Discovery of dermorphin-based affinity labels with subnanomolar affinity for mu opioid receptors

Abstract

A series of potent electrophilic affinity labels (IC(50) = 0.1-5 nM) containing either a bromoacetamide or isothiocyanate based on the mu opioid receptor (MOR) selective peptide dermorphin were prepared. All four analogues exhibited wash resistant inhibition of [(3)H]DAMGO binding at subnanomolar to nanomolar concentrations, suggesting that these analogues bind covalently to MOR. To our knowledge, these peptides are the highest affinity peptide-based affinity labels for MOR reported to date.

Figure 1

Affinity label derivatives for MOR and the corresponding reversible control peptides based on the parent peptide dermorphin

Figure 2

(A) WRIB by [D-Orn²]dermorphin and (B) [D-Lys²]dermorphin derivatives. The concentrations of the peptides in the incubations, which are approximately equal to their IC₅₀ values, are indicated in parenthesis. *p<0.05, *** p<0.001 compared to control

Figure 3

Concentration-dependent WRIB by [D-Orn(-COCH₂Br)²]dermorphin (2). *** p<0.001 compared to control

Figure 4

Concentration-dependent WRIB by [D-Lys(C=S)²]dermorphin (4). ***p<0.001 compared to control