Glutamate transporters are involved in direct inhibitory synaptic transmission in the vertebrate retina
Stephanie Niklaus,
Stella M. K. Glasauer,
Peter Kovermann,
Kulsum F. Farshori,
Lucia Cadetti,
Simon Früh,
Nicolas N. Rieser,
Matthias Gesemann,
Jingjing Zang,
Christoph Fahlke,
Stephan C. F. Neuhauss
Affiliations
Stephanie Niklaus
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Stella M. K. Glasauer
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Peter Kovermann
Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Leo-Brandt-Strasse , 52425 Jülich, Germany
Kulsum F. Farshori
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Lucia Cadetti
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Simon Früh
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Nicolas N. Rieser
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Matthias Gesemann
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Jingjing Zang
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
Christoph Fahlke
Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Leo-Brandt-Strasse , 52425 Jülich, Germany
Stephan C. F. Neuhauss
Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190 , 8057 Zurich, Switzerland
In the central nervous system of vertebrates, glutamate serves as the primary excitatory neurotransmitter. However, in the retina, glutamate released from photoreceptors causes hyperpolarization in post-synaptic ON-bipolar cells through a glutamate-gated chloride current, which seems paradoxical. Our research reveals that this current is modulated by two excitatory glutamate transporters, EAAT5b and EAAT7. In the zebrafish retina, these transporters are located at the dendritic tips of ON-bipolar cells and interact with all four types of cone photoreceptors. The absence of these transporters leads to a decrease in ON-bipolar cell responses, with eaat5b mutants being less severely affected than eaat5b/eaat7 double mutants, which also exhibit altered response kinetics. Biophysical investigations establish that EAAT7 is an active glutamate transporter with a predominant anion conductance. Our study is the first to demonstrate the direct involvement of post-synaptic glutamate transporters in inhibitory direct synaptic transmission at a central nervous system synapse.
