Investigating the interactions of the first 17 amino acid residues of Huntingtin with lipid vesicles using mass spectrometry and molecular dynamics

Abstract

The first 17 amino acid residues of Huntingtin protein (Nt17 of htt) are thought to play an important role in the protein's function; Nt17 is one of two membrane binding domains in htt. In this study the binding ability of Nt17 peptide with vesicles comprised of two subclasses of phospholipids is studied using electrospray ionization -mass spectrometry (ESI-MS) and molecular dynamics (MD) simulations. Overall, the peptide is shown to have a greater propensity to interact with vesicles of phosphatidylcholine (PC) rather than phosphatidylethanolamine (PE) lipids. Mass spectra show an increase in lipid-bound peptide adducts where the ordering of the number of such specie is 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) > 1-palmitoyl-2-oleoylglycero-3-phosphocholine (POPC) > 1-palmitoyl-2-oleoyl-sn-glycero-3 phosphoethanolamine (POPE). MD simulations suggest that the compactness of the bilayer plays a role in governing peptide interactions. The peptide shows greater disruption of the DOPC bilayer order at the surface and interacts with the hydrophobic tails of lipid molecules via hydrophobic residues. Conversely, the POPE vesicle remains ordered and lipids display transient interactions with the peptide through the formation of hydrogen bonds with hydrophilic residues. The POPC system displays intermediate behavior with regard to the degree of peptide-membrane interaction. Finally, the simulations suggest a helix stabilizing effect resulting from the interactions between hydrophobic residues and the lipid tails of the DOPC bilayer. K E Y W O R D S peptide interactions, native MS, molecular dynamics simulations, Huntingtin, Protein aggregation

Scratching the surface: native mass spectrometry of peripheral membrane protein complexes

“…More recently, a similar strategy was adopted to study lipid preferences of the N-terminal amphipathic helix of the huntingtin protein, aggregation of which is associated with amyotrophic lateral sclerosis. Valentine and co-workers used nMS to monitor the interactions of a peptide encompassing huntingtin residues 1-17 with lipid vesicles composed of different zwitterionic lipids [76]. By comparing the signal intensities and stoichiometries of the resulting complexes, the authors were able to show that peptide oligomerization is enhanced by the presence of vesicles, and preferential binding of doubly unsaturated lipids.…”

“…• Based on these developments, we predict that nMS will enable new insights into elusive lipidprotein interactions. nMS has the potential to continue to make significant contributions to poorly understood disease mechanisms such as the membrane-mediated formation of protein aggregates in neurodegeneration [75], the mechanism of action of novel antimicrobial peptides [76], and lipid-encoded signaling in cancer [77]. • nMS can be integrated with other structural biology methods to yield detailed molecular models [81].…”

Liposomen als Überträger membranassoziierter Proteine und Peptide für die massenspektrometrische Analyse

“…Eine erste Studie, die Liposomen mittels MS untersuchte, zeigte, dass Wechselwirkungen von bis zu 100 Lipidmolekülen in nativen MS‐Experimenten erhalten bleiben können [21] . Die Spezifität von Peptiden gegenüber bestimmten Lipiden wurde ebenfalls untersucht [21, 22] . In einer früheren Studie haben wir bereits verschiedene Phospholipide direkt aus den Lipiddoppelschichten von Liposomen identifiziert und quantifiziert [23] .…”

Membrane Interactions Accelerate the Self-Aggregation of Huntingtin Exon 1 Fragments in a Polyglutamine Length-Dependent Manner

“…Recent structural investigations reveal high conformational plasticity of htt17 and the subsequent polyQ domain where htt17 association [26], its interactions with the membrane [43][44][45][46][47] or with other polypeptide domains are associated with random coil-helix structural transitions [48,49]. A recent NMR study has shown that in the solution, the htt17 sequence associates in a dimer of dimers preaggregation state [50,51].…”