An Enantiomeric Fragment Pair (EFP) Approach for the Study of Cellular Uptake of Intrinsically Disordered Proteins.

The study of intrinsically disordered and amyloidogenic proteins poses a major challenge to researchers due to the propensity of the system to aggregate and to form amyloid fibrils and deposits. This intrinsic nature limits the way amyloids can be studied and increases the level of complexity of the techniques needed to study the system of interest. Recent reports suggest that cellular recognition and internalization of pre-fibrillary species of amyloidogenic peptides and proteins may initiate some of its toxic actions. Therefore, developing novels tools to facilitate the understanding and determination of the interactions between intrinsically disordered proteins and the cellular membrane is becoming increasingly valuable. Here, we present and propose an approach for the study of the interactions of intrinsically disordered proteins with the cellular surface based on the use of enantiomeric fragment pairs (EFPs). By following a stepwise methodology in which the amyloidogenic peptide or protein is fragmented into specific segments, we show how this approach can be exploited to differentiate between different types of cellular uptake, to determine the degree of receptor-mediated cellular internalization of intrinsically disordered peptides and proteins, and to pinpoint the specific regions within the amino acid sequence responsible for the cellular recognition. Adopting this approach overcomes aggregation-related challenges and offers a particularly well-suited platform for the elucidation of receptor-intermediated recognition, uptake, and toxicity.