Backbone Cyclic Peptide Antagonists, Derived from the Insect Pheromone Biosynthesis Activating Neuropeptide, Inhibit Sex Pheromone Biosynthesis in Moths

Abstract

We describe an application of the backbone cyclization and cycloscan concept for the design and synthesis of pheromone biosynthesis activating neuropeptide (PBAN) antagonists capable of inhibiting sex pheromone biosynthesis in Heliothis peltigera female moths. Two backbone cyclic (BBC) sub-libraries were designed and synthesized. The structure of the first sub-library ([Arg 27 ]PBAN27-33NH 2 , termed the Ser sub-library) was based on the active C-terminal hexapeptide sequence (Tyr-Phe-Ser-Pro-Arg-Leu-NH 2 ) of PBAN1-33NH 2 , which was found to comprise its active core. It is well established that the activation of multiple receptors by the same peptide arises from the ability of a given peptide to exist in different interchangeable bioactive conformations (1). To attain receptor selectivity it is, therefore, essential to restrict the conformational space of a peptide so it can attain one bioactive conformation.Cyclization is an important and attractive way to restrict the conformational space of peptidic structures (1). Conformationally restricted peptides containing medium and long range cyclizations have been mainly prepared following the same modes of cyclization of naturally occurring peptides. These include end-to-end, side-chain-to-side-chain, and side-chain-toend (2). These modes of cyclization involve modifications of side chains and ends which in many cases are essential for bioactivity, and therefore their modification causes loss of activity. Also, these modes of cyclization are not sufficient to screen effectively the conformational space available for a linear peptide with a given sequence. To overcome these limitations, we have introduced two methods called backbone cyclization (2) and cycloscan (3).Backbone cyclization is a general method by which a conformational constraint is imposed on peptides through the connection of the N ␣ and/or C ␣ atoms in the peptide backbone to each other or to side chains or to the carboxyl and amino ends (2). Thus, the cyclization can be performed while retaining the functionality and the activity of the side chains. Backbone cyclization allows nine new modes of cyclization in addition to the four modes in naturally occurring peptides. Preparation of backbone cyclic (BBC) 1 peptides involves the use of a large variety of orthogonally protected N ␣ and C ␣ (-amino-, -carboxy-, and -thio-alkyl) amino acids building units (4 -6). Synthetic procedures have been developed to incorporate these building units into peptides using the solid phase methodology (7,8).The advantages of backbone cyclization over the naturally occurring modes of cyclization are because of the immense variability of spatial orientation of the constitute residues which result from the multiple anchoring points within a chain or between chains. This allows us to screen the conformational space of a given peptide in an extremely efficient manner. Furthermore, most of the modes of backbone cyclization do not involve chemical modifications of side chains which are essential for biological activity. Ba...

Development of a Functional Backbone Cyclic Mimetic of the HIV-1 Tat Arginine-rich Motif

“…These parameters include ring size, position, and chemistry. The feasibility of these methodologies has been demonstrated with several naturally occurring peptides, including substance P (6,7,10,11), somatostatin (9), and pheromone biosynthesis activating neuropeptide (5), resulting in the development of receptor-selective and metabolically stable BC peptides.…”

“…Backbone cyclization of peptides is the method of cyclization developed and used in our lab. It results in peptides with improved selectivity, enhanced metabolic stability, and high bioavailability (5)(6)(7)(8)(9). To select the most active backbone cyclic (BC) 1 peptide based on a given sequence, we have developed the "cycloscan" technology (10), which involves the structure-based design, synthesis, and screening of BC peptide libraries.…”

Cloning and characterization of the pheromone biosynthesis activating neuropeptide receptor gene in Spodoptera littoralis larvae

“…The hypothesis was further supported by the behavior of a library of backbone cyclic (BBC) conformationally constrained PBANderived peptides, which, because of their rigid structure are much more receptor selective. The BBC peptides, all of which have the same primary sequence, same bridge location, and chemistry but differ from each other in their bridge sizes (Altstein et al, 1999), exhibited selective agonistic and antagonistic pheromonotropic and melanotropic activities (Ben-Aziz et al, 2006). It should be noted, however, that although the above results do imply that the differing sequences in the N-terminal and extracellular region may affect the docking and interaction of the peptide ligands with the receptors, which in turn may account for the differing and selective activities of the tested peptides, the possibility that the different assay conditions accounted for the differences in bioactivity should not be excluded.…”

Disruption of insect diapause using agonists and an antagonist of diapause hormone

“…Synthesis of the analog DH-Jo (Ac-GLWA[Jo]RLa) was accomplished by adapting the previously described solution phase synthesis of Jones and Ward (14) to a solid phase strategy using Rink Amide resin utilizing Fmocprotected amino acids on an ABI 433A peptide synthesizer under previously described conditions (21 (17,22), and synthesis of the "head-to-tail" cyclic octapeptide DH analog cyclo[GLWFGPRL] was carried out by adopting previously described procedures (15) used for synthesis of the related cyclic pyrokinin octapeptide analog cycloLPK (cyclo [NTSFTPRL]). …”

“…The primary method utilized previously to develop antagonists to the pyrokinin/PBAN family was to use a D-Phe substitution (17,18), such as found in the PBAN antagonist PPK-AA (18). Another method for antagonist development is to incorporate β-amino acids (16,19), but our preliminary data evaluation showed that neither PPK-AA nor other compounds containing either D-Phe or both D-Phe and β-amino acids could effectively inhibit DH activity in our diapause termination assay.…”