G-protein-independent signaling mediated by metabotropic glutamate receptors |
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Authors: | Heuss C Scanziani M Gähwiler B H Gerber U |
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Affiliation: | Brain Research Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland. |
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Abstract: | Synaptically released glutamate activates ionotropic and metabotropic receptors at central synapses. Metabotropic glutamate receptors (mGluRs) are thought to modulate membrane conductances through transduction cascades involving G proteins. Here we show, in CA3 pyramidal cells from rat hippocampus, that synaptic activation of type 1 mGluRs by mossy fiber stimulation evokes an excitatory postsynaptic response independent of G-protein function, while inhibiting an afterhyperpolarization current through a G-protein-coupled mechanism. Experiments using peptide activators and specific inhibitors identified a Src-family protein tyrosine kinase as a component of the G-protein-independent transduction pathway. These results represent the first functional evidence for a dual signaling mechanism associated with a heptahelical receptor such as mGluR1, in which intracellular transduction involves activation of either G proteins or tyrosine kinases. |
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