Glycosaminoglycan Binding and Non-Endocytic Membrane Translocation of Cell-Permeable Octaarginine Monitored by Real-Time In-Cell NMR Spectroscopy
pharmaceuticals Article Glycosaminoglycan Binding and Non-Endocytic Membrane Translocation of Cell-Permeable Octaarginine Monitored by Real-Time In-Cell NMR Spectroscopy Yuki Takechi-Haraya 1,†, Kenzo Aki 1, Yumi Tohyama 1, Yuichi Harano 1, Toru Kawakami 2, Hiroyuki Saito 3 and Emiko Okamura 1,* 1 Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 7-2-1 Kamiohno, Himeji 670-8524, Japan; haraya@nihs.go.jp (Y.T.-H.); aki@gm.himeji-du.ac.jp (K.A.); ytohyama@himeji-du.ac.jp (Y.T.); harano@gm.himeji-du.ac.jp (Y.H.) 2 Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan; kawa@protein.osaka-u.ac.jp 3 Department of Biophysical Chemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan; hsaito@mb.kyoto-phu.ac.jp * Correspondence: emiko@himeji-du.ac.jp; Tel.: +81-79-223-6847 † Present address: Division of Drugs, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan. Academic Editor: Barbara Mulloy Received: 16 February 2017; Accepted: 12 April 2017; Published: 15 April 2017 Abstract: Glycosaminoglycans (GAGs), which are covalently-linked membrane proteins at the cell surface have recently been suggested to involve in not only endocytic cellular uptake but also non-endocytic direct cell membrane translocation of arginine-rich cell-penetrating peptides (CPPs). However, in-situ comprehensive observation and the quantitative analysis of the direct membrane translocation processes are challenging, and the mechanism therefore remains still unresolved. In this work, real-time in-cell NMR spectroscopy was applied to investigate the direct membrane translocation of octaarginine (R8) into living cells.
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