Abstract
Purpose: :
Recent studies reported alterations in the expression levels of some proteins in glaucomatous retinae. However, up to now mostly single proteins were analyzed, thus a broad insight into proteome alterations related to glaucomatous neurodegeneration is still missing. To address this question we performed a mass spectrometry based study, analyzing the retinae of glaucoma patients in comparison to those of healthy subjects.
Methods: :
Retinae were obtained from donor eyes of 5 healthy and 5 glaucomatous donors. Retina proteins were extracted, fractionated via SDS-PAGE and digested tryptically. In the second dimension tryptic peptides were fractionated by use of C18 chromatographie. Mass spectrometry analysis was performed using a MALDI-Orbitrap-XL. Identified proteins were quantified and assignment of protein functions was carried out by Gene Ontology data base search.
Results: :
The explorative protein analysis leads to the identification of 278 proteins. 44 of these were found to be significantly decreased (P≤0.01) in glaucomatous retinae, e.g. RAB1C (fold decrease: -19.1±8.5), alpha/beta-tubulin (fd: -12.6±5.6; - 15.9±4.5) or superoxide dismutase and peroxiredoxin1 (fd: -5.2±3.4; -7.8±3.2). 25 proteins were found in higher quantities, e.g. A/B-crystallin (fold increase: +6.4±4.2; +7.8±6.7) or members of the HSP family (HSP90:+10.3±8.9; HSP77: +2.9±2.2). The annotation of protein functions revealed functional groups, such as vesicular trafficking, cytoskeleton associated proteins or proteins involved into the removal of ROS to be significantly overrepresented (P≤5E-6) within the groups of differential expressed proteins.
Conclusions: :
The present data disclose deep insights into processes associated with glaucomatous neurodegeneration. For example, several proteins involved into the regulation of apoptotic pathways revealed to be differentially expressed, reflecting the apoptotic events within the retinal ganglion cell layer. Proteins involved into the elemination of ROS were found to be considerably diminished in glaucomatous retinae, thus suggesting an insufficient ability of patients to counterbalance the increased level of ROS in glaucomatous retinae. All in all the generated data demonstrate that proteins involved in manifold different pathways and mechanisms are affected in context of glaucomatous neurodegeneration.
Keywords: proteomics • retina