Biosynthesis and intracellular targeting of the CLN3 protein defective in Batten disease

Batten disease (juvenile-onset neuronal ceroid lipofuscinosis, JNCL), the most common neurodegenerative disorder of childhood, is caused by mutations in a recently identified gene ( CLN3 ) localized to chromosome 16p11.2-12.1. To elucidate the biosynthesis and localization of the CLN3 protein, we expressed CLN3 cDNA in COS-1 and HeLa cell lines. In vitro translation, immunoprecipitation and Western blotting analyses detected an approximately 43 kDa polypeptide. Pulse-chase experiments indicated that the CLN3 protein is synthesized as an N -glycosylated single-chain polypeptide, which was not detected in growth medium. Confocal immunofluorescence microscopy revealed that the CLN3 protein is localized to the lysosomal compartment. These results provide evidence that Batten disease can be classified as a member of lysosomal diseases.