Cathepsin D is the main lysosomal enzyme involved in the degradation of α-synuclein and generation of its carboxy-terminally truncated species

Daniel Sevlever, Peizhou Jiang, Shu Hui C Yen

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Abstract

α-Synuclein is likely to play a key role in the development of Parkinson's disease as well as other synucleinopathies. In animal models, overexpression of full-length or carboxy-terminally truncated α-synuclein has been shown to produce pathology. Although the proteosome and lysosome have been proposed to play a role in the degradation of α-synuclein, the enzyme(s) involved in α-synuclein clearance and generation of its carboxy-terminally truncated species have not been identified. In this study, the role of cathepsin D and calpain I in these processes was analyzed. In vitro experiments, using either recombinant or endogenous α-synuclein as substrates and purified cathepsin D or lysosomes, demonstrated that cathepsin D degraded α-synuclein very efficiently, and that limited proteolysis resulted in the generation of carboxy-terminally truncated species. Purified calpain I also cleaved α-synuclein, but carboxy-terminally truncated species were not the main cleavage products, and calpain I activity present in cellular lysates was not able to degrade the protein. Knockdown of cathepsin D in cells overexpressing wild-type α-synuclein increased total α-synuclein levels by 28% and lysosomal α-synuclein by 2-fold. In in vitro experiments, pepstatin A completely blocked the degradation of α-synuclein in purified lysosomes. Furthermore, lysosomes isolated from cathepsin D knockdown cells showed a marked reduction in α-synuclein degrading activity, indicating that cathepsin D is the main lysosomal enzyme involved in α-synuclein degradation. Our findings suggest that upregulation of cathepsin D could be an additional therapeutic strategy to lessen α-synuclein burden in synucleinopathies.

Original languageEnglish (US)
Pages (from-to)9678-9687
Number of pages10
JournalBiochemistry
Volume47
Issue number36
DOIs
StatePublished - Sep 9 2008

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Synucleins
Cathepsin D
Degradation
Enzymes
Lysosomes
Calpain
Proteolysis

ASJC Scopus subject areas

  • Biochemistry

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Cathepsin D is the main lysosomal enzyme involved in the degradation of α-synuclein and generation of its carboxy-terminally truncated species. / Sevlever, Daniel; Jiang, Peizhou; Yen, Shu Hui C.

In: Biochemistry, Vol. 47, No. 36, 09.09.2008, p. 9678-9687.

Research output: Contribution to journalArticle

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abstract = "α-Synuclein is likely to play a key role in the development of Parkinson's disease as well as other synucleinopathies. In animal models, overexpression of full-length or carboxy-terminally truncated α-synuclein has been shown to produce pathology. Although the proteosome and lysosome have been proposed to play a role in the degradation of α-synuclein, the enzyme(s) involved in α-synuclein clearance and generation of its carboxy-terminally truncated species have not been identified. In this study, the role of cathepsin D and calpain I in these processes was analyzed. In vitro experiments, using either recombinant or endogenous α-synuclein as substrates and purified cathepsin D or lysosomes, demonstrated that cathepsin D degraded α-synuclein very efficiently, and that limited proteolysis resulted in the generation of carboxy-terminally truncated species. Purified calpain I also cleaved α-synuclein, but carboxy-terminally truncated species were not the main cleavage products, and calpain I activity present in cellular lysates was not able to degrade the protein. Knockdown of cathepsin D in cells overexpressing wild-type α-synuclein increased total α-synuclein levels by 28{\%} and lysosomal α-synuclein by 2-fold. In in vitro experiments, pepstatin A completely blocked the degradation of α-synuclein in purified lysosomes. Furthermore, lysosomes isolated from cathepsin D knockdown cells showed a marked reduction in α-synuclein degrading activity, indicating that cathepsin D is the main lysosomal enzyme involved in α-synuclein degradation. Our findings suggest that upregulation of cathepsin D could be an additional therapeutic strategy to lessen α-synuclein burden in synucleinopathies.",
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