Non-Metabolic Membrane Tubulation and Permeability Induced by Bioactive Peptides

Abstract

BackgroundBasic cell-penetrating peptides are potential vectors for therapeutic molecules and display antimicrobial activity. The peptide-membrane contact is the first step of the sequential processes leading to peptide internalization and cell activity. However, the molecular mechanisms involved in peptide-membrane interaction are not well understood and are frequently controversial. Herein, we compared the membrane activities of six basic peptides with different size, charge density and amphipaticity: Two cell-penetrating peptides (penetratin and R9), three amphipathic peptides and the neuromodulator substance P.Methodology/Principal FindingsExperiments of X ray diffraction, video-microscopy of giant vesicles, fluorescence spectroscopy, turbidimetry and calcein leakage from large vesicles are reported. Permeability and toxicity experiments were performed on cultured cells. The peptides showed differences in bilayer thickness perturbations, vesicles aggregation and local bending properties which form lipidic tubular structures. These structures invade the vesicle lumen in the absence of exogenous energy.Conclusions/SignificanceWe showed that the degree of membrane permeabilization with amphipathic peptides is dependent on both peptide size and hydrophobic nature of the residues. We propose a model for peptide-induced membrane perturbations that explains the differences in peptide membrane activities and suggests the existence of a facilitated “physical endocytosis,” which represents a new pathway for peptide cellular internalization.

The Interaction of Polyglutamine Peptides with Lipid Membranes Is Regulated by Flanking Sequences Associated with Huntingtin

“…3B). Contrary to previous studies in free solution (11) (without the presence of a surface), Nt17-Q 35 -KK aggregated at a slower rate than KK-Q 35 -KK as measured by the percentage of surface covered by peptide aggregates. The addition of just the poly(P) region (KK-Q 35 -P 10 -KK) appeared to retard aggregation on the surface as well; however, the addition of the Nt17 and poly(P) flanking sequences (Nt17-Q 35 -P 10 -KK) resulted in a similar aggregation rate as KK-Q 35 -KK.…”

“…Peptide Preparation-KK-Q 35 -KK, KK-Q 35 -P 10 -KK, Nt17-Q 35 -KK, and Nt17-Q 35 -P 10 -KK were obtained via custom synthesis (Keck Biotechnology Resource Laboratory, New Haven, CT). Lysines were added to the N-and C-terminal sides to aid in solubility.…”

“…Therefore, a higher surface pressure measurement means the peptide is more surface active and this may correlate to increased insertion into or association with the amphipathic cell membrane. The addition of monomeric htt peptides containing the Nt17 region to the subphase at a final concentration of 900 nM gives rise to an equilibrium spreading pressure of 19.2 mN/m for Nt17-Q 35 -KK and 17.3 mN/m for Nt17-Q 35 -P 10 -KK (Table 1). The peptides without Nt17, KK-Q 35 -KK and KK-Q 35 -P 10 -KK, induced a negligible change in surface pressure (Table 1) indicating the Nt17 lipid binding domain (Fig.…”

Massive Formation of Intracellular Membrane Vesicles in Escherichia coli by a Monotopic Membrane-bound Lipid Glycosyltransferase

“…An identified amphipathic helix with multiple plus charges ( 65 SLKGFRLVLFVKRYVRKMRKLKL 87 ) was experimentally proven to exhibit strong bilayer binding, with similar lipid preferences as the full-size protein (45). Because fairly short peptides, usually with a cationic character, can also induce bilayer reorganization (27), the potential influence of the alMGS-binding peptide was analyzed here. To efficiently express the peptide in E. coli, and also monitor membrane binding in situ, it was fused at the gene level C-terminally behind the green fluorescent protein and a proper linker (46).…”

“…Finally, a large number of "bioactive" peptides may yield analogous morphological membrane changes in both cells and liposome systems, e.g. temporins, penetratin, and polyarginines (26,27).…”