In vitro AMPylation/Adenylylation of Alpha-synuclein by HYPE/FICD

Abstract

One of the major histopathological hallmarks of Parkinson's disease are Lewy bodies (LBs) -cytoplasmic inclusions, enriched with fibrillar forms of the presynaptic protein alpha-synuclein (α-syn). Progressive deposition of α-syn into LBs is enabled by its propensity to fibrillize into insoluble aggregates. We recently described a marked reduction in α-syn fibrillation in vitro upon posttranslational modification (PTM) by the Fic (Filamentation induced by cAMP) family adenylyltransferase HYPE/FICD (Huntingtin yeast-interacting protein E/FICD). Specifically, HYPE utilizes ATP to covalently decorate key threonine residues in α-syn's N-terminal and NAC (non-amyloid-β component) regions with AMP (adenosine monophosphate), in a PTM termed AMPylation or adenylylation. Status quo in vitro AMPylation reactions of HYPE substrates, such as α-syn, use a variety of ATP analogs, including radiolabeled α-³²P-ATP or α-³³P-ATP, fluorescent ATP analogs, biotinylated-ATP analogs (N6-[6-hexamethyl]-ATP-Biotin), as well as click-chemistry-based alkyl-ATP methods for gel-based detection of AMPylation. Current literature describing a step-by-step protocol of HYPE-mediated AMPylation relies on an α-³³P-ATP nucleotide instead of the more commonly available α-³²P-ATP. Though effective, this former procedure requires a lengthy and hazardous DMSO-PPO (dimethyl sulfoxide-polyphenyloxazole) precipitation. Thus, we provide a streamlined alternative to the α-³³P-ATP-based method, which obviates the DMSO-PPO precipitation step. Described here is a detailed procedure for HYPE mediated AMPylation of α-syn using α-³²P-ATP as a nucleotide source. Moreover, our use of a reusable Phosphor screen for AMPylation detection, in lieu of the standard, single-use autoradiography film, provides a faster, more sensitive and cost-effective alternative.

Keywords: AMPylation; Adenylylation; Alpha-synuclein; FICD; HYPE; Post-translational modification.