Addition of human melanopsin renders mammalian cells photoresponsive

Z. Melyan, E. E. Tarttelin, J. Bellingham, R. J. Lucas, M. W. Hankins

    Research output: Contribution to journalArticlepeer-review


    A small number of mammalian retinal ganglion cells act as photoreceptors for regulating certain non-image forming photoresponses. These intrinsically photosensitive retinal ganglion cells express the putative photopigment melanopsin. Ablation of the melanopsin gene renders these cells insensitive to light; however, the precise role of melanopsin in supporting cellular photosensitivity is unconfirmed. Here we show that heterologous expression of human melanopsin in a mouse paraneuronal cell line (Neuro-2a) is sufficient to render these cells photoreceptive. Under such conditions, melanopsin acts as a sensory photopigment, coupled to a native ion channel via a G-protein signalling cascade, to drive physiological light detection. The melanopsin photoresponse relies on the presence of cis-isoforms of retinaldehyde and is selectively sensitive to short-wavelength light. We also present evidence to show that melanopsin functions as a bistable pigment in this system, having an intrinsic photoisomerase regeneration function that is chromatically shifted to longer wavelengths.
    Original languageEnglish
    Pages (from-to)741-745
    Number of pages4
    Issue number7027
    Publication statusPublished - 17 Feb 2005


    • Animals
    • radiation effects: Calcium Signaling
    • Cell Line
    • metabolism: Cyclic GMP
    • Gene Expression
    • antagonists & inhibitors: Heterotrimeric GTP-Binding Proteins
    • Humans
    • Light
    • Mice
    • metabolism: Neurons
    • genetics: Opsin
    • radiation effects: Phototransduction
    • chemistry: Protein Isoforms
    • chemistry: Retinaldehyde


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