title: KLK6 proteolysis is implicated in the turnover and uptake of extracellular alpha-synuclein species.
abstract: KLK6 is a serine protease highly expressed in the nervous system. In synucleinopathies, including Parkinson disease, the levels of KLK6 inversely correlate with α-synuclein in CSF. Recently, we suggested that recombinant KLK6 mediates the degradation of extracellular α-synuclein directly and via a proteolytic cascade that involves unidentified metalloproteinase(s). Here, we show that recombinant and naturally secreted KLK6 can readily cleave α-synuclein fibrils that have the potential for cell-to-cell propagation in "a prion-like mechanism". Importantly, KLK6-deficient primary cortical neurons have increased ability for α-synuclein fibril uptake. We also demonstrate that KLK6 activates proMMP2, which in turn can cleave α-synuclein. The repertoire of proteases activated by KLK6 in a neuronal environment was analyzed by degradomic profiling, which also identified ADAMTS19 and showed that KLK6 has a limited number of substrates indicating specific biological functions such as the regulation of α-synuclein turnover. We generated adenoviral vectors for KLK6 delivery and demonstrated that the levels of extracellular α-synuclein can be reduced by neuronally secreted KLK6. Our findings open the possibility to exploit KLK6 as a novel therapeutic target for Parkinson disease and other synucleinopathies.
authors.affiliation: Department of Pharmacy, School of Health Sciences, University of Patras, Rion-Patras, Athens, Greece.
authors.forename: Georgios
authors.initials: G
authors.lastname: Pampalakis
authors.affiliation: Center for Neurosciences, Biomedical Research Foundation, Academy of Athens, Athens, Greece.
authors.forename: Vasia-Samantha
authors.initials: VS
authors.lastname: Sykioti
authors.affiliation: Center for Neurosciences, Biomedical Research Foundation, Academy of Athens, Athens, Greece.
authors.forename: Methodios
authors.initials: M
authors.lastname: Ximerakis
authors.affiliation: Department of Pharmacy, School of Health Sciences, University of Patras, Rion-Patras, Athens, Greece.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Stefanakou-Kalakou
authors.affiliation: Paris-Saclay Institute of Neuroscience, Centre National de la Recherche Scientifique, Gif-Sur-Yvette, France.
authors.forename: Ronald
authors.initials: R
authors.lastname: Melki
authors.affiliation: Center for Neurosciences, Biomedical Research Foundation, Academy of Athens, Athens, Greece.
authors.forename: Kostas
authors.initials: K
authors.lastname: Vekrellis
authors.affiliation: Department of Pharmacy, School of Health Sciences, University of Patras, Rion-Patras, Athens, Greece.|Center for Neurosciences, Biomedical Research Foundation, Academy of Athens, Athens, Greece.
authors.forename: Georgia
authors.initials: G
authors.lastname: Sotiropoulou
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000818:Animals; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism*; D007610:Kallikreins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D059748:Proteolysis; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D051844:alpha-Synuclein; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; D007610:Kallikreins; C491223:Prss18 protein, mouse
keywords: KLK6; degradomics; in vitro substrates; metalloproteases; α-synuclein