Differential effects of transition metal cations on the conformation and biological activities of nerve growth factor

Abstract

Direct effects of Zn 2+ on the conformation and biological activity of nerve growth factor (NGF) have previously been described. Zn 2+ binds to specific coordination sites within NGF and induces conformational changes within domains that participate in receptor recognition processes. Recent theoretical considerations indicate that other transition metal cations (particularly, Cu2+and Pd 2+) are capable of forming similar complexes with NGF. Inactivation of NGF by transition metal cations is inhibitory to neuronal regeneration and sprouting, and can lead to, cell death under conditions where NGF is required for survival in PC12 cells. In this study we investigated the influence of various metal ions on NGF conformation, geometry of NGF amino terminal peptide and NGF-mediated biological effects in PC12 cells. A number of metal ions (Zn 2+, Cu 2+ and Pd 2+) alter NGF conformation in cell-free assays and inhibit NGF-mediated cell survival. Other metalshave been shown to be either toxic to PC12 cells b~ mechanisms independent of NGF activity (e.g. Ag , Hg 2 § or non-toxic to the cells under conditions tested (e.g. A13+, Cr3+). In conclusion, several metal cations are capable of inhibiting NGF activity, thereby blocking NGF-mediated cell survival and plasticity.

The Inorganic Perspective of Nerve Growth Factor: Interactions of Cu2+ and Zn2+ with the N‐Terminus Fragment of Nerve Growth Factor Encompassing the Recognition Domain of the TrkA Receptor

“…Potentiometry was also employed to check the peptide purity of the stock solutions to be employed for the biological and spectroscopic experiments. To this end a peptide solution ( % 2.0 10 À3 mol dm À3 ) was titrated to determine the initial peptide and TFA concentrations, [48] with the latter concentration being double-checked by 19 F NMR spectroscopy; interestingly, the TFA concentration independently obtained by using 19 F NMR spectroscopy nicely matched (within the experimental error) the values determined by using potentiometry.…”

“…: PRIN2007Y4ZAL3 003). Prof. E. Amato (University of Catania) is gratefully acknowledged for performing and discussing the 19 F NMR experiments.…”

“…[16][17][18][19][20][21][22] High concentrations of Zn 2 + and Cu 2 + have been shown to inhibit the in vitro effects of NGF as well as other neurotrophins (brain-derived neurotrophic factor (BDNF), neurotrophin-3 and neurotrophin-4/5). In addition to the decrease in cell viability, due to the inhibition of the trophic signalling of NGF after interaction with TrkA receptors, [19] Zn 2 + and Cu 2 + have been reported to inhibit NGF-mediated protection from oxidative-stress-induced apoptosis. [17] Zn 2 + (10-300 mm) has been shown to slightly inhibit TrkB phosphorylation caused by exposure to BDNF in cortical culture systems, whereas similar amounts of the same metal ion activate TrkB when administered without BDNF.…”

The inorganic perspectives of neurotrophins and Alzheimer's disease

“…High concentrations of Zn 2 + and Cu 2 + have been reported to inhibit the effects of NGF as well as BDNF, NT-3 and NT-4/ 5 in vitro. Namely, these metal ions have been shown: i) to block the NGF-mediated neurite outgrowth in chick dorsal root ganglia (DRG); ii) to decrease the cell viability [114]; and iii) to counteract the NGFmediated protection from oxidative stress in pheochromocytoma (PC12) cells [115]. These effects have been attributed to metalinduced conformational changes, which can alter the NGF binding to TrkA receptor, and, as a consequence, the activation of its downstream pathways [116].…”

“…Interestingly, 100 μM of zinc(II) or copper(II) ions, but not other cations, block the NGF binding to p75, attenuating its pro-apoptotic signaling cascade in chick embryonic cell cultures. Therefore, metal ions have been proposed to cause an apoptotic outcome, avoiding the activation of the TrkA mediated signal and, at the same time, they show an anti apoptotic effect, interrupting p75 cascades [114][115][116]118].…”