title: Proteomic analysis of the retina: removal of RPE alters outer segment assembly and retinal protein expression.
abstract: The mechanisms that regulate the complex physiological task of photoreceptor outer segment assembly remain an enigma. One limiting factor in revealing the mechanism(s) by which this process is modulated is that not all of the role players who participate in this process are known. The purpose of this study was to determine some of the retinal proteins that likely play a critical role in regulating photoreceptor outer segment assembly. To do so, we analyzed and compared the proteome map of tadpole Xenopus laevis retinal pigment epithelium (RPE)-supported retinas containing organized outer segments with that of RPE-deprived retinas containing disorganized outer segments. Solubilized proteins were labeled with CyDye fluors followed by multiplexed two-dimensional separation. The intensity of protein spots and comparison of proteome maps was performed using DeCyder software. Identification of differentially regulated proteins was determined using nanoLC-ESI-MS/MS analysis. We found a total of 27 protein spots, 21 of which were unique proteins, which were differentially expressed in retinas with disorganized outer segments. We predict that in the absence of the RPE, oxidative stress initiates an unfolded protein response. Subsequently, downregulation of several candidate Müller glial cell proteins may explain the inability of photoreceptors to properly fold their outer segment membranes. In this study, we have used identification and bioinformatics assessment of proteins that are differentially expressed in retinas with disorganized outer segments as a first step in determining probable key molecules involved in regulating photoreceptor outer segment assembly.
authors.affiliation: Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Wang
authors.forename: Suba
authors.initials: S
authors.lastname: Nookala
authors.forename: Chidambarathanu
authors.initials: C
authors.lastname: Narayanan
authors.forename: Francesco
authors.initials: F
authors.lastname: Giorgianni
authors.forename: Sarka
authors.initials: S
authors.lastname: Beranova-Giorgianni
authors.forename: Gary
authors.initials: G
authors.lastname: McCollum
authors.forename: Ivan
authors.initials: I
authors.lastname: Gerling
authors.forename: John S
authors.initials: JS
authors.lastname: Penn
authors.forename: Monica M
authors.initials: MM
authors.lastname: Jablonski
mesh_terms: D000818:Animals; D019295:Computational Biology / Q000379:methods; D015180:Electrophoresis, Gel, Two-Dimensional; D005136:Eye Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D007814:Larva; D013058:Mass Spectrometry / Q000379:methods; D008954:Models, Biological; D009457:Neuroglia / Q000378:metabolism; D009924:Organ Culture Techniques; D040901:Proteomics / Q000379:methods*; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D012160:Retina / Q000033:anatomy & histology / Q000378:metabolism*; D055214:Retinal Photoreceptor Cell Outer Segment / Q000502:physiology*; D055213:Retinal Pigment Epithelium / Q000502:physiology*; D014981:Xenopus
chemical_list: D005136:Eye Proteins; C516774:Ptprf protein, rat; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2