Neuraminidase 1 (NEU1) is a lysosomal exo-glycosidase and cleaves glycoside bonds of non-reducing terminal sialic acid. The association of NEU1 with cathepsin A activates NEU1. Overexpression of NEU1 in mammalian cells causes self-association and crystallization of NEU1 in rough endoplasmic reticulum (ER). NEU1 deficiency, called sialidosis, is a type of lysosomal storage disease. There is no fundamental treatment for NEU1 deficiency. Gene therapy seems effective, but it is assumed to be dangerous because NEU1 crystallizes intracellularly and damages cells by rupturing biological membranes. In this mini-review, we summarize about functions of NEU1 and CTSA. We also describe NEU1 or CTSA deficiencies.

Receptor tyrosine kinases are important targets for drug development, and elucidating the mechanisms responsible for their functional regulation is important. Because most receptor tyrosine kinases are regulated by glycans, they are intimately involved in cellular signaling. Based on the site-specific analysis of N-glycans of the ErbB family, the fibroblast growth factor receptor (FGFR) family, and the hepatocyte growth factor receptor (MET), the role of N-glycosylation of each receptor is now being revealed. Site-specific N-glycan occupancy and N-glycan structure are, to some extent, common to different cell types. Given this, it is assumed that there is a mechanism that is responsible for the status of site-specific N-glycosylation. Further site-specific analyses of N-glycans that are associated with receptors promises to be useful for the elucidation of not only the mechanisms responsible for regulation of cell signaling by glycans, but also the mechanisms associated with glycan biosynthesis in general.

Neuraminidase 1 (NEU1) is a lysosomal exo-glycosidase and cleaves glycoside bonds of non-reducing terminal sialic acid. The association of NEU1 with cathepsin A activates NEU1. Overexpression of NEU1 in mammalian cells causes self-association and crystallization of NEU1 in rough endoplasmic reticulum (ER). NEU1 deficiency, called sialidosis, is a type of lysosomal storage disease. There is no fundamental treatment for NEU1 deficiency. Gene therapy seems effective, but it is assumed to be dangerous because NEU1 crystallizes intracellularly and damages cells by rupturing biological membranes. In this mini-review, we summarize about functions of NEU1 and CTSA. We also describe NEU1 or CTSA deficiencies.

Receptor tyrosine kinases are important targets for drug development, and elucidating the mechanisms responsible for their functional regulation is important. Because most receptor tyrosine kinases are regulated by glycans, they are intimately involved in cellular signaling. Based on the site-specific analysis of N-glycans of the ErbB family, the fibroblast growth factor receptor (FGFR) family, and the hepatocyte growth factor receptor (MET), the role of N-glycosylation of each receptor is now being revealed. Site-specific N-glycan occupancy and N-glycan structure are, to some extent, common to different cell types. Given this, it is assumed that there is a mechanism that is responsible for the status of site-specific N-glycosylation. Further site-specific analyses of N-glycans that are associated with receptors promises to be useful for the elucidation of not only the mechanisms responsible for regulation of cell signaling by glycans, but also the mechanisms associated with glycan biosynthesis in general.