title: Cysteine cathepsins are essential in lysosomal degradation of α-synuclein.
abstract: A cellular feature of Parkinson's disease is cytosolic accumulation and amyloid formation of α-synuclein (α-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 α-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 α-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 α-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 α-syn within its amyloid region and circumvent fibril formation. For CtsD, only in the presence of anionic phospholipids can this protease cleave throughout the α-syn sequence, suggesting that phospholipids are crucial for its activity. Taken together, an interplay exists between α-syn conformation and cathepsin activity with CtsL as the most efficient under the conditions examined. Notably, we discovered that CtsL efficiently degrades α-syn amyloid fibrils, which by definition are resistant to broad spectrum proteases. This work implicates CtsB and CtsL as essential in α-syn lysosomal degradation, establishing groundwork to explore mechanisms to enhance their cellular activity and levels as a potential strategy for clearance of α-syn.
authors.affiliation: Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, MD 20892.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: McGlinchey
authors.affiliation: Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, MD 20892 leej4@mail.nih.gov.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism*; D002402:Cathepsin D / Q000378:metabolism; D056668:Cathepsin L / Q000378:metabolism*; D002853:Chromatography, Liquid; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry*; D006801:Humans; D008099:Liver / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D013058:Mass Spectrometry; D051379:Mice; D019636:Neurodegenerative Diseases / Q000378:metabolism; D010300:Parkinson Disease / Q000378:metabolism*; D010449:Peptide Mapping; D010455:Peptides / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D010455:Peptides; D010743:Phospholipids; D051844:alpha-Synuclein; D002401:Cathepsin B; D056668:Cathepsin L; D002402:Cathepsin D; D003545:Cysteine
keywords: Parkinson’s disease; amyloid; lysosomes; mass spectrometry; protein–lipid interactions