Juvenile ceroid lipofuscinosis. Evidence for methylated lysine in neural storage body protein.
Juvenile ceroid lipofuscinosis, or Batten disease, is a hereditary disorder characterized by progressive visual loss, seizures, cognitive and psychomotor deterioration, and early death, usually between 15 and 35 years of age. Individuals with this disease have massive deposits of autofluorescent inclusion bodies in cells of most tissues. The accumulation of these intracellular deposits suggests that juvenile ceroid-lipofuscinosis is a storage disease resulting from the inability of cells to metabolize some normal cellular constituent. It has been reported that the storage material is largely protein, much of which is a specific mitochondrial protein that apparently is not properly metabolized in subjects with Batten disease. The storage bodies were partially purified from the retinas of two siblings who died as a result of juvenile ceroid lipofuscinosis, as well as from the cerebral cortex of an unrelated individual with this disorder. Chromatographic analysis of storage body protein acid hydrolysates indicated that they contained a large amount of the modified amino acid epsilon-N-trimethyllysine. The abundance of this amino acid in the storage protein suggests that the disease may result from excessive methylation or from a failure to demethylate intermediate forms of the stored proteins. Acid hydrolysis also solubilized a fluorescent component from the retinal storage material, suggesting that the stored protein has a bound fluorescent adduct.