A neurotensin receptor type 1-derived pepducin acts as a biased allosteric modulator to regulate target receptor function

Pepducins are synthetic membrane-tethered lipopeptides designed to allosterically modulate G protein-coupled receptor (GPCR) signaling. Here, we characterize a series of pepducins targeting the neurotensin receptor type 1 (NTSR1), revealing their complex and multifaceted modulation properties. Using BRET-based biosensors, we show that PP-001, a pepducin derived from NTSR1's first intracellular loop, preferentially activates G protein over β-arrestin signaling while inhibiting NT binding, NT-induced β-arrestin recruitment, and NTSR1 internalization, thereby acting as biased allosteric agonist and negative allosteric modulator. PP-001 also promotes the formation of both homo- and heteromeric multi-receptor complexes. In vivo, PP-001 elicits potent, sustained hypotensive effects, reversible by the NTSR1 antagonist SR48692. Although the precise mechanism of pepducin-receptor interaction remains unclear, we identify a critical N-terminal RKK motif for PP-001's biological activity. Finally, thermodenaturation assays using purified NTSR1, combined with mutagenesis and molecular docking, provide evidence for the role of the receptor's H8 domain in direct pepducin interaction. Together, these findings highlight pepducins as versatile modulators of GPCR function and as valuable pharmacological tools for GPCR-targeted drug development.