HC fragment (C-terminal portion of the heavy chain) of tetanus toxin activates protein kinase C isoforms and phosphoproteins involved in signal transduction.
A recent report [Gil, Chaib-Oukadour, Pelliccioni and Aguilera (2000) FEBS Lett. 481, 177-182] describes activation of signal transduction pathways by tetanus toxin (TeTx), a Zn(2+)-dependent endopeptidase synthesized by the Clostridium tetani bacillus, which is responsible for tetanus disease. In the present work, specific activation of protein kinase C (PKC) isoforms and of intracellular signal-transduction pathways, which include nerve-growth-factor (NGF) receptor trkA, phospholipase C(PLC)gamma-1 and extracellular regulated kinases (ERKs) 1 and 2, by the recombinant C-terminal portion of the TeTx heavy chain (H(C)-TeTx) is reported. The activation of PKC isoforms was assessed through their translocation from the soluble (cytosolic) compartment to the membranous compartment, showing that clear translocation of PKC-alpha, -beta, -gamma and -delta isoforms exists, whereas PKC-epsilon showed a slight decrease in its soluble fraction immunoreactivity. The PKC-zeta isoform showed no consistent response. Using immunoprecipitation assays against phosphotyrosine residues, time- and dose-dependent increases in tyrosine phosphorylation were observed in the trkA receptor, PLCgamma-1 and ERK-1/2. The effects shown by the H(C)-TeTx fragment on tyrosine phosphorylation were compared with the effects produced by NGF. The trkA and ERK-1/2 activation were corroborated using phospho-specific antibodies against trkA phosphorylated on Tyr(490), and antibodies against Thr/Tyr phosphorylated ERK-1/2. Moreover, PLCgamma-1 phosphorylation was supported by its H(C)-TeTx-induced translocation to the membranous compartment, an event related to PLCgamma-1 activation. Since H(C)-TeTx is the domain responsible for membrane binding and lacks catalytic activity, the activations described here must be exclusively triggered by the interaction of TeTx with a membrane component.
Gil
C
C
Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
Chaib-Oukadour
I
I
Blasi
J
J
Aguilera
J
J
D000818:Animals; D001921:Brain / Q000378:metabolism; D002451:Cell Compartmentation; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010446:Peptide Fragments / Q000494:pharmacology*; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA; D015398:Signal Transduction; D013574:Synaptosomes / Q000187:drug effects*; D013744:Tetanus Toxin / Q000494:pharmacology*; D010738:Type C Phospholipases
D007527:Isoenzymes; D010446:Peptide Fragments; D010750:Phosphoproteins; D020800:Receptor, Nerve Growth Factor; D013744:Tetanus Toxin; D020917:Receptor, trkA; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma