Hybrid Cyclobutane/Proline-Containing Peptidomimetics: The Conformational Constraint Influences Their Cell-Penetration Ability.

Ona Illa,Ximena Pulido,Daniel Carbajo,María Ángeles Abengozar,Nerea Gaztelumendi,Luis Rivas,Jean-Didier Maréchal,Carme Nogués,Jimena Ospina,Rosa M Ortuño,Miriam Royo,José-Emilio Sánchez-Aparicio

doi:10.3390/ijms22105092

Abstract

A new family of hybrid β,γ-peptidomimetics consisting of a repetitive unit formed by a chiral cyclobutane-containing trans-β-amino acid plus a Nα-functionalized trans-γ-amino-l-proline joined in alternation were synthesized and evaluated as cell penetrating peptides (CPP). They lack toxicity on the human tumoral cell line HeLa, with an almost negligible cell uptake. The dodecapeptide showed a substantial microbicidal activity on Leishmania parasites at 50 µM but with a modest intracellular accumulation. Their previously published γ,γ-homologues, with a cyclobutane γ-amino acid, showed a well-defined secondary structure with an average inter-guanidinium distance of 8–10 Å, a higher leishmanicidal activity as well as a significant intracellular accumulation. The presence of a very rigid cyclobutane β-amino acid in the peptide backbone precludes the acquisition of a defined conformation suitable for their cell uptake ability. Our results unveiled the preorganized charge-display as a relevant parameter, additional to the separation among the charged groups as previously described. The data herein reinforce the relevance of these descriptors in the design of CPPs with improved properties.

Highlights

We reported the biological performance as cell penetrating peptides (CPP) of hybrid γ,γpeptides formed by repetition of a dimeric unit constituted by a protected derivative of either cyclobutane γ-amino acids (γ-CBAA), 1 or 2 combined with cis-γ-amino-L-proline, 3 (Figure 1)
Toxicity on Leishmania pifanoi amastigotes and especially on Leishmania donovani promastigotes was remarkable at 50 μM, with a toxicity ranking: 12-mer ∼
Peptide internalization by Leishmania was practically nil on L. pifanoi amastigotes and modest on L. donovani promastigotes with a substantial increase with the length of the peptide

Summary

Introduction

Cell penetrating peptides (CPPs) [1,2,3] are potential carriers for drug delivery systems (DDS). They usually consist of peptide oligomers that convey the molecular payload into the intracellular space in the absence of a cognate transporter/receptor. One of their major drawbacks is their poor cellular specificity. This can be partially overcome by their local activation through the degradation of an inhibitory fragment carried out by specific proteinases, under environmental conditions (pH, hypoxia, etc.) or by the inclusion into their sequence of recognition motifs for a specific receptor located in the targeted cell [4]. A step ahead is the delivery of a cargo molecule into a certain organelle by inclusion of a particular

Methods

Results

Conclusion