Gangliosides Activate Trk Receptors by Inducing the Release of Neurotrophins

Abstract

We used NIH-3T3 fibroblasts expressing the different Trk receptors to examine whether GM1 ganglioside and its semisynthetic derivative LIGA20 activate various neurotrophin receptors. GM1 induced autophosphorylation of TrkC more potently than TrkA or TrkB receptors. In contrast, LIGA20 activated TrkB tyrosine phosphorylation only. Therefore, Scatchard analysis was performed to determine whether GM1 binds to TrkC. GM1 failed to displace neurotrophin-3 binding, suggesting that this ganglioside does not act as a ligand for Trk receptors. In addition, GM1 failed to induce autophosphorylation of a chimeric receptor consisting of the extracellular domain of the tumor necrosis factor receptor and the intracellular domain of TrkA, suggesting that GM1 does not affect the tyrosine kinase domain. We next determined whether GM1 induces the release of neurotrophins from fibroblast cells. GM1 induced a rapid and significant increase in the amount of neurotrophin-3, but not other neurotrophins. This effect was independent of the presence of Trk because K252a did not prevent GM1-mediated release of neurotrophin-3. Moreover, GM1-mediated TrkC autophosphorylation was blocked by TrkC-IgG (but not TrkB-IgG) receptor bodies, further suggesting that GM1 activates TrkC by inducing the release of neurotrophin-3. This hypothesis was also tested in cultured cerebellar granule cells. GM1 induced neurotrophin-3 (but not brain-derived neurotrophic factor or nerve growth factor) release. In contrast, LIGA20 increased the secretion of brain-derived neurotrophic factor. Our data show that gangliosides may activate different Trk receptors by differentially affecting the release of neurotrophins.Gangliosides constitute a heterogeneous family of sialic acidcontaining glycosphingolipids found in relative abundance in the nervous system (1, 2), where they influence the development and/or differentiation of neurons (3-5). Interest in these molecules has grown since the discovery that gangliosides display neurotrophic properties in neurons of the central nervous system both in vitro and in vivo. Indeed, the monosialotetrahexosylganglio (GM1) 1 prevents the dramatic loss of cholinergic neurons subsequent to hippocampal ablation or cortical lesion (6 -9). GM1 also stimulates the regeneration of dopaminergic neurons (10), improves cell survival in injured substantia nigra (11), and ameliorates the abnormal motor responses in animals treated with the dopamine neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (12). Moreover, GM1 and other gangliosides have been shown to possess a neuroprotective action against excitatory amino acid toxicity in vitro (13-15) and after stroke or brain ischemia (16, 17) as well as after spinal cord injury (18). Despite these findings, the mechanisms of ganglioside trophic activity are still unclear. Potential substrates of GM1 that would explain its neurotrophic effects are the neurotrophins and their receptors. The neurotrophin family of neurotrophic factors includes nerve growth factor (NGF), brain-derived neurotrophi...

GM1 induces p38 and microtubule dependent ramification of rat primary microglia in vitro

“…Furthermore, several studies indicated that gangliosides increase the rates of neuritogenesis both in vivo and in vitro (Ferrari et al, 1983;Mendez-Otero and Santiago, 2003;Roisen et al, 1984) and possess a neuroprotective action (Favaron et al, 1988;Geisler et al, 1991;Karpiak et al, 1990;Manev et al, 1990;Seren et al, 1990). These effects have partly been explained by the fact that GM1 induces a rapid and significant increase in the amount of NT-3, which was observed in fibroblast cells and cerebellar granule cells (Rabin et al, 2002). Neurotrophins are a family of structurally and functionally related molecules, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, and NT-4/5.…”

“…GM1 increased the expression of NT-3 in cultured primary microglia GM1 has previously been reported to induce the release of neurotrophin-3 (NT-3), one of neurotrophins of nerve growth factor family, from neuronal and non-neuronal cells (Rabin et al, 2002). Therefore, to verify whether GM1 also induces the release of NT-3 in microglia, we initially performed RT-PCR analysis.…”

Factors influencing neurotrophic effects of electrical stimulation in the deafened developing auditory system

“…We recently reported a study of the effects of GM1 ganglioside , a glycosphingolipid that has been reported to promote neuronal survival after injury (Wu et al, 2004;Wu et al, 2005;Zhang et al, 2005;Fighera et al, 2006) by potentiating the release of neurotrophins and activating trkB signaling Rabin et al, 2002;Duchemin et al, 2002;Bachis and Mocchetti, 2006). Some clinical trials in humans have reported GM1 to be of benefit in treating stroke, spinal cord injury and Alzheimers disease (Kharlamov et al, 1994;Geisler et al, 1993;Svennerholm, 1994), and in animal studies exogenous administration of GM1 has been reported to reduce SG degeneration after deafness Walsh and Webster, 1994).…”

Gangliosides Trigger Inflammatory Responses via TLR4 in Brain Glia

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