Mapping the active site in vasoactive intestinal peptide to a core of fouramino acids: Neuroprotective drug design

The understanding of the molecular mechanisms leading to peptide action ent ails the identification of a core active site. The major 28-aa neuropeptide , vasoactive intestinal peptide (VIP), provides neuroprotection. A lipophil ic derivative with a stearyl moiety at the N-terminal and norleucine residu e replacing the Met-17 was 100-fold more potent than VIP in promoting neuro nal survival, acting at femtomolar-picomolar concentration. To identify the active site in VIP, over 50 related fragments containing an N-terminal ste aric acid attachment and an amidated C terminus were designed, synthesized, and tested for neuroprotective properties. Stearyl-Lys-Lys-Tyr-Leu-NH2 (de rived from the C terminus of VIP and the related peptide, pituitary adenyla te cyclase activating peptide) captured the neurotrophic effects offered by the entire 28-aa parent lipophilic derivative and protected against beta-a myloid toxicity in vitro. Furthermore, the 4-aa lipophilic peptide recogniz ed VIP-binding sites and enhanced choline acetyltransferase activity as wel l as cognitive functions in Alzheimer's disease-related in vivo models. Bio distribution studies following intranasal administration of radiolabeled p eptide demonstrated intact peptide in the brain 30 min after administration . Thus, lipophilic peptide fragments offer bioavailability and stability, p roviding lead compounds for drug design against neurodegenerative diseases.