Lysosomal enzyme delivery by ICAM-1-targeted nanocarriers bypassing glycosylation- and clathrin-dependent endocytosis

TLDR

Enzyme replacement therapy for lysosomal storage disorders depends on carbohydrate‑mediated binding to receptors that mediate lysosomal delivery via clathrin‑dependent endocytosis, but suboptimal glycosylation and clathrin deficiency in some cells limit its efficacy. The study investigates a nanocarrier strategy that targets the glycosylation‑ and clathrin‑independent receptor ICAM‑1 to deliver lysosomal enzymes. Recombinant human acid sphingomyelinase was loaded onto anti‑ICAM‑1–coated nanocarriers to target ICAM‑1 on affected cells. Anti‑ICAM‑1/ASM nanocarriers bound ICAM‑1–positive cells independently of glycosylation, entered via CAM‑mediated endocytosis bypassing clathrin, trafficked to lysosomes, and delivered active ASM that reduced lipid accumulation, indicating improved therapeutic potential for Niemann–Pick disease.

Abstract

Enzyme replacement therapy, a state-of-the-art treatment for many lysosomal storage disorders, relies on carbohydrate-mediated binding of recombinant enzymes to receptors that mediate lysosomal delivery via clathrin-dependent endocytosis. Suboptimal glycosylation of recombinant enzymes and deficiency of clathrin-mediated endocytosis in some lysosomal enzyme-deficient cells limit delivery and efficacy of enzyme replacement therapy for lysosomal disorders. We explored a novel delivery strategy utilizing nanocarriers targeted to a glycosylation- and clathrin-independent receptor, intercellular adhesion molecule (ICAM)-1, a glycoprotein expressed on diverse cell types, up-regulated and functionally involved in inflammation, a hallmark of many lysosomal disorders. We targeted recombinant human acid sphingomyelinase (ASM), deficient in types A and B Niemann–Pick disease, to ICAM-1 by loading this enzyme to nanocarriers coated with anti-ICAM. Anti-ICAM/ASM nanocarriers, but not control ASM or ASM nanocarriers, bound to ICAM-1-positive cells (activated endothelial cells and Niemann–Pick disease patient fibroblasts) via ICAM-1, in a glycosylation-independent manner. Anti-ICAM/ASM nanocarriers entered cells via CAM-mediated endocytosis, bypassing the clathrin-dependent pathway, and trafficked to lysosomes, where delivered ASM displayed stable activity and alleviated lysosomal lipid accumulation. Therefore, lysosomal enzyme targeting using nanocarriers targeted to ICAM-1 bypasses defunct pathways and may improve the efficacy of enzyme replacement therapy for lysosomal disorders, such as Niemann–Pick disease.