Abnormal cathepsin B activity in Batten disease.
Fibroblasts cultured from patients with various forms of neuronal ceroid-lipofuscinosis (NCL; Batten disease) showed variably decreasing cathepsin B activity with increasing passage number and months in culture in the presence of fetal calf serum. Cathepsin H activity and that of a wide range of lysosomal hydrolases was unaffected by these conditions. Cathepsin B activity was assayed either colorimetrically (N alpha-benzoyl-DL-Arg-beta-naphthylamide; BANA), fluorimetrically (Z-Arg-Arg-methylcoumarin), or autoradiographically, following NaDodSO4-12.5% polyacrylamide gel electrophoresis ([125]Tyr-Ala-Lys-Arg-CH2Cl) and was found to be lysosomal in localization. Fractionation of disrupted fibroblasts on a Percoll gradient showed evidence of abnormally buoyant lysosomes in some NCL patients, and these tended to be low in cathepsin B but rich in other lysosomal hydrolases. Our data do not support a primary defect in cathepsin B as the basic defect in NCL. However, a possible explanation for various studies implicating a protease defect in NCL is that cathepsin B was highly sensitive to inactivation by peroxides and aldehydes. Thus hydrogen peroxide (0.3 mM) or 4-hydroxynonenal (1 nM) inactivated cathepsin B without inhibiting cathepsin H or lysosomal hydrolases such as alpha-L-fucosidase. Since peroxides and 4-hydroxynonenal have been shown to accumulate in NCL tissue (despite apparently normal peroxidase activity), we tested the possibility of a defect in the removal of peroxidized lipids from phospholipids as the primary defect in NCL. The nociceptive peptide bradykinin (BK) normally initiates a cascade involving receptor-mediated phospholipase C activation and release of arachidonate and prostanoids from cultured skin fibroblasts. Release of [3H]arachidonate by BK was deficient in NCL fibroblasts, suggesting that the primary defect in NCL could involve the deficiency of a specific phospholipase A2 activity.
Dawson
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Joseph P. Kennedy, Jr. Mental Retardation Research Center, Department of Pediatrics, University of Chicago, Illinois 60637.
Glaser
P T
PT
D000135:Acid Phosphatase / Q000378:metabolism; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism*; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003546:Cysteine Endopeptidases / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006867:Hydrolases / Q000378:metabolism; D007700:Kinetics; D008247:Lysosomes / Q000201:enzymology; D009472:Neuronal Ceroid-Lipofuscinoses / Q000201:enzymology*; D012867:Skin / Q000201:enzymology*
D001095:Arachidonic Acids; D016718:Arachidonic Acid; D006861:Hydrogen Peroxide; D006867:Hydrolases; D000135:Acid Phosphatase; D003546:Cysteine Endopeptidases; D002401:Cathepsin B