TY  - JOUR
A1  - Schewe, Bettina
A1  - Blenau, Wolfgang
A1  - Walz, Bernd
T1  - Intracellular pH regulation in unstimulated Calliphora salivary glands is Na+ dependent and requires V-ATPase activity
JF  - The journal of experimental biology
N2  - Salivary gland cells of the blowfly Calliphora vicina have a vacuolar-type H+-ATPase (V-ATPase) that lies in their apical membrane and energizes the secretion of a KCl-rich primary saliva upon stimulation with serotonin (5-hydroxytryptamine). Whether and to what extent V-ATPase contributes to intracellular pH (pH(i)) regulation in unstimulated gland cells is unknown. We used the fluorescent dye BCECF to study intracellular pH(i) regulation microfluorometrically and show that: (1) under resting conditions, the application of Na+-free physiological saline induces an intracellular alkalinization attributable to the inhibition of the activity of a Na+-dependent glutamate transporter; (2) the maintenance of resting pHi is Na+, Cl-, concanamycin A and DIDS sensitive; (3) recovery from an intracellular acid load is Na+ sensitive and requires V-ATPase activity; (4) the Na+/H+ antiporter is not involved in pHi recovery after a NH4Cl prepulse; and (5) at least one Na+-dependent transporter and the V-ATPase maintain recovery from an intracellular acid load. Thus, under resting conditions, the V-ATPase and at least one Na+-dependent transporter maintain normal pH(i) values of pH.7.5. We have also detected the presence of a Na+-dependent glutamate transporter, which seems to act as an acid loader. Despite this not being a common pH(i)-regulating transporter, its activity affects steady-state pH(i) in C. vicina salivary gland cells.
KW  - Calliphora vicina
KW  - salivary gland
KW  - intracellular pH regulation
KW  - Na+/H+ antiporter
KW  - NHE
KW  - vacuolar H+-ATPase
KW  - V-ATPase
KW  - intracellular pH
KW  - insect
KW  - blowfly
KW  - BCECF
KW  - NH4Cl prepulse
Y1  - 2012
U6  - https://doi.org/10.1242/jeb.063172
SN  - 0022-0949
VL  - 215
IS  - 8
SP  - 1337
EP  - 1345
PB  - Company of Biologists Limited
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Voss, Martin
A1  - Blenau, Wolfgang
A1  - Walz, Bernd
A1  - Baumann, Otto
T1  - V-ATPase deactivation in blowfly salivary glands is mediated by protein phosphatase 2C
N2  - 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.
KW  - vacuolar H+-ATPase
KW  - assembly
KW  - regulation
KW  - protein phosphatise
KW  - dephosphorylation
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44360
ER  -