G-protein coupled receptor for glutamate. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors, such as adenylate cyclase. Signaling inhibits adenylate cyclase activity (By similarity). Signaling stimulates TRPM1 channel activity and Ca(2+) uptake. Required for normal vision. Homodimer. Subject to trafficking from the endoplasmic reticulum to the Golgi apparatus and then to the cell membrane (By similarity). Detected at dendritic tips of bipolar cells. Detected in the outer plexiform layer in retina (at protein level). Retinal cells from mutant mice display a subtly altered response to cycles of light and darkness, due to a failure of the ON bipolar cells in the retina to become depolarized in response to light. As a consequence, mutant mice display little or no pupillary contraction in adaptation to low light intensity. Besides, they exhibit strongly impaired responses to moving stimuli, and fail to produce a response when the visual constrast is low. Besides, rod bipolar cells from mutant mice lack TRPM1 channel activity. Belongs to the G-protein coupled receptor 3 family.