12/31/2023 0 Comments Protein scaffold roc curves manualMultiple interactions were noted (such as Dcp2 and Tnrc6a), but Edc4 was the strongest ( Figure 2H). To determine whether this affinity was unique to Edc4 among P-body proteins, we tagged ∼50 P-body proteins by nanoluciferase and quantified their interactions with αS under overexpression conditions. MS analysis confirmed its identity ( Table S2). Silver staining of αS-Avi pull-downs ( Figure 2F) revealed a strong 150-kDa band (the expected size of Edc4), which was lost in an EDC4-null background ( Figure 2G). In our αS pull-downs, Edc4 consistently showed the highest enrichment among decapping-module proteins and along with αS, it had the highest peptide count in SILAC MS ( Figure S2E). Results P-body genes modify αS toxicity in tractable model organisms More broadly, these data shed light on how conformationally plastic proteins like αS mediate cross-compartment signaling within cells. Our data suggest a mechanism through which altered αS membrane interactions and pathology might directly impact other key cytosolic functions, including mRNA metabolism. In human neurons that express pathologic levels of αS or that are seeded with αS fibrils, mRNAs are globally tend to be stabilized. Human genetic analyses further tie this pathway to PD risk. This is seen in human neurons harboring familial synucleinopathy mutations, both iPSC-derived and in postmortem brain. When αS levels increases to pathological levels, Edc4 increasingly associates with αS, compromising interactions with other decapping-module proteins. Of these components, αS interacts most strongly with Edc4, the decapping-module scaffold. αS thus dichotomously interacts with either membranes or P-body components. This interaction is dictated by the N terminus of αS, the same region involved in membrane anchoring. We find that αS interacts closely with a core set of proteins (Edc4, Dcp1, Dcp2, Xrn1, and Edc3) involved in mRNA decapping and degradation. Beyond revealing an unexpected aspect of αS function and pathology, our data highlight the versatility of conformationally plastic proteins with high intrinsic disorder. Genetic modulation of P-body components alters αS toxicity, and human genetic analysis lends support to the disease-relevance of these interactions. mRNA decay kinetics within PD-relevant pathways are correspondingly disrupted in PD patient neurons and brain. As αS pathologically accumulates, aberrant interaction with Edc4 occurs at the expense of physiologic decapping-module interactions. αS associates with multiple decapping proteins in close proximity on the Edc4 scaffold. The N terminus of αS, but not other synucleins, dictates mutually exclusive binding either to cellular membranes or to P-bodies in the cytosol. Here, we show that αS directly modulates processing bodies (P-bodies), membraneless organelles that function in mRNA turnover and storage. It aggregates and is genetically linked to Parkinson’s disease (PD). Alpha-synuclein (αS) is a conformationally plastic protein that reversibly binds to cellular membranes.
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