Sex differences in alpha galactosidase protein processing and its impact on disease severity in Fabry disease

Abstract

Fabry disease (FD) is an X-linked disorder due to mutations in the -galactosidase A (GLA) gene. The condition is characterized by low GLA activity and accumulation of toxic sphingolipids. Some patients present full disease symptoms whereas others have one system affected, generally the heart or kidney. This suggests that a mutation in the GLA gene is necessary to cause FD, but other factors may contribute to its clinical expression. To investigates the impact of GLA mutant protein processing on GLA activity and disease expression, 26 individuals with FD (14 males) were studied. Clinical outcomes explored included the Mainz Severity Score Index (MSSI), the Age-Adjusting Severity Scores (AASS), glomerular filtration rate (GFR), and left ventricular mass index (LVMI). Globotriaosylsphingosine (lyso-Gb3) data was available for a subset of participants. Whole cell lysates were employed to assess GLA activity and GLA protein levels. Additionally, endoglycosidase H digestion was performed on cell lysates to quantify each GLA protein form: immature 50 kDa endoplasmic reticulum form and mature 46 kDa lysosomal form. The latter was employed to calculate lysosomal GLA activity and its relationship with clinical outcomes was studied. Fabry participants exhibited more of the immature form of GLA protein (0.23 vs 0.66, p= 0.04). Female patients exhibited higher total GLA activity (19.0 vs 5.1 nmol/hr/mg), total GLA protein levels 0.13 vs 0.50 GLA/LC, p= 0.003), and 46 kDa mature lysosomal form levels than male patients (0.53 vs 0.10, p= 0.001). Additionally, females showed a significant correlation between the GLA mature form and GLA activity (r2= 0.59, p= 0.04). Consistently, lysosomal GLA activity exhibited significant associations with MSSI (r2= -0.66, p= 0.02) and GFR (r2= 0.59, p= 0.04) only in this sex group. These results suggest that total GLA protein levels are linked to the severity of FD manifestations, particularly in females via enzyme activity.