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Endosomal Escape of Peptide-Photosensitizer Conjugates Is Affected by Amino Acid Sequences near the Photosensitizer
journal contribution
posted on 2020-02-18, 19:03 authored by Yuichi Miyoshi, Maho Kadono, Shigetoshi Okazaki, Ayano Nishimura, Mizuki Kitamatsu, Kazunori Watanabe, Takashi OhtsukiCell-penetrating
peptides (CPPs) are widely used for the intracellular
delivery of peptides and proteins, but CPP fusion peptides and proteins
are often transported by endocytosis and trapped in endosomes. Photochemical
internalization (PCI) is a method for the endosomal escape of the
trapped peptide or protein and release into the cytosol using light
and photosensitizers. In PCI, endosomal membranes are thought to be
destabilized by singlet oxygen (1O2) photogenerated
from photosensitizers localized in endosomes. We previously developed
CPP-cargo-photosensitizer (PS) conjugates able to photodependently
enter the cytosol via the PCI mechanism. For example, TatU1A-PS (a
covalent complex of Tat [CPP], U1A RNA-binding protein [cargo], and
PS) can photodependently deliver RNAs into the cytosol, and TatBim-PS
(a covalent complex of Tat, Bim [cargo], and PS) can photoinduce apoptosis
in mammalian cells. However, for many newly created conjugates, the
induction of PCI has been insufficient. We hypothesized that the amino
acid linker sequence (XX) adjacent to the photosensitizer is an important
determinant of PCI efficiency. In this study, using CPP-cargo-XX-PS
platforms, we examined the relationship between PCI efficiency and
the linker amino acid sequence near the photosensitizer. We found
that hydrophobic FF and LL linkers enhanced the PCI efficiencies of
both TatBim-XX-PS and TatU1A-XX-PS. The effectiveness of the linker
depended, in part, on both the cargo moiety and the photosensitizer.
These results may guide the design of CPP-cargo-PS conjugates conferring
broad target functions for PCI and photodynamic therapy.