Methods for Studying the Binding of Advanced Glycated Proteins to Receptors for Advanced Glycation Endproducts (AGE Receptors)

Advanced glycation endproducts (AGEs) are stable end-stage adducts formed by the nonenzymatic reaction of saccharide derivatives with proteins, nucleotides, and phospholipids. They are formed in physiological systems by glycation reactions of glucose and physiological α-oxoaldehydes, particularly glyoxal, methylglyoxal, and 3-deoxyglucosone (3-DG) with amino and guanidino groups. The concentration of intracellular AGEs is kept at alow level by protein, nucleotide, and phospholipid turnover and repair but AGEs formed on extracellular proteins may accumulate with age. Clearance of extracellular AGEs is achieved by binding of AGE-modified proteins to specific cell surface receptors-AGE receptors. AGE-ligand binding to AGE receptors is associated with internalization of the AGE ligand-receptor complex and proteolytic processing of the AGE-modified proteins. AGE-modified proteins are also stimuli for cell activation. AGE ligand binding is associated with increased expression of extracellular matrix (ECM) proteins, vascular adhesion molecules, cytokines, and growth factors. Depending on the cell type and concurrent signaling, this is associated with chemotaxis, angiogenesis, oxidative stress, and cell proliferation or apoptosis. These processes are thought to contribute to disease mechanisms associated with the chronic clinical complications of diabetes mellitus-retinopathy, neuropathy and nephropathy, cataract, macrovascular disease, Alzheimer’s disease (AD), and renal insufficiency.