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O.A. Mafe, E.V. Gregg, H. Xin, P. Mitchell, P. Koulen; Polycystins in Mouse Retinal Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):168.
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© ARVO (1962-2015); The Authors (2016-present)
The polycystin family of transient receptor potential (TRP) channels includes three homologous proteins, polycystin–2 (PKD2), polycystin–2LI (PKD2L1) and polycystin–2L2 (PKD2L2) which are found in invertebrates, mammals and humans. These proteins form Ca2+ regulated cation channels and have distinct subcellular localizations and functions. As part of a multiprotein complex, polycystins control intracellular Ca2+ signals. At the gene level, polycystins are potentially expressed in the retina but their expression in retinal ganglion cells (RGCs) has not been fully established. PKD2L1 is believed to be predominant in the retina while PKD2 has been cloned from retina. In the present study, the distribution of PKD2, PKD2L1 and PKD2L2 in mouse RGCs was determined to identify molecular substrates of how these proteins interact and regulate polycystin mediated Ca2+ signaling in these retinal interneurons.
Primary RGC cultures were prepared using acute isolation of neurons from adult mouse retinae by enzymatic and mechanical dissociation. Immunocytochemical labeling of PKD2, PKD2L1 and PKD2L2 in vivo and of cultured RGCs was carried out using specific antibodies and detected with fluorescence microscopy. RGCs were identified with specific immunocytochemical markers; i.e., neurofilament 68kDa, Thy1.1 and Thy1.2.
RGC morphology and immunoreactivity to neurofilament 68kDa and Thy1.1 or Thy1.2 were identified in both primary cultures and retina cryosections. RGCs express polycystin–2, polycystin–2LI and polycystin–2L2. Immunoreactivity for these polycystins was detected intracellularly throughout RGCs with intense staining for polycystin–2 and weaker signals for PKD2L1 and PKD2L2.
Expression of all polycystins by RGCs indicates that these homologous proteins potentially play a role in intracellular signaling of RGCs. In particular, based on the biophysical properties of polycystins, the presence of these ion channel proteins suggests physiological and functional activity of polycystins in the regulation of intracellular Ca2+ signaling in RGCs.
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