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Cellular uptake of a family of cationic cell-penetrating peptides (examples include Tat peptides and penetratin) have been ascribed in the literature to a mechanism that does not involve endocytosis. In this work we reevaluate the mechanisms of cellular uptake of Tat 48-60 and (Arg)(9). We demonstrate here that cell fixation, even in mild conditions, leads(More)
Electric fields promote pore formation in both biological and model membranes. We clamped unmodified planar bilayers at 150-550 mV to monitor transient single pores for a long period of time. We observed fast transitions between different conductance levels reflecting opening and closing of metastable lipid pores. Although mean lifetime of the pores was 3(More)
Myoblast fusion into multinucleated myotubes is a crucial step in skeletal muscle development and regeneration. Here, we accumulated murine myoblasts at the ready-to-fuse stage by blocking formation of early fusion intermediates with lysophosphatidylcholine. Lifting the block allowed us to explore a largely synchronized fusion. We found that initial merger(More)
Delivery of macromolecules mediated by protein transduction domains (PTDs) attracts a lot of interest due to its therapeutic and biotechnological potential. A major reevaluation of the mechanism of PTD-mediated internalization and the role of endocytosis in this mechanism has been recently initiated. Here, we demonstrate that the entry of TAT peptide (one(More)
Cell-cell fusion in animal development and in pathophysiology involves expansion of nascent fusion pores formed by protein fusogens to yield an open lumen of cell-size diameter. Here we explored the enlargement of micron-scale pores in syncytium formation, which was initiated by a well-characterized fusogen baculovirus gp64. Radial expansion of a single or,(More)
Many enveloped viruses invade cells via endocytosis and use different environmental factors as triggers for virus-endosome fusion that delivers viral genome into cytosol. Intriguingly, dengue virus (DEN), the most prevalent mosquito-borne virus that infects up to 100 million people each year, fuses only in late endosomes, while activation of DEN protein(More)
Defensins are peptides that protect the host against microorganisms. Here we show that the theta-defensin retrocyclin 2 (RC2) inhibited influenza virus infection by blocking membrane fusion mediated by the viral hemagglutinin. RC2 was effective even after hemagglutinin attained a fusogenic conformation or had induced membrane hemifusion. RC2, a multivalent(More)
Delivery of macromolecules into living cells by arginine-rich cell penetrating peptides (AR-CPPs) is an important new avenue for the development of novel therapeutic strategies. However, to date the mechanism of this delivery remains elusive. Recent data implicate endocytosis in the internalization of AR-CPPs and their macromolecular cargo and also indicate(More)
Cationic cell-penetrating peptides (CPPs) are a promising vehicle for the delivery of macromolecular drugs. Although many studies have indicated that CPPs enter cells by endocytosis, the mechanisms by which they cross endosomal membranes remain elusive. On the basis of experiments with liposomes, we propose that CPP escape into the cytosol is based on leaky(More)
Using a cation-selective gramicidin A channel as a sensor of the membrane surface charge, we studied interactions of oligoarginine peptide R9C, a prototype cationic cell-penetrating peptide (CPP), with planar lipid membranes. We have found that R9C sorption to the membrane depends strongly on its lipid composition from virtually nonexistent for membranes(More)