Neuroglobin and cytoglobin: oxygen-binding proteins in retinal neurons.
OBJECTIVE
The goal of this study was to describe the detailed localization of the novel oxygen-binding molecules, neuroglobin (Ngb) and cytoglobin (Cygb), in mammalian retinas and to determine whether Ngb and Cygb are neuronal or glial proteins in the retina.


METHODS
Antibodies directed against Ngb and Cygb were used to examine their patterns of distribution in normal canine retinas. Immunoblot analysis was performed to verify antibody specificity and the presence of Ngb and Cygb in canine tissues. Double-labeling immunohistochemistry was performed with the Ngb and Cygb antibodies along with antibodies against neuronal (MAP-2, class III beta-tubulin (TUJ1), PKCalpha, and calretinin) and glial antigens (vimentin and CRALBP). Tissue sections were analyzed with light and confocal microscopy.


RESULTS
Ngb and Cygb proteins were observed in different retinal cells. Cygb (but not Ngb) was also present in canine kidney, liver, lung, and heart tissue. Immunohistochemical analysis of canine retinas demonstrated Ngb immunoreactivity (IR) in the ganglion cell layer (GCL), inner (INL) and outer (ONL) nuclear layers, inner (IPL) and outer plexiform (OPL) layers, photoreceptor inner segments (IS), and retinal pigment epithelium (RPE). Ngb IR was localized within retinal neurons, but not in glia. Cygb IR was found in neurons and their processes in the GCL, IPL, INL, and OPL and within the RPE, but not in glia.


CONCLUSIONS
Ngb and Cygb are widely distributed in retinal neurons and RPE, but not in glial cells of the canine retina. Their structure and distribution is suggestive of a possible role in oxygen transport in the mammalian retina.
Ostojić
Jelena
J
Department of Genetics, Development and Cell Biology and Interdepartmental Neuroscience Program, Iowa State University, Ames 50011, USA.
Sakaguchi
Donald S
DS
de Lathouder
Yancy
Y
Hargrove
Mark S
MS
Trent
James T
JT
Kwon
Young H
YH
Kardon
Randy H
RH
Kuehn
Markus H
MH
Betts
Daniel M
DM
Grozdanić
Sinisa
S
D000818:Animals; D015153:Blotting, Western; D064032:Calbindin 2; D004285:Dogs; D019084:Fluorescent Antibody Technique, Indirect; D005914:Globins / Q000378:metabolism*; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism; D000078787:Neuroglobin; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D012160:Retina / Q000378:metabolism*; D012172:Retinaldehyde / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism; D014746:Vimentin / Q000378:metabolism
D064032:Calbindin 2; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D009687:Nuclear Proteins; D064030:S100 Calcium Binding Protein G; D014404:Tubulin; D014746:Vimentin; D005914:Globins; D051571:Protein Kinase C-alpha; D012172:Retinaldehyde; D010100:Oxygen