Functional G-protein heterotrimers are associated with vesicles of putative glutamatergic terminals: implications for regulation of transmitter uptake

Mol Cell Neurosci. 2003 Jul;23(3):398-413. doi: 10.1016/s1044-7431(03)00059-9.

Abstract

Changes in the vesicular transmitter content modulate synaptic strength and may contribute to synaptic plasticity. Several transporters mediating transmitter uptake into small synaptic vesicles (SSVs) have been identified but their regulation is largely unknown. Here we show by quantitative immunoelectron microscopy that the heterotrimeric G-protein subunits Galphao(2), Galpha(q/11), Gbeta(2), and Ggamma(7) are associated with vesicle-containing areas in terminals of cerebellar parallel fibers. These terminals also contain the vesicular glutamate transporter 1 (VGLUT1). In contrast, SSVs of climbing fiber terminals that contain VGLUT2 express one of the Gbeta-subunits Gbeta(1), Gbeta(3), or Gbeta(4), Ggamma(7), and one Galpha-subunit, probably Galphao(2). Glutamate uptake into cerebellar SSVs was inhibited by more than 50% by GMppNp, an activator of G proteins. Thus, vesicle populations with different subtypes of vesicular glutamate transporters contain functional G proteins with distinct subunit profiles. Heterotrimeric G proteins may play an important role in the control of vesicular filling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibody Specificity
  • Carrier Proteins / analysis
  • Carrier Proteins / immunology
  • Cerebellum / cytology
  • GABA Plasma Membrane Transport Proteins
  • GTP-Binding Proteins / immunology
  • GTP-Binding Proteins / metabolism*
  • Glutamic Acid / metabolism*
  • Immunohistochemistry
  • Membrane Proteins / analysis
  • Membrane Proteins / immunology
  • Membrane Transport Proteins*
  • Microscopy, Immunoelectron
  • Neurons / chemistry*
  • Neurons / ultrastructure
  • Organic Anion Transporters*
  • Presynaptic Terminals / metabolism
  • Presynaptic Terminals / ultrastructure
  • Rats
  • Synaptic Transmission / physiology*
  • Synaptic Vesicles / metabolism*
  • Vesicular Glutamate Transport Protein 1
  • Vesicular Glutamate Transport Protein 2
  • Vesicular Transport Proteins*
  • gamma-Aminobutyric Acid / physiology

Substances

  • Carrier Proteins
  • GABA Plasma Membrane Transport Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Organic Anion Transporters
  • Slc17a6 protein, rat
  • Slc17a7 protein, rat
  • Vesicular Glutamate Transport Protein 1
  • Vesicular Glutamate Transport Protein 2
  • Vesicular Transport Proteins
  • Glutamic Acid
  • gamma-Aminobutyric Acid
  • GTP-Binding Proteins