| [ Summary ] |
α-Klotho (αKl) is expressed as a membrane-anchored 135 kDa protein in distal convoluted tubules, parathyroid glands and choroid plexuses. The cleaved 130 kDa form is also found in circulation fluids and urine. Based on a primary structure resembling Β-D-glycosidase, αKl is capable recognizing glucuronic acid. Together with peptide interaction, αKl binds fibroblast growth factor (FGF) 23 and Na,K-ATPase in a saccharide-dependent manner. The recognition of glucuronic acid by αKl probably leads to the determination of molecular preferences and selectivity. The interactions of αKl to Na,K-ATPase and FGF23 contribute to the regulation of PTH secretion and the suppression of both active vitamin D synthesis and phosphate reabsorption in kidney, respectively. Thus, αKl integrates the network of mineral homeostasis in vivo. |