title: Retinal G-substrate, potential downstream component of NO/cGMP/PKG pathway, is located in subtype of retinal ganglion cells and amacrine cells with protein phosphatases.
abstract: The aim of this study was to determine the distribution and function of G-substrate, a specific substrate of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-cGMP-dependent protein kinase (PKG) signaling pathway, in normal rat retina and in G-substrate knockout mice. The retinas of adult wild-type rats and mice and G-substrate knockout mice were studied immunohistologically to characterize the upstream and downstream components of the NO-cGMP-PKG pathway. Immunoblot analysis showed that the molecular weight of retinal G-substrate was similar to that of cerebellar G-substrate. In adult rats and mice, retinal G-substrate was located in a subpopulation of amacrine cells and in C38-positive retinal ganglion cells (RGCs) but not in alpha RGCs. In addition, retinal G-substrate was co-expressed with other upstream and downstream signaling components of the NO-cGMP-PKG-G-substrate-phosphatase pathway in the adult retina. Electroretinographic (ERG) analysis demonstrated that there was no significant difference between the ERGs of wild-type and G-substrate knockout mice. These results suggest that retinal G-substrate plays a role as a downstream component of the NO-cGMP-PKG pathway. The co-localization of retinal G-substrate with protein Ser/Thr phosphatases suggests that it acts as an endogenous protein phosphatase inhibitor as in the cerebellum.
authors.affiliation: Department of Ophthalmology and Visual Science, Tohoku Graduate School of Medicine, 980-8574, Seiryo 1-1, Aoba, Sendai, Japan. ntoru@fa2.so-net.ne.jp
authors.forename: Toru
authors.initials: T
authors.lastname: Nakazawa
authors.forename: Shogo
authors.initials: S
authors.lastname: Endo
authors.forename: Masahiko
authors.initials: M
authors.lastname: Shimura
authors.forename: Mineo
authors.initials: M
authors.lastname: Kondo
authors.forename: Shinji
authors.initials: S
authors.lastname: Ueno
authors.forename: Makoto
authors.initials: M
authors.lastname: Tamai
mesh_terms: D025042:Amacrine Cells / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D004596:Electroretinography / Q000379:methods; D006162:Guanylate Cyclase / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D007211:Indoles; D008027:Light; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000502:physiology; D008840:Microfilament Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction / Q000502:physiology*
chemical_list: C029152:G-substrate; D007211:Indoles; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D012333:RNA, Messenger; D009569:Nitric Oxide; C007293:DAPI; D017869:Cyclic GMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D006162:Guanylate Cyclase; D006152:Cyclic GMP