Ataxic phenotype and neurodegeneration are triggered by the impairment of chaperone-mediated autophagy in cerebellar neurons.
AIMS
Chaperone-mediated autophagy (CMA) is a pathway involved in the autophagy lysosome protein degradation system. CMA has attracted attention as a contributing factor to neurodegenerative diseases since it participates in the degradation of disease-causing proteins. We previously showed that CMA is generally impaired in cells expressing the proteins causing spinocerebellar ataxias (SCAs). Therefore, we investigated the effect of CMA impairment on motor function and the neural survival of cerebellar neurons using the micro RNA (miRNA)-mediated knockdown of lysosome-associated protein 2A (LAMP2A), a CMA-related protein.


METHODS
We injected adeno-associated virus serotype 9 vectors, which express green fluorescent protein (GFP) and miRNA (negative control miRNA or LAMP2A miRNA) under neuron-specific synapsin I promoter, into cerebellar parenchyma of 4-week-old ICR mice. Motor function of mice was evaluated by beam walking and footprint tests. Immunofluorescence experiments of cerebellar slices were conducted to evaluate histological changes in cerebella.


RESULTS
GFP and miRNA were expressed in interneurons (satellite cells and basket cells) in molecular layers and granule cells in the cerebellar cortices, but not in cerebellar Purkinje cells. LAMP2A knockdown in cerebellar neurons triggered progressive motor impairment, prominent loss of cerebellar Purkinje cells, interneurons, granule cells at the late stage, and astrogliosis and microgliosis from the early stage.


CONCLUSIONS
CMA impairment in cerebellar interneurons and granule cells triggers the progressive ataxic phenotype, gliosis and the subsequent degeneration of cerebellar neurons, including Purkinje cells. Our present findings strongly suggest that CMA impairment is related to the pathogenesis of various SCAs.
['Sato|Masahiro|M|', 'Ohta|Tomoko|T|', 'Morikawa|Yuri|Y|', 'Konno|Ayumu|A|', 'Hirai|Hirokazu|H|', 'Kurauchi|Yuki|Y|', 'Hisatsune|Akinori|A|', 'Katsuki|Hiroshi|H|', 'Seki|Takahiro|T|0000-0002-9894-4768']
D000818:Animals D002524:Cerebellar Ataxia D002531:Cerebellum D000080642:Chaperone-Mediated Autophagy D052119:Lysosomal-Associated Membrane Protein 2 D008813:Mice, Inbred ICR D009410:Nerve Degeneration D009474:Neurons D010641:Phenotype
neurodegeneration chaperone-mediated autophagy spinocerebellar ataxia LAMP2A gliosis cerebellum motor dysfunction