Arginine-Rich Molecular Transporter Peptides for D Products

Definition
Arginine-rich peptides (including octaarginine (R8), HIV-1 Tat, and branched-chain arginine-rich peptides) belong to one of the major classes of cell-permeable peptides (CPPs) which deliver various proteins and macromolecules to cells.

Structural Characteristics
One of the most often used carrier peptides is the arginine-rich basic peptide derived¹ from HIV-1 Tat protein is [HIV-1 Tat (48-60)]. This peptide is rich in arginine residues; there are six arginine residues and two lysine residues in a 13-amino-acid residue stretch. It has been shown that the arginine residues play a critical role in internalization². These characteristics can be observed among other arginine-rich peptides derived from HIV-1 Rev and flock house virus coat proteins as well as oligo-arginine peptides³.

Mode of Action

Arginine-rich peptides and their internalization mechanisms: Arginine-rich peptides, including HIV-1 Tatp (transactivator of transcription peptide), are regarded as a representative class of CPPs. Evidence suggests that macropinocytosis plays a crucial role in the cellular uptake of these peptides. Further it has been shown that treatment of cells with arginine-rich peptides induces activation of Rac protein leading to F-actin (filamentous actin) organization and macropinocytosis. Also, depletion of membrane-associated proteoglycans results in the failure of this signalling pathway, suggesting that membrane-associated proteoglycans may act as a potential receptor for the induction of macropinocytic uptake of arginine-rich peptides. However, when the macropinocytic pathway is inhibited at a low temperature or by cholesterol depletion, these peptides can be internalized by alternative mechanisms, one of which appears to be direct translocation of the peptides through the plasma membrane⁴.

Functions 

Membrane permeability - arginine-rich peptides: Delivery of proteins and other macromolecules using membrane-permeable carrier peptides is a recently developed novel technology, which enables us to modulate cellular functions for biological studies with therapeutic potential. One of the most often used carrier peptides is the arginine-rich basic peptide derived from HIV-1 Tat protein [HIV-1 Tat (48-60)]. Using this peptide, efficient intracellular delivery of molecules including proteins, oligonucleic acids and liposomes has been achieved. We have demonstrated that these features were commonly shared among many arginine-rich peptides such as HIV-1 Rev (34-50) and octaarginine. Not only the linear peptides but also branched-chain peptides showed efficient internalization with an optimum number of arginines (approximately eight residues) ⁵.

Arginine-rich cell penetrating peptides - from endosomal uptake to nuclear delivery: 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 limited delivery of macromolecules into the cell cytoplasm and nucleus. Different types of endocytosis – clathrin-dependent endocytosis, raft/caveolin-dependent endocytosis and macropinocytosis – are all implicated in the uptake of AR-CPPs and their cargo into different cells. Cationic AR-CPPs dramatically increase uptake of conjugated molecules through efficient binding to surface proteoglycans⁶.

Arginine-Rich Molecular Transporters for Drug Delivery - Role of Backbone Spacing in Cellular Uptake: Short oligomers of arginine, either alone or when conjugated to therapeutic agents or large biopolymers, have been shown to cross readily a variety of biological barriers (e.g., lipid bilayers and epithelial tissue). Molecular modeling suggests that only a subset of the side chain guanidinium groups of these transporters might be required for transport involving contact with a common surface such as a plasma membrane or cell surface receptor. In a study, a series of decamers were prepared that incorporated seven arginines and three nonarginine residues, to evaluate this hypothesis. Several of these mixed decamers were comparable to the all arginine decamer in their ability to enter cells. More significantly, these decamers containing seven arginines performed almost without exception better than heptaarginine itself, suggesting that spacing between residues is also important for transport⁷.

References

1. Vivès E, Brodin P, Lebleu B (1997). A truncated HIV-1 Tat protein basic domain rapidly translocates through the plasma membrane and accumulates in the cell nucleus. J. Biol. Chem., 272(25):16010-16017.
2. Futaki S, Suzuki T, Ohashi W, Yagami T, Tanaka S, Ueda K, Sugiura Y (2001). Arginine-rich peptides. An abundant source of membrane-permeable peptides having potential as carriers for intracellular protein delivery. J. Biol. Chem., 276(8):5836-5840.
3. Futaki S, Goto S, Suzuki T, Nakase I, Sugiura Y (2003). Structural variety of membrane permeable peptides. Curr. Protein. Pept. Sci., 4(2):87-96.
4. Futaki S, Nakase I, Tadokoro A, Takeuchi T, Jones AT (2007). Arginine-rich peptides and their internalization mechanisms. Biocheml Soc Trans., 35:784-787.  
5. Futaki S, Goto S, Sugiura Y (2003). Membrane permeability commonly shared among arginine-rich peptides. J. Mol. Recognit., 16(5):260-264.
6. Melikov K,Chernomordik LV (2005). Arginine-rich cell penetrating peptides: from endosomal uptake to nuclear delivery. Cellular and Molecular Life Sciences, 62(23): 2739-2749.
7. Rothbard JB, Kreider E, VanDeusen CL, Wright L, Wylie BL, Wender PA (2002). Arginine-Rich Molecular Transporters for Drug Delivery:  Role of Backbone Spacing in Cellular Uptake. J. Med. Chem., 45(17):3612–3618.