Abstract
Purpose: :
The aqueous humor (AH), a clear fluid secreted into the anterior segment of the eye, has well defined homeostatic functions and potentially influences the pathogenesis of various eye diseases. However, the human AH proteome has previously not been well defined, in part because of inherent limitations in the techniques used to investigate it. Our objective was to provide an extensive and definitive list of human AH proteins using a comprehensive proteomic approach.
Methods: :
Samples from patients undergoing standard cataract surgery were pooled and depleted of interfering abundant albumin and IgG proteins. Albumin-bound and albumin-depleted AH fractions were tryptically digested and further fractionated using strong cation exchange chromatography. Each of these fractions was analyzed by LC-MS/MS using an Agilent 1100 nano pump and a Thermo LTQ mass spectrometer. IPI and NCBI human databases were searched using Sequest and X!Tandem algorithms.
Results: :
Twelve albumin-bound proteins and 50 proteins in the albumin-depleted fraction were identified with high confidence (multiple peptides with a min q-value ≤ 0.1). Most proteins identified appear to be novel, and several AH proteins previously identified with high confidence, such as transthyretin and vitamin D-binding protein, were confirmed. Apolipoproteins A-I, A-II, A-IV, D, E, and J were included among those proteins as well as anti-inflammatory protein S100-A8 and anti-oxidative protein glutathione peroxidase 3.
Conclusions: :
With previous reports demonstrating only a few high confidence human AH protein identifications, this work represents a vast improvement in AH proteome analyses and provides a molecular foundation for future work regarding AH function and pathophysiology.
Keywords: proteomics • aqueous • cataract