Lysosomal proteases are involved in generation of N-terminal huntingtin fragments.
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.
Kim
Yun J
YJ
Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
Sapp
Ellen
E
Cuiffo
Benjamin G
BG
Sobin
Lindsay
L
Yoder
Jennifer
J
Kegel
Kimberly B
KB
Qin
Zheng-Hong
ZH
Detloff
Peter
P
Aronin
Neil
N
DiFiglia
Marian
M
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
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