Distinct Roles of Gαq and Gα11 for Purkinje Cell Signaling and Motor Behavior

G-protein-coupled metabotropic glutamate group I receptors (mGluR1s) mediate synaptic transmission and plasticity in Purkinje cells and, therefore, critically determine cerebellar motor control and learning. Purkinje cells express two members of the G-protein Gq family, namely Gq and G11. Although in vitro coexpression of mGluR1 with either G11 or Gq produces equally well functioning signaling cascades, Gq- and G11-deficient mice exhibit distinct alterations in motor coordination. By using whole-cell recordings and Ca 2 imaging in Purkinje cells, we show that Gq is required for mGluR-dependent synaptic transmission and for long-term depression (LTD). G11 has no detectable contribution for synaptic transmission but also contributes to LTD. Quantitative single-cell RT-PCR analyses in Purkinje cells demonstrate a more than 10-fold stronger expression of Gq versus G11. Our findings suggest an expression leveldependent action of Gq and G11 for Purkinje cell signaling and assign specific roles of these two Gq isoforms for motor coordination.