ABSTRACT
Lysosomes have many roles, including degrading macromolecules and signalling to the nucleus1. Lysosomal dysfunction occurs in various human conditions, such as common neurodegenerative diseases and monogenic lysosomal storage disorders (LSDs)2-4. For most LSDs, the causal genes have been identified but, in some, the function of the implicated gene is unknown, in part because lysosomes occupy a small fraction of the cellular volume so that changes in lysosomal contents are difficult to detect. Here we develop the LysoTag mouse for the tissue-specific isolation of intact lysosomes that are compatible with the multimodal profiling of their contents. We used the LysoTag mouse to study CLN3, a lysosomal transmembrane protein with an unknown function. In children, the loss of CLN3 causes juvenile neuronal ceroid lipofuscinosis (Batten disease), a lethal neurodegenerative LSD. Untargeted metabolite profiling of lysosomes from the brains of mice lacking CLN3 revealed a massive accumulation of glycerophosphodiesters (GPDs)-the end products of glycerophospholipid catabolism. GPDs also accumulate in the lysosomes of CLN3-deficient cultured cells and we show that CLN3 is required for their lysosomal egress. Loss of CLN3 also disrupts glycerophospholipid catabolism in the lysosome. Finally, we found elevated levels of glycerophosphoinositol in the cerebrospinal fluid of patients with Batten disease, suggesting the potential use of glycerophosphoinositol as a disease biomarker. Our results show that CLN3 is required for the lysosomal clearance of GPDs and reveal Batten disease as a neurodegenerative LSD with a defect in glycerophospholipid metabolism.
Subject(s)
Esters , Glycerophospholipids , Inositol Phosphates , Lysosomes , Membrane Glycoproteins , Molecular Chaperones , Animals , Biomarkers/cerebrospinal fluid , Biomarkers/metabolism , Child , Esters/metabolism , Glycerophospholipids/cerebrospinal fluid , Glycerophospholipids/metabolism , Humans , Inositol Phosphates/cerebrospinal fluid , Inositol Phosphates/metabolism , Lysosomal Storage Diseases/cerebrospinal fluid , Lysosomal Storage Diseases/genetics , Lysosomal Storage Diseases/metabolism , Lysosomes/metabolism , Lysosomes/pathology , Membrane Glycoproteins/deficiency , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Mice , Molecular Chaperones/genetics , Molecular Chaperones/metabolism , Neuronal Ceroid-Lipofuscinoses/cerebrospinal fluid , Neuronal Ceroid-Lipofuscinoses/genetics , Neuronal Ceroid-Lipofuscinoses/metabolismABSTRACT
The effect of the inositol trisphosphate analog alpha-trinositol on noxious-evoked behavior, amino acid and prostaglandin E2 (PGE2) release was examined in unanesthetized rats using intrathecal microdialysis probes. Subcutaneous injection of 50 microliters 5% formalin solution produced two phases of pain-like behavior and significant elevation of glutamate, aspartate, glycine, taurine and serine during phase 1. PGE2 concentrations were increased during both phases 1 and 2. Intraperitoneal delivery of 300 mg/kg alpha-trinositol significantly suppressed both phases 1 and 2 of formalin-induced behavior and the associated elevation of amino acids and PGE2. These data demonstrate that the antinociceptive effect of alpha-trinositol corresponds to suppression of noxious-evoked release of amino acids and PGE2 from the spinal cord.
