Part:BBa_K5267002

Usage and Biology

MT2(melatonin receptor type 2) is an integral membrane protein that is a G protein coupled receptor (GPCR), 7-transmembrane receptor. It is found primarily in the retina and brain. It is thought to participate in light-dependent functions in the retina and may be involved in the neurobiological effects of melatonin.[1] MT2 has been reported to modulate many physiological processes, especially those related to sleep and circadian rhythm regulation, but also in retina physiology, pain and neuronal and immune functions. Figure: Overall structures of MT2 (F: inactive state [PDB ID: 6ME6], J: active state [PDB ID: 7VH0]). Overall TM6 movement during receptor activation of MT 2(inactive state: [PDB ID: 6ME9] and active state: [PDB ID: 7VH0]). (G) Ligand binding site of crystal structures of MT 2 (left: [PDB ID: 6ME6], right: [PDB ID: 6ME9]). (K) Ligand binding site of cryo‐EM structure of MT2 [PDB ID: 7VH0]. [3]

Signal transduction features

As a class of GPCR, MT2 mainly transmits signals through G protein coupling. MT2 regulates the activities of protein kinase A (PKA) and cAMP response element-binding protein by activating Gαi/oA, inhibiting the intracellular AC activity and reducing the intracellular cAMP concentration. MT2 also inhibits the activity of guanylyl cyclase (GC) and reducing the intracellular cGMP concentration, to regulate cGMP-dependent signaling pathways. MT2 can also regulate gene expression by coupling with Gαq/11 protein to activate PLC, increase intracellular Ca2+ level, and activate PKC pathway to promote downstream signal transduction. [2] In terms of transcriptional regulation, melatonin signaling typically inhibits cAMP-responsive element binding (CREB), which activates gene transcription though the ERK pathway. [3] The figure from Okamoto, H. H., Cecon, E., Nureki, O., Rivara, S., & Jockers, R. (2024) shows melatonin receptor-mediated signal transduction. (Fig.1) Figure 1. Melatonin receptor signaling pathways. [3]

References

[1] R. Jockers et al., “Update on melatonin receptors: IUPHAR Review 20,” Br. J. Pharmacol., vol. 173, no. 18, pp. 2702–2725, Sep. 2016, doi: 10.1111/bph.13536.

[2] “Melatonin receptor structure and signaling,” J. Pineal Res., vol. 76, no. 3, p. e12952, Apr. 2024, doi: 10.1111/jpi.12952.

[3] Y. Gao, S. Zhao, Y. Zhang, and Q. Zhang, “Melatonin Receptors: A Key Mediator in Animal Reproduction,” Vet. Sci., vol. 9, no. 7, p. 309, Jun. 2022, doi: 10.3390/vetsci9070309.