Autophagy\u2013lysosome pathway alterations and alpha-synuclein up-regulation in the subtype of neuronal ceroid lipofuscinosis, CLN5 disease

Jessie Adams,Stella Y Lee,Melissa Feuerborn,Babita Adhikari,Joshua A Molina,Alexa R Wilden,Theodore Budden

doi:10.1038/s41598-018-36379-z

Abstract

Neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative lysosomal storage disorders. CLN5 deficiency causes a subtype of NCL, referred to as CLN5 disease. CLN5 is a soluble lysosomal protein with an unclear function in the cell. Increased levels of the autophagy marker protein LC3-II have been reported in several subtypes of NCLs. In this report, we examine whether autophagy is altered in CLN5 disease. We found that the basal level of LC3-II was elevated in both CLN5 disease patient fibroblasts and CLN5-deficient HeLa cells. Further analysis using tandem fluorescent mRFP-GFP-LC3 showed the autophagy flux was increased. We found the alpha-synuclein (α-syn) gene SNCA was highly up-regulated in CLN5 disease patient fibroblasts. The aggregated form of α-syn is well known for its role in the pathogenicity of Parkinson’s disease. Higher α-syn protein levels confirmed the SNCA up-regulation in both patient cells and CLN5 knockdown HeLa cells. Furthermore, α-syn was localized to the vicinity of lysosomes in CLN5 deficient cells, indicating it may have a lysosome-related function. Intriguingly, knocking down SNCA reversed lysosomal perinuclear clustering caused by CLN5 deficiency. These results suggest α-syn may affect lysosomal clustering in non-neuronal cells, similar to its role in presynaptic vesicles in neurons.

Highlights

Neuronal ceroid lipofuscinoses (NCLs) are a group of progressive neurodegenerative lysosomal disorders that predominantly affect children[1,2]
We show in CLN5-deficient cells the basal level of LC3-II is elevated, the autophagy flux is increased, and the expression level of α-syn gene SNCA is up-regulated. α-syn is highly expressed in presynaptic neurons and primarily localized to synaptic vesicles[21,22]
As an initial step to examine whether the autophagy process might be altered with CLN5 deficiency, we compared the basal levels of an autophagy marker, LC3-II, in fibroblasts from control healthy individuals and fibroblasts derived from CLN5-deficient patients

Summary

Introduction

Neuronal ceroid lipofuscinoses (NCLs) are a group of progressive neurodegenerative lysosomal disorders that predominantly affect children[1,2]. There are thirteen genetically distinct subtypes of the NCLs that are named based on the genes in which the mutations have been identified[3] These genes encode a variety of unrelated proteins that are localized to various cellular compartments. We show in CLN5-deficient cells the basal level of LC3-II is elevated, the autophagy flux is increased, and the expression level of α-syn gene SNCA is up-regulated. Despite being primarily associated with neurodegenerative disorders, both CLN5 and α-syn can be detected in a variety of tissues and cell types[26,27,28,29,30,31]. We uncovered a potential role for α-syn in regulating lysosomal positioning

Methods

Results

Conclusion