the protein encoded by this gene is a member of the transient receptor potential (trp) family of non-selective cation channels. it is expressed in the retina, in a subset of bipolar cells termed on bipolar cells. these cells form synapses with either rods or cones, collecting signals from them. in the dark, the signal arrives in the form of the neurotransmitter glutamate, which is detected by a g protein-coupled receptor (gpcr) signal transduction cascade. detection of glutamate by the gpcr metabotropic glutamate receptor 6 results in closing of the trpm1 channel. at the onset of light, glutamate release is halted and mglur6 is deactivated; this results in opening of the trpm1 channel, influx of sodium and calcium, and depolarization of the bipolar cell.