Mucopolysaccharidosis type IVA (MPS
IVA) is a rare disease caused
by mutations in the gene encoding the lysosomal enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS). We report here
two GALNS pharmacological chaperones, ezetimibe and pranlukast, identified
by molecular docking-based virtual screening. These compounds bound
to the active cavity of GALNS and increased its thermal stability
as well as the production of recombinant GALNS in bacteria, yeast,
and HEK293 cells. MPS IVA fibroblasts treated with these chaperones
exhibited increases in GALNS protein and enzyme activity and reduced
the size of enlarged lysosomes. Abnormalities in autophagy markers
p62 and LC3B-II were alleviated by ezetimibe and pranlukast. Combined
treatment of recombinant GALNS with ezetimibe or pranlukast produced
an additive effect. Altogether, the results demonstrate that ezetimibe
and pranlukast can increase the yield of recombinant GALNS and be
used as a monotherapy or combination therapy to improve the therapeutic
efficacy of MPS IVA enzyme replacement therapy.
Mucopolysaccharidosis
IVA (MPS IVA) is a lysosomal storage disease
caused by mutations in the gene encoding for the enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS), leading to lysosomal
accumulation of keratan sulfate (KS) and chondroitin-6-sulfate. In
this study, we identified and characterized bromocriptine (BC) as
a novel PC for MPS IVA. BC was identified through virtual screening
and predicted to be docked within the active cavity of GALNS in a
similar conformation to that observed for KS. BC interacted with similar
residues to those predicted for natural GALNS substrates. In vitro inhibitory assay showed that BC at 50 μM
reduced GALNS activity up to 30%. However, the activity of hrGALNS
produced in HEK293 cells was increased up to 1.48-fold. BC increased
GALNS activity and reduced lysosomal mass in MPS IVA fibroblasts in
a mutation-dependent manner. Overall, these results show the potential
of BC as a novel PC for MPS IVA and contribute to the consolidation
of PCs as a potential therapy for this disease.
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