Activation of signal transduction pathways involving trkA, PLCγ‐1, PKC isoforms and ERK‐1/2 by tetanus toxin

Abstract

Previous reports have demonstrated that tetanus toxin (TeTx) induces activation and down-regulation of protein kinase C (PKC). In the present work the differential activation of PKC isoforms and of signal transduction pathways, including nerve growth factor receptor trkA, phospholipase CQ Q-1 (PLCQ Q-1), and extracellular regulated kinases 1 and 2 (ERK-1/2) by TeTx in a synaptosome-enriched P 2 fraction from rat brain is reported. TeTx induces clear translocation from the soluble (cytosolic) compartment to the particulate (membranous) compartment of PKC-L L, -Q Q and -N N isoforms, whereas PKC-O O showed a slight decrease of its soluble fraction immunoreactivity. On the contrary, the PKC-j j isoform shows no consistent response, whereas down-regulation of total PKC-K K immunoreactivity is shown. Immunoprecipitation assays against phosphotyrosine show an increase of trkA and PLCQ Q-1 phosphorylation. Moreover, trkA activation is corroborated using phospho-specific antibodies against phosphorylated trkA. On the other hand, TeTx-induced stimulation of mitogen-activated protein (MAP) kinase activity is observed, this event also being detected by Western analysis using phospho-specific antibodies against ERK-1/2. ß

HC fragment (C-terminal portion of the heavy chain) of tetanus toxin activates protein kinase C isoforms and phosphoproteins involved in signal transduction

“…The treatment of synaptosomes with 100 nM PMA (results not shown) induced a typical response in PKC isoforms, as described previously [25], proving the reliability of the system. The incubation of synaptosomes with increasing concentrations of H C -TeTx for 15 min induced changes in the distribution of PKC isoforms (Figure 1).…”

“…The differential translocation of synaptosomal PKC isoforms in response to TeTx, as well as the induction of phosphorylation of trkA, PLCγ-1 and ERK-1\2 and activation of PKC isoforms, has recently been demonstrated by our group [25]. As a consequence of the results presented in the present work, we can attribute this signal activation to the H C -TeTx fragment.…”

“…Thus the H C -TeTx fragment could exert similar effects on some cellular events as entire TeTx. In addition, we have shown now that H C -TeTx acts in a similar way to the whole toxin in the activation of intracellular signalling pathways, an effect described recently [25]. The triggering of this effect could be related to the interaction of TeTx through its H C fragment with a still undefined membrane component.…”

“…In a recent publication, the activation of several enzymes involved in signal transduction by the whole TeTx protein (trkA, PKC isoforms, ERK-1\2 and PLCγ-1) is described [25]. In the present study, the existence of a differential activation of PKC isoenzymes by the H C fragment of TeTx, which has been described as being responsible for toxin binding to cellular membrane, is addressed.…”

Antiapoptotic activity maintenance of Brain Derived Neurotrophic Factor and the C fragment of the tetanus toxin genetic fusion protein

“…Our experiments indicate that the fused protein BDNF-TTC is functional in early apoptosis inhibition processes of the Neuro2A cell line as described for BDNF [40,41]. The present study, as well as previous work has shown that TTC can activate survival pathways in cells [34,35,42,43]. We report here that TTC also displays an antiapoptotic effect compared to control, although this effect was lower than the ones resulting from the treatment with the other two recombinant proteins ( Figure 3B) and also given that the TTC effect was lower than the others, we consider that the activity of the neurotrophic factor was maintained in our study.…”