title: Human ProNGF: biological effects and binding profiles at TrkA, P75NTR and sortilin.
abstract: Nerve growth factor (NGF) promotes cell survival via binding to the tyrosine kinase receptor A (TrkA). Its precursor, proNGF, binds to p75(NTR) and sortilin receptors to initiate apoptosis. Current disagreement exists over whether proNGF acts neurotrophically following binding to TrkA. As in Alzheimer's disease the levels of proNGF increase and TrkA decrease, it is important to clarify the properties of proNGF. Here, wild-type and cleavage-resistant mutated forms (M) of proNGF were engineered and their binding characteristics determined. M-proNGF and NGF bound to p75(NTR) with similar affinities, whilst M-proNGF had a lower affinity than NGF for TrkA. M-proNGF behaved neurotrophically, albeit less effectively than NGF. M-proNGF addition resulted in phosphorylation of TrkA and ERK1/2, and in PC12 cells elicited neurite outgrowth and supported cell survival. Conversely, M-proNGF addition to cultured cortical neurons initiated caspase 3 cleavage. Importantly, these biological effects were shown to be mediated by unprocessed M-proNGF. Surprisingly, binding of the pro region alone to TrkA, at a site other than that of NGF, caused TrkA and ERK1/2 phosphorylation. Our data show that M-proNGF stimulates TrkA to a lesser degree than NGF, suggesting that in Alzheimer brain the increased proNGF : NGF and p75(NTR) : TrkA ratios may permit apoptotic effects to predominate over neurotrophic effects.
authors.affiliation: Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, UK.
authors.forename: Oliver
authors.initials: O
authors.lastname: Clewes
authors.forename: Mark S
authors.initials: MS
authors.lastname: Fahey
authors.forename: Sue J
authors.initials: SJ
authors.lastname: Tyler
authors.forename: Judy J
authors.initials: JJ
authors.lastname: Watson
authors.forename: Heon
authors.initials: H
authors.lastname: Seok
authors.forename: Caterina
authors.initials: C
authors.lastname: Catania
authors.forename: Kwangwook
authors.initials: K
authors.lastname: Cho
authors.forename: David
authors.initials: D
authors.lastname: Dawbarn
authors.forename: Shelley J
authors.initials: SJ
authors.lastname: Allen
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D006801:Humans; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D020932:Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D016501:Neurites / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011869:Radioligand Assay / Q000379:methods; D051381:Rats; D020917:Receptor, trkA / Q000378:metabolism*; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*; D011994:Recombinant Proteins; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors; D000099183:Sortilin
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D053148:Caspase 3; D048052:Mitogen-Activated Protein Kinase 3; D020932:Nerve Growth Factor; D009419:Nerve Tissue Proteins; D011498:Protein Precursors; D020917:Receptor, trkA; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor; D011994:Recombinant Proteins; D000099183:Sortilin; C061397:pro-nerve growth factor, human; C068313:Ngfr protein, rat