Tubular structures in heterogeneous membranes induced by the cell penetrating peptide penetratin

Abstract

The delivery of active molecules into cells requires the efficient translocation of the plasma membrane barrier. Penetratin is a promising cell penetrating peptide is which crosses the cell membrane by a receptor and metabolic energy-independent mechanism. In previous work, we have shown that basic peptides induce membrane invaginations (i.e., tubes formation by induction of negative curvature of membranes) suggesting a new mechanism for cellular uptake of cell penetrating peptides: "physical endocytosis". These effects on membrane curvature are favored in pure liquid disordered but not in pure liquid ordered (raft-like) membrane domains. Herein, we present experiments in heterogeneous membranes composed of mixed domains. The results show that Penetratin is able to induce invaginations in membranes in which liquid ordered and liquid disordered membranes coexist. We suggest that Penetratin is able to recruit specific lipids locally forming fluid membrane patches dispersed inside a liquid ordered membrane zone resulting in the invagination of tubes composed of heterogeneous membrane domains.

Keywords: membrane domains; membrane invagination; penetratin; physical endocytosis.

Figure 1

Penetratin induced tubulation in heterogeneous GUVs. (A) PC/SM/Chol/Di-Q (60/20/20/1) GUV showing the fluorescent liquid disordered domain (fluorescent Di-Q is a marker of liquid disordered domains), and a dark non fluorescent liquid ordered domain in the top of the GUV. The fluorescent tubes inside indicate that Penetratin is able to induce invaginations of membrane disordered domains. (B) PC/SM/Chol/GM1 (60/20/20/1) GUV showing the dark non fluorescent liquid disordered domain, and three fluorescent liquid ordered domains. The fluorescence from rhodamine-labelled cholera toxin binds specifically to the liquid ordered lipid marker GM1. The fluorescent tubes inside indicate that Penetratin is able to induce invaginations containing cholera toxin associated membrane ordered domains.