title: Nerve growth factor (NGF) loop 4 dimeric mimetics activate ERK and AKT and promote NGF-like neurotrophic effects.
abstract: Previous work indicating that nerve growth factor (NGF) protein loops 2 and 4 interact with TrkA receptors raise the possibility that small molecule mimetics corresponding to TrkA-interacting domains that have NGF agonist activity can be developed. We applied our previously developed strategy of dimeric peptidomimetics to address the hypothesis that loop 4 small molecule dimeric mimetics would activate TrkA-related signal transduction and mimic NGF neurotrophic effects in a structure-specific manner. A loop 4 cyclized peptide dimer demonstrated NGF-like neurotrophic activity, whereas peptides with scrambled sequence, added or substituted residues, or cyclized in monomeric form were inactive. Activity was blocked by the TrkA inhibitors K252a and AG879 but not by NGF p75 receptor blocking antibody. Dimeric, but not monomeric, peptides partially blocked NGF activity. This profile was consistent with that of a NGF partial agonist. ERK and AKT phosphorylation was stimulated only by biologically active peptides and was blocked by K252a. The ERK inhibitor U0126 blocked the neurite- but not the survival-promoting activity of both NGF and active peptide. These studies support the proof of concept that small molecule NGF loop 4 mimetics can activate NGF signaling pathways and can mimic death-preventing and neurite-promoting effects of NGF. This finding will guide the rational design of NGF single-domain mimetics and contribute to elucidating NGF signal transduction mechanisms.
authors.affiliation: Department of Neurology, Veterans Affairs Medical Center and University of California, San Francisco, California 94121, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Xie
authors.forename: M A
authors.initials: MA
authors.lastname: Tisi
authors.forename: T T
authors.initials: TT
authors.lastname: Yeo
authors.forename: F M
authors.initials: FM
authors.lastname: Longo
mesh_terms: D000818:Animals; D002642:Chick Embryo; D019281:Dimerization; D004789:Enzyme Activation; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020932:Nerve Growth Factor / Q000737:chemistry* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D010446:Peptide Fragments; D020932:Nerve Growth Factor; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases