Functional G-protein heterotrimers are associated with vesicles of putative glutamatergic terminals: implications for regulation of transmitter uptake.
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.
Pahner
Ingrid
I
Institut für Anatomie/Neurowissenschaftliches Zentrum der Charité, Humboldt-Universität zu Berlin, Philippstrasse 12, D-10115 Berlin, Germany.
Höltje
Markus
M
Winter
Sandra
S
Takamori
Shigeo
S
Bellocchio
Elizabeth E
EE
Spicher
Karsten
K
Laake
Petter
P
Nürnberg
Bernd
B
Ottersen
Ole Petter
OP
Ahnert-Hilger
Gudrun
G
Nümberg
Bernd
B
D000818:Animals; D000918:Antibody Specificity; D002352:Carrier Proteins / Q000032:analysis / Q000276:immunology; D002531:Cerebellum / Q000166:cytology; D050485:GABA Plasma Membrane Transport Proteins; D019204:GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000032:analysis / Q000276:immunology; D026901:Membrane Transport Proteins; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000737:chemistry* / Q000648:ultrastructure; D027361:Organic Anion Transporters; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism*; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D019204:GTP-Binding Proteins