Analysis of protein-protein interactions and proteomic profiles of normal human lenses

To investigate proteomic profiles of normal human lenses and their key proteins in protein-protein interactions (PPIs).

Water-soluble and water-insoluble proteins extracted from human lenses were first separated by one-dimensional sodium dodecyl sulfate polyacrylamide gel, and then in-gel digested with trypsin into peptides eluted by reversed-phase high-performance liquid chromatography. The eluted peptides were analyzed by linear ion trap tandem mass spectrometry (MS/MS). The raw data was filtered by TurboSEQUEST algorithm. The reverse database was used for peptide false-positive rate estimation. A network chart was constructed by the identified lens PPIs in accordance with interaction database systems.

From normal human lenses 339 proteins in total were identified, including many formerly unidentified low-abundance proteins. Key proteins we recognized included plectin, actin, spectrin (alpha, beta), vimentin, 14-3-3 protein (beta/alpha, zeta/delta, epsilon, gamma, eta), TSC2, guanine nucleotide-releasing protein, laminin gamma, mitogen-activated protein kinase, alpha-A-crystallin, heat-shock protein (alpha, beta), glyceraldehyde 3-phosphate dehydrogenase, and collagen IV alpha.

Key proteins of normal human lenses were studied by constructing a network chart of the identified lens PPIs. The results suggest that linear ion trap MS/MS is an effective tool for detecting low-abundance proteins of human lenses. This study provides valuable data for further proteomic research of the human lens development and lens diseases.