Comparative Molecular Transporter Efficiency of Cyclic Peptides Containing Tryptophan and Arginine Residues

Abstract

Cyclic peptides containing tryptophan (W) and arginine (R) residues, [WR] 5 , [WR] 6 , [WR] 7 , [WR] 8 , and [WR] 9 , were synthesized through Fmoc solid-phase chemistry to compare their molecular transporter efficiency. The in vitro cytotoxicity of the peptides was evaluated using human leukemia carcinoma cell line (CCRF-CEM) and normal kidney cell line (LLC-PK1). [WR] 6 , [WR] 7 , [WR] 8 , and [WR] 9 were not significantly cytotoxic to LLC-PK1cells at a concentration of 10 μM after 3 h incubation. Among all the peptides, [WR] 9 was found to be a more efficient transporter than [WR] 5 , [WR] 6 , [WR] 7 , and [WR] 8 in CCRF-CEM cells for delivery of a cell-impermeable fluorescence-labeled negatively charged phosphopeptide (F′-GpYEEI). [WR] 9 (10 μM) improved the cellular uptake of F′-GpYEEI (2 μM) by 20-fold. The cellular uptake of a fluorescent conjugate of [WR] 9 , F′-[W 9 R 8 K], was increased in a concentration- and time-dependent pattern in CCRF-CEM cells. The uptake of F′-[W 9 R 8 K] was slightly reduced in CCRF-CEM cells in the presence of different endocytic inhibitors, such as nystatin, 5-( N -ethyl- N -isopropyl)amiloride, chlorpromazine, chloroquine, and methyl β-cyclodextrin. Furthermore, the uptake of F′-[W 9 R 8 K] was shown to be temperature-dependent and slightly adenosine 5′-triphosphate-dependent. The intracellular/cellular localization (in the nucleus and cytoplasm) of F′-[W 9 R 8 K] was confirmed by fluorescent microscopy in CCRF-CEM cells. These studies suggest that large cyclic peptides containing arginine and tryptophan can be used as a molecular transporter of specific compounds.

[(WR)8WKβA]-Doxorubicin Conjugate: A Delivery System to Overcome Multi-Drug Resistance against Doxorubicin

“…The rationale for designing [(WR) 8 WKβA]-Dox conjugate was based on the fact that we found cyclic peptide [WR] 9 composed of alternate R and W was a more potent kinase inhibitor than [WR] 5 and [R 5 K]W 7 against c-Src, Abl, PKCa, Braf, Cdk2/cyclin A1, and that Lck [ 28 ]. [WR] 9 was a superior molecular transporter versus [WR] 5 [ 27 ]. We hypothesized that a Dox conjugate of [(WR) 8 WKβA], a derivative of [WR] 9 , with a large cyclic ring of alternate R and W residues would have a higher antiproliferative activity than [R 5 K]W 7 A-Dox [ 29 ] and [W(RW) 4 ]-Dox [ 23 ], as Dox conjugates of [R 5 K]W 7 and [WR] 5 , respectively.…”

“…Recently, we have reported amphiphilic cyclic CPPs composed of increasing numbers of W and R residues [WR] 6–9 , and compared their efficiency with the previously published cyclic [WR] 5 in improving the cellular uptake of cell-impermeable compounds and their molecular transporter efficiency [ 27 ]. Among all synthesized peptides, [WR] 9 was found to be the most effective peptide as a molecular transporter of fluorescence-labeled phosphopeptide (F′-GpYEEI) by 20-fold, compared to 4-fold when [WR] 5 was used.…”

A gold mine for drug discovery: Strategies to develop cyclic peptides into therapies

“…According to the sequences of the synthetic cyclic CPPs, most of them are rich in arginine, tryptophan, lysine, or histidine residues. For example, the peptides [WR] n ( n = 3 − 9), exhibit significant cell permeability and have been developed to deliver anti‐HIV drugs or small interfering RNA molecules (siRNA) . The cyclic CPPs derived from natural products like disulfide‐rich cyclic CPPs, have also been studied by various research groups.…”

De Novo Design of Cell‐Penetrating Foldamers

“…Based on these advantages, cell-penetrating macrocyclic peptides have been investigated in numerous sudies. [59][60][61][62][63][64][65][66][67][68] Qian and co-workers synthesized cyclic CPP derivatives based on the Tat-1 peptide and investigated the modes of action they employed to enter cells. The cyclic CPPs entered mammalian cells via endocytosis, before being efficiently released from endosomes.…”