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Modulation of Neuropeptide‐lnduced Membrane Currents by Protein Kinase C in Xenopus Oocytes Injected with GH 3 Pituitary Cell Poly(A) + RNA
Author(s) -
Mahlmann Stefan,
Schwarz Jürgen R.,
Meyerhof Wolfgang
Publication year - 1989
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1989.tb00078.x
Subject(s) - protein kinase c , inositol , medicine , inositol phosphate , endocrinology , xenopus , gtpgammas , second messenger system , protein kinase a , pertussis toxin , biology , signal transduction , g protein , receptor , chemistry , microbiology and biotechnology , kinase , biochemistry , gene
Protein kinase C was activated in Xenopus laevis oocytes by phorbol ester treatment and its effects on the inositol trisphosphate/Ca 2+ transmembrane signalling pathway analysed. Induction of the pathway was achieved by ligand stimulation of TRH receptors translated from GH 3 pituitary cell mRNA. In voltage‐clamped oocytes bath application of peptide, injection of guanosine 5′‐(3‐O‐thio) triphosphate (GTPγS), inositol trisphosphate or Ca 2+ all elicited inward membrane currents. Treatment of oocytes with tumour‐promoting phorbol esters for 35 min almost completely abolished the ligand and GTPγS‐induced responses. In contrast, phorbol ester treatment enhanced inositol trisphosphate‐generated membrane currents. Ca 2+ ‐mediated responses remained unaffected by tumour promoters. The data indicate a dual role for protein kinase C in the modulation of transmembrane signalling: a feedback mechanism prevents phosphoinositide turnover whereas a feedforward reaction triggers the effect of intracellular inositol trisphosphate on the Ca 2+ release.