Neuron
Volume 11, Issue 1, July 1993, Pages 165-172
Journal home page for Neuron

Article
GTPγS stimulates exocytosis in patch-clamped rat melanotrophs

https://doi.org/10.1016/0896-6273(93)90280-5Get rights and content

Abstract

We investigated the molecular mechanisms regulating exocytosis in patch-clamped melanotrophs by measuring the membrane capacitance. Ca2+-dependent exocytosis could be induced by membrane depolarization or by including solutions containing 2 μM free Ca2+ in the patch pipette. Caz+-dependent exocytosis was inhibited by GDPβS, suggesting involvement of a GTP-binding protein. The hydrolysis-resistant GTP analogs, GTPγS and GppNHp, were able to stimulate exocytosis at low free Ca2+ concentrations. The stimulatory response to GTPγS was abolished by both GDPβS and GTP. The latter suggests that a sustained activation of a GTP-binding protein is necessary for exocytosis. This behavior is similar to the stimulation of exocytosis by guanine nucleotides in mast cells and other nonexcitable cells and suggests a common regulatory mechanism.

References (49)

  • C. Joshi et al.

    Capacitance measurements: an analysis of the phase detector technique used to study exocytosis and endocytosis

    Biophys. J.

    (1988)
  • R.A. Kahn

    Fluoride is not an activator of the smaller (2025 kDa) GTP-binding proteins

    J. Biol. Chem.

    (1991)
  • M. Lindau et al.

    Techniques and concepts in exocytosis: focus on mast cells

    Biochim. Biophys. Acta

    (1991)
  • Y. Matsui et al.

    Nucleotide and deduced amino acid sequences of a GTP-binding protein family with molecular weights of 25,000 from bovine brain

    J. Biol. Chem.

    (1988)
  • S.R. Pfeffer

    GTP-binding proteins in intracellular transport

    Trends Cell Biol.

    (1992)
  • S.A. Ronning et al.

    Characterization of Ca2+-stimulated secretion in permeable GH3 pituitary cells

    J. Biol. Chem.

    (1986)
  • J. Senyshyn et al.

    Synthetic peptides of the effector-binding domain of rab enhance secretion from digitonin-permeabilized chromaffin cells

    FEBS Lett.

    (1992)
  • S.K. Sikdar et al.

    cAMP directly facilitates Ca-induced exocytosis in bovine lactotrophs

    FEBS Lett.

    (1990)
  • T. Tamaoki

    Use and specificity of staurosporine, UCN-01, and calphostin C as protein kinase inhibitors

    Meth. Enzymol.

    (1991)
  • P. Thomas et al.

    Cytosolic Ca2+, exocytosis, and endocytosis in single melanotrophs of the rat pituitary

    Neuron

    (1990)
  • L. Vallar et al.

    Guanine nucleotides induce Ca2+-independent insulin secretion from permeabilized RINm5F cells

    J. Biol. Chem.

    (1987)
  • A. Zahraoui et al.

    The human Rabgenes encode a family of GTP-binding proteins related to yeast YPT1 and SEC4 products involved in secretion

    J. Biol. Chem.

    (1989)
  • G. Baldini et al.

    Cloning of a Rab3 isotype predominately expressed in adipocytes

  • J. Bigay et al.

    Fluoride complexes of aluminum or beryllium act on G proteins as reversibly bound analogues of the γ phosphate of GTP

    EMBO J.

    (1987)
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      In this study, we have discovered the long sought after signaling pathway that mediates GTP-dependent exocytosis. In various mammalian cell types, sustained activation of one or more GTPases by nonhydrolyzable GTP induces exocytotic secretion (1–9). Therefore, the discovery of a mediating GTPase for this process is important for the cell biology of secretion.

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