TY  - JOUR
A1  - Fechner, Lennart
A1  - Baumann, Otto
A1  - Walz, Bernd
T1  - Activation of the cyclic AMP pathway promotes serotonin-induced Ca2+ oscillations in salivary glands of the blowfly Calliphora vicina
JF  - Cell calcium
N2  - 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.
KW  - Calcium
KW  - Ca2+
KW  - Calcium oscillations
KW  - cAMP
KW  - Signalling
KW  - Crosstalk
KW  - Salivary gland
KW  - Calliphora
KW  - Blowfly
KW  - Insect
Y1  - 2013
U6  - https://doi.org/10.1016/j.ceca.2012.10.004
SN  - 0143-4160
VL  - 53
IS  - 2
SP  - 94
EP  - 101
PB  - Churchill Livingstone
CY  - Edinburgh
ER  - 
TY  - JOUR
A1  - Heindorff, Kristoffer
A1  - Baumann, Otto
T1  - Calcineurin is part of a negative feedback loop in the InsP(3)/Ca2+ signalling pathway in blowfly salivary glands
JF  - Cell calcium
N2  - The ubiquitous InsP(3)/Ca2+ signalling pathway is modulated by diverse mechanisms, i.e. feedback of Ca2+ and interactions with other signalling pathways. In the salivary glands of the blowfly Calliphora vicina, the hormone serotonin (5-HT) causes a parallel rise in intracellular [Ca2+] and [cAMP] via two types of 5-HT receptors. We have shown recently that cAMP/protein kinase A (PKA) sensitizes InsP(3)-induced Ca2+ release. We have now identified the protein phosphatase that counteracts the effect of PKA on 5-HT-induced InsP(3)/Ca2+ signalling. We demonstrate that (1) tautomycin and okadaic acid, inhibitors of protein phosphatases PP1 and PP2A, have no effect on 5-HT-induced Ca2+ signals; (2) cyclosporin A and FK506, inhibitors of Ca2+/calmodulin-activated protein phosphatase calcineurin, cause an increase in the frequency of 5-HT-induced Ca2+ oscillations; (3) the sensitizing effect of cyclosporin A on 5-HT-induced Ca2+ responses does not involve Ca2+ entry into the cells; (4) cyclosporin A increases InsP(3)-dependent Ca2+ release; (5) inhibition of PKA abolishes the effect of cyclosporin A on the 5-HT-induced Ca2+ responses, indicating that PKA and calcineurin act antagonistically on the InsP(3)/Ca2+ signalling pathway. These findings suggest that calcineurin provides a negative feedback on InsP(3)/Ca2+ signalling in blowfly salivary glands, counteracting the effect of PKA and desensitizing the signalling cascade at higher 5-HT concentrations. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Calcineurin
KW  - Ca2+
KW  - Ca2+ oscillations
KW  - cAMP
KW  - Protein kinase A
KW  - Intracellular signalling
KW  - Salivary gland
KW  - Blowfly
KW  - Insect
Y1  - 2014
U6  - https://doi.org/10.1016/j.ceca.2014.07.009
SN  - 0143-4160
SN  - 1532-1991
VL  - 56
IS  - 3
SP  - 215
EP  - 224
PB  - Churchill Livingstone
CY  - Edinburgh
ER  -