Distinct roles of Gα_q Gα₁₁ and 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 G_q family, namely G_q and G₁₁. Although in vitro coexpression of mGluR1 with either Gα₁₁ or Gα_q produces equally well functioning signaling cascades, Gα_q- and Gα₁₁-deficient mice exhibit distinct alterations in motor coordination. By using whole-cell recordings and Ca²⁺ imaging in Purkinje cells, we show that Gα_q is required for mGluR-dependent synaptic transmission and for long-term depression (LTD). Gα₁₁ 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 Gα_q versus Gα ₁₁. Our findings suggest an expression level-dependent action of Gα_q and Gα₁₁ for Purkinje cell signaling and assign specific roles of these two G_q isoforms for motor coordination.