Human melanopsin forms a pigment maximally sensitive to blue light (λmax ≈ 479 nm) supporting activation of Gq/11 and Gi/o signalling cascades

A subset of mammalian retinal ganglion cells expresses an opsin photopigment (melanopsin, Opn4) and is intrinsically photosensitive. The human retina contains melanopsin, but the literature lacks a direct investigation of its spectral sensitivity or G-protein selectivity. Here, we address this deficit by studying physiological responses driven by human melanopsin under heterologous expression in HEK293 cells. Luminescent reporters for common second messenger systems revealed that light induces a high amplitude increase in intracellular calcium and a modest reduction in cAMP in cells expressing human melanopsin, implying that this pigment is able to drive responses via both Gq and Gi/o class G-proteins. Melanopsins from mouse and amphioxus had a similar profile of G-protein coupling in HEK293 cells, but chicken Opn4m and Opn4x pigments exhibited some Gs activity in addition to a strong Gq/11 response. An action spectrum for the calcium response in cells expressing human melanopsin had the predicted form for an opsin : vitamin A1 pigment and peaked at 479 nm. The G-protein selectivity and spectral sensitivity of human melanopsin is similar to that previously described for rodents, supporting the utility of such laboratory animals for developing methods of manipulating this system using light or pharmacological agents.

[1]  D. Skene,et al.  An action spectrum for melatonin suppression: evidence for a novel non‐rod, non‐cone photoreceptor system in humans , 2001, The Journal of physiology.

[2]  J. Pokorny,et al.  Human and macaque pupil responses driven by melanopsin-containing retinal ganglion cells , 2007, Vision Research.

[3]  M. Rollag,et al.  Melanopsin Triggers the Release of Internal Calcium Stores in Response to Light † , 2007, Photochemistry and photobiology.

[4]  Hisao Tsukamoto,et al.  Cephalochordate Melanopsin: Evolutionary Linkage between Invertebrate Visual Cells and Vertebrate Photosensitive Retinal Ganglion Cells , 2005, Current Biology.

[5]  Satchidananda Panda,et al.  Illumination of the Melanopsin Signaling Pathway , 2005, Science.

[6]  Morven A. Cameron,et al.  Evolution of Melanopsin Photoreceptors: Discovery and Characterization of a New Melanopsin in Nonmammalian Vertebrates , 2006, PLoS biology.

[7]  Russell G Foster,et al.  Non-rod, non-cone photoreception in the vertebrates , 2002, Progress in Retinal and Eye Research.

[8]  G. E. Pickard,et al.  Light-Evoked Calcium Responses of Isolated Melanopsin-Expressing Retinal Ganglion Cells , 2007, The Journal of Neuroscience.

[9]  D. Arendt.  Evolution of eyes and photoreceptor cell types. , 2003, The International journal of developmental biology.

[10]  Victoria Revell,et al.  A “Melanopic” Spectral Efficiency Function Predicts the Sensitivity of Melanopsin Photoreceptors to Polychromatic Lights , 2011, Journal of biological rhythms.

[11]  R. Foster,et al.  Regulation of the mammalian pineal by non-rod, non-cone, ocular photoreceptors. , 1999, Science.

[12]  Jianguo Jin,et al.  Coordinated Signaling through Both G12/13 and Gi Pathways Is Sufficient to Activate GPIIb/IIIa in Human Platelets* , 2002, The Journal of Biological Chemistry.

[13]  Y. Shichida,et al.  Photochemical properties of mammalian melanopsin. , 2012, Biochemistry.

[14]  Russell G Foster,et al.  The acute light-induction of sleep is mediated by OPN4-based photoreception , 2008, Nature Neuroscience.

[15]  K. Donner,et al.  In search of the visual pigment template , 2000, Visual Neuroscience.

[16]  W. P. Hayes,et al.  Melanopsin: An opsin in melanophores, brain, and eye. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[17]  Thomas W Cronin,et al.  Melanopsin forms a functional short-wavelength photopigment. , 2003, Biochemistry.

[18]  Robert J. Lucas,et al.  Calcium Imaging Reveals a Network of Intrinsically Light-Sensitive Inner-Retinal Neurons , 2003, Current Biology.

[19]  Izzo,et al.  SUPPRESSION OF MELATONIN SECRETION IN SOME BLIND PATIENTS BY EXPOSURE TO BRIGHT LIGHT , 2001 .

[20]  Jack M. Sullivan,et al.  HEK293S Cells Have Functional Retinoid Processing Machinery , 2002, The Journal of general physiology.

[21]  Kosuke Takano,et al.  Jellyfish vision starts with cAMP signaling mediated by opsin-Gs cascade , 2008, Proceedings of the National Academy of Sciences.

[22]  C. Zuker,et al.  Gqα protein function in vivo: Genetic dissection of its role in photoreceptor cell physiology , 1995, Neuron.

