Stress-inducible phosphoprotein 1 (HOP/STI1/STIP1) regulates the accumulation and toxicity of α-synuclein in vivo

  Manuscript accepted for publication in journal Acta Neuropathologica.

Rachel E. Lackie1,2, Aline S de Miranda1,3, Mei Peng Lim1,2, Vladislav Novikov1,2, Nimrod Madner4, Nadun C. Karunatilleke5, Benjamin S. Rutledge5, Stephanie Tullo6, Anne Brickenden5,  Matthew E.R. Maitland1,5, David Greenberg4, Daniel Gallino6, Wen Luo7, Anoosha Attaran1, Irina Shlafer7, Esther Del Cid Pellitero7, Caroline Schild-Poulter1,5, Thomas M. Durcan7, Edward A. Fon7, Martin Duennwald8, Flavio H. Beraldo1,  M. Mallar Chakravarty6, Timothy J. Bussey1,2,9, Lisa M. Saksida1,2,9, Hermona Soreq4, Wing-Yiu Choy5*, Vania F. Prado1,2,8,9*, Marco A.M. Prado1,2,8,9*

1Robarts Research Institute, 2Program in Neuroscience, The University of Western Ontario, Canada, 3Laboratory of Neurobiology, Department of Morphology, Institute of Biological Science, Universidade Federal de Minas Gerais (UFMG), 4The Edmond and Lily Safra Center for Brain Sciences, Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel, 5Department of Biochemistry, The University of Western Ontario, 6Cerebral Imaging Centre, Douglas Research Institute, McGill University, 7Early Drug Discovery Unit, Montreal Neurological Institute, McGill University, McGill Parkinson Program, Neurodegenerative Diseases Group, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 8Department of Anatomy & Cell Biology, The University of Western Ontario, 9Department of Physiology and Pharmacology, The University of Western Ontario 

The predominantly presynaptic intrinsically disordered protein α-synuclein is prone to misfolding and aggregation in synucleinopathies, such as Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB). Molecular chaperones play important roles in protein misfolding diseases and members of the chaperone machinery are often deposited in Lewy bodies. Here, we show that the Hsp90 co-chaperone STI1 co-immunoprecipitated α-synuclein, and co-deposited with Hsp90 and Hsp70 in insoluble protein fractions in two mouse models of α-synuclein misfolding. STI1 and Hsp90 also co-localized extensively with filamentous S129 phosphorylated α-synuclein in ubiquitin-positive inclusions. In PD human brains, STI1 transcripts were increased, and in neurologically healthy brains STI1 and α-synuclein transcripts correlated. Nuclear Magnetic Resonance (NMR) analyses revealed direct interaction of α-synuclein with STI1 and indicated that the STI1 TPR2A, but not TPR1 or TPR2B domains, interacted with the C-terminal domain of α-synuclein. In vitro, the TPR2A STI1 domain facilitated S129 phosphorylation by Polo-like kinase 3. Moreover, mice overexpressing STI1 and Hsp90ß presented elevated α-synuclein S129 phosphorylation accompanied by inclusions when injected with α-synuclein preformed fibrils. In contrast, reduced STI1 function decreased protein inclusion formation, S129 α-synuclein phosphorylation, while mitigating motor and cognitive deficits as well as mesoscopic brain atrophy in α-synuclein-overexpressing mice. Our findings reveal a vicious cycle in which STI1 facilitates the generation and accumulation of toxic α-synuclein conformers, while α-synuclein-induced proteostatic stress increased insoluble STI1 and Hsp90.