RESUMO
Neuronal ceroid lipofuscinoses (NCL) are a group of inherited neurodegenerative disorders with lysosomal pathology (CLN1-14). Recently, mutations in the DNAJC5/CLN4 gene, which encodes the presynaptic co-chaperone CSPα were shown to cause autosomal-dominant NCL. Although 14 NCL genes have been identified, it is unknown if they act in common disease pathways. Here we show that two disease-associated proteins, CSPα and the depalmitoylating enzyme palmitoyl-protein thioesterase 1 (PPT1/CLN1) are biochemically linked. We find that in DNAJC5/CLN4 patient brains, PPT1 is massively increased and mis-localized. Surprisingly, the specific enzymatic activity of PPT1 is dramatically reduced. Notably, we demonstrate that CSPα is depalmitoylated by PPT1 and hence its substrate. To determine the consequences of PPT1 accumulation, we compared the palmitomes from control and DNAJC5/CLN4 patient brains by quantitative proteomics. We discovered global changes in protein palmitoylation, mainly involving lysosomal and synaptic proteins. Our findings establish a functional link between two forms of NCL and serve as a springboard for investigations of NCL disease pathways.
Assuntos
Encéfalo/metabolismo , Proteínas de Choque Térmico HSP40/genética , Proteínas de Membrana/genética , Mutação/genética , Lipofuscinoses Ceroides Neuronais/genética , Lipofuscinoses Ceroides Neuronais/patologia , Tioléster Hidrolases/metabolismo , Animais , Encéfalo/patologia , Células Cultivadas , Córtex Cerebral/citologia , Feminino , Proteínas de Choque Térmico HSP40/deficiência , Humanos , Lipoilação/genética , Lipoilação/fisiologia , Masculino , Proteínas de Membrana/deficiência , Camundongos , Camundongos Knockout , Modelos Biológicos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Mapas de Interação de Proteínas , Proteômica , Frações Subcelulares/metabolismo , Frações Subcelulares/patologia , TransfecçãoRESUMO
Cysteine string protein α (CSPα), a presynaptic cochaperone for Hsc70, is required for synapse maintenance. Deletion of CSPα leads to neuronal dysfunction, synapse loss, and neurodegeneration. We utilized unbiased, systematic proteomics to identify putative CSPα protein clients. We found 22 such proteins whose levels are selectively decreased in CSPα knockout synapses. Of these putative CSPα protein clients, two directly bind to the CSPα chaperone complex and are bona fide clients. They are the t-SNARE SNAP-25 and the GTPase dynamin 1, which are necessary for synaptic vesicle fusion and fission, respectively. Using hippocampal cultures, we show that CSPα regulates the stability of client proteins and synaptic vesicle number. Our analysis of CSPα-dynamin 1 interactions reveals unexpectedly that CSPα regulates the polymerization of dynamin 1. CSPα, therefore, participates in synaptic vesicle endocytosis and may facilitate exo- and endocytic coupling. These findings advance the understanding of how synapses are functionally and structurally maintained.