The function of GRM1 (glutamate metabotropic receptor 1, Ensembl gene identifier ENSG00000152822) is as follows. 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. Signaling activates a phosphatidylinositol- calcium second messenger system. May participate in the central action of glutamate in the CNS, such as long-term potentiation in the hippocampus and long-term depression in the cerebellum (PubMed:24603153, PubMed:28886343, PubMed:7476890). May function in the light response in the retina (By similarity). Induces GRID1 and GRID2 cation-channel activation via GNAQ-PLC-PKC pathway in dopaminergic neurons and cerebellar Purkinje cell, respectively (PubMed:24357660, PubMed:27276689). {ECO:0000250|UniProtKB:P97772, ECO:0000269|PubMed:24357660, ECO:0000269|PubMed:24603153, ECO:0000269|PubMed:27276689, ECO:0000269|PubMed:28886343, ECO:0000269|PubMed:7476890}.