Cysteine cathepsins are essential in lysosomal degradation of ?-synuclein.

ABSTRACT: A cellular feature of Parkinson's disease is cytosolic accumulation and amyloid formation of ?-synuclein (?-syn), implicating a misregulation or impairment of protein degradation pathways involving the proteasome and lysosome. Within lysosomes, cathepsin D (CtsD), an aspartyl protease, is suggested to be the main protease for ?-syn clearance; however, the protease alone only generates amyloidogenic C terminal-truncated species (e.g., 1-94, 5-94), implying that other proteases and/or environmental factors are needed to facilitate degradation and to avoid ?-syn aggregation in vivo. Using liquid chromatography-mass spectrometry, to our knowledge, we report the first peptide cleavage map of the lysosomal degradation process of ?-syn. Studies of purified mouse brain and liver lysosomal extracts and individual human cathepsins demonstrate a direct involvement of cysteine cathepsin B (CtsB) and L (CtsL). Both CtsB and CtsL cleave ?-syn within its amyloid region and circumvent fibril formation. For CtsD, only in the presence of anionic phospholipids can this protease cleave throughout the ?-syn sequence, suggesting that phospholipids are crucial for its activity. Taken together, an interplay exists between ?-syn conformation and cathepsin activity with CtsL as the most efficient under the conditions examined. Notably, we discovered that CtsL efficiently degrades ?-syn amyloid fibrils, which by definition are resistant to broad spectrum proteases. This work implicates CtsB and CtsL as essential in ?-syn lysosomal degradation, establishing groundwork to explore mechanisms to enhance their cellular activity and levels as a potential strategy for clearance of ?-syn.

SUBMITTER: McGlinchey RP 

PROVIDER: S-EPMC4522768 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature