Cellular uptake of an alpha-helical amphipathic model peptide with the potential to deliver polar compounds into the cell interior non-endocytically.

Evidence that multiple, probably non-endocytic mechanisms are involved in the uptake into mammalian cells of the alpha-helical amphipathic model peptide FLUOS-KLALKLALKALKAALKLA-NH2 (I) is presented. Extensive cellular uptake of N-terminally GC-elongated derivatives of I, conjugated by disufide bridges to differently charged peptides, indicated that I-like model peptides might serve as vectors for intracellular delivery of polar bioactive compounds. The mode of the cellular internalization of I comprising energy-, temperature-, pH- and ion-dependent as well as -independent processes suggests analogy to that displayed by small unstructured peptides reported previously (Oehlke et al., Biochim. Biophys. Acta 1330 (1997) 50-60). The uptake behavior of I also showed analogy to that of several protein-derived helical peptide sequences, recently found to be capable of efficiently carrying tagged oligonucleotides and peptides directly into the cytosol of mammalian cells (Derossi et al., J. Biol. Chem. 269 (1994) 10444-10450; Lin et al., J. Biol. Chem. 270 (1995) 14255-14258; Fawell et al., Proc. Natl. Acad. Sci. USA 91 (1994) 664-668; Chaloin et al., Biochemistry 36 (1997) 11179-11187; Vives et al., J. Biol. Chem., 272 (1997) 16010-16017).