New Insights into Physiological Function of ARMS2/LOC387715

Abstract

Purpose: : Age-related macular degeneration (AMD) is strongly associated with polymorphisms on chromosomal region 10q26. Recent data suggest a causal relationship between the lack of ARMS2 synthesis and the development of AMD. The present study was undertaken to gain an understanding of the genuine (patho)physiological role of the poorly characterized ARMS2 protein.

Methods: : Yeast two-hybrid screen was performed using ARMS2 as bait and a human placental cDNA library as prey, in order to identify interacting partners of ARMS2. Co-precipitation and pull-down assays were employed to validate these interactions. Rat monoclonal antibodies to ARMS2 were raised against two peptides corresponding to the predicted amino acid sequence (NP_001093137) and used in immunohistochemical analyses.

Results: : Fifty-four clones isolated form quadruple dropout plates were deemed potential binding partners of ARMS2. Sequence analyses of the prey plasmids showed that the majority code for extracellular proteins; many of them are known constituents of the extracellular matrix. Our in vitro experiments also confirmed the secretion of ARMS2, and the specificity of these interactions. Additionally, ARMS2-specific immunohistochemical staining of human tissues was confined to cell-sparse regions mostly comprised of matrix proteins.

Conclusions: : These results demonstrate a new role for ARMS2, as constituent of the extracellular matrix. Hence, our work challenges recent results suggesting a mitochondrial function of ARMS2. Besides, the data obtained from these experiments enabled us to propose a protein interaction map, which links ARMS2 to proteins already implicated in AMD and other macular dystrophies.

Keywords: age-related macular degeneration • extracellular matrix • choroid