title: Distribution and function of polycystin-2 in mouse retinal ganglion cells.
abstract: The polycystin family of transient receptor potential (TRP) channels form Ca(2+) regulated cation channels with distinct subcellullar localizations and functions. As part of heteromultimeric channels and multi-protein complexes, polycystins control intracellular Ca(2+) signals and more generally the translation of extracellular signals and stimuli to intracellular responses. Polycystin-2 channels have been cloned from retina, but their distribution and function in retinal ganglion cells (RGCs) have not yet been established. In the present study, we determined cellular and subcellular localization as well as functional properties of polycystin-2 channels in RGCs. Polycystin-2 expression and distribution in RGCs was assessed by immunohistochemistry on vertical cryostat section of mouse retina as well as primary cultured mouse RGCs, using fluorescence microscopy. Biophysical and pharmacological properties of polycystin-2 channels isolated from primary cultured RGCs were determined using planar lipid bilayer electrophysiology. We detected polycystin-2 immunoreactivity both in the ganglion cell layer as well as in primary cultured RGCs. Subcellular analysis revealed strong cytosolic localization pattern of polycystin-2. Polycystin-2 channel current was Ca(2+) activated, had a maximum slope conductance of 114 pS, and could be blocked in a dose-dependent manner by increasing concentrations of Mg(2+). The cytosolic localization of polycystin-2 in RGCs is in accordance with its function as intracellular Ca(2+) release channel. We conclude that polycystin-2 forms functional channels in RGCs, of which biophysical and pharmacological properties are similar to polycystin-2 channels reported for other tissues and organisms. Our data suggest a potential role for polycystin-2 in RGC Ca(2+) signaling.
authors.affiliation: Vision Research Center and Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes Street, Kansas City, MO 64108, USA.
authors.forename: S
authors.initials: S
authors.lastname: Kaja
authors.forename: O A
authors.initials: OA
authors.lastname: Mafe
authors.forename: R A
authors.initials: RA
authors.lastname: Parikh
authors.forename: P
authors.initials: P
authors.lastname: Kandula
authors.forename: C A
authors.initials: CA
authors.lastname: Reddy
authors.forename: E V
authors.initials: EV
authors.lastname: Gregg
authors.forename: H
authors.initials: H
authors.lastname: Xin
authors.forename: P
authors.initials: P
authors.lastname: Mitchell
authors.forename: M A
authors.initials: MA
authors.lastname: Grillo
authors.forename: P
authors.initials: P
authors.lastname: Koulen
mesh_terms: D000818:Animals; D001703:Biophysics; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D055724:Electrophysiological Phenomena; D007150:Immunohistochemistry; D007473:Ion Channels / Q000187:drug effects; D008051:Lipid Bilayers; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D018408:Patch-Clamp Techniques; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D050396:TRPP Cation Channels / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D008274:Magnesium; D050396:TRPP Cation Channels