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V‐ATPase deactivation in blowfly salivary glands is mediated by protein phosphatase 2C
Author(s) -
Voss Martin,
Blenau Wolfgang,
Walz Bernd,
Baumann Otto
Publication year - 2009
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.20310
Subject(s) - dephosphorylation , phosphatase , atpase , protein phosphatase 2 , okadaic acid , phosphorylation , biology , protein subunit , biochemistry , calliphora vicina , protein kinase a , v atpase , microbiology and biotechnology , kinase , enzyme , botany , larva , gene , calliphoridae
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 Mg 2+ 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 Mg 2+ , 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.