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  - 
TY  - JOUR
A1  - Gerhardt, Matthias
A1  - Walz, Michael
A1  - Beta, Carsten
T1  - Signaling in chemotactic amoebae remains spatially confined to stimulated membrane regions
JF  - Journal of cell science
N2  - Recent work has demonstrated that the receptor-mediated signaling system in chemotactic amoeboid cells shows typical properties of an excitable system. Here, we delivered spatially confined stimuli of the chemoattractant cAMP to the membrane of differentiated Dictyostelium discoideum cells to investigate whether localized receptor stimuli can induce the spreading of excitable waves in the G-protein-dependent signal transduction system. By imaging the spatiotemporal dynamics of fluorescent markers for phosphatidylinositol (3,4,5)-trisphosphate (PIP3), PTEN and filamentous actin, we observed that the activity of the signaling pathway remained spatially confined to the stimulated membrane region. Neighboring parts of the membrane were not excited and no receptor-initiated spatial spreading of excitation waves was observed. To generate localized cAMP stimuli, either particles that carried covalently bound cAMP molecules on their surface were brought into contact with the cell or a patch of the cell membrane was aspirated into a glass micropipette to shield this patch against freely diffusing cAMP molecules in the surrounding medium. Additionally, the binding site of the cAMP receptor was probed with different surface-immobilized cAMP molecules, confirming results from earlier ligand-binding studies.
KW  - Signal transduction
KW  - Excitable dynamics
KW  - Dictyostelium
KW  - cAMP
KW  - PIP3
KW  - PIP2
KW  - PI3K
KW  - PTEN
KW  - Micropipette aspiration
KW  - cAMP receptor
KW  - Patch clamp
Y1  - 2014
U6  - https://doi.org/10.1242/jcs.161133
SN  - 0021-9533
SN  - 1477-9137
VL  - 127
IS  - 23
SP  - 5115
EP  - 5125
PB  - Company of Biologists Limited
CY  - Cambridge
ER  -