Pampalakis Georgios, Sykioti Vasia-Samantha, Ximerakis Methodios, Stefanakou-Kalakou Ioanna, Melki Ronald, Vekrellis Kostas, Sotiropoulou Georgia
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.
Oncotarget. 2017 Feb 28;8(9):14502-14515. doi: 10.18632/oncotarget.13264.
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.
KLK6是一种在神经系统中高表达的丝氨酸蛋白酶。在包括帕金森病在内的突触核蛋白病中，脑脊液中KLK6的水平与α-突触核蛋白呈负相关。最近，我们提出重组KLK6可直接并通过涉及未知金属蛋白酶的蛋白水解级联反应介导细胞外α-突触核蛋白的降解。在此，我们表明重组的和天然分泌的KLK6能够轻易切割具有“朊病毒样机制”中细胞间传播潜力的α-突触核蛋白原纤维。重要的是，缺乏KLK6的原代皮质神经元摄取α-突触核蛋白原纤维的能力增强。我们还证明KLK6可激活前MMP2，而前MMP2反过来又能切割α-突触核蛋白。通过降解组分析对神经元环境中被KLK6激活的蛋白酶谱进行了分析，该分析还鉴定出ADAMTS19，并表明KLK6的底物数量有限，表明其具有特定的生物学功能，如调节α-突触核蛋白的周转。我们构建了用于递送KLK6的腺病毒载体，并证明神经元分泌的KLK6可降低细胞外α-突触核蛋白的水平。我们的研究结果为将KLK6开发为帕金森病和其他突触核蛋白病的新型治疗靶点开辟了可能性。
