Fig. 8.

Schematic representation of the proposed mechanism of Homer function. A, When Homer 1a associates with group I mGluRs (or without any Homer proteins bound), receptors are diffusely distributed in the membrane. In this state, voltage-gated ion channels on the cell membrane are efficiently modulated, but the calcium signal via mGluRs and the IP₃ receptor is weak.B, In the presence of long forms of Homer, group I mGluRs cluster together, presumably because of the interaction of the coiled coil, C-terminal tails of Homer. This interaction may also bring the complex in association with the IP₃ receptor (schematic not shown). Under this condition, the intracellular calcium signal is strong, but modulation of voltage-gated ion channels is weak.