Evidence that the pertussis toxin-sensitive trimeric GTP-binding protein Gi2 is required for agonist- and store-activated Ca2+ inflow in hepatocytes

Leise A. Berven, Michael F. Crouch, Frosa Katsis, Bruce E. Kemp, Lyn M. Harland, Greg J. Barritt

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    Abstract

    The role of a trimeric GTP-binding protein (G-protein) in the mechanism of vasopressin-dependent Ca2+ inflow in hepatocytes was investigated using both antibodies against the carboxyl termini of trimeric G-protein α subunits, and carboxyl-terminal α-subunit synthetic peptides. An anti-Gi1-2α antibody and a Gi2α peptide (Gi2α Ile345-Phe355), but not a Gi3α peptide (Gi3α Ile344-Phe354), inhibited vasopressin- and thapsigargin-stimulated Ca2+ inflow, had no effect on vasopressin-stimulated release of Ca2+ from intracellular stores, and caused partial inhibition of thapsigargin-stimulated release of Ca2+. An anti-G antibody also inhibited vasopressin-stimulated Ca2+ inflow and partially inhibited vasopressin-induced release of Ca2+ from intracellular stores. Immunofluorescence measurements showed that Gi2α is distributed throughout much of the interior of the hepatocyte as well as at the periphery of the cell. By contrast, Gq/11α was found principally at the cell periphery. It is concluded that the trimeric G-protein, Gi2, is required for store-activated Ca2+ inflow in hepatocytes and acts between the release of Ca2+ from the endoplasmic reticulum (presumably adjacent to the plasma membrane) and the receptor-activated Ca2+ channel protein(s) in the plasma membrane.

    Original languageEnglish
    Pages (from-to)25893-25897
    Number of pages5
    JournalJournal of Biological Chemistry
    Volume270
    Issue number43
    DOIs
    Publication statusPublished - 27 Oct 1995

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