In Vitro Analysis of Stable, Receptor-Selective Neurotensin[8−13] Analogues

Abstract

A set of neurotensin[8-13] (NT[8-13]) analogues featuring substitution of non-natural cationic amino acids in the Arg(8) position have been synthesized and tested for binding potencies against the three cloned human NT receptors (hNTR-1, hNTR-2, hNTR-3), functional agonism of the hNTR1 and for rat serum stability. Three distinct classes of peptides have been identified: Class 1 features alkyl-Arg analogues at Arg(8), Class 2 features alpha-azido-cationic amino acids at Arg(8), and Class 3 feature modified Arg(8) and Tyr(11) residues. Most of the peptides maintain or exceed the binding potency of NT[8-13] to hNTR-1. Class 2 analogues exceed the binding potency of NT[8-13] to hNTR-2 with KK19 binding with higher affinity to hNTR-2 than hNTR-1. Peptides with enhanced binding potencies for hNTR-3 were not found. All analogues are functional agonists of the hNTR1 receptor as indicated by phosphoinositide (PI) determination. Serum stability increased with peptide classification where the half-life of Class 1 < Class 2 < Class 3 which are stable to rat serum for > 24 h.

Identification and Functional Characterization of a Stable, Centrally Active Derivative of the Neurotensin (8−13) Fragment as a Potential First-in-Class Analgesic

“…NTR binding assays were performed as previously described 19. LTK cells expressing rat NTR were propagated in using standard cell culture techniques.…”

“…These studies were performed essentially as described previously 19. Briefly, cells transfected with either the hNTR-1 or hNTR-2 plasmids were homogenized and prepared as previously described 47.…”

Synthesis and biological activity of stable branched neurotensin peptides for tumor targeting

“…To circumvent this problem, various neurotensin analogues have been synthesized, including linear peptides (8,10,19), cyclic peptides (20), and nonpeptide molecules (21), but chemical modification of the native peptide may radically modify receptor affinity and specificity.…”

Peptide Drugs

“…The main drawback in the use of neurotensin, like any other peptide, as a drug is its extremely short halflife in human plasma due to very rapid cleavage by different peptidases. To circumvent this problem various neurotensin analogs were synthesized, including linear peptides [70,72,80], cyclic peptides [81], and nonpeptide molecules [82], but affinity of most neurotensin stabilized analogs reported in the literature is lower than that of native neurotensin.…”