dopamine receptors, but we can confirm that the pharmacology of invertebrate dopamine receptors is remarkably different from that of their vertebrate counterparts. (C) 2004 Elsevier Ltd. All rights reserved
The blowfly salivary gland - A model system for analyzing the regulation of plasma membrane V-ATPase
(2012)
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.
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