[23]  T. Cronin,et al.  Photochemistry of retinal chromophore in mouse melanopsin , 2008, Proceedings of the National Academy of Sciences.

[24]  Satchidananda Panda,et al.  Melanopsin (Opn4) Requirement for Normal Light-Induced Circadian Phase Shifting , 2002, Science.

[25]  David Sliney,et al.  Sensitivity of the Human Circadian System to Short-Wavelength (420-nm) Light , 2008, Journal of biological rhythms.

[26]  R. Crouch,et al.  Identification of RPE65 in transformed kidney cells1 , 1999, FEBS letters.

[27]  G. Salvador,et al.  Light activation of the phosphoinositide cycle in intrinsically photosensitive chicken retinal ganglion cells. , 2010, Investigative ophthalmology & visual science.

[28]  Robert J. Lucas,et al.  Characterization of an ocular photopigment capable of driving pupillary constriction in mice , 2001, Nature Neuroscience.

[29]  M. Hankins,et al.  The Primary Visual Pathway in Humans Is Regulated According to Long-Term Light Exposure through the Action of a Nonclassical Photopigment , 2002, Current Biology.

[30]  D. Clapham,et al.  Melanopsin Signaling in Mammalian Iris and Retina Hhs Public Access Intrinsic Plr in Mouse and Other Mammals Involvement of Melanopsin in Mammalian Intrinsic Plr Phototransduction Mechanism Underlying Intrinsic Plr Phototransduction Pathway in Iprgcs Functional Contribution of Intrinsic Plr in Mouse , 2022 .

[31]  S. Peirson,et al.  Profound defects in pupillary responses to light in TRPM‐channel null mice: a role for TRPM channels in non‐image‐forming photoreception , 2012, The European journal of neuroscience.

[32]  J. Bellingham,et al.  Addition of human melanopsin renders mammalian cells photoresponsive , 2005, Nature.

[33]  G. Brainard,et al.  Action Spectrum for Melatonin Regulation in Humans: Evidence for a Novel Circadian Photoreceptor , 2001, The Journal of Neuroscience.

[34]  O. Shimomura,et al.  Light-emitting properties of recombinant semi-synthetic aequorins and recombinant fluorescein-conjugated aequorin for measuring cellular calcium. , 1993, Cell calcium.

[35]  M. Biel,et al.  Melanopsin and rod–cone photoreceptive systems account for all major accessory visual functions in mice , 2003, Nature.

[36]  L. Stryer,et al.  Flow of information in the light-triggered cyclic nucleotide cascade of vision. , 1981, Proceedings of the National Academy of Sciences of the United States of America.

[37]  Kwoon Y. Wong,et al.  Induction of photosensitivity by heterologous expression of melanopsin , 2005, Nature.

[38]  Glen T. Prusky,et al.  Melanopsin-Expressing Retinal Ganglion-Cell Photoreceptors: Cellular Diversity and Role in Pattern Vision , 2010, Neuron.

[39]  Y Sakaki,et al.  Cloning and sequence analysis of cDNA for the luminescent protein aequorin. , 1985, Proceedings of the National Academy of Sciences of the United States of America.

[40]  K. Yau,et al.  Diminished Pupillary Light Reflex at High Irradiances in Melanopsin-Knockout Mice , 2003, Science.

[41]  J. Rizzo,et al.  Suppression of melatonin secretion in some blind patients by exposure to bright light. , 1995, The New England journal of medicine.

[42]  S. Kunapuli,et al.  Negative Regulation of Gq-mediated Pathways in Platelets by G12/13 Pathways through Fyn Kinase* , 2011, The Journal of Biological Chemistry.

[43]  Y. Tsukahara,et al.  A Novel Go-mediated Phototransduction Cascade in Scallop Visual Cells* , 1997, The Journal of Biological Chemistry.

[44]  M. Rollag,et al.  Rhabdomeric phototransduction initiated by the vertebrate photopigment melanopsin. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[45]  Bruce F O'Hara,et al.  Role of Melanopsin in Circadian Responses to Light , 2002, Science.

[46]  Z. Vogel,et al.  Adenylyl cyclase type-VIII activity is regulated by Gβγ subunits , 2006 .

[47]  Annette E. Allen,et al.  Melanopsin-Based Brightness Discrimination in Mice and Humans , 2012, Current Biology.

[48]  S. Peirson,et al.  Melanopsin phototransduction: slowly emerging from the dark. , 2012, Progress in brain research.

[49]  D. Berson,et al.  Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock , 2002, Science.

[50]  K. Yau,et al.  Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity , 2002, Science.

[51]  I. Fraser,et al.  Regulation of cAMP Responses by the G12/13 Pathway Converges on Adenylyl Cyclase VII* , 2008, Journal of Biological Chemistry.