Journal Article

Protein kinase R dependent phosphorylation of α-synuclein regulates its membrane binding and aggregation

Kirik, Deniz, Fusco, Giuliana, Gram, Hjalte, De Simone, Alfonso, Reimer, Lasse, Yang, Li, Jensen, Poul Henning, Betzer, Cristine, Jensen, Nanna Møller, Zhang, Jing, Shi, Min, Boudeffa, Driss, Lashuel, Hilal A, Jin, Lorrain

2022

Overview

Aggregated α-synuclein (α-syn) accumulates in the neuronal Lewy body (LB) inclusions in Parkinson's disease (PD) and LB dementia. Yet, under nonpathological conditions, monomeric α-syn is hypothesized to exist in an equilibrium between disordered cytosolic- and partially α-helical lipid-bound states: a feature presumably important in synaptic vesicle release machinery. The exact underlying role of α-syn in these processes, and the mechanisms regulating membrane-binding of α-syn remains poorly understood. Herein we demonstrate that Protein kinase R (PKR) can phosphorylate α-syn at several Ser/Thr residues located in the membrane-binding region that is essential for α-syn's vesicle-interactions. α-Syn phosphorylated by PKR or α-syn isolated from PKR overexpressing cells, exhibit decreased binding to lipid membranes. Phosphorylation of Thr64 and Thr72 appears as the major contributor to this effect, as the phosphomimetic Thr64Glu/Thr72Glu-α-syn mutant displays reduced overall attachment to brain vesicles due to a decrease in vesicle-affinity of the last two thirds of α-syn's membrane binding region. This allows enhancement of the “double-anchor” vesicle-binding mechanism that tethers two vesicles and thus promote the clustering of presynaptic vesicles in vitro. Furthermore, phosphomimetic Thr64Glu/Thr72Glu-α-syn inhibits α-syn oligomerization and completely abolishes nucleation, elongation, and seeding of α-syn fibrillation in vitro and in cells, and prevents trans-synaptic spreading of aggregated α-syn pathology in organotypic hippocampal slice cultures. Overall, our findings demonstrate that normal and abnormal functions of α-syn, like membrane-binding, synaptic vesicle clustering and aggregation can be regulated by phosphorylation, e.g., via PKR. Mechanisms that could potentially be modulated for the benefit of patients suffering from α-syn aggregate-related diseases.

• Publisher: Oxford University Press
• Subject: Binding / Biological, Health, and Medical Sciences / Brain slice preparation / Clustering / Dementia disorders / eIF-2 kinase / Hippocampus / Inclusions / Kinases / Lewy bodies / Lipid membranes / Lipids / Membranes / Movement disorders / Neurodegenerative diseases / Nucleation / Oligomerization / Parkinson's disease / Phosphorylation / Protein kinase R / Protein seeding / Proteins / Synuclein / Vesicles