Experiments and Simulations of the Internalization of Heterologously Expressed Mouse Melanopsin

G protein-coupled receptors (GPCRs), the largest family of eukaryote transmembrane receptors, respond to extracellular stimuli and trigger a response within the cell. Opsins are specialized GPCRs that are involved in the conversion of light into a biological signal. Melanopsin is an opsin that is found in intrinsically photosensitive retinal ganglion cells (ipRGCs) in the mammalian retina and regulates non-image forming vision functions such as circadian photoentrainment and pupillary constriction. While much of the phototransduction pathway activated by melanopsin has not been fully elucidated, we hypothesize that melanopsin is internalized after light-activation and deactivation by β-arrestin. To test this hypothesis, we synthesized GFP-tagged melanopsin constructs in a mammalian expression vector, PMT3, through cassette mutagenesis and expressed these constructs in Human Embryonic Kidney (HEK) cells. We then assayed the localization of melanopsin within the cell using confocal microscopy. Preliminary results from confocal imaging confirms internalization of the melanopsin constructs in HEK cells. To model this phenomenon, a series of stoichiometric equations based on the underlying biological processes were converted to ordinary differential equations (ODEs), and incorporated into a model of the phototransduction pathway of melanopsin.This work was funded by NSF DBI 1031420.