Frankel, Lisa B6; Di Malta, Chiara4; Wen, Jiayu7; Eskelinen, Eeva-Liisa5; Ballabio, Andrea4; Lund, Anders H.6
1 Lund Group, BRIC Research Groups, BRIC, Københavns Universitet2 Computational and RNA Biology, Department of Biology, Faculty of Science, Københavns Universitet3 Lund Group, BRIC, Faculty of Health and Medical Sciences, Københavns Universitet4 Federico II University5 University of Helsinki6 Lund Group, BRIC, Faculty of Health and Medical Sciences, Københavns Universitet7 Computational and RNA Biology, Department of Biology, Faculty of Science, Københavns Universitet
Sulfatases are key enzymatic regulators of sulfate homeostasis with several biological functions including degradation of glycosaminoglycans (GAGs) and other macromolecules in lysosomes. In a severe lysosomal storage disorder, multiple sulfatase deficiency (MSD), global sulfatase activity is deficient due to mutations in the sulfatase-modifying factor 1 (SUMF1) gene, encoding the essential activator of all sulfatases. We identify a novel regulatory layer of sulfate metabolism mediated by a microRNA. miR-95 depletes SUMF1 protein levels and suppresses sulfatase activity, causing the disruption of proteoglycan catabolism and lysosomal function. This blocks autophagy-mediated degradation, causing cytoplasmic accumulation of autophagosomes and autophagic substrates. By targeting miR-95 in cells from MSD patients, we can effectively increase residual SUMF1 expression, allowing for reactivation of sulfatase activity and increased clearance of sulfated GAGs. The identification of this regulatory mechanism opens the opportunity for a unique therapeutic approach in MSD patients where the need for exogenous enzyme replacement is circumvented.