Neurotensin-SPDP-poly-L-lysine conjugate: a nonviral vector for targeted gene delivery to neural cells

We report herein the synthesis of a novel DNA delivery system and in vitro evidence of its ability to transfect cell lines by binding to the high-affi nity neurotensin receptor and subsequent internalization of ligand-receptor complexes. The targeting vehicle consisted of neurotensin crosslinked with poly-L-lysine via N-succinimidyl-3-(2-pyridyldithio) propionate (SPDP). Th e SPDP-derivatives with either neurotensin or poly-L-lysine were purified b y gel filtration. The conjugate resulting of the reaction of neurotensin-SP DP with HS-SPDP-poly-L-lysine was purified through Biogel A 1.5. The neurot ensin-SPDP-poly-L-lysine conjugate was able to bind plasmidic DNAs (pSV2cat and pGreen Lantern-1) at optimal molar ratios of 1:5 and 1:6 (DNA: conjuga te), respectively. The conjugate internalized those plasmids in the cell li nes (N1E-115 and HT-29) bearing the high-affinity neurotensin receptor. Exp ression of the plasmid products, chloramphenicol acetyltransferase and gree n fluorescent protein, was observed in such cell lines. Both internalizatio n and expression of the plasmids transferred by the neurotensin-SPDP-poly-L -lysine conjugate were prevented by neurotensin (1 mu M) and SR-48692 (100 nM), a specific antagonist of the high-affinity neurotensin receptor. The n eurotensin-SPDP-poly-L-lysine conjugate was unable to transfect cell lines lacking the neurotensin receptor (COS-7 and L-929). In rat brain, the high- affinity neurotensin receptor is expressed by specific neurons such as thos e of the nigrostriatal and mesolimbic dopaminergic systems. Therefore, the neurotensin-SPDP-poly-L-lysine conjugate could be a useful tool for gene de livery to those neuronal systems. (C) 1999 Elsevier Science B.V. All rights reserved.