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Identification of novel substrates for the serine protease HTRA1 in the human RPE secretome.

ABSTRACT: PURPOSE. To define the role of the serine protease HTRA1 in age-related macular degeneration (AMD) by examining its expression level and identifying its potential substrates in the context of primary RPE cell extracellular milieu. METHODS. Primary RPE cell cultures were established from human donor eyes and screened for CFH, ARMS2, and HTRA1 risk genotypes by using an allele-discrimination assay. HTRA1 expression in genotyped RPE cells was determined by using real-time PCR and quantitative proteomics. Potential HTRA1 substrates were identified by incubating RPE-conditioned medium with or without human recombinant HTRA1. Selectively cleaved proteins were quantified by using the differential stable isotope labeling by amino acids in cell culture (SILAC) strategy. RESULTS. HTRA1 mRNA levels were threefold higher in primary RPE cells homozygous for the HTRA1 promoter risk allele than in RPE cells with the wild-type allele, which translated into a twofold increase in HTRA1 secretion by RPE cells with the risk genotype. A total of 196 extracellular proteins were identified in the RPE secretome, and only 8 were found to be selectively cleaved by the human recombinant HTRA1. These include fibromodulin with 90% cleavage, clusterin (50%), ADAM9 (54%), vitronectin (54%), and alpha2-macroglobulin (55%), as well as some cell surface proteins including talin-1 (21%), fascin (40%), and chloride intracellular channel protein 1 (51%). CONCLUSIONS. Recombinant HTRA1 cleaves RPE-secreted proteins involved in regulation of the complement pathway (clusterin, vitronectin, and fibromodulin) and of amyloid deposition (clusterin, alpha2-macroglobulin, and ADAM9). These findings suggest a link between HTRA1, complement regulation, and amyloid deposition in AMD pathogenesis.

SUBMITTER: An E

PROVIDER: S-EPMC2904004 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Identification of novel substrates for the serine protease HTRA1 in the human RPE secretome.

An Eunkyung E Sen Supti S Park Sung Kyu SK Gordish-Dressman Heather H Hathout Yetrib Y

Investigative ophthalmology & visual science 20100305 7

PURPOSE. To define the role of the serine protease HTRA1 in age-related macular degeneration (AMD) by examining its expression level and identifying its potential substrates in the context of primary RPE cell extracellular milieu. METHODS. Primary RPE cell cultures were established from human donor eyes and screened for CFH, ARMS2, and HTRA1 risk genotypes by using an allele-discrimination assay. HTRA1 expression in genotyped RPE cells was determined by using real-time PCR and quantitative prote ...[more]

PMID: 20207970

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Project description:HTRA1 is a highly conserved serine protease which has been implicated in suppression of epithelial-to-mesenchymal-transition (EMT) and cell motility in breast cancer. Its prognostic relevance for breast cancer is unclear so far. Therefore, we evaluated the impact of HTRA1 mRNA expression on patient outcome using a cohort of 131 breast cancer patients as well as a validation cohort including 2809 publically available data sets. Additionally, we aimed at investigating for the presence of promoter hypermethylation as a mechanism for silencing the HTRA1 gene in breast tumors. HTRA1 downregulation was detected in more than 50% of the breast cancer specimens and was associated with higher tumor stage (p?=?0.025). By applying Cox proportional hazard models, we observed favorable overall (OS) and disease-free survival (DFS) related to high HTRA1 expression (HR?=?0.45 [CI 0.23-0.90], p?=?0.023; HR?=?0.55 [CI 0.32-0.94], p?=?0.028, respectively), with even more pronounced impact in node-positive patients (HR?=?0.21 [CI 0.07-0.63], p?=?0.006; HR?=?0.29 [CI 0.13-0.65], p?=?0.002, respectively). Moreover, HTRA1 remained a statistically significant factor predicting DFS among established clinical parameters in the multivariable analysis. Its impact on patient outcome was independently confirmed in the validation set (for relapse-free survival (n?=?2809): HR?=?0.79 [CI 0.7-0.9], log-rank p?=?0.0003; for OS (n?=?971): HR?=?0.63 [CI 0.48-0.83], log-rank p?=?0.0009). In promoter analyses, we in fact detected methylation of HTRA1 in a small subset of breast cancer specimens (two out of a series of 12), and in MCF-7 breast cancer cells which exhibited 22-fold lower HTRA1 mRNA expression levels compared to unmethylated MDA-MB-231 cells. In conclusion, we show that downregulation of HTRA1 is associated with shorter patient survival, particularly in node-positive breast cancer. Since HTRA1 loss was demonstrated to induce EMT and cancer cell invasion, these patients might benefit from demethylating agents or histone deacetylase inhibitors previously reported to lead to HTRA1 upregulation, or from novel small-molecule inhibitors targeting EMT-related processes.

Dataset Information

Identification of novel substrates for the serine protease HTRA1 in the human RPE secretome.

Publications

Identification of novel substrates for the serine protease HTRA1 in the human RPE secretome.

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