Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.
Biochemistry. 2014 Jun 24;53(24):4034-46. doi: 10.1021/bi5004102. Epub 2014 Jun 11.
Cyclic heptapeptide cyclo(FΦRRRRQ) (cFΦR4, where Φ is l-2-naphthylalanine) was recently found to be efficiently internalized by mammalian cells. In this study, its mechanism of internalization was investigated by perturbing various endocytic events through the introduction of pharmacologic agents and genetic mutations. The results show that cFΦR4 binds directly to membrane phospholipids, is internalized into human cancer cells through endocytosis, and escapes from early endosomes into the cytoplasm. Its cargo capacity was examined with a wide variety of molecules, including small-molecule dyes, linear and cyclic peptides of various charged states, and proteins. Depending on the nature of the cargos, they may be delivered by endocyclic (insertion of cargo into the cFΦR4 ring), exocyclic (attachment of cargo to the Gln side chain), or bicyclic approaches (fusion of cFΦR4 and cyclic cargo rings). The overall delivery efficiency (i.e., delivery of cargo into the cytoplasm and nucleus) of cFΦR4 was 4-12-fold higher than those of nonaarginine, HIV Tat-derived peptide, or penetratin. The higher delivery efficiency, coupled with superior serum stability, minimal toxicity, and synthetic accessibility, renders cFΦR4 a useful transporter for intracellular cargo delivery and a suitable system for investigating the mechanism of endosomal escape.
最近发现环状七肽环（FΦRRRRQ）（cFΦR4，其中Φ是 l-2-萘丙氨酸）能够被哺乳动物细胞有效内化。在这项研究中，通过引入药理试剂和基因突变来干扰各种内吞作用，研究了其内化的机制。结果表明，cFΦR4 直接与膜磷脂结合，通过内吞作用进入人癌细胞，并从早期内体逃逸到细胞质中。其载物能力通过各种分子进行了检测，包括小分子染料、各种荷电状态的线性和环状肽以及蛋白质。根据货物的性质，它们可能通过内环（将货物插入 cFΦR4 环中）、外环（将货物连接到 Gln 侧链上）或双环途径（cFΦR4 和环状货物环融合）进行递送。cFΦR4 的整体递送效率（即将货物递送到细胞质和细胞核中）比九聚精氨酸、HIV Tat 衍生肽或穿透肽高 4-12 倍。更高的递送效率，加上卓越的血清稳定性、最小的毒性和合成可及性，使 cFΦR4 成为一种用于细胞内货物递送的有用载体，也是研究内体逃逸机制的合适系统。
