GRM3, also known as metabotropic glutamate receptor 3 (mGluR3 or mGlu3), is a key modulator of glutamate neurotransmission and synaptic plasticity. It belongs to the group II metabotropic glutamate receptors and is mainly expressed in the mammalian central nervous system. GRM3 is involved in multiple biological processes, with its activation regulating various signaling pathways such as those related to protein kinase A, Protein kinase B (AKT), and TGFβ [1,2].

In colon cancer, knockdown of GRM3 expression or inhibition of its activation reduces cell survival, anchorage-independent growth in vitro, and inhibits tumor growth in vivo. Mechanistically, GRM3 antagonizes TGFβ-mediated activation of protein kinase A and inhibition of AKT [1].

In schizophrenia, some studies find genetic association of GRM3 polymorphisms with psychosis and schizophrenia-related endophenotypes, and the dimeric form of mGluR3 may be reduced in the brain [2,4,6].

In melanoma, oncogenic GRM3 variants dysregulate cAMP signaling and disrupt melanosome trafficking [3].

Also, in lupus-like disease in mice, activation of Grm3 ameliorates the disease by reducing B cell numbers [5].

In conclusion, GRM3 plays essential roles in multiple biological processes and disease conditions. Its functions in diseases like colon cancer, schizophrenia, melanoma, and lupus-like disease have been revealed through various functional studies. Research on GRM3 provides insights into disease mechanisms and potential therapeutic targets for these diseases.