Suppression of agrin‐22 production and synaptic dysfunction in Cln1−/− mice

摘要

AbstractObjectiveOxidative stress in the brain is highly prevalent in many neurodegenerative disorders including lysosomal storage disorders, in which neurodegeneration is a devastating manifestation. Despite intense studies, a precise mechanism linking oxidative stress to neuropathology in specific neurodegenerative diseases remains largely unclear.MethodsInfantile neuronal ceroid lipofuscinosis (INCL) is a devastating neurodegenerative lysosomal storage disease caused by mutations in the ceroid lipofuscinosis neuronal-1 (CLN1) gene encoding palmitoyl-protein thioesterase-1. Previously, we reported that in the brain of Cln1−/− mice, which mimic INCL, and in postmortem brain tissues from INCL patients, increased oxidative stress is readily detectable. We used molecular, biochemical, immunohistological, and electrophysiological analyses of brain tissues of Cln1−/− mice to study the role(s) of oxidative stress in mediating neuropathology.ResultsOur results show that in Cln1−/− mice oxidative stress in the brain via upregulation of the transcription factor, CCAAT/enhancer-binding protein-δ, stimulated expression of serpina1, which is an inhibitor of a serine protease, neurotrypsin. Moreover, in the Cln1−/− mice, suppression of neurotrypsin activity by serpina1 inhibited the cleavage of agrin (a large proteoglycan), which substantially reduced the production of agrin-22, essential for synaptic homeostasis. Direct whole-cell recordings at the nerve terminals of Cln1−/− mice showed inhibition of Ca2+ currents attesting to synaptic dysfunction. Treatment of these mice with a thioesterase-mimetic small molecule, N-tert (Butyl) hydroxylamine (NtBuHA), increased agrin-22 levels.InterpretationOur findings provide insight into a novel pathway linking oxidative stress with synaptic pathology in Cln1−/− mice and suggest that NtBuHA, which increased agrin-22 levels, may ameliorate synaptic dysfunction in this devastating neurodegenerative disease.