title: The light-induced FOS response in melanopsin expressing HEK-293 cells is correlated with melanopsin quantity and dependent on light duration and irradiance.
abstract: We established a cell line (HEK-hMel) expressing melanopsin in a tetracycline dependent manner to elucidate new aspects of melanopsin's light response. Different light stimuli were evaluated using FOS expression as response parameter. Immunoblotting was used to evaluate expression of melanopsin and FOS and qPCR to quantify FOS mRNA responses. The magnitude of the FOS response was found to correlate with the amount of melanopsin expressed by the cells, and a transient FOS mRNA induction followed by FOS protein still elevated after 24 h of illumination was revealed. Exposing the cells to darkness after light resulted in reduction of the response compared to exposure to light solely showing dependency on continuous light. Increasing irradiances of blue light (480 nm) up to 10(11) quanta cm(-2)  s(-1) elicited steep increases in FOS mRNA, while increases between 10(12) and 5 × 10(13) quanta  cm(-2)  s(-1) resulted in equally high FOS expression. The HEK-hMel cells were used to characterize facets of melanopsin's light-induced FOS response not approachable in vivo. Novel information such as dependency of the FOS response on both melanopsin amount and light intensity in addition to a detailed time-course of both FOS mRNA and protein were revealed.
authors.affiliation: Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark.
authors.forename: Birgitte
authors.initials: B
authors.lastname: Georg
authors.forename: Lene
authors.initials: L
authors.lastname: Rask
authors.forename: Jens
authors.initials: J
authors.lastname: Hannibal
authors.forename: Jan
authors.initials: J
authors.lastname: Fahrenkrug
mesh_terms: D004307:Dose-Response Relationship, Radiation; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D008027:Light; D055668:Photochemical Processes; D017440:Photoperiod; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D011829:Radiation Dosage; D017299:Rod Opsins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014170:Transformation, Genetic; D000099210:Melanopsin
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D017299:Rod Opsins; D000099210:Melanopsin