The function of ENSG00000054277 (OPN3, opsin 3) is as follows. G protein-coupled photoreceptor that selectively activates G(i/o) proteins in response to light, thereby decreasing intracellular cAMP levels (PubMed:28842328, PubMed:30168605, PubMed:31380578, PubMed:36869204). Activation occurs when the opsin-bound cis-retinal chromophore absorbs a photon and isomerizes to all-trans-retinal, inducing a conformational change in the opsin that triggers a G protein-mediated phototransduction cascade (PubMed:36869204). Mediates blue light-induced pigmentation in melanocytes by activating calcium/CAMK2 signaling, followed by phosphorylation of CREB, p38, ERK and MITF. Required for TYR and DCT blue light-induced complex formation in melanocytes (PubMed:28842328). Involved in keratinocyte differentiation in response to blue-light (PubMed:30168605). Plays a role in melanocyte survival through regulation of intracellular calcium levels and subsequent BCL2/RAF1 signaling. Additionally, regulates apoptosis via cytochrome c release and subsequent activation of the caspase cascade (PubMed:31730232). Responsible for ultraviolet A (UVA)- induced keratinocytes supranuclear melanin cap formation via activating calcium/CAMK2, CREB, and Akt signal transduction, and ultimately increasing DYNC1I1 and DCTN1 expression levels, thereby playing a role in the skin response to UV radiation (PubMed:36869204). Required for the UVA-mediated induction of calcium and MAPK signaling resulting in the expression of MMP1, MMP2, MMP3, MMP9 and TIMP1 in dermal fibroblasts (PubMed:31380578). Also plays a role in light-mediated glucose uptake, mitochondrial respiration and fatty acid metabolism in brown adipocyte tissues. May be involved in photorelaxation of airway smooth muscle cells, via blue light-dependent GPCR signaling pathways (By similarity). Also inhibits melanogenesis in melanocytes by specifically inhibiting MC1R-evoked cAMP signaling in a constitutive, light-independent manner (PubMed:31097585). In the paraventricular nucleus of the hypothalamus, inhibits MC4R-mediated cAMP signaling and activates KCNJ13 channel opening in a constitutive manner, thereby promoting food intake and modulating spontaneous firing of neurons (PubMed:39951488). {ECO:0000250|UniProtKB:Q9WUK7, ECO:0000269|PubMed:28842328, ECO:0000269|PubMed:30168605, ECO:0000269|PubMed:31097585, ECO:0000269|PubMed:31380578, ECO:0000269|PubMed:31730232, ECO:0000269|PubMed:36869204, ECO:0000269|PubMed:39951488}.