Pseudoexfoliation (PEX) syndrome is an age-related progressive disease of the extracellular matrix with ocular manifestations. PEX is clinically diagnosed by the presence of extracellular exfoliative Show more
Pseudoexfoliation (PEX) syndrome is an age-related progressive disease of the extracellular matrix with ocular manifestations. PEX is clinically diagnosed by the presence of extracellular exfoliative deposits on the anterior surface of the ocular lens. PEX syndrome is a major risk factor for developing glaucoma, the leading cause of irreversible blindness in the world, and is often associated with the development of cataract. PEX reportedly coexists with Alzheimer disease and increases the risk of heart disease and stroke. PEX material deposited on the anterior surface of the ocular lens is highly proteinaceous, complex, and insoluble, making deciphering the protein composition of the material challenging. Thus, to date, only a small proportion of the protein composition of PEX material is known. The aim of this study was to decipher the protein composition of pathological PEX material deposited on the ocular lens in patients and advance the understanding of pathophysiology of PEX syndrome. Liquid-chromatography and tandem mass spectrometry (LC-MS/MS) was employed to discover novel proteins in extracts of neat PEX material surgically isolated from patients (n = 4) with PEX syndrome undergoing cataract surgery. A sub-set of the identified proteins was validated with immunohistochemistry using lens capsule specimens from independent patients (n=3); lens capsules from patients with cataract but without PEX syndrome were used as controls (n=4). Expression of transcripts of the validated proteins in the human lens epithelium was analyzed with reverse transcription PCR (RT-PCR). Functional relationships among the proteins identified in this study and genes and proteins previously implicated in the disease were bioinformatically determined using InnateDB. Peptides corresponding to 66 proteins, including ten proteins previously known to be present in PEX material, were identified. Thirteen newly identified proteins were chosen for validation. Of those proteins, 12 were found to be genuine components of the material. The novel protein constituents include apolipoproteins (APOA1 and APOA4), stress response proteins (CRYAA and PRDX2), and blood-related proteins (fibrinogen and hemoglobin subunits), including iron-free hemoglobin. The gene expression data suggest that the identified stress-response proteins and hemoglobin are contributed by the lens epithelium and apolipoproteins and fibrinogen by the aqueous humor to the PEX material. Pathway analysis of the identified novel protein constituents and genes or proteins previously implicated in the disease reiterated the involvement of extracellular matrix organization and degradation, elastic fiber formation, and complement cascade in PEX syndrome. Network analysis suggested a central role of fibronectin in the pathophysiology of the disease. The identified novel protein constituents of PEX material also shed light on the molecular basis of the association of PEX syndrome with heart disease, stroke, and Alzheimer disease. This study expands the understanding of the protein composition of pathological PEX material deposited on the ocular lens in patients with PEX syndrome and provides useful insights into the pathophysiology of this disease. This study together with the previous study by our group (Sharma et al. Experimental Eye Research 2009;89(4):479-85) demonstrate that using neat PEX material, devoid of the underlying lens capsule, for proteomics analysis is an effective approach for deciphering the protein composition of complex and highly insoluble extracellular pathological ocular deposits present in patients with PEX syndrome. Show less
Batten disease (juvenile neuronal ceroid lipofuscinosis) is a recessive neurodegenerative disorder of childhood. The gene, CLN3, was recently identified and found to encode a novel 438 amino acid prot Show more
Batten disease (juvenile neuronal ceroid lipofuscinosis) is a recessive neurodegenerative disorder of childhood. The gene, CLN3, was recently identified and found to encode a novel 438 amino acid protein of unknown function. In order to gain insight into the function of the Batten disease protein (CLN3p), we investigated its subcellular localization. Protein constructs incorporating CLN3p fused to the green fluorescence protein or an eight amino acid peptide tag were transiently expressed in fibroblasts, HeLa and COS-7 cells. A juxtanuclear, asymmetric localization pattern was observed that correlated with the Golgi apparatus in all three cell types. However, a proportion of transiently transfected cells exhibited a punctate vesicular distribution throughout the cytoplasm in addition to or without the Golgi localization. In order to account for localization patterns arising from intracellular protein transport disruption due to exaggerated overexpression in transiently transfected cells, we isolated a stably transfected cell line expressing only one copy of the CLN3 -GFP DNA construct. Fluorescence and biochemical analyses using this cell line demonstrated that CLN3p is an integral membrane protein that localizes primarily in the Golgi apparatus. The functional implications of this finding are discussed. Show less