Characterization of two potential pharmacological chaperones for N-acetylgalactosamine-6-sulfate sulfates (GALNS) enzyme

The deficiency of N-acetylgalactosamine-6-sulfate-sulfatase (GALNS) is an autosomal recessive disease characterized by the lysosomal accumulation of Keratan sulfate and Chondroitin 6-sulfate associated with Mucopolysaccharidosis IVA (MPS IVA, Morquio syndrome type A). The main alternative of treatment for Morquio syndrome type A is enzyme replacement therapy (ERT), however it has some limitations, such as reduced effect on clinical bone, ocular and cardiac manifestations, and short half-life in blood. As an alternative, we propose the use of two small molecules for oral administration as potential pharmacological chaperones. These two molecules (MoIEIM-1 and MoIEIM-2) were previously identified through a virtual screening approach. In this study, we evaluated the effect of these two molecules on HEK293 cells and fibroblasts derived from Morquio syndrome type A patients. The MoIEIM-1 and MoIEIM-2 showed the ability to bind to the active site of the GALNS enzyme by using of computational molecular docking. The results demonstrated that the enzymatic activity of intracellular GALNS increases in fibroblasts when treated for 24h with both molecules, reaching wild-type enzyme activity levels. In addition, HEK 293 cells were transfected with pCXN-GALNS plasmid to evaluate the effect of MoIEIM-1 and MoIEIM-2 in a recombinant human GALNS. A significant increase in the enzyme activity values after treatment with the two chaperones was observed. Similar results were observed with recombinant GALNS produced in microorganisms. In conclusion, these results show the potential of these molecules as pharmacological chaperones for GALNS, which increase the activity of both the mutated and the recombinant enzymes. These pharmacological chaperones might be a feasible treatment for Morquio syndrome type A alone or in combination with the ERT.