An In-Depth View of the Porcine Trabecular Meshwork Proteome.

Sebastian Funke,Vanessa M Beutgen,Natarajan Perumal,Vanessa Zurawski,Carsten Schmelter,Lea Bechter,Franz H Grus,Norbert Pfeiffer

doi:10.3390/ijms20102526

Abstract

The house swine (Sus scrofa domestica Linnaeus 1758) is an important model organism regarding the study of neurodegenerative diseases, especially ocular neuropathies such as glaucoma. This is due to the high comparability of the porcine and human eye regarding anatomy and molecular features. In the pathogenesis of glaucoma, the trabecular meshwork (TM) forms a key ocular component in terms of intraocular pressure (IOP) elevation. Thereby, functional TM abnormalities are correlated with distinct proteomic alterations. However, a detailed analysis of the TM proteome has not been realized so far. Since the porcine eye has high potential as a model system to study ocular diseases such as glaucoma, the present study focuses on the in-depth analysis of the porcine TM proteome. By use of a bottom-up (BU) mass spectrometric (MS) platform utilizing electrospray ionization liquid chromatography tandem MS (LC-ESI-MS/MS) considering database-dependent and peptide de novo sequencing, more than 3000 TM proteins were documented with high confidence (FDR < 1%). A distinct number of proteins with neuronal association were revealed. To the best to our knowledge, many of these protein species have not been reported for TM tissue before such as reelin, centlein and high abundant neuroblast differentiation-associated protein AHNAK (AHNAK). Thereby, AHNAK might play a superordinate role in the TM regarding proposed tissue involvement in barrier function. Also, a high number of secretory proteins could be identified. The generated TM proteomic landscape underlines a multifunctional character of the TM beyond representing a simple drainage system. Finally, the protein catalogue of the porcine TM provides an in-depth view of the TM molecular landscape and will serve as an important reference map in terms of glaucoma research utilizing porcine animal models, porcine TM tissues and/or cultured TM cells.

Highlights

The trabecular meshwork (TM) is a highly specialized eye tissue responsible for the regulation of the anterior eye chamber aqueous humor (AH) outflow and the control of the intraocular pressure (IOP) [1,2]
Thereby, besides the identification of collagens (I, III, IV), tenascins and laminins, further important extracellular matrix (ECM) proteins comprising lumican, nidigen-1 and 2, sushi nidogen and EGF-like domain-containing protein 1, γ, podocan, fibulin-5, retinoic acid receptor responder protein 2, calreticulin, EGF-containing fibulin-like ECM protein 1, prolyl 3-hydroxylase 1, biglycan, prolargin, matrix metalloprotease 9 and thrombospondins could be catalogued confidently with respect to the current literature concerning the composition of TM ECM subproteomes [17,18,19]
Extracellular as well as intracellular TM protein species could be recovered providing an in-depth view into the TM extracellular matrix (ECM) and TM cellular proteome of the house swine

Summary

Introduction

The trabecular meshwork (TM) is a highly specialized eye tissue responsible for the regulation of the anterior eye chamber aqueous humor (AH) outflow and the control of the intraocular pressure (IOP) [1,2]. Considering the anatomical ocular architecture and neuronal comparability of pigs and humans, the house swine (Sus scrofa domestica Linnaeus 1758) represents an attractive model organism, especially for the study of ocular neuropathies including glaucoma [11,12,13,14]. Since TM structural and functional changes are associated with aberrant proteomic alterations [6] only a few works have characterized the complex TM proteome with high sensitivity, and a detailed protein catalogue of the porcine TM is still missing. In correspondence with research on anatomical features of the porcine eye [14], the present proteomic work should assist with the establishment of the house swine as a reliable model system organism for ocular diseases with a special focus on glaucoma on the molecular level

Objectives

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Results

Conclusion