Abstract
BackgroundThis study aimed at developing nerve growth factor (NGF) mimetics that selectively activate specific biological signals and, as a result, lack the side effects of the full-length protein. Two dimeric dipeptides, bis-(N-aminocaproyl-glycyl-L-lysine) hexamethylenediamide (GK-6) and bis(N-succinyl-L-glutamyl-L-lysine) hexamethylenediamide (GK-2), were designed based on the most exposed outside fragments of NGF, namely, the loop 1 and loop 4 β-turn sequences, respectively. These dipeptides exhibited neuroprotective activity in vitro at micro-nanomolar concentrations.ResultsStudies on the mechanism of action revealed that both compounds elevate the level of tyrosine kinase A (TrkA) receptor phosphorylation and that they each have different postreceptor signaling patterns. GK-6 increases the levels of extracellular signal-regulated kinase (ERK) and AKT kinase phosphorylation, whereas GK-2 only increases the level of AKT phosphorylation. Apart from the neuroprotective activity, GK-6 promoted differentiation in PC12 cells, whereas GK-2 did not. Furthermore, it was established that the neuroprotective activity of GK-2 was completely abolished by a selective inhibitor of phosphatidylinositol 3-kinase (LY294002) but not by a specific inhibitor of mitogen-activated protein kinases MEK1 and MEK2 (PD98059). In vivo experiments demonstrated that GK-2 did not induce hyperalgesia, which is one of the primary adverse effects of NGF. By contrast, GK-6 produced a significant decrease in the pain threshold of rats as determined by the tail flick test.ConclusionThe data obtained suggest that dimeric dipeptide NGF mimetics are promising candidates in the development of pharmacological agents with NGF-like activity that are free of the main side effect of NGF.
Highlights
This study aimed at developing nerve growth factor (NGF) mimetics that selectively activate specific biological signals and, as a result, lack the side effects of the full-length protein
GK-6 and GK-2, activate tyrosine kinase A (TrkA) receptors The dipeptides GK-6 (10−6M) and GK-2 (10−8M) added to HT-22 hippocampal neurons induced the elevation of TrkA receptor phosphorylation after incubation for 15, 30, 60 and 180 min, to NGF (10−9M) (Fig. 1)
Western blot densitometry analysis revealed that AKT1/2/3 phosphorylation was increased after stimulation of the cells by GK-6 (10−6M), GK-2 (10−8M) or NGF (10−9M) at the time intervals observed for TrkA (i.e., 15, 30, 60, and 180 min incubations) (Fig. 2)
Summary
This study aimed at developing nerve growth factor (NGF) mimetics that selectively activate specific biological signals and, as a result, lack the side effects of the full-length protein. Bis-(N-aminocaproyl-glycyl-L-lysine) hexamethylenediamide (GK-6) and bis(N-succinyl-L-glutamyl-L-lysine) hexamethylenediamide (GK-2), were designed based on the most exposed outside fragments of NGF, namely, the loop 1 and loop 4 β-turn sequences, respectively These dipeptides exhibited neuroprotective activity in vitro at micro-nanomolar concentrations. Nerve growth factor (NGF), a member of the neurotrophin family, is essential for the development and survival of several populations of neurons and a number of nonneural cells. Despite this factor’s considerable therapeutic potential, the clinical application of NGF is limited by its strong side effects, the most important of which are hyperalgesia and weight loss [1]. The design of small, proteolytically stable NGF mimetics that exert defined biological activities via the selective
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
