title: Lysosomal proteases are involved in generation of N-terminal huntingtin fragments.
abstract: N-terminal mutant huntingtin (N-mhtt) fragments form inclusions and cause cell death in vitro. Mutant htt expression stimulates autophagy and increases levels of lysosomal proteases. Here, we show that lysosomal proteases, cathepsins D, B and L, affected mhtt processing and levels of cleavage products (cp) known as A and B, which form inclusions. Adding inhibitors of cathepsin D, B and L to clonal striatal cells reduced mhtt, especially mhtt fragment cp A. Mutant htt fully degraded in cathepsin-L-treated lysates but formed stable N-mhtt fragments upon exposure to cathepsin D. Mutagenesis analysis of htt cDNA suggested that cathepsin D and the protease for cp A may cleave htt in the same region. Brain lysates from HD knock-in mice expressed N-mhtt fragments that accumulated with cathepsin D treatment and declined with aspartyl protease inhibition. Findings implicate lysosomal proteases in formation of N-mhtt fragments and clearance of mhtt.
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Yun J
authors.initials: YJ
authors.lastname: Kim
authors.forename: Ellen
authors.initials: E
authors.lastname: Sapp
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Cuiffo
authors.forename: Lindsay
authors.initials: L
authors.lastname: Sobin
authors.forename: Jennifer
authors.initials: J
authors.lastname: Yoder
authors.forename: Kimberly B
authors.initials: KB
authors.lastname: Kegel
authors.forename: Zheng-Hong
authors.initials: ZH
authors.lastname: Qin
authors.forename: Peter
authors.initials: P
authors.lastname: Detloff
authors.forename: Neil
authors.initials: N
authors.lastname: Aronin
authors.forename: Marian
authors.initials: M
authors.lastname: DiFiglia
mesh_terms: D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D002402:Cathepsin D / Q000037:antagonists & inhibitors / Q000378:metabolism; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002461:Cell Line, Transformed; D003342:Corpus Striatum / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D008247:Lysosomes / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008818:Mice, Neurologic Mutants; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology / Q000473:pathology; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000187:drug effects / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D002403:Cathepsins; D010447:Peptide Hydrolases; D016282:Aspartic Acid Endopeptidases; D002402:Cathepsin D