Lysosomal localization of the neuronal ceroid lipofuscinosis CLN5 protein.
The Finnish variant late infantile neuronal ceroid lipofuscinosis (vLINCL) belongs to the neuronal ceroid lipofuscinosis group of common recessively inherited neurodegenerative disorders. The CLN 5 gene responsible for this brain disorder codes for a novel protein with no homology to previously reported proteins. In this study, we have investigated the biosynthesis and intracellular localization of this protein in transiently transfected BHK-21 cells using a CLN5-specific peptide antibody. Confocal immunofluorescence microscopy showed that wild-type CLN5 is predominantly targeted to lysosomes and immunoprecipitation analysis recognized a 60 kDa polypeptide. The molecular weight of this protein was reduced to 40 kDa by deglycosylation with Endo H and to 38 kDa with PNGase F. The same-sized glycosylated polypeptides were also observed in the media, suggesting that the 60 kDa glycosylated CLN5 polypeptide represents a soluble lysosomal glycoprotein, not an integral transmembrane protein as predicted earlier. The most common human vLINCL mutation blocked the lysosomal targeting of expressed polypeptides. This would imply that the pathogenesis of vLINCL would be associated with the defective lysosomal trafficking, preventing the normal biological function of the corresponding polypeptide.
Isosomppi
Juha
J
Department of Molecular Medicine, National Public Health Institute and Department of Medical Genetics, University of Helsinki, Finland.
Vesa
Jouni
J
Jalanko
Anu
A
Peltonen
Leena
L
D002460:Cell Line; D002474:Cell-Free System; D003513:Cycloheximide / Q000378:metabolism; D006801:Humans; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism*; D009472:Neuronal Ceroid-Lipofuscinoses / Q000209:etiology / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D020539:Sequence Analysis, Protein
C113332:CLN5 protein, human; D051907:Lysosomal Membrane Proteins; D008565:Membrane Proteins; D003513:Cycloheximide