LIMP-2 is a receptor for lysosomal mannose-6-phosphate-independent targeting of beta-glucocerebrosidase

Abstract

beta-glucocerebrosidase, the enzyme defective in Gaucher disease, is targeted to the lysosome independently of the mannose-6-phosphate receptor. Affinity-chromatography experiments revealed that the lysosomal integral membrane protein LIMP-2 is a specific binding partner of beta-glucocerebrosidase. This interaction involves a coiled-coil domain within the lumenal domain. beta-glucocerebrosidase activity and protein levels were severely decreased in LIMP-2-deficient mouse tissues. Analysis of fibroblasts and macrophages isolated from these mice indicated that the majority of beta-glucocerebrosidase was secreted. Missorting of beta-glucocerebrosidase was also evident in vivo, as protein and activity levels were significantly higher in sera from LIMP-2-deficient mice compared to wild-type. Reconstitution of LIMP-2 in LIMP-2-deficient fibroblasts led to a rescue of beta-glucocerebrosidase levels and distribution. LIMP-2 expression also led to lysosomal transport of a beta-glucocerebrosidase endoplasmic reticulum retention mutant. These data support a role for LIMP-2 as the mannose-6-phosphate-independent trafficking receptor for beta-glucocerebrosidase.