Misfolding of Lysosomal α-Galactosidase a in a Fly Model and Its Alleviation by the Pharmacological Chaperone Migalastat.

Fabry disease, an X-linked recessive lysosomal disease, results from mutations in the GLA gene encoding lysosomal alpha-galactosidase A (alpha-Gal A). Due to these mutations, there is accumulation of globotriaosylceramide (GL-3) in plasma and in a wide range of cells throughout the body. Like other lysosomal enzymes, alpha-Gal A is synthesized on endoplasmic reticulum (ER) bound polyribosomes, and upon entry into the ER it undergoes glycosylation and folding. It was previously suggested that alpha-Gal A variants are recognized as misfolded in the ER and undergo ER-associated degradation (ERAD). In the present study, we used Drosophila melanogaster to model misfolding of alpha-Gal A mutants. We did so by creating transgenic flies expressing mutant alpha-Gal A variants and assessing development of ER stress, activation of the ER stress response and their relief with a known alpha-Gal A chaperone, migalastat. Our results showed that the A156V and the A285D alpha-Gal A mutants underwent ER retention, which led to activation of unfolded protein response (UPR) and ERAD. UPR could be alleviated by migalastat. When expressed in the fly's dopaminergic cells, misfolding of alpha-Gal A and UPR activation led to death of these cells and to a shorter life span, which could be improved, in a mutation-dependent manner, by migalastat.