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O.A. Mafe, E.V. Gregg, W.E. Medina–Ortiz, P. Koulen; Localization of Inositol 1, 4, 5–Trisphosphate Receptors in Mouse Retina Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4016.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Inositol–1, 4, 5–triphosphate receptors (IP3Rs) are intracellular Ca2+ channels known to be involved in several intracellular signaling pathways. IP3R mediated changes in cytosolic Ca2+ concentrations control neuronal functions ranging from synaptic transmission to differentiation and apoptosis. Similarly, cytosolic Ca2+ transients determine retinal ganglion cell physiology and pathophysiology. Determining the distribution of biophysically distinct IP3Rs in retina ganglion cells provides necessary information on the molecular substrates of IP3R mediated Ca2+ signaling in these interneurons. Methods:Primary cultures were prepared following a modified protocol (Luo et al., 2001) using acute isolation of retinal ganglion cells from adult mouse followed by enzymatic and mechanical dissociation. Cell cultures were maintained for 14 days. Cryo–sections of adult mouse retina were prepared as described previously (Koulen and Brandstätter, 2002). Immunocytochemical labeling of IP3Rs in cultured retinal ganglion cells and of retinal ganglion cells in vertical sections of the retina was carried out using isoform specific antibodies and was detected with fluorescence microscopy. Retinal ganglion cells were identified by the use of morphological criteria and retinal ganglion cell specific immunocytochemical markers, neurofilament 68 kDa and Thy1.1. Results: Retinal ganglion cell morphology and immunoreactivity to neurofilament 68 kDa and Thy1.1 were identified in both the retinal ganglion cell primary cultures and tissue cryosections. Retinal ganglion cells showed differential distribution of IP3R isoforms 1, 2 and 3. The IP3R types 1 and 3 were detected intracellularly throughout the cell, whereas type 2 was localized mainly in the soma. Conclusions:Expression of all three IP3Rs by retinal ganglion cells indicates that all IP3R types potentially play a role in Ca2+ homeostasis and Ca2+ signaling in these cells. Differential localization of IP3 receptor subtypes may be an important molecular mechanism by which retinal ganglion cells organize their cytosolic Ca2+ signals. These data will help to delineate the potential involvement of IP3R channels in signal processing and neuroprotection of retinal ganglion cells. References: Luo X, Heidinger V, Picaud S, Lambrou G, Dreyfus H, Sahel J, Hicks D. Invest Ophthalmol Vis Sci. 2001;42:1096–1106. Koulen P, Brandstatter JH. Invest Ophthalmol Vis Sci. 2002;43:1933–1940. Supported by NIH grant EY14227 (PK).
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